Add m-esr52 at 52.6.0

11 files changed, 3748 insertions, 0 deletions

diff --git a/xpcom/typelib/moz.build b/xpcom/typelib/moz.build
new file mode 100644
index 000000000..3d82a998d
--- /dev/null
+++ b/xpcom/typelib/moz.build
@@ -0,0 +1,8 @@
+# -*- Mode: python; indent-tabs-mode: nil; tab-width: 40 -*-
+# vim: set filetype=python:
+# This Source Code Form is subject to the terms of the Mozilla Public
+# License, v. 2.0. If a copy of the MPL was not distributed with this
+# file, You can obtain one at http://mozilla.org/MPL/2.0/.
+
+DIRS += ['xpt']
+
diff --git a/xpcom/typelib/xpt/moz.build b/xpcom/typelib/xpt/moz.build
new file mode 100644
index 000000000..80b9160b0
--- /dev/null
+++ b/xpcom/typelib/xpt/moz.build
@@ -0,0 +1,40 @@
+# -*- Mode: python; indent-tabs-mode: nil; tab-width: 40 -*-
+# vim: set filetype=python:
+# This Source Code Form is subject to the terms of the Mozilla Public
+# License, v. 2.0. If a copy of the MPL was not distributed with this
+# file, You can obtain one at http://mozilla.org/MPL/2.0/.
+
+Library('xpt')
+
+DIRS += ['tools']
+
+UNIFIED_SOURCES += [
+    'xpt_arena.cpp',
+    'xpt_struct.cpp',
+    'xpt_xdr.cpp',
+]
+
+EXPORTS += [
+    'xpt_arena.h',
+    'xpt_struct.h',
+    'xpt_xdr.h',
+]
+
+FINAL_LIBRARY = 'xul'
+
+LOCAL_INCLUDES += [
+    '!/xpcom/base',
+    '/xpcom/base',
+]
+
+if CONFIG['_MSC_VER']:
+    CFLAGS += ['-Zl']
+
+# Code with FINAL_LIBRARY = 'xul' shouldn't do this, but the code
+# here doesn't use malloc functions anyways, while not setting
+# MOZ_NO_MOZALLOC makes the code include mozalloc.h, which includes
+# inline operator new definitions that MSVC linker doesn't strip
+# when linking the xpt tests.
+DEFINES['MOZ_NO_MOZALLOC'] = True
+
+DIST_INSTALL = True
diff --git a/xpcom/typelib/xpt/tools/moz.build b/xpcom/typelib/xpt/tools/moz.build
new file mode 100644
index 000000000..bd4a2836b
--- /dev/null
+++ b/xpcom/typelib/xpt/tools/moz.build
@@ -0,0 +1,13 @@
+# -*- Mode: python; indent-tabs-mode: nil; tab-width: 40 -*-
+# vim: set filetype=python:
+# This Source Code Form is subject to the terms of the Mozilla Public
+# License, v. 2.0. If a copy of the MPL was not distributed with this
+# file, You can obtain one at http://mozilla.org/MPL/2.0/.
+
+PYTHON_UNIT_TESTS += [
+    'runtests.py',
+]
+
+SDK_FILES.bin += [
+    'xpt.py',
+]
diff --git a/xpcom/typelib/xpt/tools/runtests.py b/xpcom/typelib/xpt/tools/runtests.py
new file mode 100644
index 000000000..a86e6625d
--- /dev/null
+++ b/xpcom/typelib/xpt/tools/runtests.py
@@ -0,0 +1,770 @@
+#!/usr/bin/env python
+# Copyright 2010,2011 Mozilla Foundation. All rights reserved.
+#
+# Redistribution and use in source and binary forms, with or without
+# modification, are permitted provided that the following conditions are
+# met:
+#
+#   1. Redistributions of source code must retain the above copyright
+#      notice, this list of conditions and the following disclaimer.
+#
+#   2. Redistributions in binary form must reproduce the above copyright
+#      notice, this list of conditions and the following disclaimer in
+#      the documentation and/or other materials provided with the
+#      distribution.
+#
+# THIS SOFTWARE IS PROVIDED BY THE MOZILLA FOUNDATION ``AS IS'' AND ANY
+# EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+# IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
+# PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE MOZILLA FOUNDATION OR
+# CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
+# EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
+# PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
+# PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY
+# OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+# (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+# OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+#
+# The views and conclusions contained in the software and documentation
+# are those of the authors and should not be interpreted as representing
+# official policies, either expressed or implied, of the Mozilla
+# Foundation.
+
+import difflib
+import os
+from StringIO import StringIO
+import subprocess
+import tempfile
+import mozunit
+import unittest
+import xpt
+
+
+def get_output(bin, file):
+    p = subprocess.Popen([bin, file], stdout=subprocess.PIPE)
+    stdout, _ = p.communicate()
+    return stdout
+
+if "MOZILLA_OBJDIR" in os.environ:
+    class CheckXPTDump(unittest.TestCase):
+        def test_xpt_dump_diffs(self):
+            MOZILLA_OBJDIR = os.environ["MOZILLA_OBJDIR"]
+            xptdump = os.path.abspath(os.path.join(MOZILLA_OBJDIR,
+                                                   "dist", "bin", "xpt_dump"))
+            components = os.path.abspath(os.path.join(MOZILLA_OBJDIR,
+                                                      "dist", "bin", "components"))
+            for f in os.listdir(components):
+                if not f.endswith(".xpt"):
+                    continue
+                fullpath = os.path.join(components, f)
+                # read a Typelib and dump it to a string
+                t = xpt.Typelib.read(fullpath)
+                self.assert_(t is not None)
+                outf = StringIO()
+                t.dump(outf)
+                out = outf.getvalue()
+                # now run xpt_dump on it
+                out2 = get_output(xptdump, fullpath)
+                if out != out2:
+                    print "diff %s" % f
+                    for line in difflib.unified_diff(out2.split("\n"), out.split("\n"), lineterm=""):
+                        print line
+                self.assert_(out == out2, "xpt_dump output should be identical for %s" % f)
+
+
+class TestIIDString(unittest.TestCase):
+    def test_iid_str_roundtrip(self):
+        iid_str = "11223344-5566-7788-9900-aabbccddeeff"
+        iid = xpt.Typelib.string_to_iid(iid_str)
+        self.assertEqual(iid_str, xpt.Typelib.iid_to_string(iid))
+
+    def test_iid_roundtrip(self):
+        iid = "\x11\x22\x33\x44\x55\x66\x77\x88\x99\x00\xaa\xbb\xcc\xdd\xee\xff"
+        iid_str = xpt.Typelib.iid_to_string(iid)
+        self.assertEqual(iid, xpt.Typelib.string_to_iid(iid_str))
+
+
+class TypelibCompareMixin:
+    def assertEqualTypelibs(self, t1, t2):
+        self.assert_(t1 is not None, "Should not be None")
+        self.assert_(t2 is not None, "Should not be None")
+        self.assertEqual(t1.version, t2.version, "Versions should be equal")
+        self.assertEqual(len(t1.interfaces), len(t2.interfaces),
+                         "Number of interfaces should be equal")
+        for i, j in zip(t1.interfaces, t2.interfaces):
+            self.assertEqualInterfaces(i, j)
+
+    def assertEqualInterfaces(self, i1, i2):
+        self.assert_(i1 is not None, "Should not be None")
+        self.assert_(i2 is not None, "Should not be None")
+        self.assertEqual(i1.name, i2.name, "Names should be equal")
+        self.assertEqual(i1.iid, i2.iid, "IIDs should be equal")
+        self.assertEqual(i1.namespace, i2.namespace,
+                         "Namespaces should be equal")
+        self.assertEqual(i1.resolved, i2.resolved,
+                         "Resolved status should be equal")
+        if i1.resolved:
+            if i1.parent or i2.parent:
+                # Can't test exact equality, probably different objects
+                self.assertEqualInterfaces(i1.parent, i2.parent)
+            self.assertEqual(len(i1.methods), len(i2.methods))
+            for m, n in zip(i1.methods, i2.methods):
+                self.assertEqualMethods(m, n)
+            self.assertEqual(len(i1.constants), len(i2.constants))
+            for c, d in zip(i1.constants, i2.constants):
+                self.assertEqualConstants(c, d)
+            self.assertEqual(i1.scriptable, i2.scriptable,
+                             "Scriptable status should be equal")
+            self.assertEqual(i1.function, i2.function,
+                             "Function status should be equal")
+
+    def assertEqualMethods(self, m1, m2):
+        self.assert_(m1 is not None, "Should not be None")
+        self.assert_(m2 is not None, "Should not be None")
+        self.assertEqual(m1.name, m2.name, "Names should be equal")
+        self.assertEqual(m1.getter, m2.getter, "Getter flag should be equal")
+        self.assertEqual(m1.setter, m2.setter, "Setter flag should be equal")
+        self.assertEqual(m1.notxpcom, m2.notxpcom,
+                         "notxpcom flag should be equal")
+        self.assertEqual(m1.constructor, m2.constructor,
+                         "constructor flag should be equal")
+        self.assertEqual(m1.hidden, m2.hidden, "hidden flag should be equal")
+        self.assertEqual(m1.optargc, m2.optargc, "optargc flag should be equal")
+        self.assertEqual(m1.implicit_jscontext, m2.implicit_jscontext,
+                         "implicit_jscontext flag should be equal")
+        for p1, p2 in zip(m1.params, m2.params):
+            self.assertEqualParams(p1, p2)
+        self.assertEqualParams(m1.result, m2.result)
+
+    def assertEqualConstants(self, c1, c2):
+        self.assert_(c1 is not None, "Should not be None")
+        self.assert_(c2 is not None, "Should not be None")
+        self.assertEqual(c1.name, c2.name)
+        self.assertEqual(c1.value, c2.value)
+        self.assertEqualTypes(c1.type, c2.type)
+
+    def assertEqualParams(self, p1, p2):
+        self.assert_(p1 is not None, "Should not be None")
+        self.assert_(p2 is not None, "Should not be None")
+        self.assertEqualTypes(p1.type, p2.type)
+        self.assertEqual(p1.in_, p2.in_)
+        self.assertEqual(p1.out, p2.out)
+        self.assertEqual(p1.retval, p2.retval)
+        self.assertEqual(p1.shared, p2.shared)
+        self.assertEqual(p1.dipper, p2.dipper)
+        self.assertEqual(p1.optional, p2.optional)
+
+    def assertEqualTypes(self, t1, t2):
+        self.assert_(t1 is not None, "Should not be None")
+        self.assert_(t2 is not None, "Should not be None")
+        self.assertEqual(type(t1), type(t2), "type types should be equal")
+        self.assertEqual(t1.pointer, t2.pointer,
+                         "pointer flag should be equal for %s and %s" % (t1, t2))
+        self.assertEqual(t1.reference, t2.reference)
+        if isinstance(t1, xpt.SimpleType):
+            self.assertEqual(t1.tag, t2.tag)
+        elif isinstance(t1, xpt.InterfaceType):
+            self.assertEqualInterfaces(t1.iface, t2.iface)
+        elif isinstance(t1, xpt.InterfaceIsType):
+            self.assertEqual(t1.param_index, t2.param_index)
+        elif isinstance(t1, xpt.ArrayType):
+            self.assertEqualTypes(t1.element_type, t2.element_type)
+            self.assertEqual(t1.size_is_arg_num, t2.size_is_arg_num)
+            self.assertEqual(t1.length_is_arg_num, t2.length_is_arg_num)
+        elif isinstance(t1, xpt.StringWithSizeType) or isinstance(t1, xpt.WideStringWithSizeType):
+            self.assertEqual(t1.size_is_arg_num, t2.size_is_arg_num)
+            self.assertEqual(t1.length_is_arg_num, t2.length_is_arg_num)
+
+
+class TestTypelibReadWrite(unittest.TestCase, TypelibCompareMixin):
+    def test_read_file(self):
+        """
+        Test that a Typelib can be read/written from/to a file.
+        """
+        t = xpt.Typelib()
+        # add an unresolved interface
+        t.interfaces.append(xpt.Interface("IFoo"))
+        fd, f = tempfile.mkstemp()
+        os.close(fd)
+        t.write(f)
+        t2 = xpt.Typelib.read(f)
+        os.remove(f)
+        self.assert_(t2 is not None)
+        self.assertEqualTypelibs(t, t2)
+
+
+# TODO: test flags in various combinations
+class TestTypelibRoundtrip(unittest.TestCase, TypelibCompareMixin):
+    def checkRoundtrip(self, t):
+        s = StringIO()
+        t.write(s)
+        s.seek(0)
+        t2 = xpt.Typelib.read(s)
+        self.assert_(t2 is not None)
+        self.assertEqualTypelibs(t, t2)
+
+    def test_simple(self):
+        t = xpt.Typelib()
+        # add an unresolved interface
+        t.interfaces.append(xpt.Interface("IFoo"))
+        self.checkRoundtrip(t)
+
+        t = xpt.Typelib()
+        # add an unresolved interface with an IID
+        t.interfaces.append(xpt.Interface("IBar", "11223344-5566-7788-9900-aabbccddeeff"))
+        self.checkRoundtrip(t)
+
+    def test_parent(self):
+        """
+        Test that an interface's parent property is correctly serialized
+        and deserialized.
+
+        """
+        t = xpt.Typelib()
+        pi = xpt.Interface("IParent")
+        t.interfaces.append(pi)
+        t.interfaces.append(xpt.Interface("IChild", iid="11223344-5566-7788-9900-aabbccddeeff",
+                                          parent=pi, resolved=True))
+        self.checkRoundtrip(t)
+
+    def test_ifaceFlags(self):
+        """
+        Test that an interface's flags are correctly serialized
+        and deserialized.
+
+        """
+        t = xpt.Typelib()
+        t.interfaces.append(xpt.Interface("IFlags", iid="11223344-5566-7788-9900-aabbccddeeff",
+                                          resolved=True,
+                                          scriptable=True,
+                                          function=True))
+        self.checkRoundtrip(t)
+
+    def test_constants(self):
+        c = xpt.Constant("X", xpt.SimpleType(xpt.Type.Tags.uint32),
+                         0xF000F000)
+        i = xpt.Interface("IFoo", iid="11223344-5566-7788-9900-aabbccddeeff",
+                          constants=[c])
+        t = xpt.Typelib(interfaces=[i])
+        self.checkRoundtrip(t)
+        # tack on some more constants
+        i.constants.append(xpt.Constant("Y",
+                                        xpt.SimpleType(xpt.Type.Tags.int16),
+                                        -30000))
+        i.constants.append(xpt.Constant("Z",
+                                        xpt.SimpleType(xpt.Type.Tags.uint16),
+                                        0xB0B0))
+        i.constants.append(xpt.Constant("A",
+                                        xpt.SimpleType(xpt.Type.Tags.int32),
+                                        -1000000))
+        self.checkRoundtrip(t)
+
+    def test_methods(self):
+        p = xpt.Param(xpt.SimpleType(xpt.Type.Tags.void))
+        m = xpt.Method("Bar", p)
+        i = xpt.Interface("IFoo", iid="11223344-5566-7788-9900-aabbccddeeff",
+                          methods=[m])
+        t = xpt.Typelib(interfaces=[i])
+        self.checkRoundtrip(t)
+        # add some more methods
+        i.methods.append(xpt.Method("One", xpt.Param(xpt.SimpleType(xpt.Type.Tags.int32)),
+                                    params=[
+                                        xpt.Param(xpt.SimpleType(xpt.Type.Tags.int64)),
+                                        xpt.Param(xpt.SimpleType(xpt.Type.Tags.float, pointer=True))
+                                        ]))
+        self.checkRoundtrip(t)
+        # test some other types (should really be more thorough)
+        i.methods.append(xpt.Method("Two", xpt.Param(xpt.SimpleType(xpt.Type.Tags.int32)),
+                                    params=[
+                                        xpt.Param(xpt.SimpleType(xpt.Type.Tags.UTF8String, pointer=True)),
+                                        xpt.Param(xpt.SimpleType(xpt.Type.Tags.wchar_t_ptr, pointer=True))
+                                        ]))
+        self.checkRoundtrip(t)
+        # add a method with an InterfaceType argument
+        bar = xpt.Interface("IBar")
+        t.interfaces.append(bar)
+        i.methods.append(xpt.Method("IFaceMethod", xpt.Param(xpt.SimpleType(xpt.Type.Tags.int32)),
+                                    params=[
+                                        xpt.Param(xpt.InterfaceType(bar))
+                                        ]))
+        self.checkRoundtrip(t)
+
+        # add a method with an InterfaceIsType argument
+        i.methods.append(xpt.Method("IFaceIsMethod", xpt.Param(xpt.SimpleType(xpt.Type.Tags.void)),
+                                    params=[
+                                        xpt.Param(xpt.InterfaceIsType(1)),
+                                        xpt.Param(xpt.SimpleType(xpt.Type.Tags.nsIID))
+                                        ]))
+        self.checkRoundtrip(t)
+
+        # add a method with an ArrayType argument
+        i.methods.append(xpt.Method("ArrayMethod", xpt.Param(xpt.SimpleType(xpt.Type.Tags.void)),
+                                    params=[
+                                        xpt.Param(xpt.ArrayType(
+                                            xpt.SimpleType(xpt.Type.Tags.int32),
+                                            1, 2)),
+                                        xpt.Param(xpt.SimpleType(xpt.Type.Tags.int32)),
+                                        xpt.Param(xpt.SimpleType(xpt.Type.Tags.int32)),
+                                        ]))
+        self.checkRoundtrip(t)
+
+        # add a method with a StringWithSize and WideStringWithSize arguments
+        i.methods.append(xpt.Method("StringWithSizeMethod", xpt.Param(xpt.SimpleType(xpt.Type.Tags.void)),
+                                    params=[
+                                        xpt.Param(xpt.StringWithSizeType(
+                                            1, 2)),
+                                        xpt.Param(xpt.SimpleType(xpt.Type.Tags.int32)),
+                                        xpt.Param(xpt.SimpleType(xpt.Type.Tags.int32)),
+                                        xpt.Param(xpt.WideStringWithSizeType(
+                                            4, 5)),
+                                        xpt.Param(xpt.SimpleType(xpt.Type.Tags.int32)),
+                                        xpt.Param(xpt.SimpleType(xpt.Type.Tags.int32)),
+                                        ]))
+        self.checkRoundtrip(t)
+
+
+class TestInterfaceCmp(unittest.TestCase):
+    def test_unresolvedName(self):
+        """
+        Test comparison function on xpt.Interface by name.
