Add m-esr52 at 52.6.0

1 files changed, 1799 insertions, 0 deletions

diff --git a/js/xpconnect/src/XPCConvert.cpp b/js/xpconnect/src/XPCConvert.cpp
new file mode 100644
index 000000000..37932b452
--- /dev/null
+++ b/js/xpconnect/src/XPCConvert.cpp
@@ -0,0 +1,1799 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 4 -*- */
+/* vim: set ts=8 sts=4 et sw=4 tw=99: */
+/* 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/. */
+
+/* Data conversion between native and JavaScript types. */
+
+#include "mozilla/ArrayUtils.h"
+#include "mozilla/Range.h"
+
+#include "xpcprivate.h"
+#include "nsIAtom.h"
+#include "nsWrapperCache.h"
+#include "nsJSUtils.h"
+#include "nsQueryObject.h"
+#include "WrapperFactory.h"
+
+#include "nsWrapperCacheInlines.h"
+
+#include "jsapi.h"
+#include "jsfriendapi.h"
+#include "js/CharacterEncoding.h"
+#include "jsprf.h"
+
+#include "mozilla/dom/BindingUtils.h"
+#include "mozilla/dom/DOMException.h"
+#include "mozilla/dom/PrimitiveConversions.h"
+#include "mozilla/dom/Promise.h"
+#include "mozilla/jsipc/CrossProcessObjectWrappers.h"
+
+using namespace xpc;
+using namespace mozilla;
+using namespace mozilla::dom;
+using namespace JS;
+
+//#define STRICT_CHECK_OF_UNICODE
+#ifdef STRICT_CHECK_OF_UNICODE
+#define ILLEGAL_RANGE(c) (0!=((c) & 0xFF80))
+#else // STRICT_CHECK_OF_UNICODE
+#define ILLEGAL_RANGE(c) (0!=((c) & 0xFF00))
+#endif // STRICT_CHECK_OF_UNICODE
+
+#define ILLEGAL_CHAR_RANGE(c) (0!=((c) & 0x80))
+
+/***********************************************************/
+
+// static
+bool
+XPCConvert::IsMethodReflectable(const XPTMethodDescriptor& info)
+{
+    if (XPT_MD_IS_NOTXPCOM(info.flags) || XPT_MD_IS_HIDDEN(info.flags))
+        return false;
+
+    for (int i = info.num_args-1; i >= 0; i--) {
+        const nsXPTParamInfo& param = info.params[i];
+        const nsXPTType& type = param.GetType();
+
+        // Reflected methods can't use native types. All native types end up
+        // getting tagged as void*, so this check is easy.
+        if (type.TagPart() == nsXPTType::T_VOID)
+            return false;
+    }
+    return true;
+}
+
+static JSObject*
+UnwrapNativeCPOW(nsISupports* wrapper)
+{
+    nsCOMPtr<nsIXPConnectWrappedJS> underware = do_QueryInterface(wrapper);
+    if (underware) {
+        JSObject* mainObj = underware->GetJSObject();
+        if (mainObj && mozilla::jsipc::IsWrappedCPOW(mainObj))
+            return mainObj;
+    }
+    return nullptr;
+}
+
+/***************************************************************************/
+
+// static
+bool
+XPCConvert::GetISupportsFromJSObject(JSObject* obj, nsISupports** iface)
+{
+    const JSClass* jsclass = js::GetObjectJSClass(obj);
+    MOZ_ASSERT(jsclass, "obj has no class");
+    if (jsclass &&
+        (jsclass->flags & JSCLASS_HAS_PRIVATE) &&
+        (jsclass->flags & JSCLASS_PRIVATE_IS_NSISUPPORTS)) {
+        *iface = (nsISupports*) xpc_GetJSPrivate(obj);
+        return true;
+    }
+    *iface = UnwrapDOMObjectToISupports(obj);
+    return !!*iface;
+}
+
+/***************************************************************************/
+
+// static
+bool
+XPCConvert::NativeData2JS(MutableHandleValue d, const void* s,
+                          const nsXPTType& type, const nsID* iid, nsresult* pErr)
+{
+    NS_PRECONDITION(s, "bad param");
+
+    AutoJSContext cx;
+    if (pErr)
+        *pErr = NS_ERROR_XPC_BAD_CONVERT_NATIVE;
+
+    switch (type.TagPart()) {
+    case nsXPTType::T_I8    :
+        d.setInt32(*static_cast<const int8_t*>(s));
+        return true;
+    case nsXPTType::T_I16   :
+        d.setInt32(*static_cast<const int16_t*>(s));
+        return true;
+    case nsXPTType::T_I32   :
+        d.setInt32(*static_cast<const int32_t*>(s));
+        return true;
+    case nsXPTType::T_I64   :
+        d.setNumber(static_cast<double>(*static_cast<const int64_t*>(s)));
+        return true;
+    case nsXPTType::T_U8    :
+        d.setInt32(*static_cast<const uint8_t*>(s));
+        return true;
+    case nsXPTType::T_U16   :
+        d.setInt32(*static_cast<const uint16_t*>(s));
+        return true;
+    case nsXPTType::T_U32   :
+        d.setNumber(*static_cast<const uint32_t*>(s));
+        return true;
+    case nsXPTType::T_U64   :
+        d.setNumber(static_cast<double>(*static_cast<const uint64_t*>(s)));
+        return true;
+    case nsXPTType::T_FLOAT :
+        d.setNumber(*static_cast<const float*>(s));
+        return true;
+    case nsXPTType::T_DOUBLE:
+        d.setNumber(*static_cast<const double*>(s));
+        return true;
+    case nsXPTType::T_BOOL  :
+        d.setBoolean(*static_cast<const bool*>(s));
+        return true;
+    case nsXPTType::T_CHAR  :
+    {
+        char p = *static_cast<const char*>(s);
+
+#ifdef STRICT_CHECK_OF_UNICODE
+        MOZ_ASSERT(! ILLEGAL_CHAR_RANGE(p) , "passing non ASCII data");
+#endif // STRICT_CHECK_OF_UNICODE
+
+        JSString* str = JS_NewStringCopyN(cx, &p, 1);
+        if (!str)
+            return false;
+
+        d.setString(str);
+        return true;
+    }
+    case nsXPTType::T_WCHAR :
+    {
+        char16_t p = *static_cast<const char16_t*>(s);
+
+        JSString* str = JS_NewUCStringCopyN(cx, &p, 1);
+        if (!str)
+            return false;
+
+        d.setString(str);
+        return true;
+    }
+
+    case nsXPTType::T_JSVAL :
+    {
+        d.set(*static_cast<const Value*>(s));
+        return JS_WrapValue(cx, d);
+    }
+
+    case nsXPTType::T_VOID:
+        XPC_LOG_ERROR(("XPCConvert::NativeData2JS : void* params not supported"));
+        return false;
+
+    case nsXPTType::T_IID:
+    {
+        nsID* iid2 = *static_cast<nsID* const*>(s);
+        if (!iid2) {
+            d.setNull();
+            return true;
+        }
+
+        RootedObject scope(cx, JS::CurrentGlobalOrNull(cx));
+        JSObject* obj = xpc_NewIDObject(cx, scope, *iid2);
+        if (!obj)
+            return false;
+
+        d.setObject(*obj);
+        return true;
+    }
+
+    case nsXPTType::T_ASTRING:
+        // Fall through to T_DOMSTRING case
+
+    case nsXPTType::T_DOMSTRING:
+    {
+        const nsAString* p = *static_cast<const nsAString* const*>(s);
+        if (!p || p->IsVoid()) {
+            d.setNull();
+            return true;
+        }
+
+        nsStringBuffer* buf;
+        if (!XPCStringConvert::ReadableToJSVal(cx, *p, &buf, d))
+            return false;
+        if (buf)
+            buf->AddRef();
+        return true;
+    }
+
+    case nsXPTType::T_CHAR_STR:
+    {
+        const char* p = *static_cast<const char* const*>(s);
+        if (!p) {
+            d.setNull();
+            return true;
+        }
+
+#ifdef STRICT_CHECK_OF_UNICODE
+        bool isAscii = true;
+        for (char* t = p; *t && isAscii; t++) {
+          if (ILLEGAL_CHAR_RANGE(*t))
+              isAscii = false;
+        }
+        MOZ_ASSERT(isAscii, "passing non ASCII data");
+#endif // STRICT_CHECK_OF_UNICODE
+
+        JSString* str = JS_NewStringCopyZ(cx, p);
+        if (!str)
+            return false;
+
+        d.setString(str);
+        return true;
+    }
+
+    case nsXPTType::T_WCHAR_STR:
+    {
+        const char16_t* p = *static_cast<const char16_t* const*>(s);
+        if (!p) {
+            d.setNull();
+            return true;
+        }
+
+        JSString* str = JS_NewUCStringCopyZ(cx, p);
+        if (!str)
+            return false;
+
+        d.setString(str);
+        return true;
+    }
+    case nsXPTType::T_UTF8STRING:
+    {
+        const nsACString* utf8String = *static_cast<const nsACString* const*>(s);
+
+        if (!utf8String || utf8String->IsVoid()) {
+            d.setNull();
+            return true;
+        }
+
+        if (utf8String->IsEmpty()) {
+            d.set(JS_GetEmptyStringValue(cx));
+            return true;
+        }
+
+        const uint32_t len = CalcUTF8ToUnicodeLength(*utf8String);
+        // The cString is not empty at this point, but the calculated
+        // UTF-16 length is zero, meaning no valid conversion exists.
+        if (!len)
+            return false;
+
+        const size_t buffer_size = (len + 1) * sizeof(char16_t);
+        char16_t* buffer =
+            static_cast<char16_t*>(JS_malloc(cx, buffer_size));
+        if (!buffer)
+            return false;
+
+        uint32_t copied;
+        if (!UTF8ToUnicodeBuffer(*utf8String, buffer, &copied) ||
+            len != copied) {
+            // Copy or conversion during copy failed. Did not copy the
+            // whole string.
+            JS_free(cx, buffer);
+            return false;
+        }
+
+        // JS_NewUCString takes ownership on success, i.e. a
+        // successful call will make it the responsiblity of the JS VM
+        // to free the buffer.
+        JSString* str = JS_NewUCString(cx, buffer, len);
+        if (!str) {
+            JS_free(cx, buffer);
+            return false;
+        }
+
+        d.setString(str);
+        return true;
+    }
+    case nsXPTType::T_CSTRING:
+    {
+        const nsACString* cString = *static_cast<const nsACString* const*>(s);
+
+        if (!cString || cString->IsVoid()) {
+            d.setNull();
+            return true;
+        }
+
+        // c-strings (binary blobs) are deliberately not converted from
+        // UTF-8 to UTF-16. T_UTF8Sting is for UTF-8 encoded strings
+        // with automatic conversion.
+        JSString* str = JS_NewStringCopyN(cx, cString->Data(),
+                                          cString->Length());
+        if (!str)
+            return false;
+
+        d.setString(str);
+        return true;
+    }
+
+    case nsXPTType::T_INTERFACE:
+    case nsXPTType::T_INTERFACE_IS:
+    {
+        nsISupports* iface = *static_cast<nsISupports* const*>(s);
+        if (!iface) {
+            d.setNull();
+            return true;
+        }
+
+        if (iid->Equals(NS_GET_IID(nsIVariant))) {
+            nsCOMPtr<nsIVariant> variant = do_QueryInterface(iface);
+            if (!variant)
+                return false;
+
+            return XPCVariant::VariantDataToJS(variant,
+                                               pErr, d);
+        }
+
+        xpcObjectHelper helper(iface);
+        return NativeInterface2JSObject(d, nullptr, helper, iid, true, pErr);
+    }
+
+    default:
+        NS_ERROR("bad type");
+        return false;
+    }
+    return true;
+}
+
+/***************************************************************************/
+
+#ifdef DEBUG
+static bool
+CheckChar16InCharRange(char16_t c)
+{
+    if (ILLEGAL_RANGE(c)) {
+        /* U+0080/U+0100 - U+FFFF data lost. */
+        static const size_t MSG_BUF_SIZE = 64;
+        char msg[MSG_BUF_SIZE];
+        snprintf(msg, MSG_BUF_SIZE, "char16_t out of char range; high bits of data lost: 0x%x", int(c));
+        NS_WARNING(msg);
+        return false;
+    }
+
+    return true;
+}
+
+template<typename CharT>
+static void
+CheckCharsInCharRange(const CharT* chars, size_t len)
+{
+    for (size_t i = 0; i < len; i++) {
+        if (!CheckChar16InCharRange(chars[i]))
+            break;
+    }
+}
+#endif
+
+template<typename T>
+bool ConvertToPrimitive(JSContext* cx, HandleValue v, T* retval)
+{
+    return ValueToPrimitive<T, eDefault>(cx, v, retval);
+}
+
+// static
+bool
+XPCConvert::JSData2Native(void* d, HandleValue s,
+                          const nsXPTType& type,
+                          const nsID* iid,
+                          nsresult* pErr)
+{
+    NS_PRECONDITION(d, "bad param");
+
+    AutoJSContext cx;
+    if (pErr)
+        *pErr = NS_ERROR_XPC_BAD_CONVERT_JS;
+
+    switch (type.TagPart()) {
+    case nsXPTType::T_I8     :
+        return ConvertToPrimitive(cx, s, static_cast<int8_t*>(d));
+    case nsXPTType::T_I16    :
+        return ConvertToPrimitive(cx, s, static_cast<int16_t*>(d));
+    case nsXPTType::T_I32    :
+        return ConvertToPrimitive(cx, s, static_cast<int32_t*>(d));
+    case nsXPTType::T_I64    :
+        return ConvertToPrimitive(cx, s, static_cast<int64_t*>(d));
+    case nsXPTType::T_U8     :
+        return ConvertToPrimitive(cx, s, static_cast<uint8_t*>(d));
+    case nsXPTType::T_U16    :
+        return ConvertToPrimitive(cx, s, static_cast<uint16_t*>(d));
+    case nsXPTType::T_U32    :
+        return ConvertToPrimitive(cx, s, static_cast<uint32_t*>(d));
+    case nsXPTType::T_U64    :
+        return ConvertToPrimitive(cx, s, static_cast<uint64_t*>(d));
+    case nsXPTType::T_FLOAT  :
+        return ConvertToPrimitive(cx, s, static_cast<float*>(d));
+    case nsXPTType::T_DOUBLE :
+        return ConvertToPrimitive(cx, s, static_cast<double*>(d));
+    case nsXPTType::T_BOOL   :
+        return ConvertToPrimitive(cx, s, static_cast<bool*>(d));
+    case nsXPTType::T_CHAR   :
+    {
+        JSString* str = ToString(cx, s);
+        if (!str) {
+            return false;
+        }
+
+        char16_t ch;
+        if (JS_GetStringLength(str) == 0) {
+            ch = 0;
+        } else {
+            if (!JS_GetStringCharAt(cx, str, 0, &ch))
+                return false;
+        }
+#ifdef DEBUG
+        CheckChar16InCharRange(ch);
+#endif
+        *((char*)d) = char(ch);
+        break;
+    }
+    case nsXPTType::T_WCHAR  :
+    {
+        JSString* str;
+        if (!(str = ToString(cx, s))) {
+            return false;
+        }
+        size_t length = JS_GetStringLength(str);
+        if (length == 0) {
+            *((uint16_t*)d) = 0;
+            break;
+        }
+
+        char16_t ch;
+        if (!JS_GetStringCharAt(cx, str, 0, &ch))
+            return false;
+
+        *((uint16_t*)d) = uint16_t(ch);
+        break;
+    }
+    case nsXPTType::T_JSVAL :
+        *((Value*)d) = s;
+        break;
+    case nsXPTType::T_VOID:
+        XPC_LOG_ERROR(("XPCConvert::JSData2Native : void* params not supported"));
+        NS_ERROR("void* params not supported");
+        return false;
+    case nsXPTType::T_IID:
+    {
+        const nsID* pid = nullptr;
+
+        // There's no good reason to pass a null IID.