+
+        """
+        i1 = xpt.Interface("ABC")
+        i2 = xpt.Interface("DEF")
+        self.assert_(i1 < i2)
+        self.assert_(i1 != i2)
+
+    def test_unresolvedEqual(self):
+        """
+        Test comparison function on xpt.Interface with equal names and IIDs.
+
+        """
+        i1 = xpt.Interface("ABC")
+        i2 = xpt.Interface("ABC")
+        self.assert_(i1 == i2)
+
+    def test_unresolvedIID(self):
+        """
+        Test comparison function on xpt.Interface with different IIDs.
+
+        """
+        # IIDs sort before names
+        i1 = xpt.Interface("ABC", iid="22334411-5566-7788-9900-aabbccddeeff")
+        i2 = xpt.Interface("DEF", iid="11223344-5566-7788-9900-aabbccddeeff")
+        self.assert_(i2 < i1)
+        self.assert_(i2 != i1)
+
+    def test_unresolvedResolved(self):
+        """
+        Test comparison function on xpt.Interface with interfaces with
+        identical names and IIDs but different resolved status.
+
+        """
+        i1 = xpt.Interface("ABC", iid="11223344-5566-7788-9900-aabbccddeeff")
+        p = xpt.Param(xpt.SimpleType(xpt.Type.Tags.void))
+        m = xpt.Method("Bar", p)
+        i2 = xpt.Interface("ABC", iid="11223344-5566-7788-9900-aabbccddeeff",
+                           methods=[m])
+        self.assert_(i2 < i1)
+        self.assert_(i2 != i1)
+
+    def test_resolvedIdentical(self):
+        """
+        Test comparison function on xpt.Interface with interfaces with
+        identical names and IIDs, both of which are resolved.
+
+        """
+        p = xpt.Param(xpt.SimpleType(xpt.Type.Tags.void))
+        m = xpt.Method("Bar", p)
+        i1 = xpt.Interface("ABC", iid="11223344-5566-7788-9900-aabbccddeeff",
+                           methods=[m])
+        i2 = xpt.Interface("ABC", iid="11223344-5566-7788-9900-aabbccddeeff",
+                           methods=[m])
+        self.assert_(i2 == i1)
+
+
+class TestXPTLink(unittest.TestCase):
+    def test_mergeDifferent(self):
+        """
+        Test that merging two typelibs with completely different interfaces
+        produces the correctly merged typelib.
+
+        """
+        t1 = xpt.Typelib()
+        # add an unresolved interface
+        t1.interfaces.append(xpt.Interface("IFoo", scriptable=True))
+        t2 = xpt.Typelib()
+        # add an unresolved interface
+        t2.interfaces.append(xpt.Interface("IBar", scriptable=True))
+        t3 = xpt.xpt_link([t1, t2])
+
+        self.assertEqual(2, len(t3.interfaces))
+        # Interfaces should wind up sorted
+        self.assertEqual("IBar", t3.interfaces[0].name)
+        self.assertEqual("IFoo", t3.interfaces[1].name)
+
+        # Add some IID values
+        t1 = xpt.Typelib()
+        # add an unresolved interface
+        t1.interfaces.append(xpt.Interface("IFoo", iid="11223344-5566-7788-9900-aabbccddeeff", scriptable=True))
+        t2 = xpt.Typelib()
+        # add an unresolved interface
+        t2.interfaces.append(xpt.Interface("IBar", iid="44332211-6655-8877-0099-aabbccddeeff", scriptable=True))
+        t3 = xpt.xpt_link([t1, t2])
+
+        self.assertEqual(2, len(t3.interfaces))
+        # Interfaces should wind up sorted
+        self.assertEqual("IFoo", t3.interfaces[0].name)
+        self.assertEqual("IBar", t3.interfaces[1].name)
+
+    def test_mergeConflict(self):
+        """
+        Test that merging two typelibs with conflicting interface definitions
+        raises an error.
+
+        """
+        # Same names, different IIDs
+        t1 = xpt.Typelib()
+        # add an unresolved interface
+        t1.interfaces.append(xpt.Interface("IFoo", iid="11223344-5566-7788-9900-aabbccddeeff"))
+        t2 = xpt.Typelib()
+        # add an unresolved interface, same name different IID
+        t2.interfaces.append(xpt.Interface("IFoo", iid="44332211-6655-8877-0099-aabbccddeeff"))
+        self.assertRaises(xpt.DataError, xpt.xpt_link, [t1, t2])
+
+        # Same IIDs, different names
+        t1 = xpt.Typelib()
+        # add an unresolved interface
+        t1.interfaces.append(xpt.Interface("IFoo", iid="11223344-5566-7788-9900-aabbccddeeff"))
+        t2 = xpt.Typelib()
+        # add an unresolved interface, same IID different name
+        t2.interfaces.append(xpt.Interface("IBar", iid="11223344-5566-7788-9900-aabbccddeeff"))
+        self.assertRaises(xpt.DataError, xpt.xpt_link, [t1, t2])
+
+    def test_mergeUnresolvedIID(self):
+        """
+        Test that merging a typelib with an unresolved definition of
+        an interface that's also unresolved in this typelib, but one
+        has a valid IID copies the IID value to the resulting typelib.
+
+        """
+        # Unresolved in both, but t1 has an IID value
+        t1 = xpt.Typelib()
+        # add an unresolved interface with a valid IID
+        t1.interfaces.append(xpt.Interface("IFoo", iid="11223344-5566-7788-9900-aabbccddeeff", scriptable=True))
+        t2 = xpt.Typelib()
+        # add an unresolved interface, no IID
+        t2.interfaces.append(xpt.Interface("IFoo"))
+        t3 = xpt.xpt_link([t1, t2])
+
+        self.assertEqual(1, len(t3.interfaces))
+        self.assertEqual("IFoo", t3.interfaces[0].name)
+        self.assertEqual("11223344-5566-7788-9900-aabbccddeeff", t3.interfaces[0].iid)
+        # Unresolved in both, but t2 has an IID value
+        t1 = xpt.Typelib()
+        # add an unresolved interface, no IID
+        t1.interfaces.append(xpt.Interface("IFoo"))
+        t2 = xpt.Typelib()
+        # add an unresolved interface with a valid IID
+        t2.interfaces.append(xpt.Interface("IFoo", iid="11223344-5566-7788-9900-aabbccddeeff", scriptable=True))
+        t3 = xpt.xpt_link([t1, t2])
+
+        self.assertEqual(1, len(t3.interfaces))
+        self.assertEqual("IFoo", t3.interfaces[0].name)
+        self.assertEqual("11223344-5566-7788-9900-aabbccddeeff", t3.interfaces[0].iid)
+
+    def test_mergeResolvedUnresolved(self):
+        """
+        Test that merging two typelibs, one of which contains an unresolved
+        reference to an interface, and the other of which contains a
+        resolved reference to the same interface results in keeping the
+        resolved reference.
+
+        """
+        # t1 has an unresolved interface, t2 has a resolved version
+        t1 = xpt.Typelib()
+        # add an unresolved interface
+        t1.interfaces.append(xpt.Interface("IFoo"))
+        t2 = xpt.Typelib()
+        # add a resolved interface
+        p = xpt.Param(xpt.SimpleType(xpt.Type.Tags.void))
+        m = xpt.Method("Bar", p)
+        t2.interfaces.append(xpt.Interface("IFoo", iid="11223344-5566-7788-9900-aabbccddeeff",
+                                           methods=[m], scriptable=True))
+        t3 = xpt.xpt_link([t1, t2])
+
+        self.assertEqual(1, len(t3.interfaces))
+        self.assertEqual("IFoo", t3.interfaces[0].name)
+        self.assertEqual("11223344-5566-7788-9900-aabbccddeeff", t3.interfaces[0].iid)
+        self.assert_(t3.interfaces[0].resolved)
+        self.assertEqual(1, len(t3.interfaces[0].methods))
+        self.assertEqual("Bar", t3.interfaces[0].methods[0].name)
+
+        # t1 has a resolved interface, t2 has an unresolved version
+        t1 = xpt.Typelib()
+        # add a resolved interface
+        p = xpt.Param(xpt.SimpleType(xpt.Type.Tags.void))
+        m = xpt.Method("Bar", p)
+        t1.interfaces.append(xpt.Interface("IFoo", iid="11223344-5566-7788-9900-aabbccddeeff",
+                                           methods=[m], scriptable=True))
+        t2 = xpt.Typelib()
+        # add an unresolved interface
+        t2.interfaces.append(xpt.Interface("IFoo"))
+        t3 = xpt.xpt_link([t1, t2])
+
+        self.assertEqual(1, len(t3.interfaces))
+        self.assertEqual("IFoo", t3.interfaces[0].name)
+        self.assertEqual("11223344-5566-7788-9900-aabbccddeeff", t3.interfaces[0].iid)
+        self.assert_(t3.interfaces[0].resolved)
+        self.assertEqual(1, len(t3.interfaces[0].methods))
+        self.assertEqual("Bar", t3.interfaces[0].methods[0].name)
+
+    def test_mergeReplaceParents(self):
+        """
+        Test that merging an interface results in other interfaces' parent
+        member being updated properly.
+
+        """
+        # t1 has an unresolved interface, t2 has a resolved version,
+        # but t1 also has another interface whose parent is the unresolved
+        # interface.
+        t1 = xpt.Typelib()
+        # add an unresolved interface
+        pi = xpt.Interface("IFoo")
+        t1.interfaces.append(pi)
+        # add a child of the unresolved interface
+        t1.interfaces.append(xpt.Interface("IChild", iid="11111111-1111-1111-1111-111111111111",
+                                           resolved=True, parent=pi, scriptable=True))
+        t2 = xpt.Typelib()
+        # add a resolved interface
+        p = xpt.Param(xpt.SimpleType(xpt.Type.Tags.void))
+        m = xpt.Method("Bar", p)
+        t2.interfaces.append(xpt.Interface("IFoo", iid="11223344-5566-7788-9900-aabbccddeeff",
+                                           methods=[m], scriptable=True))
+        t3 = xpt.xpt_link([t1, t2])
+
+        self.assertEqual(2, len(t3.interfaces))
+        self.assertEqual("IChild", t3.interfaces[0].name)
+        self.assertEqual("11111111-1111-1111-1111-111111111111", t3.interfaces[0].iid)
+        self.assertEqual("IFoo", t3.interfaces[1].name)
+        self.assertEqual("11223344-5566-7788-9900-aabbccddeeff", t3.interfaces[1].iid)
+        self.assert_(t3.interfaces[0].resolved)
+        # Ensure that IChild's parent has been updated
+        self.assertEqual(t3.interfaces[1], t3.interfaces[0].parent)
+        self.assert_(t3.interfaces[0].parent.resolved)
+
+        # t1 has a resolved interface, t2 has an unresolved version,
+        # but t2 also has another interface whose parent is the unresolved
+        # interface.
+        t1 = xpt.Typelib()
+        # add a resolved interface
+        p = xpt.Param(xpt.SimpleType(xpt.Type.Tags.void))
+        m = xpt.Method("Bar", p)
+        t1.interfaces.append(xpt.Interface("IFoo", iid="11223344-5566-7788-9900-aabbccddeeff",
+                                           methods=[m], scriptable=True))
+        t2 = xpt.Typelib()
+        # add an unresolved interface
+        pi = xpt.Interface("IFoo")
+        t2.interfaces.append(pi)
+        # add a child of the unresolved interface
+        t2.interfaces.append(xpt.Interface("IChild", iid="11111111-1111-1111-1111-111111111111",
+                                           resolved=True, parent=pi, scriptable=True))
+        t3 = xpt.xpt_link([t1, t2])
+
+        self.assertEqual(2, len(t3.interfaces))
+        self.assertEqual("IChild", t3.interfaces[0].name)
+        self.assertEqual("11111111-1111-1111-1111-111111111111", t3.interfaces[0].iid)
+        self.assertEqual("IFoo", t3.interfaces[1].name)
+        self.assertEqual("11223344-5566-7788-9900-aabbccddeeff", t3.interfaces[1].iid)
+        self.assert_(t3.interfaces[0].resolved)
+        # Ensure that IChild's parent has been updated
+        self.assertEqual(t3.interfaces[1], t3.interfaces[0].parent)
+        self.assert_(t3.interfaces[0].parent.resolved)
+
+    def test_mergeReplaceRetval(self):
+        """
+        Test that merging an interface correctly updates InterfaceType
+        return values on methods of other interfaces.
+
+        """
+        # t1 has an unresolved interface and an interface that uses the
+        # unresolved interface as a return value from a method. t2
+        # has a resolved version of the unresolved interface.
+        t1 = xpt.Typelib()
+        # add an unresolved interface
+        i = xpt.Interface("IFoo")
+        t1.interfaces.append(i)
+        # add an interface that uses the unresolved interface
+        # as a return value in a method.
+        p = xpt.Param(xpt.InterfaceType(i))
+        m = xpt.Method("ReturnIface", p)
+        t1.interfaces.append(xpt.Interface("IRetval", iid="11111111-1111-1111-1111-111111111111",
+                                           methods=[m], scriptable=True))
+        t2 = xpt.Typelib()
+        # add a resolved interface
+        p = xpt.Param(xpt.SimpleType(xpt.Type.Tags.void))
+        m = xpt.Method("Bar", p)
+        t2.interfaces.append(xpt.Interface("IFoo", iid="11223344-5566-7788-9900-aabbccddeeff",
+                                           methods=[m], scriptable=True))
+        t3 = xpt.xpt_link([t1, t2])
+
+        self.assertEqual(2, len(t3.interfaces))
+        self.assertEqual("IRetval", t3.interfaces[0].name)
+        self.assertEqual("11111111-1111-1111-1111-111111111111", t3.interfaces[0].iid)
+        self.assertEqual("IFoo", t3.interfaces[1].name)
+        self.assertEqual("11223344-5566-7788-9900-aabbccddeeff", t3.interfaces[1].iid)
+        self.assert_(t3.interfaces[1].resolved)
+        # Ensure that IRetval's method's return value type has been updated.
+        self.assertEqual(1, len(t3.interfaces[0].methods))
+        self.assert_(t3.interfaces[0].methods[0].result.type.iface.resolved)
+        self.assertEqual(t3.interfaces[1],
+                         t3.interfaces[0].methods[0].result.type.iface)
+
+        # t1 has a resolved interface. t2 has an unresolved version and
+        # an interface that uses the unresolved interface as a return value
+        # from a method.
+        t1 = xpt.Typelib()
+        # add a resolved interface
+        p = xpt.Param(xpt.SimpleType(xpt.Type.Tags.void))
+        m = xpt.Method("Bar", p)
+        t1.interfaces.append(xpt.Interface("IFoo", iid="11223344-5566-7788-9900-aabbccddeeff",
+                                           methods=[m], scriptable=True))
+        t2 = xpt.Typelib()
+        # add an unresolved interface
+        i = xpt.Interface("IFoo")
+        t2.interfaces.append(i)
+        # add an interface that uses the unresolved interface
+        # as a return value in a method.
+        p = xpt.Param(xpt.InterfaceType(i))
+        m = xpt.Method("ReturnIface", p)
+        t2.interfaces.append(xpt.Interface("IRetval", iid="11111111-1111-1111-1111-111111111111",
+                                           methods=[m], scriptable=True))
+        t3 = xpt.xpt_link([t1, t2])
+
+        self.assertEqual(2, len(t3.interfaces))
+        self.assertEqual("IRetval", t3.interfaces[0].name)
+        self.assertEqual("11111111-1111-1111-1111-111111111111", t3.interfaces[0].iid)
+        self.assertEqual("IFoo", t3.interfaces[1].name)
+        self.assertEqual("11223344-5566-7788-9900-aabbccddeeff", t3.interfaces[1].iid)
+        self.assert_(t3.interfaces[1].resolved)
+        # Ensure that IRetval's method's return value type has been updated.
+        self.assertEqual(1, len(t3.interfaces[0].methods))
+        self.assert_(t3.interfaces[0].methods[0].result.type.iface.resolved)
+        self.assertEqual(t3.interfaces[1],
+                         t3.interfaces[0].methods[0].result.type.iface)
+
+    def test_mergeReplaceParams(self):
+        """
+        Test that merging an interface correctly updates InterfaceType
+        params on methods of other interfaces.
+
+        """
+        # t1 has an unresolved interface and an interface that uses the
+        # unresolved interface as a param value in a method. t2
+        # has a resolved version of the unresolved interface.
+        t1 = xpt.Typelib()
+        # add an unresolved interface
+        i = xpt.Interface("IFoo")
+        t1.interfaces.append(i)
+        # add an interface that uses the unresolved interface
+        # as a param value in a method.
+        vp = xpt.Param(xpt.SimpleType(xpt.Type.Tags.void))
+        p = xpt.Param(xpt.InterfaceType(i))
+        m = xpt.Method("IfaceParam", vp, params=[p])
+        t1.interfaces.append(xpt.Interface("IParam", iid="11111111-1111-1111-1111-111111111111",
+                                           methods=[m], scriptable=True))
+        t2 = xpt.Typelib()
+        # add a resolved interface
+        m = xpt.Method("Bar", vp)
+        t2.interfaces.append(xpt.Interface("IFoo", iid="11223344-5566-7788-9900-aabbccddeeff",
+                                           methods=[m], scriptable=True))
+        t3 = xpt.xpt_link([t1, t2])
+
+        self.assertEqual(2, len(t3.interfaces))
+        self.assertEqual("IParam", t3.interfaces[0].name)
+        self.assertEqual("11111111-1111-1111-1111-111111111111", t3.interfaces[0].iid)
+        self.assertEqual("IFoo", t3.interfaces[1].name)
+        self.assertEqual("11223344-5566-7788-9900-aabbccddeeff", t3.interfaces[1].iid)
+        self.assert_(t3.interfaces[1].resolved)
+        # Ensure that IRetval's method's param type has been updated.
+        self.assertEqual(1, len(t3.interfaces[0].methods))
+        self.assert_(t3.interfaces[0].methods[0].params[0].type.iface.resolved)
+        self.assertEqual(t3.interfaces[1],
+                         t3.interfaces[0].methods[0].params[0].type.iface)
+
+        # t1 has a resolved interface. t2 has an unresolved version
+        # and an interface that uses the unresolved interface as a
+        # param value in a method.
+        t1 = xpt.Typelib()
+        # add a resolved interface
+        m = xpt.Method("Bar", vp)
+        t1.interfaces.append(xpt.Interface("IFoo", iid="11223344-5566-7788-9900-aabbccddeeff",
+                                           methods=[m], scriptable=True))
+        t2 = xpt.Typelib()
+        # add an unresolved interface
+        i = xpt.Interface("IFoo")
+        t2.interfaces.append(i)
+        # add an interface that uses the unresolved interface
+        # as a param value in a method.
+        vp = xpt.Param(xpt.SimpleType(xpt.Type.Tags.void))
+        p = xpt.Param(xpt.InterfaceType(i))
+        m = xpt.Method("IfaceParam", vp, params=[p])
+        t2.interfaces.append(xpt.Interface("IParam", iid="11111111-1111-1111-1111-111111111111",
+                                           methods=[m], scriptable=True))
+        t3 = xpt.xpt_link([t1, t2])
+
+        self.assertEqual(2, len(t3.interfaces))
+        self.assertEqual("IParam", t3.interfaces[0].name)
+        self.assertEqual("11111111-1111-1111-1111-111111111111", t3.interfaces[0].iid)
+        self.assertEqual("IFoo", t3.interfaces[1].name)
+        self.assertEqual("11223344-5566-7788-9900-aabbccddeeff", t3.interfaces[1].iid)
+        self.assert_(t3.interfaces[1].resolved)
+        # Ensure that IRetval's method's param type has been updated.
+        self.assertEqual(1, len(t3.interfaces[0].methods))
+        self.assert_(t3.interfaces[0].methods[0].params[0].type.iface.resolved)
+        self.assertEqual(t3.interfaces[1],
+                         t3.interfaces[0].methods[0].params[0].type.iface)
+
+    def test_mergeReplaceArrayTypeParams(self):
+        """
+        Test that merging an interface correctly updates ArrayType
+        params whose element_type is an InterfaceType on methods
+        of other interfaces.
+
+        """
+        # t1 has an unresolved interface and an interface that uses the
+        # unresolved interface as a type in an ArrayType in a parameter
+        # of a method. t2 has a resolved version of the unresolved interface.
+        t1 = xpt.Typelib()
+        # add an unresolved interface
+        i = xpt.Interface("IFoo")
+        t1.interfaces.append(i)
+        # add an interface that uses the unresolved interface
+        # as a type in an ArrayType in a param value in a method.
+        vp = xpt.Param(xpt.SimpleType(xpt.Type.Tags.void))
+        intp = xpt.Param(xpt.SimpleType(xpt.Type.Tags.int32))
+        p = xpt.Param(xpt.ArrayType(xpt.InterfaceType(i), 1, 2))
+        m = xpt.Method("ArrayIfaceParam", vp, params=[p, intp, intp])
+        t1.interfaces.append(xpt.Interface("IParam", iid="11111111-1111-1111-1111-111111111111",
+                                           methods=[m], scriptable=True))
+        t2 = xpt.Typelib()
+        # add a resolved interface
+        m = xpt.Method("Bar", vp)
+        t2.interfaces.append(xpt.Interface("IFoo", iid="11223344-5566-7788-9900-aabbccddeeff",
+                                           methods=[m], scriptable=True))
+        t3 = xpt.xpt_link([t1, t2])
+
+        self.assertEqual(2, len(t3.interfaces))
+        self.assertEqual("IParam", t3.interfaces[0].name)
+        self.assertEqual("11111111-1111-1111-1111-111111111111", t3.interfaces[0].iid)
+        self.assertEqual("IFoo", t3.interfaces[1].name)
+        self.assertEqual("11223344-5566-7788-9900-aabbccddeeff", t3.interfaces[1].iid)
+        self.assert_(t3.interfaces[1].resolved)
+        # Ensure that IRetval's method's param type has been updated.
+        self.assertEqual(1, len(t3.interfaces[0].methods))
+        self.assert_(t3.interfaces[0].methods[0].params[0].type.element_type.iface.resolved)
+        self.assertEqual(t3.interfaces[1],
+                         t3.interfaces[0].methods[0].params[0].type.element_type.iface)
+
+if __name__ == '__main__':
+    mozunit.main()
diff --git a/xpcom/typelib/xpt/tools/xpt.py b/xpcom/typelib/xpt/tools/xpt.py
new file mode 100755
index 000000000..67d40f7b2
--- /dev/null
+++ b/xpcom/typelib/xpt/tools/xpt.py
@@ -0,0 +1,1540 @@
+#!/usr/bin/env python
+# Copyright 2010,2011 Mozilla Foundation. All rights reserved.
+#
+# Redistribution and use in source and binary forms, with or without
+# modification, are permitted provided that the following conditions are
+# met:
+#
+#   1. Redistributions of source code must retain the above copyright
+#      notice, this list of conditions and the following disclaimer.
+#
+#   2. Redistributions in binary form must reproduce the above copyright
+#      notice, this list of conditions and the following disclaimer in
+#      the documentation and/or other materials provided with the
+#      distribution.
+#
+# THIS SOFTWARE IS PROVIDED BY THE MOZILLA FOUNDATION ``AS IS'' AND ANY
+# EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+# IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
+# PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE MOZILLA FOUNDATION OR
+# CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
+# EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
+# PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
+# PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY
+# OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+# (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+# OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+#
+# The views and conclusions contained in the software and documentation
+# are those of the authors and should not be interpreted as representing
+# official policies, either expressed or implied, of the Mozilla
+# Foundation.
+
+"""
+A module for working with XPCOM Type Libraries.
+
+The XPCOM Type Library File Format is described at:
+http://www.mozilla.org/scriptable/typelib_file.html . It is used
+to provide type information for calling methods on XPCOM objects
+from scripting languages such as JavaScript.
+
+This module provides a set of classes representing the parts of
+a typelib in a high-level manner, as well as methods for reading
+and writing them from files.
+
+The usable public interfaces are currently:
+Typelib.read(input_file) - read a typelib from a file on disk or file-like
+                           object, return a Typelib object.
+
+xpt_dump(filename)     - read a typelib from a file on disk, dump
+                         the contents to stdout in a human-readable
+                         format.
+
+Typelib()              - construct a new Typelib object
+Interface()            - construct a new Interface object
+Method()               - construct a new object representing a method
+                         defined on an Interface
+Constant()             - construct a new object representing a constant
+                         defined on an Interface
+Param()                - construct a new object representing a parameter
+                         to a method
+SimpleType()           - construct a new object representing a simple
+                         data type
+InterfaceType()        - construct a new object representing a type that
+                         is an IDL-defined interface
+
+"""
+
+from __future__ import with_statement
+import os
+import sys
+import struct
+import operator
+
+# header magic
+XPT_MAGIC = "XPCOM\nTypeLib\r\n\x1a"
+TYPELIB_VERSION = (1, 2)
+
+
+class FileFormatError(Exception):
+    pass
+
+
+class DataError(Exception):
+    pass
+
+
+# Magic for creating enums
+def M_add_class_attribs(attribs):
+    def foo(name, bases, dict_):
+        for v, k in attribs:
+            dict_[k] = v
+        return type(name, bases, dict_)
+    return foo
+
+
+def enum(*names):
+    class Foo(object):
+        __metaclass__ = M_add_class_attribs(enumerate(names))
+
+        def __setattr__(self, name, value):  # this makes it read-only
+            raise NotImplementedError
+    return Foo()
+
+
+# Descriptor types as described in the spec
+class Type(object):
+    """
+    Data type of a method parameter or return value. Do not instantiate
+    this class directly. Rather, use one of its subclasses.
+
+    """
+    _prefixdescriptor = struct.Struct(">B")
+    Tags = enum(
+        # The first 18 entries are SimpleTypeDescriptor
+        'int8',
+        'int16',
+        'int32',
+        'int64',
+        'uint8',
+        'uint16',
+        'uint32',
+        'uint64',
+        'float',
+        'double',
+        'boolean',
+        'char',
+        'wchar_t',
+        'void',
+        # the following four values are only valid as pointers
+        'nsIID',
+        'DOMString',
+        'char_ptr',
+        'wchar_t_ptr',
+        # InterfaceTypeDescriptor
+        'Interface',
+        # InterfaceIsTypeDescriptor
+        'InterfaceIs',
+        # ArrayTypeDescriptor
+        'Array',
+        # StringWithSizeTypeDescriptor
+        'StringWithSize',
+        # WideStringWithSizeTypeDescriptor
+        'WideStringWithSize',
+        # XXX: These are also SimpleTypes (but not in the spec)
+        # http://hg.mozilla.org/mozilla-central/annotate/0e0e2516f04e/xpcom/typelib/xpt/tools/xpt_dump.c#l69
+        'UTF8String',
+        'CString',
+        'AString',
+        'jsval',
+        )
+
+    def __init__(self, pointer=False, reference=False):
+        self.pointer = pointer
+        self.reference = reference
+        if reference and not pointer:
+            raise Exception("If reference is True pointer must be True too")
+
+    def __cmp__(self, other):
+        return (
+            # First make sure we have two Types of the same type (no pun intended!)
+            cmp(type(self), type(other)) or
+            cmp(self.pointer, other.pointer) or
+            cmp(self.reference, other.reference)
+        )
+
+    @staticmethod
+    def decodeflags(byte):
+        """
+        Given |byte|, an unsigned uint8 containing flag bits,
+        decode the flag bits as described in
+        http://www.mozilla.org/scriptable/typelib_file.html#TypeDescriptor
+        and return a dict of flagname: (True|False) suitable
+        for passing to Type.__init__ as **kwargs.
+
+        """
+        return {'pointer': bool(byte & 0x80),
+                'reference': bool(byte & 0x20),
+                }
+
+    def encodeflags(self):
+        """
+        Encode the flag bits of this Type object. Returns a byte.
+
+        """
+        flags = 0
+        if self.pointer:
+            flags |= 0x80
+        if self.reference:
+            flags |= 0x20
+        return flags
+
+    @staticmethod
+    def read(typelib, map, data_pool, offset):
+        """
+        Read a TypeDescriptor at |offset| from the mmaped file |map| with
+        data pool offset |data_pool|. Returns (Type, next offset),
+        where |next offset| is an offset suitable for reading the data
+        following this TypeDescriptor.
+
+        """
+        start = data_pool + offset - 1
+        (data,) = Type._prefixdescriptor.unpack_from(map, start)
+        # first three bits are the flags
+        flags = data & 0xE0
+        flags = Type.decodeflags(flags)
+        # last five bits is the tag
+        tag = data & 0x1F
+        offset += Type._prefixdescriptor.size
+        t = None
+        if tag <= Type.Tags.wchar_t_ptr or tag >= Type.Tags.UTF8String:
+            t = SimpleType.get(data, tag, flags)
+        elif tag == Type.Tags.Interface:
+            t, offset = InterfaceType.read(typelib, map, data_pool, offset, flags)
+        elif tag == Type.Tags.InterfaceIs:
+            t, offset = InterfaceIsType.read(typelib, map, data_pool, offset, flags)
+        elif tag == Type.Tags.Array:
+            t, offset = ArrayType.read(typelib, map, data_pool, offset, flags)
+        elif tag == Type.Tags.StringWithSize:
+            t, offset = StringWithSizeType.read(typelib, map, data_pool, offset, flags)
+        elif tag == Type.Tags.WideStringWithSize:
+            t, offset = WideStringWithSizeType.read(typelib, map, data_pool, offset, flags)
+        return t, offset
+
+    def write(self, typelib, file):
+        """
+        Write a TypeDescriptor to |file|, which is assumed
+        to be seeked to the proper position. For types other than
+        SimpleType, this is not sufficient for writing the TypeDescriptor,
+        and the subclass method must be called.
+
+        """
+        file.write(Type._prefixdescriptor.pack(self.encodeflags() | self.tag))
+
+
+class SimpleType(Type):
+    """
+    A simple data type. (SimpleTypeDescriptor from the typelib specification.)
+
+    """
+    _cache = {}
+
+    def __init__(self, tag, **kwargs):
+        Type.__init__(self, **kwargs)
+        self.tag = tag
+
+    def __cmp__(self, other):
+        return (
+            Type.__cmp__(self, other) or
+            cmp(self.tag, other.tag)
+        )
+
+    @staticmethod
+    def get(data, tag, flags):
+        """
+        Get a SimpleType object representing |data| (a TypeDescriptorPrefix).
+        May return an already-created object. If no cached object is found,
+        construct one with |tag| and |flags|.
+
+        """
+        if data not in SimpleType._cache:
+            SimpleType._cache[data] = SimpleType(tag, **flags)
+        return SimpleType._cache[data]
+
+    def __str__(self):
+        s = "unknown"
+        if self.tag == Type.Tags.char_ptr and self.pointer:
+            return "string"
+        if self.tag == Type.Tags.wchar_t_ptr and self.pointer:
+            return "wstring"
+        for t in dir(Type.Tags):
+            if self.tag == getattr(Type.Tags, t):
+                s = t
+                break
+
+        if self.pointer:
+            if self.reference:
+                s += " &"
+            else:
+                s += " *"
+        return s
+
+
+class InterfaceType(Type):
+    """
+    A type representing a pointer to an IDL-defined interface.
+    (InterfaceTypeDescriptor from the typelib specification.)
+
+    """
+    _descriptor = struct.Struct(">H")
+
+    def __init__(self, iface, pointer=True, **kwargs):
+        if not pointer:
+            raise DataError("InterfaceType is not valid with pointer=False")
+        Type.__init__(self, pointer=pointer, **kwargs)
+        self.iface = iface
+        self.tag = Type.Tags.Interface
+
+    def __cmp__(self, other):
+        return (
+            Type.__cmp__(self, other) or
+            # When comparing interface types, only look at the name.
+            cmp(self.iface.name, other.iface.name) or
+            cmp(self.tag, other.tag)
+        )
+
+    @staticmethod
+    def read(typelib, map, data_pool, offset, flags):
+        """
+        Read an InterfaceTypeDescriptor at |offset| from the mmaped
+        file |map| with data pool offset |data_pool|.
+        Returns (InterfaceType, next offset),
+        where |next offset| is an offset suitable for reading the data
+        following this InterfaceTypeDescriptor.
+
+        """
+        if not flags['pointer']:
+            return None, offset
+        start = data_pool + offset - 1
+        (iface_index,) = InterfaceType._descriptor.unpack_from(map, start)
+        offset += InterfaceType._descriptor.size
+        iface = None
+        # interface indices are 1-based
+        if iface_index > 0 and iface_index <= len(typelib.interfaces):
+            iface = typelib.interfaces[iface_index - 1]
+        return InterfaceType(iface, **flags), offset
+
+    def write(self, typelib, file):
+        """
+        Write an InterfaceTypeDescriptor to |file|, which is assumed
+        to be seeked to the proper position.
+
+        """
+        Type.write(self, typelib, file)
+        # write out the interface index (1-based)
+        file.write(InterfaceType._descriptor.pack(typelib.interfaces.index(self.iface) + 1))
+
+    def __str__(self):
+        if self.iface:
+            return self.iface.name
+        return "unknown interface"
+
+
+class InterfaceIsType(Type):
+    """
+    A type representing an interface described by one of the other
+    arguments to the method. (InterfaceIsTypeDescriptor from the
+    typelib specification.)
+
+    """
+    _descriptor = struct.Struct(">B")
+    _cache = {}
+
+    def __init__(self, param_index, pointer=True, **kwargs):
+        if not pointer:
+            raise DataError("InterfaceIsType is not valid with pointer=False")
+        Type.__init__(self, pointer=pointer, **kwargs)
+        self.param_index = param_index
+        self.tag = Type.Tags.InterfaceIs
+
+    def __cmp__(self, other):
+        return (
+            Type.__cmp__(self, other) or
+            cmp(self.param_index, other.param_index) or
+            cmp(self.tag, other.tag)
+        )
+
+    @staticmethod
+    def read(typelib, map, data_pool, offset, flags):
+        """
+        Read an InterfaceIsTypeDescriptor at |offset| from the mmaped
+        file |map| with data pool offset |data_pool|.
+        Returns (InterfaceIsType, next offset),
+        where |next offset| is an offset suitable for reading the data
+        following this InterfaceIsTypeDescriptor.
+        May return a cached value.
+
+        """
+        if not flags['pointer']:
+            return None, offset
+        start = data_pool + offset - 1
+        (param_index,) = InterfaceIsType._descriptor.unpack_from(map, start)
+        offset += InterfaceIsType._descriptor.size
+        if param_index not in InterfaceIsType._cache:
+            InterfaceIsType._cache[param_index] = InterfaceIsType(param_index, **flags)
+        return InterfaceIsType._cache[param_index], offset
+
+    def write(self, typelib, file):
+        """
+        Write an InterfaceIsTypeDescriptor to |file|, which is assumed
+        to be seeked to the proper position.
+
+        """
+        Type.write(self, typelib, file)
+        file.write(InterfaceIsType._descriptor.pack(self.param_index))
+
+    def __str__(self):
+        return "InterfaceIs *"
+
+
+class ArrayType(Type):
+    """
+    A type representing an Array of elements of another type, whose
+    size and length are passed as separate parameters to a method.
+    (ArrayTypeDescriptor from the typelib specification.)