+        if (s.isNullOrUndefined()) {
+            if (pErr)
+                *pErr = NS_ERROR_XPC_BAD_CONVERT_JS;
+            return false;
+        }
+
+        if (!s.isObject() ||
+            (!(pid = xpc_JSObjectToID(cx, &s.toObject()))) ||
+            (!(pid = (const nsID*) nsMemory::Clone(pid, sizeof(nsID))))) {
+            return false;
+        }
+        *((const nsID**)d) = pid;
+        return true;
+    }
+
+    case nsXPTType::T_ASTRING:
+    {
+        if (s.isUndefined()) {
+            (**((nsAString**)d)).SetIsVoid(true);
+            return true;
+        }
+        MOZ_FALLTHROUGH;
+    }
+    case nsXPTType::T_DOMSTRING:
+    {
+        if (s.isNull()) {
+            (**((nsAString**)d)).SetIsVoid(true);
+            return true;
+        }
+        size_t length = 0;
+        JSString* str = nullptr;
+        if (!s.isUndefined()) {
+            str = ToString(cx, s);
+            if (!str)
+                return false;
+
+            length = JS_GetStringLength(str);
+            if (!length) {
+                (**((nsAString**)d)).Truncate();
+                return true;
+            }
+        }
+
+        nsAString* ws = *((nsAString**)d);
+
+        if (!str) {
+            ws->AssignLiteral(u"undefined");
+        } else if (XPCStringConvert::IsDOMString(str)) {
+            // The characters represent an existing nsStringBuffer that
+            // was shared by XPCStringConvert::ReadableToJSVal.
+            const char16_t* chars = JS_GetTwoByteExternalStringChars(str);
+            if (chars[length] == '\0') {
+                // Safe to share the buffer.
+                nsStringBuffer::FromData((void*)chars)->ToString(length, *ws);
+            } else {
+                // We have to copy to ensure null-termination.
+                ws->Assign(chars, length);
+            }
+        } else if (XPCStringConvert::IsLiteral(str)) {
+            // The characters represent a literal char16_t string constant
+            // compiled into libxul, such as the string "undefined" above.
+            const char16_t* chars = JS_GetTwoByteExternalStringChars(str);
+            ws->AssignLiteral(chars, length);
+        } else {
+            if (!AssignJSString(cx, *ws, str))
+                return false;
+        }
+        return true;
+    }
+
+    case nsXPTType::T_CHAR_STR:
+    {
+        if (s.isUndefined() || s.isNull()) {
+            *((char**)d) = nullptr;
+            return true;
+        }
+
+        JSString* str = ToString(cx, s);
+        if (!str) {
+            return false;
+        }
+#ifdef DEBUG
+        if (JS_StringHasLatin1Chars(str)) {
+            size_t len;
+            AutoCheckCannotGC nogc;
+            const Latin1Char* chars = JS_GetLatin1StringCharsAndLength(cx, nogc, str, &len);
+            if (chars)
+                CheckCharsInCharRange(chars, len);
+        } else {
+            size_t len;
+            AutoCheckCannotGC nogc;
+            const char16_t* chars = JS_GetTwoByteStringCharsAndLength(cx, nogc, str, &len);
+            if (chars)
+                CheckCharsInCharRange(chars, len);
+        }
+#endif // DEBUG
+        size_t length = JS_GetStringEncodingLength(cx, str);
+        if (length == size_t(-1)) {
+            return false;
+        }
+        char* buffer = static_cast<char*>(moz_xmalloc(length + 1));
+        if (!buffer) {
+            return false;
+        }
+        JS_EncodeStringToBuffer(cx, str, buffer, length);
+        buffer[length] = '\0';
+        *((void**)d) = buffer;
+        return true;
+    }
+
+    case nsXPTType::T_WCHAR_STR:
+    {
+        JSString* str;
+
+        if (s.isUndefined() || s.isNull()) {
+            *((char16_t**)d) = nullptr;
+            return true;
+        }
+
+        if (!(str = ToString(cx, s))) {
+            return false;
+        }
+        int len = JS_GetStringLength(str);
+        int byte_len = (len+1)*sizeof(char16_t);
+        if (!(*((void**)d) = moz_xmalloc(byte_len))) {
+            // XXX should report error
+            return false;
+        }
+        mozilla::Range<char16_t> destChars(*((char16_t**)d), len + 1);
+        if (!JS_CopyStringChars(cx, destChars, str))
+            return false;
+        destChars[len] = 0;
+
+        return true;
+    }
+
+    case nsXPTType::T_UTF8STRING:
+    {
+        if (s.isNull() || s.isUndefined()) {
+            nsCString* rs = *((nsCString**)d);
+            rs->SetIsVoid(true);
+            return true;
+        }
+
+        // The JS val is neither null nor void...
+        JSString* str = ToString(cx, s);
+        if (!str)
+            return false;
+
+        size_t length = JS_GetStringLength(str);
+        if (!length) {
+            nsCString* rs = *((nsCString**)d);
+            rs->Truncate();
+            return true;
+        }
+
+        JSFlatString* flat = JS_FlattenString(cx, str);
+        if (!flat)
+            return false;
+
+        size_t utf8Length = JS::GetDeflatedUTF8StringLength(flat);
+        nsACString* rs = *((nsACString**)d);
+        rs->SetLength(utf8Length);
+
+        JS::DeflateStringToUTF8Buffer(flat, mozilla::RangedPtr<char>(rs->BeginWriting(), utf8Length));
+
+        return true;
+    }
+
+    case nsXPTType::T_CSTRING:
+    {
+        if (s.isNull() || s.isUndefined()) {
+            nsACString* rs = *((nsACString**)d);
+            rs->SetIsVoid(true);
+            return true;
+        }
+
+        // The JS val is neither null nor void...