+
+    """
+    _descriptor = struct.Struct(">BB")
+
+    def __init__(self, element_type, size_is_arg_num, length_is_arg_num,
+                 pointer=True, **kwargs):
+        if not pointer:
+            raise DataError("ArrayType is not valid with pointer=False")
+        Type.__init__(self, pointer=pointer, **kwargs)
+        self.element_type = element_type
+        self.size_is_arg_num = size_is_arg_num
+        self.length_is_arg_num = length_is_arg_num
+        self.tag = Type.Tags.Array
+
+    def __cmp__(self, other):
+        return (
+            Type.__cmp__(self, other) or
+            cmp(self.element_type, other.element_type) or
+            cmp(self.size_is_arg_num, other.size_is_arg_num) or
+            cmp(self.length_is_arg_num, other.length_is_arg_num) or
+            cmp(self.tag, other.tag)
+        )
+
+    @staticmethod
+    def read(typelib, map, data_pool, offset, flags):
+        """
+        Read an ArrayTypeDescriptor at |offset| from the mmaped
+        file |map| with data pool offset |data_pool|.
+        Returns (ArrayType, next offset),
+        where |next offset| is an offset suitable for reading the data
+        following this ArrayTypeDescriptor.
+        """
+        if not flags['pointer']:
+            return None, offset
+        start = data_pool + offset - 1
+        (size_is_arg_num, length_is_arg_num) = ArrayType._descriptor.unpack_from(map, start)
+        offset += ArrayType._descriptor.size
+        t, offset = Type.read(typelib, map, data_pool, offset)
+        return ArrayType(t, size_is_arg_num, length_is_arg_num, **flags), offset
+
+    def write(self, typelib, file):
+        """
+        Write an ArrayTypeDescriptor to |file|, which is assumed
+        to be seeked to the proper position.
+
+        """
+        Type.write(self, typelib, file)
+        file.write(ArrayType._descriptor.pack(self.size_is_arg_num,
+                                              self.length_is_arg_num))
+        self.element_type.write(typelib, file)
+
+    def __str__(self):
+        return "%s []" % str(self.element_type)
+
+
+class StringWithSizeType(Type):
+    """
+    A type representing a UTF-8 encoded string whose size and length
+    are passed as separate arguments to a method. (StringWithSizeTypeDescriptor
+    from the typelib specification.)
+
+    """
+    _descriptor = struct.Struct(">BB")
+
+    def __init__(self, size_is_arg_num, length_is_arg_num,
+                 pointer=True, **kwargs):
+        if not pointer:
+            raise DataError("StringWithSizeType is not valid with pointer=False")
+        Type.__init__(self, pointer=pointer, **kwargs)
+        self.size_is_arg_num = size_is_arg_num
+        self.length_is_arg_num = length_is_arg_num
+        self.tag = Type.Tags.StringWithSize
+
+    def __cmp__(self, other):
+        return (
+            Type.__cmp__(self, other) or
+            cmp(self.size_is_arg_num, other.size_is_arg_num) or
+            cmp(self.length_is_arg_num, other.length_is_arg_num) or
+            cmp(self.tag, other.tag)
+        )
+
+    @staticmethod
+    def read(typelib, map, data_pool, offset, flags):
+        """
+        Read an StringWithSizeTypeDescriptor at |offset| from the mmaped
+        file |map| with data pool offset |data_pool|.
+        Returns (StringWithSizeType, next offset),
+        where |next offset| is an offset suitable for reading the data
+        following this StringWithSizeTypeDescriptor.
+        """
+        if not flags['pointer']:
+            return None, offset
+        start = data_pool + offset - 1
+        (size_is_arg_num, length_is_arg_num) = StringWithSizeType._descriptor.unpack_from(map, start)
+        offset += StringWithSizeType._descriptor.size
+        return StringWithSizeType(size_is_arg_num, length_is_arg_num, **flags), offset
+
+    def write(self, typelib, file):
+        """
+        Write a StringWithSizeTypeDescriptor to |file|, which is assumed
+        to be seeked to the proper position.
+
+        """
+        Type.write(self, typelib, file)
+        file.write(StringWithSizeType._descriptor.pack(self.size_is_arg_num,
+                                                       self.length_is_arg_num))
+
+    def __str__(self):
+        return "string_s"
+
+
+class WideStringWithSizeType(Type):
+    """
+    A type representing a UTF-16 encoded string whose size and length
+    are passed as separate arguments to a method.
+    (WideStringWithSizeTypeDescriptor from the typelib specification.)
+
+    """
+    _descriptor = struct.Struct(">BB")
+
+    def __init__(self, size_is_arg_num, length_is_arg_num,
+                 pointer=True, **kwargs):
+        if not pointer:
+            raise DataError("WideStringWithSizeType is not valid with pointer=False")
+        Type.__init__(self, pointer=pointer, **kwargs)
+        self.size_is_arg_num = size_is_arg_num
+        self.length_is_arg_num = length_is_arg_num
+        self.tag = Type.Tags.WideStringWithSize
+
+    def __cmp__(self, other):
+        return (
+            Type.__cmp__(self, other) or
+            cmp(self.size_is_arg_num, other.size_is_arg_num) or
+            cmp(self.length_is_arg_num, other.length_is_arg_num) or
+            cmp(self.tag, other.tag)
+        )
+
+    @staticmethod
+    def read(typelib, map, data_pool, offset, flags):
+        """
+        Read an WideStringWithSizeTypeDescriptor at |offset| from the mmaped
+        file |map| with data pool offset |data_pool|.
+        Returns (WideStringWithSizeType, next offset),
+        where |next offset| is an offset suitable for reading the data
+        following this WideStringWithSizeTypeDescriptor.
+        """
+        if not flags['pointer']:
+            return None, offset
+        start = data_pool + offset - 1
+        (size_is_arg_num, length_is_arg_num) = WideStringWithSizeType._descriptor.unpack_from(map, start)
+        offset += WideStringWithSizeType._descriptor.size
+        return WideStringWithSizeType(size_is_arg_num, length_is_arg_num, **flags), offset
+
+    def write(self, typelib, file):
+        """
+        Write a WideStringWithSizeTypeDescriptor to |file|, which is assumed
+        to be seeked to the proper position.
+
+        """
+        Type.write(self, typelib, file)
+        file.write(WideStringWithSizeType._descriptor.pack(self.size_is_arg_num,
+                                                           self.length_is_arg_num))
+
+    def __str__(self):
+        return "wstring_s"
+
+
+class Param(object):
+    """
+    A parameter to a method, or the return value of a method.
+    (ParamDescriptor from the typelib specification.)
+
+    """
+    _descriptorstart = struct.Struct(">B")
+
+    def __init__(self, type, in_=True, out=False, retval=False,
+                 shared=False, dipper=False, optional=False):
+        """
+        Construct a Param object with the specified |type| and
+        flags. Params default to "in".
+
+        """
+
+        self.type = type
+        self.in_ = in_
+        self.out = out
+        self.retval = retval
+        self.shared = shared
+        self.dipper = dipper
+        self.optional = optional
+
+    def __cmp__(self, other):
+        return (
+            cmp(self.type, other.type) or
+            cmp(self.in_, other.in_) or
+            cmp(self.out, other.out) or
+            cmp(self.retval, other.retval) or
+            cmp(self.shared, other.shared) or
+            cmp(self.dipper, other.dipper) or
+            cmp(self.optional, other.optional)
+        )
+
+    @staticmethod
+    def decodeflags(byte):
+        """
+        Given |byte|, an unsigned uint8 containing flag bits,
+        decode the flag bits as described in
+        http://www.mozilla.org/scriptable/typelib_file.html#ParamDescriptor
+        and return a dict of flagname: (True|False) suitable
+        for passing to Param.__init__ as **kwargs
+        """
+        return {'in_': bool(byte & 0x80),
+                'out': bool(byte & 0x40),
+                'retval': bool(byte & 0x20),
+                'shared': bool(byte & 0x10),
+                'dipper': bool(byte & 0x08),
+                # XXX: Not in the spec, see:
+                # http://hg.mozilla.org/mozilla-central/annotate/0e0e2516f04e/xpcom/typelib/xpt/public/xpt_struct.h#l456
+                'optional': bool(byte & 0x04),
+                }
+
+    def encodeflags(self):
+        """
+        Encode the flags of this Param. Return a byte suitable for
+        writing to a typelib file.
+
+        """
+        flags = 0
+        if self.in_:
+            flags |= 0x80
+        if self.out:
+            flags |= 0x40
+        if self.retval:
+            flags |= 0x20
+        if self.shared:
+            flags |= 0x10
+        if self.dipper:
+            flags |= 0x08
+        if self.optional:
+            flags |= 0x04
+        return flags
+
+    @staticmethod
+    def read(typelib, map, data_pool, offset):
+        """
+        Read a ParamDescriptor at |offset| from the mmaped file |map| with
+        data pool offset |data_pool|. Returns (Param, next offset),
+        where |next offset| is an offset suitable for reading the data
+        following this ParamDescriptor.
+        """
+        start = data_pool + offset - 1
+        (flags,) = Param._descriptorstart.unpack_from(map, start)
+        # only the first five bits are flags
+        flags &= 0xFC
+        flags = Param.decodeflags(flags)
+        offset += Param._descriptorstart.size
+        t, offset = Type.read(typelib, map, data_pool, offset)
+        p = Param(t, **flags)
+        return p, offset
+
+    def write(self, typelib, file):
+        """
+        Write a ParamDescriptor to |file|, which is assumed to be seeked
+        to the correct position.
+
+        """
+        file.write(Param._descriptorstart.pack(self.encodeflags()))
+        self.type.write(typelib, file)
+
+    def prefix(self):
+        """
+        Return a human-readable string representing the flags set
+        on this Param.
+
+        """
+        s = ""
+        if self.out:
+            if self.in_:
+                s = "inout "
+            else:
+                s = "out "
+        else:
+            s = "in "
+        if self.dipper:
+            s += "dipper "
+        if self.retval:
+            s += "retval "
+        if self.shared:
+            s += "shared "
+        if self.optional:
+            s += "optional "
+        return s
+
+    def __str__(self):
+        return self.prefix() + str(self.type)
+
+
+class Method(object):
+    """
+    A method of an interface, defining its associated parameters
+    and return value.
+    (MethodDescriptor from the typelib specification.)
+
+    """
+    _descriptorstart = struct.Struct(">BIB")
+
+    def __init__(self, name, result,
+                 params=[], getter=False, setter=False, notxpcom=False,
+                 constructor=False, hidden=False, optargc=False,
+                 implicit_jscontext=False):
+        self.name = name
+        self._name_offset = 0
+        self.getter = getter
+        self.setter = setter
+        self.notxpcom = notxpcom
+        self.constructor = constructor
+        self.hidden = hidden
+        self.optargc = optargc
+        self.implicit_jscontext = implicit_jscontext
+        self.params = list(params)
+        if result and not isinstance(result, Param):
+            raise Exception("result must be a Param!")
+        self.result = result
+
+    def __cmp__(self, other):
+        return (
+            cmp(self.name, other.name) or
+            cmp(self.getter, other.getter) or
+            cmp(self.setter, other.setter) or
+            cmp(self.notxpcom, other.notxpcom) or
+            cmp(self.constructor, other.constructor) or
+            cmp(self.hidden, other.hidden) or
+            cmp(self.optargc, other.optargc) or
+            cmp(self.implicit_jscontext, other.implicit_jscontext) or
+            cmp(self.params, other.params) or
+            cmp(self.result, other.result)
+        )
+
+    def read_params(self, typelib, map, data_pool, offset, num_args):
+        """
+        Read |num_args| ParamDescriptors representing this Method's arguments
+        from the mmaped file |map| with data pool at the offset |data_pool|,
+        starting at |offset| into self.params. Returns the offset
+        suitable for reading the data following the ParamDescriptor array.
+
+        """
+        for i in range(num_args):
+            p, offset = Param.read(typelib, map, data_pool, offset)
+            self.params.append(p)
+        return offset
+
+    def read_result(self, typelib, map, data_pool, offset):
+        """
+        Read a ParamDescriptor representing this Method's return type
+        from the mmaped file |map| with data pool at the offset |data_pool|,
+        starting at |offset| into self.result. Returns the offset
+        suitable for reading the data following the ParamDescriptor.
+
+        """
+        self.result, offset = Param.read(typelib, map, data_pool, offset)
+        return offset
+
+    @staticmethod
+    def decodeflags(byte):
+        """
+        Given |byte|, an unsigned uint8 containing flag bits,
+        decode the flag bits as described in
+        http://www.mozilla.org/scriptable/typelib_file.html#MethodDescriptor
+        and return a dict of flagname: (True|False) suitable
+        for passing to Method.__init__ as **kwargs
+
+        """
+        return {'getter': bool(byte & 0x80),
+                'setter': bool(byte & 0x40),
+                'notxpcom': bool(byte & 0x20),
+                'constructor': bool(byte & 0x10),
+                'hidden': bool(byte & 0x08),
+                # Not in the spec, see
+                # http://hg.mozilla.org/mozilla-central/annotate/0e0e2516f04e/xpcom/typelib/xpt/public/xpt_struct.h#l489
+                'optargc': bool(byte & 0x04),
+                'implicit_jscontext': bool(byte & 0x02),
+                }
+
+    def encodeflags(self):
+        """
+        Encode the flags of this Method object, return a byte suitable
+        for writing to a typelib file.
+
+        """
+        flags = 0
+        if self.getter:
+            flags |= 0x80
+        if self.setter:
+            flags |= 0x40
+        if self.notxpcom:
+            flags |= 0x20
+        if self.constructor:
+            flags |= 0x10
+        if self.hidden:
+            flags |= 0x08
+        if self.optargc:
+            flags |= 0x04
+        if self.implicit_jscontext:
+            flags |= 0x02
+        return flags
+
+    @staticmethod
+    def read(typelib, map, data_pool, offset):
+        """
+        Read a MethodDescriptor at |offset| from the mmaped file |map| with
+        data pool offset |data_pool|. Returns (Method, next offset),
+        where |next offset| is an offset suitable for reading the data
+        following this MethodDescriptor.
+
+        """
+        start = data_pool + offset - 1
+        flags, name_offset, num_args = Method._descriptorstart.unpack_from(map, start)
+        # only the first seven bits are flags
+        flags &= 0xFE
+        flags = Method.decodeflags(flags)
+        name = Typelib.read_string(map, data_pool, name_offset)
+        m = Method(name, None, **flags)
+        offset += Method._descriptorstart.size
+        offset = m.read_params(typelib, map, data_pool, offset, num_args)
+        offset = m.read_result(typelib, map, data_pool, offset)
+        return m, offset
+
+    def write(self, typelib, file):
+        """
+        Write a MethodDescriptor to |file|, which is assumed to be
+        seeked to the right position.
+
+        """
+        file.write(Method._descriptorstart.pack(self.encodeflags(),
+                                                self._name_offset,
+                                                len(self.params)))
+        for p in self.params:
+            p.write(typelib, file)
+        self.result.write(typelib, file)
+
+    def write_name(self, file, data_pool_offset):
+        """
+        Write this method's name to |file|.
+        Assumes that |file| is currently seeked to an unused portion
+        of the data pool.
+
+        """
+        if self.name:
+            self._name_offset = file.tell() - data_pool_offset + 1
+            file.write(self.name + "\x00")
+        else:
+            self._name_offset = 0
+
+
+class Constant(object):
+    """
+    A constant value of a specific type defined on an interface.
+    (ConstantDesciptor from the typelib specification.)
+
+    """
+    _descriptorstart = struct.Struct(">I")
+    # Actual value is restricted to this set of types
+    # XXX: the spec lies, the source allows a bunch more
+    # http://hg.mozilla.org/mozilla-central/annotate/9c85f9aaec8c/xpcom/typelib/xpt/src/xpt_struct.c#l689
+    typemap = {Type.Tags.int16: '>h',
+               Type.Tags.uint16: '>H',
+               Type.Tags.int32: '>i',
+               Type.Tags.uint32: '>I'}
+
+    def __init__(self, name, type, value):
+        self.name = name
+        self._name_offset = 0
+        self.type = type
+        self.value = value
+
+    def __cmp__(self, other):
+        return (
+            cmp(self.name, other.name) or
+            cmp(self.type, other.type) or
+            cmp(self.value, other.value)
+        )
+
+    @staticmethod
+    def read(typelib, map, data_pool, offset):
+        """
+        Read a ConstDescriptor at |offset| from the mmaped file |map| with
+        data pool offset |data_pool|. Returns (Constant, next offset),
+        where |next offset| is an offset suitable for reading the data
+        following this ConstDescriptor.
+
+        """
+        start = data_pool + offset - 1
+        (name_offset,) = Constant._descriptorstart.unpack_from(map, start)
+        name = Typelib.read_string(map, data_pool, name_offset)
+        offset += Constant._descriptorstart.size
+        # Read TypeDescriptor
+        t, offset = Type.read(typelib, map, data_pool, offset)
+        c = None
+        if isinstance(t, SimpleType) and t.tag in Constant.typemap:
+            tt = Constant.typemap[t.tag]
+            start = data_pool + offset - 1
+            (val,) = struct.unpack_from(tt, map, start)
+            offset += struct.calcsize(tt)
+            c = Constant(name, t, val)
+        return c, offset
+
+    def write(self, typelib, file):
+        """
+        Write a ConstDescriptor to |file|, which is assumed
+        to be seeked to the proper position.
+
+        """
+        file.write(Constant._descriptorstart.pack(self._name_offset))
+        self.type.write(typelib, file)
+        tt = Constant.typemap[self.type.tag]
+        file.write(struct.pack(tt, self.value))
+
+    def write_name(self, file, data_pool_offset):
+        """
+        Write this constants's name to |file|.
+        Assumes that |file| is currently seeked to an unused portion
+        of the data pool.
+
+        """
+        if self.name:
+            self._name_offset = file.tell() - data_pool_offset + 1
+            file.write(self.name + "\x00")
+        else:
+            self._name_offset = 0
+
+    def __repr__(self):
+        return "Constant(%s, %s, %d)" % (self.name, str(self.type), self.value)
+
+
+class Interface(object):
+    """
+    An Interface represents an object, with its associated methods
+    and constant values.