+        JSString* str = ToString(cx, s);
+        if (!str) {
+            return false;
+        }
+
+        size_t length = JS_GetStringEncodingLength(cx, str);
+        if (length == size_t(-1)) {
+            return false;
+        }
+
+        if (!length) {
+            nsCString* rs = *((nsCString**)d);
+            rs->Truncate();
+            return true;
+        }
+
+        nsACString* rs = *((nsACString**)d);
+        rs->SetLength(uint32_t(length));
+        if (rs->Length() != uint32_t(length)) {
+            return false;
+        }
+        JS_EncodeStringToBuffer(cx, str, rs->BeginWriting(), length);
+
+        return true;
+    }
+
+    case nsXPTType::T_INTERFACE:
+    case nsXPTType::T_INTERFACE_IS:
+    {
+        MOZ_ASSERT(iid,"can't do interface conversions without iid");
+
+        if (iid->Equals(NS_GET_IID(nsIVariant))) {
+            nsCOMPtr<nsIVariant> variant = XPCVariant::newVariant(cx, s);
+            if (!variant)
+                return false;
+
+            variant.forget(static_cast<nsISupports**>(d));
+            return true;
+        } else if (iid->Equals(NS_GET_IID(nsIAtom)) && s.isString()) {
+            // We're trying to pass a string as an nsIAtom.  Let's atomize!
+            JSString* str = s.toString();
+            nsAutoJSString autoStr;
+            if (!autoStr.init(cx, str)) {
+                if (pErr)
+                    *pErr = NS_ERROR_XPC_BAD_CONVERT_JS_NULL_REF;
+                return false;
+            }
+            nsCOMPtr<nsIAtom> atom = NS_Atomize(autoStr);
+            atom.forget((nsISupports**)d);
+            return true;
+        }
+        //else ...
+
+        if (s.isNullOrUndefined()) {
+            *((nsISupports**)d) = nullptr;
+            return true;
+        }
+
+        // only wrap JSObjects
+        if (!s.isObject()) {
+            if (pErr && s.isInt32() && 0 == s.toInt32())
+                *pErr = NS_ERROR_XPC_BAD_CONVERT_JS_ZERO_ISNOT_NULL;
+            return false;
+        }
+
+        RootedObject src(cx, &s.toObject());
+        return JSObject2NativeInterface((void**)d, src, iid, nullptr, pErr);
+    }
+    default:
+        NS_ERROR("bad type");
+        return false;
+    }
+    return true;
+}
+
+static inline bool
+CreateHolderIfNeeded(HandleObject obj, MutableHandleValue d,
+                     nsIXPConnectJSObjectHolder** dest)
+{
+    if (dest) {
+        if (!obj)
+            return false;
+        RefPtr<XPCJSObjectHolder> objHolder = new XPCJSObjectHolder(obj);
+        objHolder.forget(dest);
+    }
+
+    d.setObjectOrNull(obj);
+
+    return true;
+}
+
+/***************************************************************************/
+// static
+bool
+XPCConvert::NativeInterface2JSObject(MutableHandleValue d,
+                                     nsIXPConnectJSObjectHolder** dest,
+                                     xpcObjectHelper& aHelper,
+                                     const nsID* iid,
+                                     bool allowNativeWrapper,
+                                     nsresult* pErr)
+{
+    if (!iid)
+        iid = &NS_GET_IID(nsISupports);
+
+    d.setNull();
+    if (dest)
+        *dest = nullptr;
+    if (!aHelper.Object())
+        return true;
+    if (pErr)
+        *pErr = NS_ERROR_XPC_BAD_CONVERT_NATIVE;
+
+    // We used to have code here that unwrapped and simply exposed the
+    // underlying JSObject. That caused anomolies when JSComponents were
+    // accessed from other JS code - they didn't act like other xpconnect
+    // wrapped components. So, instead, we create "double wrapped" objects
+    // (that means an XPCWrappedNative around an nsXPCWrappedJS). This isn't
+    // optimal -- we could detect this and roll the functionality into a
+    // single wrapper, but the current solution is good enough for now.
+    AutoJSContext cx;
+    XPCWrappedNativeScope* xpcscope = ObjectScope(JS::CurrentGlobalOrNull(cx));
+    if (!xpcscope)
+        return false;
+
+    // First, see if this object supports the wrapper cache.
+    // Note: If |cache->IsDOMBinding()| is true, then it means that the object
+    // implementing it doesn't want a wrapped native as its JS Object, but
+    // instead it provides its own proxy object. In that case, the object
+    // to use is found as cache->GetWrapper(). If that is null, then the
+    // object will create (and fill the cache) from its WrapObject call.
+    nsWrapperCache* cache = aHelper.GetWrapperCache();
+
+    RootedObject flat(cx, cache ? cache->GetWrapper() : nullptr);
+    if (!flat && cache && cache->IsDOMBinding()) {
+        RootedObject global(cx, xpcscope->GetGlobalJSObject());
+        js::AssertSameCompartment(cx, global);
+        flat = cache->WrapObject(cx, nullptr);
+        if (!flat)
+            return false;
+    }
+    if (flat) {
+        if (allowNativeWrapper && !JS_WrapObject(cx, &flat))
+            return false;
+        return CreateHolderIfNeeded(flat, d, dest);
+    }
+
+#ifdef SPIDERMONKEY_PROMISE
+    if (iid->Equals(NS_GET_IID(nsISupports))) {
+        // Check for a Promise being returned via nsISupports.  In that
+        // situation, we want to dig out its underlying JS object and return
+        // that.
+        RefPtr<Promise> promise = do_QueryObject(aHelper.Object());
+        if (promise) {
+            flat = promise->PromiseObj();
+            if (!JS_WrapObject(cx, &flat))
+                return false;
+            return CreateHolderIfNeeded(flat, d, dest);
+        }
+    }
+#endif // SPIDERMONKEY_PROMISE
+
+    // Don't double wrap CPOWs. This is a temporary measure for compatibility
+    // with objects that don't provide necessary QIs (such as objects under
+    // the new DOM bindings). We expect the other side of the CPOW to have
+    // the appropriate wrappers in place.
+    RootedObject cpow(cx, UnwrapNativeCPOW(aHelper.Object()));
+    if (cpow) {
+        if (!JS_WrapObject(cx, &cpow))
+            return false;
+        d.setObject(*cpow);
+        return true;
+    }
+
+    // Go ahead and create an XPCWrappedNative for this object.
+    RefPtr<XPCNativeInterface> iface =
+        XPCNativeInterface::GetNewOrUsed(iid);
+    if (!iface)
+        return false;
+
+    RefPtr<XPCWrappedNative> wrapper;
+    nsresult rv = XPCWrappedNative::GetNewOrUsed(aHelper, xpcscope, iface,
+                                                 getter_AddRefs(wrapper));
+    if (NS_FAILED(rv) && pErr)
+        *pErr = rv;
+
+    // If creating the wrapped native failed, then return early.
+    if (NS_FAILED(rv) || !wrapper)
+        return false;
+
+    // If we're not creating security wrappers, we can return the
+    // XPCWrappedNative as-is here.
+    flat = wrapper->GetFlatJSObject();
+    if (!allowNativeWrapper) {
+        d.setObjectOrNull(flat);
+        if (dest)
+            wrapper.forget(dest);
+        if (pErr)
+            *pErr = NS_OK;
+        return true;
+    }
+
+    // The call to wrap here handles both cross-compartment and same-compartment
+    // security wrappers.