+    (InterfaceDescriptor from the typelib specification.)
+
+    """
+    _direntry = struct.Struct(">16sIII")
+    _descriptorstart = struct.Struct(">HH")
+
+    UNRESOLVED_IID = "00000000-0000-0000-0000-000000000000"
+
+    def __init__(self, name, iid=UNRESOLVED_IID, namespace="",
+                 resolved=False, parent=None, methods=[], constants=[],
+                 scriptable=False, function=False, builtinclass=False,
+                 main_process_scriptable_only=False):
+        self.resolved = resolved
+        # TODO: should validate IIDs!
+        self.iid = iid
+        self.name = name
+        self.namespace = namespace
+        # if unresolved, all the members following this are unusable
+        self.parent = parent
+        self.methods = list(methods)
+        self.constants = list(constants)
+        self.scriptable = scriptable
+        self.function = function
+        self.builtinclass = builtinclass
+        self.main_process_scriptable_only = main_process_scriptable_only
+        # For sanity, if someone constructs an Interface and passes
+        # in methods or constants, then it's resolved.
+        if self.methods or self.constants:
+            # make sure it has a valid IID
+            if self.iid == Interface.UNRESOLVED_IID:
+                raise DataError("Cannot instantiate Interface %s containing methods or constants with an unresolved IID" % self.name)
+            self.resolved = True
+        # These are only used for writing out the interface
+        self._descriptor_offset = 0
+        self._name_offset = 0
+        self._namespace_offset = 0
+        self.xpt_filename = None
+
+    def __repr__(self):
+        return "Interface('%s', '%s', '%s', methods=%s)" % (self.name, self.iid, self.namespace, self.methods)
+
+    def __str__(self):
+        return "Interface(name='%s', iid='%s')" % (self.name, self.iid)
+
+    def __hash__(self):
+        return hash((self.name, self.iid))
+
+    def __cmp__(self, other):
+        c = cmp(self.iid, other.iid)
+        if c != 0:
+            return c
+        c = cmp(self.name, other.name)
+        if c != 0:
+            return c
+        c = cmp(self.namespace, other.namespace)
+        if c != 0:
+            return c
+        # names and IIDs are the same, check resolved
+        if self.resolved != other.resolved:
+            if self.resolved:
+                return -1
+            else:
+                return 1
+        else:
+            if not self.resolved:
+                # both unresolved, but names and IIDs are the same, so equal
+                return 0
+        # When comparing parents, only look at the name.
+        if (self.parent is None) != (other.parent is None):
+            if self.parent is None:
+                return -1
+            else:
+                return 1
+        elif self.parent is not None:
+            c = cmp(self.parent.name, other.parent.name)
+            if c != 0:
+                return c
+        return (
+            cmp(self.methods, other.methods) or
+            cmp(self.constants, other.constants) or
+            cmp(self.scriptable, other.scriptable) or
+            cmp(self.function, other.function) or
+            cmp(self.builtinclass, other.builtinclass) or
+            cmp(self.main_process_scriptable_only, other.main_process_scriptable_only)
+        )
+
+    def read_descriptor(self, typelib, map, data_pool):
+        offset = self._descriptor_offset
+        if offset == 0:
+            return
+        start = data_pool + offset - 1
+        parent, num_methods = Interface._descriptorstart.unpack_from(map, start)
+        if parent > 0 and parent <= len(typelib.interfaces):
+            self.parent = typelib.interfaces[parent - 1]
+        # Read methods
+        offset += Interface._descriptorstart.size
+        for i in range(num_methods):
+            m, offset = Method.read(typelib, map, data_pool, offset)
+            self.methods.append(m)
+        # Read constants
+        start = data_pool + offset - 1
+        (num_constants, ) = struct.unpack_from(">H", map, start)
+        offset = offset + struct.calcsize(">H")
+        for i in range(num_constants):
+            c, offset = Constant.read(typelib, map, data_pool, offset)
+            self.constants.append(c)
+        # Read flags
+        start = data_pool + offset - 1
+        (flags, ) = struct.unpack_from(">B", map, start)
+        offset = offset + struct.calcsize(">B")
+        # only the first two bits are flags
+        flags &= 0xf0
+        if flags & 0x80:
+            self.scriptable = True
+        if flags & 0x40:
+            self.function = True
+        if flags & 0x20:
+            self.builtinclass = True
+        if flags & 0x10:
+            self.main_process_scriptable_only = True
+        self.resolved = True
+
+    def write_directory_entry(self, file):
+        """
+        Write an InterfaceDirectoryEntry for this interface
+        to |file|, which is assumed to be seeked to the correct offset.
+
+        """
+        file.write(Interface._direntry.pack(Typelib.string_to_iid(self.iid),
+                                            self._name_offset,
+                                            self._namespace_offset,
+                                            self._descriptor_offset))
+
+    def write(self, typelib, file, data_pool_offset):
+        """
+        Write an InterfaceDescriptor to |file|, which is assumed
+        to be seeked to the proper position. If this interface
+        is not resolved, do not write any data.
+
+        """
+        if not self.resolved:
+            self._descriptor_offset = 0
+            return
+        self._descriptor_offset = file.tell() - data_pool_offset + 1
+        parent_idx = 0
+        if self.parent:
+            parent_idx = typelib.interfaces.index(self.parent) + 1
+        file.write(Interface._descriptorstart.pack(parent_idx, len(self.methods)))
+        for m in self.methods:
+            m.write(typelib, file)
+        file.write(struct.pack(">H", len(self.constants)))
+        for c in self.constants:
+            c.write(typelib, file)
+        flags = 0
+        if self.scriptable:
+            flags |= 0x80
+        if self.function:
+            flags |= 0x40
+        if self.builtinclass:
+            flags |= 0x20
+        if self.main_process_scriptable_only:
+            flags |= 0x10
+        file.write(struct.pack(">B", flags))
+
+    def write_names(self, file, data_pool_offset):
+        """
+        Write this interface's name and namespace to |file|,
+        as well as the names of all of its methods and constants.
+        Assumes that |file| is currently seeked to an unused portion
+        of the data pool.
+
+        """
+        if self.name:
+            self._name_offset = file.tell() - data_pool_offset + 1
+            file.write(self.name + "\x00")
+        else:
+            self._name_offset = 0
+        if self.namespace:
+            self._namespace_offset = file.tell() - data_pool_offset + 1
+            file.write(self.namespace + "\x00")
+        else:
+            self._namespace_offset = 0
+        for m in self.methods:
+            m.write_name(file, data_pool_offset)
+        for c in self.constants:
+            c.write_name(file, data_pool_offset)
+
+
+class Typelib(object):
+    """
+    A typelib represents one entire typelib file and all the interfaces
+    referenced within, whether defined entirely within the typelib or
+    merely referenced by name or IID.
+
+    Typelib objects may be instantiated directly and populated with data,
+    or the static Typelib.read method may be called to read one from a file.
+
+    """
+    _header = struct.Struct(">16sBBHIII")
+
+    def __init__(self, version=TYPELIB_VERSION, interfaces=[], annotations=[]):
+        """
+        Instantiate a new Typelib.
+
+        """
+        self.version = version
+        self.interfaces = list(interfaces)
+        self.annotations = list(annotations)
+        self.filename = None
+
+    @staticmethod
+    def iid_to_string(iid):
+        """
+        Convert a 16-byte IID into a UUID string.
+
+        """
+        def hexify(s):
+            return ''.join(["%02x" % ord(x) for x in s])
+
+        return "%s-%s-%s-%s-%s" % (hexify(iid[:4]), hexify(iid[4:6]),
+                                   hexify(iid[6:8]), hexify(iid[8:10]),
+                                   hexify(iid[10:]))
+
+    @staticmethod
+    def string_to_iid(iid_str):
+        """
+        Convert a UUID string into a 16-byte IID.
+
+        """
+        s = iid_str.replace('-', '')
+        return ''.join([chr(int(s[i:i+2], 16)) for i in range(0, len(s), 2)])
+
+    @staticmethod
+    def read_string(map, data_pool, offset):
+        if offset == 0:
+            return ""
+        sz = map.find('\x00', data_pool + offset - 1)
+        if sz == -1:
+            return ""
+        return map[data_pool + offset - 1:sz]
+
+    @staticmethod
+    def read(input_file):
+        """
+        Read a typelib from |input_file| and return
+        the constructed Typelib object. |input_file| can be a filename
+        or a file-like object.
+
+        """
+        filename = ""
+        data = None
+        expected_size = None
+        if isinstance(input_file, basestring):
+            filename = input_file
+            with open(input_file, "rb") as f:
+                st = os.fstat(f.fileno())
+                data = f.read(st.st_size)
+                expected_size = st.st_size
+        else:
+            data = input_file.read()
+
+        (magic,
+         major_ver,
+         minor_ver,
+         num_interfaces,
+         file_length,
+         interface_directory_offset,
+         data_pool_offset) = Typelib._header.unpack_from(data)
+        if magic != XPT_MAGIC:
+            raise FileFormatError("Bad magic: %s" % magic)
+        xpt = Typelib((major_ver, minor_ver))
+        xpt.filename = filename
+        if expected_size and file_length != expected_size:
+            raise FileFormatError("File is of wrong length, got %d bytes, expected %d" % (expected_size, file_length))
+        # XXX: by spec this is a zero-based file offset. however,
+        # the xpt_xdr code always subtracts 1 from data offsets
+        # (because that's what you do in the data pool) so it
+        # winds up accidentally treating this as 1-based.
+        # Filed as: https://bugzilla.mozilla.org/show_bug.cgi?id=575343
+        interface_directory_offset -= 1
+        # make a half-hearted attempt to read Annotations,
+        # since XPIDL doesn't produce any anyway.
+        start = Typelib._header.size
+        (anno, ) = struct.unpack_from(">B", data, start)
+        tag = anno & 0x7F
+        if tag == 0:  # EmptyAnnotation
+            xpt.annotations.append(None)
+        # We don't bother handling PrivateAnnotations or anything
+
+        for i in range(num_interfaces):
+            # iid, name, namespace, interface_descriptor
+            start = interface_directory_offset + i * Interface._direntry.size
+            ide = Interface._direntry.unpack_from(data, start)
+            iid = Typelib.iid_to_string(ide[0])
+            name = Typelib.read_string(data, data_pool_offset, ide[1])
+            namespace = Typelib.read_string(data, data_pool_offset, ide[2])
+            iface = Interface(name, iid, namespace)
+            iface._descriptor_offset = ide[3]
+            iface.xpt_filename = xpt.filename
+            xpt.interfaces.append(iface)
+        for iface in xpt.interfaces:
+            iface.read_descriptor(xpt, data, data_pool_offset)
+        return xpt
+
+    def __repr__(self):
+        return "<Typelib with %d interfaces>" % len(self.interfaces)
+
+    def _sanityCheck(self):
+        """
+        Check certain assumptions about data contained in this typelib.
+        Sort the interfaces array by IID, check that all interfaces
+        referenced by methods exist in the array.
+
+        """
+        self.interfaces.sort()
+        for i in self.interfaces:
+            if i.parent and i.parent not in self.interfaces:
+                raise DataError("Interface %s has parent %s not present in typelib!" % (i.name, i.parent.name))
+            for m in i.methods:
+                for n, p in enumerate(m.params):
+                    if isinstance(p, InterfaceType) and \
+                       p.iface not in self.interfaces:
+                        raise DataError("Interface method %s::%s, parameter %d references interface %s not present in typelib!" % (i.name, m.name, n, p.iface.name))
+                if isinstance(m.result, InterfaceType) and m.result.iface not in self.interfaces:
+                    raise DataError("Interface method %s::%s, result references interface %s not present in typelib!" % (i.name, m.name, m.result.iface.name))
+
+    def writefd(self, fd):
+        # write out space for a header + one empty annotation,
+        # padded to 4-byte alignment.
+        headersize = (Typelib._header.size + 1)
+        if headersize % 4:
+            headersize += 4 - headersize % 4
+        fd.write("\x00" * headersize)
+        # save this offset, it's the interface directory offset.
+        interface_directory_offset = fd.tell()
+        # write out space for an interface directory
+        fd.write("\x00" * Interface._direntry.size * len(self.interfaces))
+        # save this offset, it's the data pool offset.
+        data_pool_offset = fd.tell()
+        # write out all the interface descriptors to the data pool
+        for i in self.interfaces:
+            i.write_names(fd, data_pool_offset)
+            i.write(self, fd, data_pool_offset)
+        # now, seek back and write the header
+        file_len = fd.tell()
+        fd.seek(0)
+        fd.write(Typelib._header.pack(XPT_MAGIC,
+                                      TYPELIB_VERSION[0],
+                                      TYPELIB_VERSION[1],
+                                      len(self.interfaces),
+                                      file_len,
+                                      interface_directory_offset,
+                                      data_pool_offset))
+        # write an empty annotation
+        fd.write(struct.pack(">B", 0x80))
+        # now write the interface directory
+        # XXX: bug-compatible with existing xpt lib, put it one byte
+        # ahead of where it's supposed to be.
+        fd.seek(interface_directory_offset - 1)
+        for i in self.interfaces:
+            i.write_directory_entry(fd)
+
+    def write(self, output_file):
+        """
+        Write the contents of this typelib to |output_file|,
+        which can be either a filename or a file-like object.
+
+        """
+        self._sanityCheck()
+        if isinstance(output_file, basestring):
+            with open(output_file, "wb") as f:
+                self.writefd(f)
+        else:
+            self.writefd(output_file)
+
+    def dump(self, out):
+        """
+        Print a human-readable listing of the contents of this typelib
+        to |out|, in the format of xpt_dump.
+
+        """
+        out.write("""Header:
+   Major version:         %d
+   Minor version:         %d
+   Number of interfaces:  %d
+   Annotations:\n""" % (self.version[0], self.version[1], len(self.interfaces)))
+        for i, a in enumerate(self.annotations):
+            if a is None:
+                out.write("      Annotation #%d is empty.\n" % i)
+        out.write("\nInterface Directory:\n")
+        for i in self.interfaces:
+            out.write("   - %s::%s (%s):\n" % (i.namespace, i.name, i.iid))
+            if not i.resolved:
+                out.write("      [Unresolved]\n")
+            else:
+                if i.parent:
+                    out.write("      Parent: %s::%s\n" % (i.parent.namespace,
+                                                          i.parent.name))
+                out.write("""      Flags:
+         Scriptable: %s
+         BuiltinClass: %s
+         Function: %s\n""" % (i.scriptable and "TRUE" or "FALSE",
+                              i.builtinclass and "TRUE" or "FALSE",
+                              i.function and "TRUE" or "FALSE"))
+                out.write("      Methods:\n")
+                if len(i.methods) == 0:
+                    out.write("         No Methods\n")
+                else:
+                    for m in i.methods:
+                        out.write("   %s%s%s%s%s%s%s %s %s(%s);\n" % (
+                            m.getter and "G" or " ",
+                            m.setter and "S" or " ",
+                            m.hidden and "H" or " ",
+                            m.notxpcom and "N" or " ",
+                            m.constructor and "C" or " ",
+                            m.optargc and "O" or " ",
+                            m.implicit_jscontext and "J" or " ",
+                            str(m.result.type),
+                            m.name,
+                            m.params and ", ".join(str(p) for p in m.params) or ""
+                            ))
+                out.write("      Constants:\n")
+                if len(i.constants) == 0:
+                    out.write("         No Constants\n")
+                else:
+                    for c in i.constants:
+                        out.write("         %s %s = %d;\n" % (c.type, c.name, c.value))
+
+
+def xpt_dump(file):
+    """
+    Dump the contents of |file| to stdout in the format of xpt_dump.
+
+    """
+    t = Typelib.read(file)
+    t.dump(sys.stdout)
+
+
+def xpt_link(inputs):
+    """
+    Link all of the xpt files in |inputs| together and return the result
+    as a Typelib object. All entries in inputs may be filenames or
+    file-like objects. Non-scriptable interfaces that are unreferenced
+    from scriptable interfaces will be removed during linking.
+
+    """
+    def read_input(i):
+        if isinstance(i, Typelib):
+            return i
+        return Typelib.read(i)
+
+    if not inputs:
+        print >>sys.stderr, "Usage: xpt_link <destination file> <input files>"
+        return None
+    # This is the aggregate list of interfaces.
+    interfaces = []
+    # This will be a dict of replaced interface -> replaced with
+    # containing interfaces that were replaced with interfaces from
+    # another typelib, and the interface that replaced them.
+    merged_interfaces = {}
+    for f in inputs:
+        t = read_input(f)
+        interfaces.extend(t.interfaces)
+    # Sort interfaces by name so we can merge adjacent duplicates
+    interfaces.sort(key=operator.attrgetter('name'))
+
+    Result = enum('Equal',     # Interfaces the same, doesn't matter
+                  'NotEqual',  # Interfaces differ, keep both
+                  'KeepFirst',  # Replace second interface with first
+                  'KeepSecond')  # Replace first interface with second
+
+    def compare(i, j):
+        """
+        Compare two interfaces, determine if they're equal or
+        completely different, or should be merged (and indicate which
+        one to keep in that case).
+
+        """
+        if i == j:
+            # Arbitrary, just pick one
+            return Result.Equal
+        if i.name != j.name:
+            if i.iid == j.iid and i.iid != Interface.UNRESOLVED_IID:
+                # Same IID but different names: raise an exception.
+                raise DataError(
+                    "Typelibs contain definitions of interface %s"
+                    " with different names (%s (%s) vs %s (%s))!" %
+                    (i.iid, i.name, i.xpt_filename, j.name, j.xpt_filename))
+            # Otherwise just different interfaces.
+            return Result.NotEqual
+        # Interfaces have the same name, so either they need to be merged
+        # or there's a data error. Sort out which one to keep
+        if i.resolved != j.resolved:
+            # prefer resolved interfaces over unresolved
+            if j.resolved:
+                assert i.iid == j.iid or i.iid == Interface.UNRESOLVED_IID
+                # keep j
+                return Result.KeepSecond
+            else:
+                assert i.iid == j.iid or j.iid == Interface.UNRESOLVED_IID
+                # replace j with i
+                return Result.KeepFirst
+        elif i.iid != j.iid:
+            # Prefer unresolved interfaces with valid IIDs
+            if j.iid == Interface.UNRESOLVED_IID:
+                # replace j with i
+                assert not j.resolved
+                return Result.KeepFirst
+            elif i.iid == Interface.UNRESOLVED_IID:
+                # keep j
+                assert not i.resolved
+                return Result.KeepSecond
+            else:
+                # Same name but different IIDs: raise an exception.
+                raise DataError(
+                    "Typelibs contain definitions of interface %s"
+                    " with different IIDs (%s (%s) vs %s (%s))!" %
+                               (i.name, i.iid, i.xpt_filename,
+                                j.iid, j.xpt_filename))
+        raise DataError("No idea what happened here: %s:%s (%s), %s:%s (%s)" %
+                        (i.name, i.iid, i.xpt_filename, j.name, j.iid, j.xpt_filename))
+
+    # Compare interfaces pairwise to find duplicates that should be merged.
+    i = 1
+    while i < len(interfaces):
+        res = compare(interfaces[i-1], interfaces[i])
+        if res == Result.NotEqual:
+            i += 1
+        elif res == Result.Equal:
+            # Need to drop one but it doesn't matter which
+            del interfaces[i]
+        elif res == Result.KeepFirst:
+            merged_interfaces[interfaces[i]] = interfaces[i-1]
+            del interfaces[i]
+        elif res == Result.KeepSecond:
+            merged_interfaces[interfaces[i-1]] = interfaces[i]
+            del interfaces[i-1]
+
+    # Now fixup any merged interfaces
+    def checkType(t):
+        if isinstance(t, InterfaceType) and t.iface in merged_interfaces:
+            t.iface = merged_interfaces[t.iface]
+        elif isinstance(t, ArrayType) and \
+            isinstance(t.element_type, InterfaceType) and \
+                t.element_type.iface in merged_interfaces:
+                t.element_type.iface = merged_interfaces[t.element_type.iface]
+
+    for i in interfaces:
+        # Replace parent references
+        if i.parent in merged_interfaces:
+            i.parent = merged_interfaces[i.parent]
+        for m in i.methods:
+            # Replace InterfaceType params and return values
+            checkType(m.result.type)
+            for p in m.params:
+                checkType(p.type)
+
+    # There's no need to have non-scriptable interfaces in a typelib, and
+    # removing them saves memory when typelibs are loaded.  But we can't
+    # just blindly remove all non-scriptable interfaces, since we still
+    # need to know about non-scriptable interfaces referenced from
+    # scriptable interfaces.
+    worklist = set(i for i in interfaces if i.scriptable)
+    required_interfaces = set()
+
+    def maybe_add_to_worklist(iface):
+        if iface in required_interfaces or iface in worklist:
+            return
+        worklist.add(iface)
+
+    while worklist:
+        i = worklist.pop()
+        required_interfaces.add(i)
+        if i.parent:
+            maybe_add_to_worklist(i.parent)
+        for m in i.methods:
+            if isinstance(m.result.type, InterfaceType):
+                maybe_add_to_worklist(m.result.type.iface)
+            for p in m.params:
+                if isinstance(p.type, InterfaceType):
+                    maybe_add_to_worklist(p.type.iface)
+                elif isinstance(p.type, ArrayType) and isinstance(p.type.element_type, InterfaceType):
+                    maybe_add_to_worklist(p.type.element_type.iface)
+
+    interfaces = list(required_interfaces)
+
+    # Re-sort interfaces (by IID)
+    interfaces.sort()
+    return Typelib(interfaces=interfaces)
+
+if __name__ == '__main__':
+    if len(sys.argv) < 3:
+        print >>sys.stderr, "xpt <dump|link> <files>"
+        sys.exit(1)
+    if sys.argv[1] == 'dump':
+        xpt_dump(sys.argv[2])
+    elif sys.argv[1] == 'link':
+        xpt_link(sys.argv[3:]).write(sys.argv[2])
diff --git a/xpcom/typelib/xpt/xpt_arena.cpp b/xpcom/typelib/xpt/xpt_arena.cpp
new file mode 100644
index 000000000..21be3c00b
--- /dev/null
+++ b/xpcom/typelib/xpt/xpt_arena.cpp
@@ -0,0 +1,196 @@
+/* -*- Mode: C; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 4 -*- */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+/* Quick arena hack for xpt. */
+
+/* XXX This exists because we don't want to drag in NSPR. It *seemed*
+*  to make more sense to write a quick and dirty arena than to clone
+*  plarena (like js/src did). This is not optimal, but it works. 
+*/
+
+#include "xpt_arena.h"
+#include "mozilla/MemoryReporting.h"
+#include <string.h>
+#include <stdio.h>
+#include <stdlib.h>
+
+/****************************************************/
+
+/* Block header for each block in the arena */
+struct BLK_HDR
+{
+    BLK_HDR *next;
+};
+
+#define XPT_MIN_BLOCK_SIZE 32
+
+/* XXX this is lame. Should clone the code to do this bitwise */
+#define ALIGN_RND(s,a) ((a)==1?(s):((((s)+(a)-1)/(a))*(a)))
+
+struct XPTSubArena
+{
+    BLK_HDR *first;
+    uint8_t *next;
+    size_t   space;
+    size_t   block_size;
+};
+
+struct XPTArena
+{
+    // We have one sub-arena with 8-byte alignment for most allocations, and
+    // one with 1-byte alignment for C string allocations. The latter sub-arena
+    // avoids significant amounts of unnecessary padding between C strings.
+    XPTSubArena subarena8;
+    XPTSubArena subarena1;
+};
+
+XPT_PUBLIC_API(XPTArena *)
+XPT_NewArena(size_t block_size8, size_t block_size1)
+{
+    XPTArena *arena = static_cast<XPTArena*>(calloc(1, sizeof(XPTArena)));
+    if (arena) {
+        if (block_size8 < XPT_MIN_BLOCK_SIZE)
+            block_size8 = XPT_MIN_BLOCK_SIZE;
+        arena->subarena8.block_size = ALIGN_RND(block_size8, 8);
+
+        if (block_size1 < XPT_MIN_BLOCK_SIZE)
+            block_size1 = XPT_MIN_BLOCK_SIZE;
+        arena->subarena1.block_size = block_size1;
+    }
+    return arena;
+}
+
+static void
+DestroySubArena(XPTSubArena *subarena)
+{
+    BLK_HDR* cur = subarena->first;
+    while (cur) {
+        BLK_HDR* next = cur->next;
+        free(cur);
+        cur = next;
+    }
+}
+
+XPT_PUBLIC_API(void)
+XPT_DestroyArena(XPTArena *arena)
+{
+    DestroySubArena(&arena->subarena8);
+    DestroySubArena(&arena->subarena1);
+    free(arena);
+}
+
+/* 
+* Our alignment rule is that we always round up the size of each allocation 
+* so that the 'arena->next' pointer one will point to properly aligned space.
+*/
+
+XPT_PUBLIC_API(void *)
+XPT_ArenaCalloc(XPTArena *arena, size_t size, size_t alignment)
+{
+    if (!size)
+        return NULL;
+
+    if (!arena) {
+        XPT_ASSERT(0);
+        return NULL;
+    }
+
+    XPTSubArena *subarena;
+    if (alignment == 8) {
+        subarena = &arena->subarena8;
+    } else if (alignment == 1) {
+        subarena = &arena->subarena1;
+    } else {
+        XPT_ASSERT(0);
+        return NULL;
+    }
+
+    size_t bytes = ALIGN_RND(size, alignment);
+
+    if (bytes > subarena->space) {
+        BLK_HDR* new_block;
+        size_t block_header_size = ALIGN_RND(sizeof(BLK_HDR), alignment);
+        size_t new_space = subarena->block_size;
+
+        while (bytes > new_space - block_header_size)
+            new_space += subarena->block_size;
+
+        new_block =
+            static_cast<BLK_HDR*>(calloc(new_space / alignment, alignment));
+        if (!new_block) {
+            subarena->next = NULL;
+            subarena->space = 0;
+            return NULL;
+        }
+
+        /* link block into the list of blocks for use when we destroy */
+        new_block->next = subarena->first;
+        subarena->first = new_block;
+
+        /* set info for current block */
+        subarena->next =
+            reinterpret_cast<uint8_t*>(new_block) + block_header_size;
+        subarena->space = new_space - block_header_size;
+
+#ifdef DEBUG
+        /* mark block for corruption check */
+        memset(subarena->next, 0xcd, subarena->space);
+#endif
+    }
+
+#ifdef DEBUG
+    {
+        /* do corruption check */
+        size_t i;
+        for (i = 0; i < bytes; ++i) {
+            XPT_ASSERT(subarena->next[i] == 0xcd);
+        }
+        /* we guarantee that the block will be filled with zeros */
+        memset(subarena->next, 0, bytes);
+    }
+#endif
+
+    uint8_t* p = subarena->next;
+    subarena->next  += bytes;
+    subarena->space -= bytes;
+
+    return p;
+}
+
+/***************************************************************************/
+
+#ifdef DEBUG
+XPT_PUBLIC_API(void)
+XPT_AssertFailed(const char *s, const char *file, uint32_t lineno)
+{
+    fprintf(stderr, "Assertion failed: %s, file %s, line %d\n",
+            s, file, lineno);
+    abort();
+}        
+#endif
+
+static size_t
+SizeOfSubArenaExcludingThis(XPTSubArena *subarena, MozMallocSizeOf mallocSizeOf)
+{
+    size_t n = 0;
+
+    BLK_HDR* cur = subarena->first;
+    while (cur) {
+        BLK_HDR* next = cur->next;
+        n += mallocSizeOf(cur);
+        cur = next;
+    }
+
+    return n;
+}
+
+XPT_PUBLIC_API(size_t)
+XPT_SizeOfArenaIncludingThis(XPTArena *arena, MozMallocSizeOf mallocSizeOf)
+{
+    size_t n = mallocSizeOf(arena);
+    n += SizeOfSubArenaExcludingThis(&arena->subarena8, mallocSizeOf);
+    n += SizeOfSubArenaExcludingThis(&arena->subarena1, mallocSizeOf);
+    return n;
+}
diff --git a/xpcom/typelib/xpt/xpt_arena.h b/xpcom/typelib/xpt/xpt_arena.h
new file mode 100644
index 000000000..6ac146ffe
--- /dev/null
+++ b/xpcom/typelib/xpt/xpt_arena.h
@@ -0,0 +1,70 @@
+/* -*- Mode: C; tab-width: 4; indent-tabs-mode: nil; c-basic-offset: 4 -*- */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+/*
+ * Simple arena allocator for xpt (which avoids using NSPR).
+ */
+
+#ifndef __xpt_arena_h__
+#define __xpt_arena_h__
+
+#include <stdlib.h>
+#include "mozilla/Attributes.h"
+#include "mozilla/MemoryReporting.h"
+#include <stdint.h>
+
+
+/*
+ * The XPT library is statically linked: no functions are exported from
+ * shared libraries.
+ */
+#define XPT_PUBLIC_API(t)    t
+#define XPT_PUBLIC_DATA(t)   t
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+/*
+ * Simple Arena support. Use with caution!
+ */ 
+
+typedef struct XPTArena XPTArena;
+
+XPT_PUBLIC_API(XPTArena *)
+XPT_NewArena(size_t block_size8, size_t block_size1);
+
+XPT_PUBLIC_API(void)
+XPT_DestroyArena(XPTArena *arena);
+
+XPT_PUBLIC_API(void *)
+XPT_ArenaCalloc(XPTArena *arena, size_t size, size_t alignment);
+
+XPT_PUBLIC_API(size_t)
+XPT_SizeOfArenaIncludingThis(XPTArena *arena, MozMallocSizeOf mallocSizeOf);
+
+/* --------------------------------------------------------- */
+
+#define XPT_CALLOC8(_arena, _bytes) XPT_ArenaCalloc((_arena), (_bytes), 8)
+#define XPT_CALLOC1(_arena, _bytes) XPT_ArenaCalloc((_arena), (_bytes), 1)
+#define XPT_NEWZAP(_arena, _struct) ((_struct *) XPT_CALLOC8((_arena), sizeof(_struct)))
+
+/* --------------------------------------------------------- */
+
+#ifdef DEBUG
+XPT_PUBLIC_API(void)
+XPT_AssertFailed(const char *s, const char *file, uint32_t lineno)
+  MOZ_PRETEND_NORETURN_FOR_STATIC_ANALYSIS;
+#define XPT_ASSERT(_expr) \
+    ((_expr)?((void)0):XPT_AssertFailed(# _expr, __FILE__, __LINE__))
+#else
+#define XPT_ASSERT(_expr) ((void)0)
+#endif
+
+#ifdef __cplusplus
+}
+#endif
+
+#endif /* __xpt_arena_h__ */
diff --git a/xpcom/typelib/xpt/xpt_struct.cpp b/xpcom/typelib/xpt/xpt_struct.cpp
new file mode 100644
index 000000000..c2e09abf0
--- /dev/null
+++ b/xpcom/typelib/xpt/xpt_struct.cpp
@@ -0,0 +1,432 @@
+/* -*- Mode: C; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 4 -*- */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+/* Implementation of XDR routines for typelib structures. */
+
+#include "xpt_xdr.h"
+#include "xpt_struct.h"
+#include <string.h>
+#include <stdio.h>
+
+using mozilla::WrapNotNull;
+
+/***************************************************************************/
+/* Forward declarations. */
+
+static bool
+DoInterfaceDirectoryEntry(XPTArena *arena, NotNull<XPTCursor*> cursor,
+                          XPTInterfaceDirectoryEntry *ide);
+
+static bool
+DoConstDescriptor(XPTArena *arena, NotNull<XPTCursor*> cursor,
+                  XPTConstDescriptor *cd, XPTInterfaceDescriptor *id);
+
+static bool
+DoMethodDescriptor(XPTArena *arena, NotNull<XPTCursor*> cursor,
+                   XPTMethodDescriptor *md, XPTInterfaceDescriptor *id);
+
+static bool
+SkipAnnotation(NotNull<XPTCursor*> cursor, bool *isLast);
+
+static bool
+DoInterfaceDescriptor(XPTArena *arena, NotNull<XPTCursor*> outer,
+                      XPTInterfaceDescriptor **idp);
+
+static bool
+DoTypeDescriptorPrefix(XPTArena *arena, NotNull<XPTCursor*> cursor,
+                       XPTTypeDescriptorPrefix *tdp);
+
+static bool
+DoTypeDescriptor(XPTArena *arena, NotNull<XPTCursor*> cursor,
+                 XPTTypeDescriptor *td, XPTInterfaceDescriptor *id);
+
+static bool
+DoParamDescriptor(XPTArena *arena, NotNull<XPTCursor*> cursor,
+                  XPTParamDescriptor *pd, XPTInterfaceDescriptor *id);
+
+/***************************************************************************/
+
+XPT_PUBLIC_API(bool)
+XPT_DoHeader(XPTArena *arena, NotNull<XPTCursor*> cursor, XPTHeader **headerp)
+{
+    unsigned int i;
+    uint32_t file_length = 0;
+    uint32_t ide_offset;
+
+    XPTHeader* header = XPT_NEWZAP(arena, XPTHeader);
+    if (!header)
+        return false;
+    *headerp = header;
+
+    uint8_t magic[16];
+    for (i = 0; i < sizeof(magic); i++) {
+        if (!XPT_Do8(cursor, &magic[i]))
+            return false;
+    }
+
+    if (strncmp((const char*)magic, XPT_MAGIC, 16) != 0) {
+        /* Require that the header contain the proper magic */
+        fprintf(stderr,
+                "libxpt: bad magic header in input file; "
+                "found '%s', expected '%s'\n",
+                magic, XPT_MAGIC_STRING);
+        return false;
+    }
+
+    if (!XPT_Do8(cursor, &header->major_version) ||
+        !XPT_Do8(cursor, &header->minor_version)) {
+        return false;
+    }
+
+    if (header->major_version >= XPT_MAJOR_INCOMPATIBLE_VERSION) {
+        /* This file is newer than we are and set to an incompatible version
+         * number. We must set the header state thusly and return.
+         */
+        header->num_interfaces = 0;
+        return true;
+    }
+
+    if (!XPT_Do16(cursor, &header->num_interfaces) ||
+        !XPT_Do32(cursor, &file_length) ||
+        !XPT_Do32(cursor, &ide_offset)) {
+        return false;
+    }
+
+    /* 
+     * Make sure the file length reported in the header is the same size as
+     * as our buffer unless it is zero (not set) 
+     */
+    if (file_length != 0 && 
+        cursor->state->pool_allocated < file_length) {
+        fputs("libxpt: File length in header does not match actual length. File may be corrupt\n",
+            stderr);
+        return false;
+    }
+
+    uint32_t data_pool;
+    if (!XPT_Do32(cursor, &data_pool))
+        return false;
+
+    XPT_SetDataOffset(cursor->state, data_pool);
+
+    if (header->num_interfaces) {
+        size_t n = header->num_interfaces * sizeof(XPTInterfaceDirectoryEntry);
+        header->interface_directory =
+            static_cast<XPTInterfaceDirectoryEntry*>(XPT_CALLOC8(arena, n));
+        if (!header->interface_directory)
+            return false;
+    }
+
+    /*
+     * Iterate through the annotations rather than recurring, to avoid blowing
+     * the stack on large xpt files. We don't actually store annotations, we
+     * just skip over them.