+    RootedObject original(cx, flat);
+    if (!JS_WrapObject(cx, &flat))
+        return false;
+
+    d.setObjectOrNull(flat);
+
+    if (dest) {
+        // The wrapper still holds the original flat object.
+        if (flat == original) {
+            wrapper.forget(dest);
+        } else {
+            if (!flat)
+                return false;
+            RefPtr<XPCJSObjectHolder> objHolder = new XPCJSObjectHolder(flat);
+            objHolder.forget(dest);
+        }
+    }
+
+    if (pErr)
+        *pErr = NS_OK;
+
+    return true;
+}
+
+/***************************************************************************/
+
+// static
+bool
+XPCConvert::JSObject2NativeInterface(void** dest, HandleObject src,
+                                     const nsID* iid,
+                                     nsISupports* aOuter,
+                                     nsresult* pErr)
+{
+    MOZ_ASSERT(dest, "bad param");
+    MOZ_ASSERT(src, "bad param");
+    MOZ_ASSERT(iid, "bad param");
+
+    AutoJSContext cx;
+    JSAutoCompartment ac(cx, src);
+
+    *dest = nullptr;
+     if (pErr)
+        *pErr = NS_ERROR_XPC_BAD_CONVERT_JS;
+
+    nsISupports* iface;
+
+    if (!aOuter) {
+        // Note that if we have a non-null aOuter then it means that we are
+        // forcing the creation of a wrapper even if the object *is* a
+        // wrappedNative or other wise has 'nsISupportness'.
+        // This allows wrapJSAggregatedToNative to work.
+
+        // If we're looking at a security wrapper, see now if we're allowed to
+        // pass it to C++. If we are, then fall through to the code below. If
+        // we aren't, throw an exception eagerly.
+        //
+        // NB: It's very important that we _don't_ unwrap in the aOuter case,
+        // because the caller may explicitly want to create the XPCWrappedJS
+        // around a security wrapper. XBL does this with Xrays from the XBL
+        // scope - see nsBindingManager::GetBindingImplementation.
+        //
+        // It's also very important that "inner" be rooted here.
+        RootedObject inner(cx,
+                           js::CheckedUnwrap(src,
+                                             /* stopAtWindowProxy = */ false));
+        if (!inner) {
+            if (pErr)
+                *pErr = NS_ERROR_XPC_SECURITY_MANAGER_VETO;
+            return false;
+        }
+
+        // Is this really a native xpcom object with a wrapper?
+        XPCWrappedNative* wrappedNative = nullptr;
+        if (IS_WN_REFLECTOR(inner))
+            wrappedNative = XPCWrappedNative::Get(inner);
+        if (wrappedNative) {
+            iface = wrappedNative->GetIdentityObject();
+            return NS_SUCCEEDED(iface->QueryInterface(*iid, dest));
+        }
+        // else...
+
+        // Deal with slim wrappers here.
+        if (GetISupportsFromJSObject(inner ? inner : src, &iface)) {
+            if (iface && NS_SUCCEEDED(iface->QueryInterface(*iid, dest))) {
+                return true;
+            }
+
+            // If that failed, and iid is for mozIDOMWindowProxy, we actually
+            // want the outer!
+            if (iid->Equals(NS_GET_IID(mozIDOMWindowProxy))) {
+                if (nsCOMPtr<mozIDOMWindow> inner = do_QueryInterface(iface)) {
+                    iface = nsPIDOMWindowInner::From(inner)->GetOuterWindow();
+                    return NS_SUCCEEDED(iface->QueryInterface(*iid, dest));
+                }
+            }
+
+            return false;
+        }
+
+#ifdef SPIDERMONKEY_PROMISE
+        // Deal with Promises being passed as nsISupports.  In that situation we
+        // want to create a dom::Promise and use that.
+        if (iid->Equals(NS_GET_IID(nsISupports))) {
+            RootedObject innerObj(cx, inner);
+            if (IsPromiseObject(innerObj)) {
+                nsIGlobalObject* glob = NativeGlobal(innerObj);
+                RefPtr<Promise> p = Promise::CreateFromExisting(glob, innerObj);
+                return p && NS_SUCCEEDED(p->QueryInterface(*iid, dest));
+            }
+        }
+#endif // SPIDERMONKEY_PROMISE
+    }
+
+    RefPtr<nsXPCWrappedJS> wrapper;
+    nsresult rv = nsXPCWrappedJS::GetNewOrUsed(src, *iid, getter_AddRefs(wrapper));
+    if (pErr)
+        *pErr = rv;
+
+    if (NS_FAILED(rv) || !wrapper)
+        return false;
+
+    // If the caller wanted to aggregate this JS object to a native,
+    // attach it to the wrapper. Note that we allow a maximum of one
+    // aggregated native for a given XPCWrappedJS.
+    if (aOuter)
+        wrapper->SetAggregatedNativeObject(aOuter);
+
+    // We need to go through the QueryInterface logic to make this return
+    // the right thing for the various 'special' interfaces; e.g.
+    // nsIPropertyBag. We must use AggregatedQueryInterface in cases where
+    // there is an outer to avoid nasty recursion.
+    rv = aOuter ? wrapper->AggregatedQueryInterface(*iid, dest) :
+        wrapper->QueryInterface(*iid, dest);
+    if (pErr)
+        *pErr = rv;
+    return NS_SUCCEEDED(rv);
+}
+
+/***************************************************************************/
+/***************************************************************************/
+
+// static
+nsresult
+XPCConvert::ConstructException(nsresult rv, const char* message,
+                               const char* ifaceName, const char* methodName,
+                               nsISupports* data,
+                               nsIException** exceptn,
+                               JSContext* cx,
+                               Value* jsExceptionPtr)
+{
+    MOZ_ASSERT(!cx == !jsExceptionPtr, "Expected cx and jsExceptionPtr to cooccur.");
+
+    static const char format[] = "\'%s\' when calling method: [%s::%s]";
+    const char * msg = message;
+    nsXPIDLString xmsg;
+    nsAutoCString sxmsg;
+
+    nsCOMPtr<nsIScriptError> errorObject = do_QueryInterface(data);
+    if (errorObject) {
+        if (NS_SUCCEEDED(errorObject->GetMessageMoz(getter_Copies(xmsg)))) {
+            CopyUTF16toUTF8(xmsg, sxmsg);
+            msg = sxmsg.get();
+        }
+    }
+    if (!msg)
+        if (!nsXPCException::NameAndFormatForNSResult(rv, nullptr, &msg) || ! msg)
+            msg = "<error>";
+
+    nsCString msgStr(msg);
+    if (ifaceName && methodName)
+        msgStr.AppendPrintf(format, msg, ifaceName, methodName);
+
+    RefPtr<Exception> e = new Exception(msgStr, rv, EmptyCString(), nullptr, data);
+
+    if (cx && jsExceptionPtr) {
+        e->StowJSVal(*jsExceptionPtr);
+    }
+
+    e.forget(exceptn);
+    return NS_OK;
+}
+
+/********************************/
+
+class MOZ_STACK_CLASS AutoExceptionRestorer
+{
+public:
+    AutoExceptionRestorer(JSContext* cx, const Value& v)
+        : mContext(cx), tvr(cx, v)
+    {
+        JS_ClearPendingException(mContext);
+    }
+
+    ~AutoExceptionRestorer()
+    {
+        JS_SetPendingException(mContext, tvr);
+    }
+
+private:
+    JSContext * const mContext;
+    RootedValue tvr;
+};
+
+static nsresult
+JSErrorToXPCException(const char* toStringResult,
+                      const char* ifaceName,
+                      const char* methodName,
+                      const JSErrorReport* report,