+     */
+    bool isLast;
+    do {
+        if (!SkipAnnotation(cursor, &isLast))
+            return false;
+    } while (!isLast);
+
+    /* shouldn't be necessary now, but maybe later */
+    XPT_SeekTo(cursor, ide_offset);
+
+    for (i = 0; i < header->num_interfaces; i++) {
+        if (!DoInterfaceDirectoryEntry(arena, cursor,
+                                       &header->interface_directory[i]))
+            return false;
+    }
+
+    return true;
+}
+
+/* InterfaceDirectoryEntry records go in the header */
+bool
+DoInterfaceDirectoryEntry(XPTArena *arena, NotNull<XPTCursor*> cursor,
+                          XPTInterfaceDirectoryEntry *ide)
+{
+    char* dummy_name_space;
+
+    /* write the IID in our cursor space */
+    if (!XPT_DoIID(cursor, &(ide->iid)) ||
+
+        /* write the name string in the data pool, and the offset in our
+           cursor space */
+        !XPT_DoCString(arena, cursor, &(ide->name)) ||
+
+        /* don't write the name_space string in the data pool, because we don't
+         * need it. Do write the offset in our cursor space */
+        !XPT_DoCString(arena, cursor, &dummy_name_space, /* ignore = */ true) ||
+
+        /* do InterfaceDescriptors */
+        !DoInterfaceDescriptor(arena, cursor, &ide->interface_descriptor)) {
+        return false;
+    }
+
+    return true;
+}
+
+static bool
+InterfaceDescriptorAddTypes(XPTArena *arena, XPTInterfaceDescriptor *id,
+                            uint16_t num)
+{
+    XPTTypeDescriptor *old = id->additional_types;
+    XPTTypeDescriptor *new_;
+    size_t old_size = id->num_additional_types * sizeof(XPTTypeDescriptor);
+    size_t new_size = (num * sizeof(XPTTypeDescriptor)) + old_size;
+
+    /* XXX should grow in chunks to minimize alloc overhead */
+    new_ = static_cast<XPTTypeDescriptor*>(XPT_CALLOC8(arena, new_size));
+    if (!new_)
+        return false;
+    if (old) {
+        memcpy(new_, old, old_size);
+    }
+    id->additional_types = new_;
+
+    if (num + uint16_t(id->num_additional_types) > 256)
+        return false;
+
+    id->num_additional_types += num;
+    return true;
+}
+
+bool
+DoInterfaceDescriptor(XPTArena *arena, NotNull<XPTCursor*> outer,
+                      XPTInterfaceDescriptor **idp)
+{
+    XPTInterfaceDescriptor *id;
+    XPTCursor curs;
+    NotNull<XPTCursor*> cursor = WrapNotNull(&curs);
+    uint32_t i, id_sz = 0;
+
+    id = XPT_NEWZAP(arena, XPTInterfaceDescriptor);
+    if (!id)
+        return false;
+    *idp = id;
+
+    if (!XPT_MakeCursor(outer->state, XPT_DATA, id_sz, cursor))
+        return false;
+
+    if (!XPT_Do32(outer, &cursor->offset))
+        return false;
+    if (!cursor->offset) {
+        *idp = NULL;
+        return true;
+    }
+    if(!XPT_Do16(cursor, &id->parent_interface) ||
+       !XPT_Do16(cursor, &id->num_methods)) {
+        return false;
+    }
+
+    if (id->num_methods) {
+        size_t n = id->num_methods * sizeof(XPTMethodDescriptor);
+        id->method_descriptors =
+            static_cast<XPTMethodDescriptor*>(XPT_CALLOC8(arena, n));
+        if (!id->method_descriptors)
+            return false;
+    }
+
+    for (i = 0; i < id->num_methods; i++) {
+        if (!DoMethodDescriptor(arena, cursor, &id->method_descriptors[i], id))
+            return false;
+    }
+
+    if (!XPT_Do16(cursor, &id->num_constants)) {
+        return false;
+    }
+
+    if (id->num_constants) {
+        size_t n = id->num_constants * sizeof(XPTConstDescriptor);
+        id->const_descriptors =
+            static_cast<XPTConstDescriptor*>(XPT_CALLOC8(arena, n));
+        if (!id->const_descriptors)
+            return false;
+    }
+
+    for (i = 0; i < id->num_constants; i++) {
+        if (!DoConstDescriptor(arena, cursor, &id->const_descriptors[i], id)) {
+            return false;
+        }
+    }
+
+    if (!XPT_Do8(cursor, &id->flags)) {
+        return false;
+    }
+
+    return true;
+}
+
+bool
+DoConstDescriptor(XPTArena *arena, NotNull<XPTCursor*> cursor,
+                  XPTConstDescriptor *cd, XPTInterfaceDescriptor *id)
+{
+    bool ok = false;
+
+    if (!XPT_DoCString(arena, cursor, &cd->name) ||
+        !DoTypeDescriptor(arena, cursor, &cd->type, id)) {
+
+        return false;
+    }
+
+    switch(XPT_TDP_TAG(cd->type.prefix)) {
+      case TD_INT8:
+        ok = XPT_Do8(cursor, (uint8_t*) &cd->value.i8);
+        break;
+      case TD_INT16:
+        ok = XPT_Do16(cursor, (uint16_t*) &cd->value.i16);
+        break;
+      case TD_INT32:
+        ok = XPT_Do32(cursor, (uint32_t*) &cd->value.i32);
+        break;
+      case TD_INT64:
+        ok = XPT_Do64(cursor, &cd->value.i64);
+        break;
+      case TD_UINT8:
+        ok = XPT_Do8(cursor, &cd->value.ui8);
+        break;
+      case TD_UINT16:
+        ok = XPT_Do16(cursor, &cd->value.ui16);
+        break;
+      case TD_UINT32:
+        ok = XPT_Do32(cursor, &cd->value.ui32);
+        break;
+      case TD_UINT64:
+        ok = XPT_Do64(cursor, (int64_t *)&cd->value.ui64);
+        break;
+      case TD_CHAR:
+        ok = XPT_Do8(cursor, (uint8_t*) &cd->value.ch);
+        break;
+      case TD_WCHAR:
+        ok = XPT_Do16(cursor, &cd->value.wch);
+        break;
+        /* fall-through */
+      default:
+        fprintf(stderr, "illegal type!\n");
+        break;
+    }
+
+    return ok;
+
+}
+
+bool
+DoMethodDescriptor(XPTArena *arena, NotNull<XPTCursor*> cursor,
+                   XPTMethodDescriptor *md, XPTInterfaceDescriptor *id)
+{
+    int i;
+
+    if (!XPT_Do8(cursor, &md->flags) ||
+        !XPT_DoCString(arena, cursor, &md->name) ||
+        !XPT_Do8(cursor, &md->num_args))
+        return false;
+
+    if (md->num_args) {
+        size_t n = md->num_args * sizeof(XPTParamDescriptor);
+        md->params = static_cast<XPTParamDescriptor*>(XPT_CALLOC8(arena, n));
+        if (!md->params)
+            return false;
+    }
+
+    for(i = 0; i < md->num_args; i++) {
+        if (!DoParamDescriptor(arena, cursor, &md->params[i], id))
+            return false;
+    }
+
+    if (!DoParamDescriptor(arena, cursor, &md->result, id))
+        return false;
+
+    return true;
+}
+
+bool
+DoParamDescriptor(XPTArena *arena, NotNull<XPTCursor*> cursor,
+                  XPTParamDescriptor *pd, XPTInterfaceDescriptor *id)
+{
+    if (!XPT_Do8(cursor, &pd->flags) ||
+        !DoTypeDescriptor(arena, cursor, &pd->type, id))
+        return false;
+
+    return true;
+}
+
+bool
+DoTypeDescriptorPrefix(XPTArena *arena, NotNull<XPTCursor*> cursor,
+                       XPTTypeDescriptorPrefix *tdp)
+{
+    return XPT_Do8(cursor, &tdp->flags);
+}
+
+bool
+DoTypeDescriptor(XPTArena *arena, NotNull<XPTCursor*> cursor,
+                 XPTTypeDescriptor *td, XPTInterfaceDescriptor *id)
+{
+    if (!DoTypeDescriptorPrefix(arena, cursor, &td->prefix)) {
+        return false;
+    }
+
+    switch (XPT_TDP_TAG(td->prefix)) {
+      case TD_INTERFACE_TYPE:
+        uint16_t iface;
+        if (!XPT_Do16(cursor, &iface))
+            return false;
+        td->u.iface.iface_hi8 = (iface >> 8) & 0xff;
+        td->u.iface.iface_lo8 = iface & 0xff;
+        break;
+      case TD_INTERFACE_IS_TYPE:
+        if (!XPT_Do8(cursor, &td->u.interface_is.argnum))
+            return false;
+        break;
+      case TD_ARRAY: {
+        // argnum2 appears in the on-disk format but it isn't used.
+        uint8_t argnum2 = 0;
+        if (!XPT_Do8(cursor, &td->u.array.argnum) ||
+            !XPT_Do8(cursor, &argnum2))
+            return false;
+
+        if (!InterfaceDescriptorAddTypes(arena, id, 1))
+            return false;
+        td->u.array.additional_type = id->num_additional_types - 1;
+
+        if (!DoTypeDescriptor(arena, cursor,
+                              &id->additional_types[td->u.array.additional_type],
+                              id))
+            return false;
+        break;
+      }
+      case TD_PSTRING_SIZE_IS:
+      case TD_PWSTRING_SIZE_IS: {
+        // argnum2 appears in the on-disk format but it isn't used.
+        uint8_t argnum2 = 0;
+        if (!XPT_Do8(cursor, &td->u.pstring_is.argnum) ||
+            !XPT_Do8(cursor, &argnum2))
+            return false;
+        break;
+      }
+      default:
+        /* nothing special */
+        break;
+    }
+    return true;
+}
+
+bool
+SkipAnnotation(NotNull<XPTCursor*> cursor, bool *isLast)
+{
+    uint8_t flags;
+    if (!XPT_Do8(cursor, &flags))
+        return false;
+
+    *isLast = XPT_ANN_IS_LAST(flags);
+
+    if (XPT_ANN_IS_PRIVATE(flags)) {
+        if (!XPT_SkipStringInline(cursor) ||
+            !XPT_SkipStringInline(cursor))
+            return false;
+    }
+
+    return true;
+}
+
diff --git a/xpcom/typelib/xpt/xpt_struct.h b/xpcom/typelib/xpt/xpt_struct.h
new file mode 100644
index 000000000..b4da4a3fd
--- /dev/null
+++ b/xpcom/typelib/xpt/xpt_struct.h
@@ -0,0 +1,366 @@
+/* -*- Mode: C; tab-width: 4; indent-tabs-mode: nil; c-basic-offset: 4 -*- */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+/*
+ * Structures matching the in-memory representation of typelib structures.
+ * http://www.mozilla.org/scriptable/typelib_file.html
+ */
+
+#ifndef __xpt_struct_h__
+#define __xpt_struct_h__
+
+#include "xpt_arena.h"
+#include <stdint.h>
+
+extern "C" {
+
+/*
+ * Originally, I was going to have structures that exactly matched the on-disk
+ * representation, but that proved difficult: different compilers can pack
+ * their structs differently, and that makes overlaying them atop a
+ * read-from-disk byte buffer troublesome.  So now I just have some structures
+ * that are used in memory, and we're going to write a nice XDR library to
+ * write them to disk and stuff.  It is pure joy. -- shaver
+ */
+
+/* Structures for the typelib components */
+
+typedef struct XPTHeader XPTHeader;
+typedef struct XPTInterfaceDirectoryEntry XPTInterfaceDirectoryEntry;
+typedef struct XPTInterfaceDescriptor XPTInterfaceDescriptor;
+typedef struct XPTConstDescriptor XPTConstDescriptor;
+typedef struct XPTMethodDescriptor XPTMethodDescriptor;
+typedef struct XPTParamDescriptor XPTParamDescriptor;
+typedef struct XPTTypeDescriptor XPTTypeDescriptor;
+typedef struct XPTTypeDescriptorPrefix XPTTypeDescriptorPrefix;
+
+#ifndef nsID_h__
+/*
+ * We can't include nsID.h, because it's full of C++ goop and we're not doing
+ * C++ here, so we define our own minimal struct.  We protect against multiple
+ * definitions of this struct, though, and use the same field naming.
+ */
+struct nsID {
+    uint32_t m0;
+    uint16_t m1;
+    uint16_t m2;
+    uint8_t  m3[8];
+};
+
+typedef struct nsID nsID;
+#endif
+
+/*
+ * Every XPCOM typelib file begins with a header.
+ */
+struct XPTHeader {
+    // Some of these fields exists in the on-disk format but don't need to be
+    // stored in memory (other than very briefly, which can be done with local
+    // variables).
+
+    //uint8_t                   magic[16];
+    uint8_t                     major_version;
+    uint8_t                     minor_version;
+    uint16_t                    num_interfaces;
+    //uint32_t                  file_length;
+    XPTInterfaceDirectoryEntry  *interface_directory;
+    //uint32_t                  data_pool;
+};
+
+#define XPT_MAGIC "XPCOM\nTypeLib\r\n\032"
+/* For error messages. */
+#define XPT_MAGIC_STRING "XPCOM\\nTypeLib\\r\\n\\032"
+#define XPT_MAJOR_VERSION 0x01
+#define XPT_MINOR_VERSION 0x02
+
+/* Any file with a major version number of XPT_MAJOR_INCOMPATIBLE_VERSION
+ * or higher is to be considered incompatible by this version of xpt and
+ * we will refuse to read it. We will return a header with magic, major and
+ * minor versions set from the file. num_interfaces will be set to zero to
+ * confirm our inability to read the file; i.e. even if some client of this
+ * library gets out of sync with us regarding the agreed upon value for
+ * XPT_MAJOR_INCOMPATIBLE_VERSION, anytime num_interfaces is zero we *know*
+ * that this library refused to read the file due to version incompatibility.
+ */
+#define XPT_MAJOR_INCOMPATIBLE_VERSION 0x02
+
+/*
+ * A contiguous array of fixed-size InterfaceDirectoryEntry records begins at 
+ * the byte offset identified by the interface_directory field in the file 
+ * header.  The array is used to quickly locate an interface description 
+ * using its IID.  No interface should appear more than once in the array.
+ */
+struct XPTInterfaceDirectoryEntry {
+    nsID                   iid;
+    char                   *name;
+
+    // This field exists in the on-disk format. But it isn't used so we don't
+    // allocate space for it in memory.
+    //char                 *name_space;
+
+    XPTInterfaceDescriptor *interface_descriptor;
+};
+
+/*
+ * An InterfaceDescriptor describes a single XPCOM interface, including all of
+ * its methods.
+ */
+struct XPTInterfaceDescriptor {
+    /* This field ordering minimizes the size of this struct.
+    *  The fields are serialized on disk in a different order.
+    *  See DoInterfaceDescriptor().
+    */
+    XPTMethodDescriptor     *method_descriptors;
+    XPTConstDescriptor      *const_descriptors;
+    XPTTypeDescriptor       *additional_types;
+    uint16_t                parent_interface;
+    uint16_t                num_methods;
+    uint16_t                num_constants;
+    uint8_t                 flags;
+
+    /* additional_types are used for arrays where we may need multiple
+    *  XPTTypeDescriptors for a single XPTMethodDescriptor. Since we still
+    *  want to have a simple array of XPTMethodDescriptor (each with a single
+    *  embedded XPTTypeDescriptor), a XPTTypeDescriptor can have a reference
+    *  to an 'additional_type'. That reference is an index in this 
+    *  "additional_types" array. So a given XPTMethodDescriptor might have 
+    *  a whole chain of these XPTTypeDescriptors to represent, say, a multi
+    *  dimensional array.
+    *
+    *  Note that in the typelib file these additional types are stored 'inline'
+    *  in the MethodDescriptor. But, in the typelib MethodDescriptors can be 
+    *  of varying sizes, where in XPT's in memory mapping of the data we want 
+    *  them to be of fixed size. This additional_types scheme is here to allow 
+    *  for that.
+    */
+    uint8_t                 num_additional_types;
+};
+
+#define XPT_ID_SCRIPTABLE           0x80
+#define XPT_ID_FUNCTION             0x40
+#define XPT_ID_BUILTINCLASS         0x20
+#define XPT_ID_MAIN_PROCESS_SCRIPTABLE_ONLY 0x10
+#define XPT_ID_FLAGMASK             0xf0
+
+#define XPT_ID_IS_SCRIPTABLE(flags) (!!(flags & XPT_ID_SCRIPTABLE))
+#define XPT_ID_IS_FUNCTION(flags) (!!(flags & XPT_ID_FUNCTION))
+#define XPT_ID_IS_BUILTINCLASS(flags) (!!(flags & XPT_ID_BUILTINCLASS))
+#define XPT_ID_IS_MAIN_PROCESS_SCRIPTABLE_ONLY(flags) (!!(flags & XPT_ID_MAIN_PROCESS_SCRIPTABLE_ONLY))
+
+/* 
+ * A TypeDescriptor is a variable-size record used to identify the type of a 
+ * method argument or return value. 
+ *
+ * There are three types of TypeDescriptors:
+ *
+ * SimpleTypeDescriptor
+ * InterfaceTypeDescriptor
+ * InterfaceIsTypeDescriptor
+ *
+ * The tag field in the prefix indicates which of the variant TypeDescriptor 
+ * records is being used, and hence the way any remaining fields should be 
+ * parsed. Values from 0 to 17 refer to SimpleTypeDescriptors. The value 18 
+ * designates an InterfaceTypeDescriptor, while 19 represents an 
+ * InterfaceIsTypeDescriptor.
+ */
+
+/* why bother with a struct?  - other code relies on this being a struct */
+struct XPTTypeDescriptorPrefix {
+    uint8_t flags;
+};
+
+/* flag bits */
+
+#define XPT_TDP_FLAGMASK         0xe0
+#define XPT_TDP_TAGMASK          (~XPT_TDP_FLAGMASK)
+#define XPT_TDP_TAG(tdp)         ((tdp).flags & XPT_TDP_TAGMASK)
+
+/* 
+ * The following enum maps mnemonic names to the different numeric values 
+ * of XPTTypeDescriptor->tag.
+ */
+enum XPTTypeDescriptorTags {
+    TD_INT8              = 0,
+    TD_INT16             = 1,
+    TD_INT32             = 2,
+    TD_INT64             = 3,
+    TD_UINT8             = 4,
+    TD_UINT16            = 5,
+    TD_UINT32            = 6,
+    TD_UINT64            = 7,
+    TD_FLOAT             = 8, 
+    TD_DOUBLE            = 9,
+    TD_BOOL              = 10,  
+    TD_CHAR              = 11,  
+    TD_WCHAR             = 12, 
+    TD_VOID              = 13,  
+    TD_PNSIID            = 14,
+    TD_DOMSTRING         = 15,
+    TD_PSTRING           = 16,
+    TD_PWSTRING          = 17,
+    TD_INTERFACE_TYPE    = 18,
+    TD_INTERFACE_IS_TYPE = 19,
+    TD_ARRAY             = 20,
+    TD_PSTRING_SIZE_IS   = 21,
+    TD_PWSTRING_SIZE_IS  = 22,
+    TD_UTF8STRING        = 23,
+    TD_CSTRING           = 24,
+    TD_ASTRING           = 25,
+    TD_JSVAL             = 26
+};
+
+struct XPTTypeDescriptor {
+    XPTTypeDescriptorPrefix prefix;
+
+    // The memory layout here doesn't exactly match (for the appropriate types)
+    // the on-disk format. This is to save memory.
+    union {
+        // Used for TD_INTERFACE_IS_TYPE.
+        struct {
+            uint8_t argnum;
+        } interface_is;
+
+        // Used for TD_PSTRING_SIZE_IS, TD_PWSTRING_SIZE_IS.
+        struct {
+            uint8_t argnum;
+            //uint8_t argnum2;          // Present on disk, omitted here.
+        } pstring_is;
+
+        // Used for TD_ARRAY.
+        struct {
+            uint8_t argnum;
+            //uint8_t argnum2;          // Present on disk, omitted here.
+            uint8_t additional_type;    // uint16_t on disk, uint8_t here;
+                                        // in practice it never exceeds 20.
+        } array;
+
+        // Used for TD_INTERFACE_TYPE.
+        struct {
+            // We store the 16-bit iface value as two 8-bit values in order to
+            // avoid 16-bit alignment requirements for XPTTypeDescriptor, which
+            // reduces its size and also the size of XPTParamDescriptor.
+            uint8_t iface_hi8;
+            uint8_t iface_lo8;
+        } iface;
+    } u;
+};
+
+/*
+ * A ConstDescriptor is a variable-size record that records the name and 
+ * value of a scoped interface constant. 
+ *
+ * The types of the method parameter are restricted to the following subset 
+ * of TypeDescriptors: 
+ *
+ * int8_t, uint8_t, int16_t, uint16_t, int32_t, uint32_t, 
+ * int64_t, uint64_t, wchar_t, char
+ * 
+ * The type (and thus the size) of the value record is determined by the 
+ * contents of the associated TypeDescriptor record. For instance, if type 
+ * corresponds to int16_t, then value is a two-byte record consisting of a 
+ * 16-bit signed integer.
+ */
+union XPTConstValue {
+    int8_t    i8;
+    uint8_t   ui8; 
+    int16_t   i16; 
+    uint16_t  ui16;
+    int32_t   i32; 
+    uint32_t  ui32;
+    int64_t   i64; 
+    uint64_t  ui64; 
+    char      ch; 
+    uint16_t  wch;
+}; /* varies according to type */
+
+struct XPTConstDescriptor {
+    char                *name;
+    XPTTypeDescriptor   type;
+    union XPTConstValue value;
+};
+
+/*
+ * A ParamDescriptor is a variable-size record used to describe either a 
+ * single argument to a method or a method's result.
+ */
+struct XPTParamDescriptor {
+    uint8_t           flags;
+    XPTTypeDescriptor type;
+};
+
+/* flag bits */
+#define XPT_PD_IN       0x80
+#define XPT_PD_OUT      0x40
+#define XPT_PD_RETVAL   0x20
+#define XPT_PD_SHARED   0x10
+#define XPT_PD_DIPPER   0x08
+#define XPT_PD_OPTIONAL 0x04
+#define XPT_PD_FLAGMASK 0xfc
+
+#define XPT_PD_IS_IN(flags)     (flags & XPT_PD_IN)
+#define XPT_PD_IS_OUT(flags)    (flags & XPT_PD_OUT)
+#define XPT_PD_IS_RETVAL(flags) (flags & XPT_PD_RETVAL)
+#define XPT_PD_IS_SHARED(flags) (flags & XPT_PD_SHARED)
+#define XPT_PD_IS_DIPPER(flags) (flags & XPT_PD_DIPPER)
+#define XPT_PD_IS_OPTIONAL(flags) (flags & XPT_PD_OPTIONAL)
+
+/*
+ * A MethodDescriptor is a variable-size record used to describe a single 
+ * interface method.
+ */
+struct XPTMethodDescriptor {
+    char                *name;
+    XPTParamDescriptor  *params;
+    XPTParamDescriptor  result;
+    uint8_t             flags;
+    uint8_t             num_args;
+};
+
+/* flag bits */
+#define XPT_MD_GETTER   0x80
+#define XPT_MD_SETTER   0x40
+#define XPT_MD_NOTXPCOM 0x20
+#define XPT_MD_HIDDEN   0x08
+#define XPT_MD_OPT_ARGC 0x04
+#define XPT_MD_CONTEXT  0x02
+#define XPT_MD_FLAGMASK 0xfe
+
+#define XPT_MD_IS_GETTER(flags)      (flags & XPT_MD_GETTER)
+#define XPT_MD_IS_SETTER(flags)      (flags & XPT_MD_SETTER)
+#define XPT_MD_IS_NOTXPCOM(flags)    (flags & XPT_MD_NOTXPCOM)
+#define XPT_MD_IS_HIDDEN(flags)      (flags & XPT_MD_HIDDEN)
+#define XPT_MD_WANTS_OPT_ARGC(flags) (flags & XPT_MD_OPT_ARGC)
+#define XPT_MD_WANTS_CONTEXT(flags)  (flags & XPT_MD_CONTEXT)
+
+/*
+ * Annotation records are variable-size records used to store secondary 
+ * information about the typelib, e.g. such as the name of the tool that 
+ * generated the typelib file, the date it was generated, etc.  The 
+ * information is stored with very loose format requirements so as to 
+ * allow virtually any private data to be stored in the typelib.
+ *
+ * There are two types of Annotations:
+ *
+ * EmptyAnnotation
+ * PrivateAnnotation
+ *
+ * The tag field of the prefix discriminates among the variant record 
+ * types for Annotation's.  If the tag is 0, this record is an 
+ * EmptyAnnotation. EmptyAnnotation's are ignored - they're only used to 
+ * indicate an array of Annotation's that's completely empty.  If the tag 
+ * is 1, the record is a PrivateAnnotation. 
+ *
+ * We don't actually store annotations; we just skip over them if they are
+ * present.
+ */
+
+#define XPT_ANN_LAST	                0x80
+#define XPT_ANN_IS_LAST(flags)          (flags & XPT_ANN_LAST)
+#define XPT_ANN_PRIVATE                 0x40
+#define XPT_ANN_IS_PRIVATE(flags)       (flags & XPT_ANN_PRIVATE)
+
+}
+
+#endif /* __xpt_struct_h__ */
diff --git a/xpcom/typelib/xpt/xpt_xdr.cpp b/xpcom/typelib/xpt/xpt_xdr.cpp
new file mode 100644
index 000000000..04b90422a
--- /dev/null
+++ b/xpcom/typelib/xpt/xpt_xdr.cpp
@@ -0,0 +1,227 @@
+/* -*- Mode: C; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 4 -*- */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+/* Implementation of XDR primitives. */
+
+#include "xpt_xdr.h"
+#include "nscore.h"
+#include <string.h>             /* strchr */
+#include "mozilla/EndianUtils.h"
+
+#define CURS_POOL_OFFSET_RAW(cursor)                                          \
+  ((cursor)->pool == XPT_HEADER                                               \
+   ? (cursor)->offset                                                         \
+   : (XPT_ASSERT((cursor)->state->data_offset),                               \
+      (cursor)->offset + (cursor)->state->data_offset))
+
+#define CURS_POOL_OFFSET(cursor)                                              \
+  (CURS_POOL_OFFSET_RAW(cursor) - 1)
+
+/* can be used as lvalue */
+#define CURS_POINT(cursor)                                                    \
+  ((cursor)->state->pool_data[CURS_POOL_OFFSET(cursor)])
+
+static bool
+CHECK_COUNT(NotNull<XPTCursor*> cursor, uint32_t space)
+{
+    // Fail if we're in the data area and about to exceed the allocation.
+    // XXX Also fail if we're in the data area and !state->data_offset
+    if (cursor->pool == XPT_DATA &&
+        (CURS_POOL_OFFSET(cursor) + space > (cursor)->state->pool_allocated)) {
+        XPT_ASSERT(0);
+        fprintf(stderr, "FATAL: no room for %d in cursor\n", space);
+        return false;
+    }
+
+    return true;
+}
+
+XPT_PUBLIC_API(void)
+XPT_InitXDRState(XPTState* state, char *data, uint32_t len)
+{
+    state->next_cursor[0] = state->next_cursor[1] = 1;
+    state->pool_data = data;
+    state->pool_allocated = len;
+}
+
+/* All offsets are 1-based */
+XPT_PUBLIC_API(void)
+XPT_SetDataOffset(XPTState *state, uint32_t data_offset)
+{
+   state->data_offset = data_offset;
+}
+
+XPT_PUBLIC_API(bool)
+XPT_MakeCursor(XPTState *state, XPTPool pool, uint32_t len,
+               NotNull<XPTCursor*> cursor)
+{
+    cursor->state = state;
+    cursor->pool = pool;
+    cursor->bits = 0;
+    cursor->offset = state->next_cursor[pool];
+
+    if (!(CHECK_COUNT(cursor, len)))
+        return false;
+
+    /* this check should be in CHECK_CURSOR */
+    if (pool == XPT_DATA && !state->data_offset) {
+        fprintf(stderr, "no data offset for XPT_DATA cursor!\n");
+        return false;
+    }
+
+    state->next_cursor[pool] += len;
+
+    return true;
+}
+
+XPT_PUBLIC_API(bool)
+XPT_SeekTo(NotNull<XPTCursor*> cursor, uint32_t offset)
+{
+    /* XXX do some real checking and update len and stuff */
+    cursor->offset = offset;
+    return true;
+}
+
+XPT_PUBLIC_API(bool)
+XPT_SkipStringInline(NotNull<XPTCursor*> cursor)
+{
+    uint16_t length;
+    if (!XPT_Do16(cursor, &length))
+        return false;
+
+    uint8_t byte;
+    for (uint16_t i = 0; i < length; i++)
+        if (!XPT_Do8(cursor, &byte))
+            return false;
+
+    return true;
+}
+
+XPT_PUBLIC_API(bool)
+XPT_DoCString(XPTArena *arena, NotNull<XPTCursor*> cursor, char **identp,
+              bool ignore)
+{
+    uint32_t offset = 0;
+    if (!XPT_Do32(cursor, &offset))
+        return false;
+
+    if (!offset) {
+        *identp = NULL;
+        return true;
+    }
+
+    XPTCursor my_cursor;
+    my_cursor.pool = XPT_DATA;
+    my_cursor.offset = offset;
+    my_cursor.state = cursor->state;
+    char* start = &CURS_POINT(&my_cursor);
+
+    char* end = strchr(start, 0); /* find the end of the string */
+    if (!end) {
+        fprintf(stderr, "didn't find end of string on decode!\n");
+        return false;
+    }
+    int len = end - start;
+    XPT_ASSERT(len > 0);
+
+    if (!ignore) {
+        char *ident = (char*)XPT_CALLOC1(arena, len + 1u);
+        if (!ident)
+            return false;
+
+        memcpy(ident, start, (size_t)len);
+        ident[len] = 0;
+        *identp = ident;
+    }
+
+    return true;
+}
+
+/*
+ * IIDs are written in struct order, in the usual big-endian way.  From the
+ * typelib file spec:
+ *
+ *   "For example, this IID:
+ *     {00112233-4455-6677-8899-aabbccddeeff}
+ *   is converted to the 128-bit value
+ *     0x00112233445566778899aabbccddeeff
+ *   Note that the byte storage order corresponds to the layout of the nsIID
+ *   C-struct on a big-endian architecture."
+ *
+ * (http://www.mozilla.org/scriptable/typelib_file.html#iid)
+ */
+XPT_PUBLIC_API(bool)
+XPT_DoIID(NotNull<XPTCursor*> cursor, nsID *iidp)
+{
+    int i;
+
+    if (!XPT_Do32(cursor, &iidp->m0) ||
+        !XPT_Do16(cursor, &iidp->m1) ||
+        !XPT_Do16(cursor, &iidp->m2))
+        return false;
+
+    for (i = 0; i < 8; i++)
+        if (!XPT_Do8(cursor, (uint8_t *)&iidp->m3[i]))
+            return false;
+
+    return true;
+}
+
+// MSVC apparently cannot handle functions as template parameters very well,
+// so we need to use a macro approach here.
+
+#define XPT_DOINT(T, func, valuep)                \
+    do {                                          \
+        const size_t sz = sizeof(T);              \
+                                                  \
+        if (!CHECK_COUNT(cursor, sz)) {           \
+            return false;                         \
+        }                                         \
+                                                  \
+        *valuep = func(&CURS_POINT(cursor));      \
+        cursor->offset += sz;                     \
+        return true;                              \
+    } while(0)
+
+XPT_PUBLIC_API(bool)
+XPT_Do64(NotNull<XPTCursor*> cursor, int64_t *u64p)
+{
+    XPT_DOINT(int64_t, mozilla::BigEndian::readInt64, u64p);
+}
+
+/*
+ * When we're handling 32- or 16-bit quantities, we handle a byte at a time to
+ * avoid alignment issues.  Someone could come and optimize this to detect
+ * well-aligned cases and do a single store, if they cared.  I might care
+ * later.
+ */
+XPT_PUBLIC_API(bool)
+XPT_Do32(NotNull<XPTCursor*> cursor, uint32_t *u32p)
+{
+    XPT_DOINT(uint32_t, mozilla::BigEndian::readUint32, u32p);
+}
+
+XPT_PUBLIC_API(bool)
+XPT_Do16(NotNull<XPTCursor*> cursor, uint16_t *u16p)
+{
+    XPT_DOINT(uint16_t, mozilla::BigEndian::readUint16, u16p);
+}
+
+#undef XPT_DOINT
+
+XPT_PUBLIC_API(bool)
+XPT_Do8(NotNull<XPTCursor*> cursor, uint8_t *u8p)
+{
+    if (!CHECK_COUNT(cursor, 1))
+        return false;
+
+    *u8p = CURS_POINT(cursor);
+
+    cursor->offset++;
+
+    return true;
+}
+
+
diff --git a/xpcom/typelib/xpt/xpt_xdr.h b/xpcom/typelib/xpt/xpt_xdr.h
new file mode 100644
index 000000000..7bf23aa40
--- /dev/null
+++ b/xpcom/typelib/xpt/xpt_xdr.h
@@ -0,0 +1,86 @@
+/* -*- Mode: C; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 4 -*- */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+/*
+ * Basic APIs for streaming typelib structures from disk.
+ */
+
+#ifndef __xpt_xdr_h__
+#define __xpt_xdr_h__
+
+#include "xpt_struct.h"
+#include "mozilla/NotNull.h"
+
+using mozilla::NotNull;
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+typedef struct XPTState         XPTState;
+typedef struct XPTCursor        XPTCursor;
+
+extern XPT_PUBLIC_API(bool)
+XPT_SkipStringInline(NotNull<XPTCursor*> cursor);
+
+extern XPT_PUBLIC_API(bool)
+XPT_DoCString(XPTArena *arena, NotNull<XPTCursor*> cursor, char **strp,
+              bool ignore = false);
+
+extern XPT_PUBLIC_API(bool)
+XPT_DoIID(NotNull<XPTCursor*> cursor, nsID *iidp);
+
+extern XPT_PUBLIC_API(bool)
+XPT_Do64(NotNull<XPTCursor*> cursor, int64_t *u64p);
+
+extern XPT_PUBLIC_API(bool)
+XPT_Do32(NotNull<XPTCursor*> cursor, uint32_t *u32p);
+
+extern XPT_PUBLIC_API(bool)
+XPT_Do16(NotNull<XPTCursor*> cursor, uint16_t *u16p);
+
+extern XPT_PUBLIC_API(bool)
+XPT_Do8(NotNull<XPTCursor*> cursor, uint8_t *u8p);
+
+extern XPT_PUBLIC_API(bool)
+XPT_DoHeader(XPTArena *arena, NotNull<XPTCursor*> cursor, XPTHeader **headerp);
+
+typedef enum {
+    XPT_HEADER = 0,
+    XPT_DATA = 1
+} XPTPool;
+
+struct XPTState {
+    uint32_t         data_offset;
+    uint32_t         next_cursor[2];
+    char             *pool_data;
+    uint32_t         pool_allocated;
+};
+
+struct XPTCursor {
+    XPTState    *state;
+    XPTPool     pool;
+    uint32_t    offset;
+    uint8_t     bits;
+};
+
+extern XPT_PUBLIC_API(void)
+XPT_InitXDRState(XPTState* state, char* data, uint32_t len);
+
+extern XPT_PUBLIC_API(bool)
+XPT_MakeCursor(XPTState *state, XPTPool pool, uint32_t len,
+               NotNull<XPTCursor*> cursor);
+
+extern XPT_PUBLIC_API(bool)
+XPT_SeekTo(NotNull<XPTCursor*> cursor, uint32_t offset);
+
+extern XPT_PUBLIC_API(void)
+XPT_SetDataOffset(XPTState *state, uint32_t data_offset);
+
+#ifdef __cplusplus
+}
+#endif
+
+#endif /* __xpt_xdr_h__ */