+                      nsIException** exceptn)
+{
+    AutoJSContext cx;
+    nsresult rv = NS_ERROR_FAILURE;
+    RefPtr<nsScriptError> data;
+    if (report) {
+        nsAutoString bestMessage;
+        if (report && report->message()) {
+            CopyUTF8toUTF16(report->message().c_str(), bestMessage);
+        } else if (toStringResult) {
+            CopyUTF8toUTF16(toStringResult, bestMessage);
+        } else {
+            bestMessage.AssignLiteral("JavaScript Error");
+        }
+
+        const char16_t* linebuf = report->linebuf();
+
+        data = new nsScriptError();
+        data->InitWithWindowID(
+            bestMessage,
+            NS_ConvertASCIItoUTF16(report->filename),
+            linebuf ? nsDependentString(linebuf, report->linebufLength()) : EmptyString(),
+            report->lineno,
+            report->tokenOffset(), report->flags,
+            NS_LITERAL_CSTRING("XPConnect JavaScript"),
+            nsJSUtils::GetCurrentlyRunningCodeInnerWindowID(cx));
+    }
+
+    if (data) {
+        nsAutoCString formattedMsg;
+        data->ToString(formattedMsg);
+
+        rv = XPCConvert::ConstructException(NS_ERROR_XPC_JAVASCRIPT_ERROR_WITH_DETAILS,
+                                            formattedMsg.get(), ifaceName,
+                                            methodName,
+                                            static_cast<nsIScriptError*>(data.get()),
+                                            exceptn, nullptr, nullptr);
+    } else {
+        rv = XPCConvert::ConstructException(NS_ERROR_XPC_JAVASCRIPT_ERROR,
+                                            nullptr, ifaceName, methodName,
+                                            nullptr, exceptn, nullptr, nullptr);
+    }
+    return rv;
+}
+
+// static
+nsresult
+XPCConvert::JSValToXPCException(MutableHandleValue s,
+                                const char* ifaceName,
+                                const char* methodName,
+                                nsIException** exceptn)
+{
+    AutoJSContext cx;
+    AutoExceptionRestorer aer(cx, s);
+
+    if (!s.isPrimitive()) {
+        // we have a JSObject
+        RootedObject obj(cx, s.toObjectOrNull());
+
+        if (!obj) {
+            NS_ERROR("when is an object not an object?");
+            return NS_ERROR_FAILURE;
+        }
+
+        // is this really a native xpcom object with a wrapper?
+        JSObject* unwrapped = js::CheckedUnwrap(obj, /* stopAtWindowProxy = */ false);
+        if (!unwrapped)
+            return NS_ERROR_XPC_SECURITY_MANAGER_VETO;
+        if (nsCOMPtr<nsISupports> supports = UnwrapReflectorToISupports(unwrapped)) {
+            nsCOMPtr<nsIException> iface = do_QueryInterface(supports);
+            if (iface) {
+                // just pass through the exception (with extra ref and all)
+                nsCOMPtr<nsIException> temp = iface;
+                temp.forget(exceptn);
+                return NS_OK;
+            } else {
+                // it is a wrapped native, but not an exception!
+                return ConstructException(NS_ERROR_XPC_JS_THREW_NATIVE_OBJECT,
+                                          nullptr, ifaceName, methodName, supports,
+                                          exceptn, nullptr, nullptr);
+            }
+        } else {
+            // It is a JSObject, but not a wrapped native...
+
+            // If it is an engine Error with an error report then let's
+            // extract the report and build an xpcexception from that
+            const JSErrorReport* report;
+            if (nullptr != (report = JS_ErrorFromException(cx, obj))) {
+                JSAutoByteString toStringResult;
+                RootedString str(cx, ToString(cx, s));
+                if (str)
+                    toStringResult.encodeUtf8(cx, str);
+                return JSErrorToXPCException(toStringResult.ptr(), ifaceName,
+                                             methodName, report, exceptn);
+            }
+
+            // XXX we should do a check against 'js_ErrorClass' here and
+            // do the right thing - even though it has no JSErrorReport,
+            // The fact that it is a JSError exceptions means we can extract
+            // particular info and our 'result' should reflect that.
+
+            // otherwise we'll just try to convert it to a string
+
+            JSString* str = ToString(cx, s);
+            if (!str)
+                return NS_ERROR_FAILURE;
+
+            JSAutoByteString strBytes(cx, str);
+            if (!strBytes)
+                return NS_ERROR_FAILURE;
+
+            return ConstructException(NS_ERROR_XPC_JS_THREW_JS_OBJECT,
+                                      strBytes.ptr(), ifaceName, methodName,
+                                      nullptr, exceptn, cx, s.address());
+        }
+    }
+
+    if (s.isUndefined() || s.isNull()) {
+        return ConstructException(NS_ERROR_XPC_JS_THREW_NULL,
+                                  nullptr, ifaceName, methodName, nullptr,
+                                  exceptn, cx, s.address());
+    }
+
+    if (s.isNumber()) {
+        // lets see if it looks like an nsresult
+        nsresult rv;
+        double number;
+        bool isResult = false;
+
+        if (s.isInt32()) {
+            rv = (nsresult) s.toInt32();
+            if (NS_FAILED(rv))
+                isResult = true;
+            else
+                number = (double) s.toInt32();
+        } else {
+            number = s.toDouble();
+            if (number > 0.0 &&
+                number < (double)0xffffffff &&
+                0.0 == fmod(number,1)) {
+                // Visual Studio 9 doesn't allow casting directly from a
+                // double to an enumeration type, contrary to 5.2.9(10) of
+                // C++11, so add an intermediate cast.
+                rv = (nsresult)(uint32_t) number;
+                if (NS_FAILED(rv))
+                    isResult = true;
+            }
+        }
+
+        if (isResult)
+            return ConstructException(rv, nullptr, ifaceName, methodName,
+                                      nullptr, exceptn, cx, s.address());
+        else {
+            // XXX all this nsISupportsDouble code seems a little redundant
+            // now that we're storing the Value in the exception...
+            nsCOMPtr<nsISupportsDouble> data;
+            nsCOMPtr<nsIComponentManager> cm;
+            if (NS_FAILED(NS_GetComponentManager(getter_AddRefs(cm))) || !cm ||
+                NS_FAILED(cm->CreateInstanceByContractID(NS_SUPPORTS_DOUBLE_CONTRACTID,
+                                                         nullptr,
+                                                         NS_GET_IID(nsISupportsDouble),
+                                                         getter_AddRefs(data))))
+                return NS_ERROR_FAILURE;
+            data->SetData(number);
+            rv = ConstructException(NS_ERROR_XPC_JS_THREW_NUMBER, nullptr,
+                                    ifaceName, methodName, data, exceptn, cx, s.address());
+            return rv;
+        }
+    }
+
+    // otherwise we'll just try to convert it to a string
+    // Note: e.g., bools get converted to JSStrings by this code.
+
+    JSString* str = ToString(cx, s);
+    if (str) {
+        JSAutoByteString strBytes(cx, str);
+        if (!!strBytes) {
+            return ConstructException(NS_ERROR_XPC_JS_THREW_STRING,
+                                      strBytes.ptr(), ifaceName, methodName,
+                                      nullptr, exceptn, cx, s.address());
+        }
+    }
+    return NS_ERROR_FAILURE;
+}
+
+/***************************************************************************/
+
+// array fun...
+
+#ifdef POPULATE
+#undef POPULATE
+#endif
+
+// static
+bool
+XPCConvert::NativeArray2JS(MutableHandleValue d, const void** s,
+                           const nsXPTType& type, const nsID* iid,
+                           uint32_t count, nsresult* pErr)
+{
+    NS_PRECONDITION(s, "bad param");
+
+    AutoJSContext cx;
+
+    // XXX add support for putting chars in a string rather than an array
+
+    // XXX add support to indicate *which* array element was not convertable
+
+    RootedObject array(cx, JS_NewArrayObject(cx, count));
+    if (!array)
+        return false;
+
+    if (pErr)
+        *pErr = NS_ERROR_XPC_BAD_CONVERT_NATIVE;
+
+    uint32_t i;
+    RootedValue current(cx, JS::NullValue());
+
+#define POPULATE(_t)                                                                    \
+    PR_BEGIN_MACRO                                                                      \
+        for (i = 0; i < count; i++) {                                                   \
+            if (!NativeData2JS(&current, ((_t*)*s)+i, type, iid, pErr) ||               \
+                !JS_DefineElement(cx, array, i, current, JSPROP_ENUMERATE))             \
+                return false;                                                           \
+        }                                                                               \
+    PR_END_MACRO
+
+    // XXX check IsPtr - esp. to handle array of nsID (as opposed to nsID*)
+
+    switch (type.TagPart()) {
+    case nsXPTType::T_I8            : POPULATE(int8_t);         break;
+    case nsXPTType::T_I16           : POPULATE(int16_t);        break;
+    case nsXPTType::T_I32           : POPULATE(int32_t);        break;
+    case nsXPTType::T_I64           : POPULATE(int64_t);        break;
+    case nsXPTType::T_U8            : POPULATE(uint8_t);        break;
+    case nsXPTType::T_U16           : POPULATE(uint16_t);       break;
+    case nsXPTType::T_U32           : POPULATE(uint32_t);       break;
+    case nsXPTType::T_U64           : POPULATE(uint64_t);       break;
+    case nsXPTType::T_FLOAT         : POPULATE(float);          break;
+    case nsXPTType::T_DOUBLE        : POPULATE(double);         break;
+    case nsXPTType::T_BOOL          : POPULATE(bool);           break;
+    case nsXPTType::T_CHAR          : POPULATE(char);           break;
+    case nsXPTType::T_WCHAR         : POPULATE(char16_t);       break;
+    case nsXPTType::T_VOID          : NS_ERROR("bad type");     return false;
+    case nsXPTType::T_IID           : POPULATE(nsID*);          break;
+    case nsXPTType::T_DOMSTRING     : NS_ERROR("bad type");     return false;
+    case nsXPTType::T_CHAR_STR      : POPULATE(char*);          break;
+    case nsXPTType::T_WCHAR_STR     : POPULATE(char16_t*);      break;
+    case nsXPTType::T_INTERFACE     : POPULATE(nsISupports*);   break;
+    case nsXPTType::T_INTERFACE_IS  : POPULATE(nsISupports*);   break;
+    case nsXPTType::T_UTF8STRING    : NS_ERROR("bad type");     return false;
+    case nsXPTType::T_CSTRING       : NS_ERROR("bad type");     return false;
+    case nsXPTType::T_ASTRING       : NS_ERROR("bad type");     return false;
+    default                         : NS_ERROR("bad type");     return false;
+    }
+
+    if (pErr)
+        *pErr = NS_OK;
+    d.setObject(*array);
+    return true;
+
+#undef POPULATE
+}
+
+
+
+// Check that the tag part of the type matches the type
+// of the array. If the check succeeds, check that the size
+// of the output does not exceed UINT32_MAX bytes. Allocate
+// the memory and copy the elements by memcpy.
+static bool
+CheckTargetAndPopulate(const nsXPTType& type,
+                       uint8_t requiredType,
+                       size_t typeSize,
+                       uint32_t count,
+                       JSObject* tArr,
+                       void** output,
+                       nsresult* pErr)
+{
+    // Check that the element type expected by the interface matches
+    // the type of the elements in the typed array exactly, including
+    // signedness.
+    if (type.TagPart() != requiredType) {
+        if (pErr)
+            *pErr = NS_ERROR_XPC_BAD_CONVERT_JS;
+
+        return false;
+    }
+
+    // Calulate the maximum number of elements that can fit in
+    // UINT32_MAX bytes.
+    size_t max = UINT32_MAX / typeSize;
+
+    // This could overflow on 32-bit systems so check max first.
+    size_t byteSize = count * typeSize;
+    if (count > max || !(*output = moz_xmalloc(byteSize))) {
+        if (pErr)
+            *pErr = NS_ERROR_OUT_OF_MEMORY;
+
+        return false;
+    }
+
+    JS::AutoCheckCannotGC nogc;
+    bool isShared;
+    void* buf = JS_GetArrayBufferViewData(tArr, &isShared, nogc);
+
+    // Require opting in to shared memory - a future project.
+    if (isShared) {
+        if (pErr)
+            *pErr = NS_ERROR_XPC_BAD_CONVERT_JS;
+
+        return false;
+    }
+
+    memcpy(*output, buf, byteSize);
+    return true;
+}
+
+// Fast conversion of typed arrays to native using memcpy.
+// No float or double canonicalization is done. Called by
+// JSarray2Native whenever a TypedArray is met. ArrayBuffers
+// are not accepted; create a properly typed array view on them
+// first. The element type of array must match the XPCOM
+// type in size, type and signedness exactly. As an exception,
+// Uint8ClampedArray is allowed for arrays of uint8_t. DataViews
+// are not supported.
+
+// static
+bool
+XPCConvert::JSTypedArray2Native(void** d,
+                                JSObject* jsArray,
+                                uint32_t count,
+                                const nsXPTType& type,
+                                nsresult* pErr)
+{
+    MOZ_ASSERT(jsArray, "bad param");
+    MOZ_ASSERT(d, "bad param");
+    MOZ_ASSERT(JS_IsTypedArrayObject(jsArray), "not a typed array");
+
+    // Check the actual length of the input array against the
+    // given size_is.
+    uint32_t len = JS_GetTypedArrayLength(jsArray);
+    if (len < count) {
+        if (pErr)
+            *pErr = NS_ERROR_XPC_NOT_ENOUGH_ELEMENTS_IN_ARRAY;
+
+        return false;
+    }
+
+    void* output = nullptr;
+
+    switch (JS_GetArrayBufferViewType(jsArray)) {
+    case js::Scalar::Int8:
+        if (!CheckTargetAndPopulate(nsXPTType::T_I8, type,
+                                    sizeof(int8_t), count,
+                                    jsArray, &output, pErr)) {
+            return false;
+        }
+        break;
+
+    case js::Scalar::Uint8:
+    case js::Scalar::Uint8Clamped:
+        if (!CheckTargetAndPopulate(nsXPTType::T_U8, type,
+                                    sizeof(uint8_t), count,
+                                    jsArray, &output, pErr)) {
+            return false;
+        }
+        break;
+
+    case js::Scalar::Int16:
+        if (!CheckTargetAndPopulate(nsXPTType::T_I16, type,
+                                    sizeof(int16_t), count,
+                                    jsArray, &output, pErr)) {
+            return false;
+        }
+        break;
+
+    case js::Scalar::Uint16:
+        if (!CheckTargetAndPopulate(nsXPTType::T_U16, type,
+                                    sizeof(uint16_t), count,
+                                    jsArray, &output, pErr)) {
+            return false;
+        }
+        break;
+
+    case js::Scalar::Int32:
+        if (!CheckTargetAndPopulate(nsXPTType::T_I32, type,
+                                    sizeof(int32_t), count,
+                                    jsArray, &output, pErr)) {
+            return false;
+        }
+        break;
+
+    case js::Scalar::Uint32:
+        if (!CheckTargetAndPopulate(nsXPTType::T_U32, type,
+                                    sizeof(uint32_t), count,
+                                    jsArray, &output, pErr)) {
+            return false;
+        }
+        break;
+
+    case js::Scalar::Float32:
+        if (!CheckTargetAndPopulate(nsXPTType::T_FLOAT, type,
+                                    sizeof(float), count,
+                                    jsArray, &output, pErr)) {
+            return false;
+        }
+        break;
+
+    case js::Scalar::Float64:
+        if (!CheckTargetAndPopulate(nsXPTType::T_DOUBLE, type,
+                                    sizeof(double), count,
+                                    jsArray, &output, pErr)) {
+            return false;
+        }
+        break;
+
+    // Yet another array type was defined? It is not supported yet...
+    default:
+        if (pErr)
+            *pErr = NS_ERROR_XPC_BAD_CONVERT_JS;
+
+        return false;
+    }
+
+    *d = output;
+    if (pErr)
+        *pErr = NS_OK;
+
+    return true;
+}
+
+// static
+bool
+XPCConvert::JSArray2Native(void** d, HandleValue s,
+                           uint32_t count, const nsXPTType& type,
+                           const nsID* iid, nsresult* pErr)
+{
+    MOZ_ASSERT(d, "bad param");
+
+    AutoJSContext cx;
+
+    // XXX add support for getting chars from strings
+
+    // XXX add support to indicate *which* array element was not convertable
+
+    if (s.isNullOrUndefined()) {
+        if (0 != count) {
+            if (pErr)
+                *pErr = NS_ERROR_XPC_NOT_ENOUGH_ELEMENTS_IN_ARRAY;
+            return false;
+        }
+
+        *d = nullptr;
+        return true;
+    }
+
+    if (!s.isObject()) {
+        if (pErr)
+            *pErr = NS_ERROR_XPC_CANT_CONVERT_PRIMITIVE_TO_ARRAY;
+        return false;
+    }
+
+    RootedObject jsarray(cx, &s.toObject());
+
+    // If this is a typed array, then try a fast conversion with memcpy.
+    if (JS_IsTypedArrayObject(jsarray)) {
+        return JSTypedArray2Native(d, jsarray, count, type, pErr);
+    }
+
+    bool isArray;
+    if (!JS_IsArrayObject(cx, jsarray, &isArray) || !isArray) {
+        if (pErr)
+            *pErr = NS_ERROR_XPC_CANT_CONVERT_OBJECT_TO_ARRAY;
+        return false;
+    }
+
+    uint32_t len;
+    if (!JS_GetArrayLength(cx, jsarray, &len) || len < count) {
+        if (pErr)
+            *pErr = NS_ERROR_XPC_NOT_ENOUGH_ELEMENTS_IN_ARRAY;
+        return false;
+    }
+
+    if (pErr)
+        *pErr = NS_ERROR_XPC_BAD_CONVERT_JS;
+
+#define POPULATE(_mode, _t)                                                    \
+    PR_BEGIN_MACRO                                                             \
+        cleanupMode = _mode;                                                   \
+        size_t max = UINT32_MAX / sizeof(_t);                                  \
+        if (count > max ||                                                     \
+            nullptr == (array = moz_xmalloc(count * sizeof(_t)))) {            \
+            if (pErr)                                                          \
+                *pErr = NS_ERROR_OUT_OF_MEMORY;                                \
+            goto failure;                                                      \
+        }                                                                      \
+        for (initedCount = 0; initedCount < count; initedCount++) {            \
+            if (!JS_GetElement(cx, jsarray, initedCount, &current) ||          \
+                !JSData2Native(((_t*)array)+initedCount, current, type,        \
+                               iid, pErr))                                     \
+                goto failure;                                                  \
+        }                                                                      \
+    PR_END_MACRO
+
+    // No Action, FRee memory, RElease object
+    enum CleanupMode {na, fr, re};
+
+    CleanupMode cleanupMode;
+
+    void* array = nullptr;
+    uint32_t initedCount;
+    RootedValue current(cx);
+
+    // XXX check IsPtr - esp. to handle array of nsID (as opposed to nsID*)
+    // XXX make extra space at end of char* and wchar* and null termintate
+
+    switch (type.TagPart()) {
+    case nsXPTType::T_I8            : POPULATE(na, int8_t);         break;
+    case nsXPTType::T_I16           : POPULATE(na, int16_t);        break;
+    case nsXPTType::T_I32           : POPULATE(na, int32_t);        break;
+    case nsXPTType::T_I64           : POPULATE(na, int64_t);        break;
+    case nsXPTType::T_U8            : POPULATE(na, uint8_t);        break;
+    case nsXPTType::T_U16           : POPULATE(na, uint16_t);       break;
+    case nsXPTType::T_U32           : POPULATE(na, uint32_t);       break;
+    case nsXPTType::T_U64           : POPULATE(na, uint64_t);       break;
+    case nsXPTType::T_FLOAT         : POPULATE(na, float);          break;
+    case nsXPTType::T_DOUBLE        : POPULATE(na, double);         break;
+    case nsXPTType::T_BOOL          : POPULATE(na, bool);           break;
+    case nsXPTType::T_CHAR          : POPULATE(na, char);           break;
+    case nsXPTType::T_WCHAR         : POPULATE(na, char16_t);       break;
+    case nsXPTType::T_VOID          : NS_ERROR("bad type");         goto failure;
+    case nsXPTType::T_IID           : POPULATE(fr, nsID*);          break;
+    case nsXPTType::T_DOMSTRING     : NS_ERROR("bad type");         goto failure;
+    case nsXPTType::T_CHAR_STR      : POPULATE(fr, char*);          break;
+    case nsXPTType::T_WCHAR_STR     : POPULATE(fr, char16_t*);      break;
+    case nsXPTType::T_INTERFACE     : POPULATE(re, nsISupports*);   break;
+    case nsXPTType::T_INTERFACE_IS  : POPULATE(re, nsISupports*);   break;
+    case nsXPTType::T_UTF8STRING    : NS_ERROR("bad type");         goto failure;
+    case nsXPTType::T_CSTRING       : NS_ERROR("bad type");         goto failure;
+    case nsXPTType::T_ASTRING       : NS_ERROR("bad type");         goto failure;
+    default                         : NS_ERROR("bad type");         goto failure;
+    }
+
+    *d = array;
+    if (pErr)
+        *pErr = NS_OK;
+    return true;
+
+failure:
+    // we may need to cleanup the partially filled array of converted stuff
+    if (array) {
+        if (cleanupMode == re) {
+            nsISupports** a = (nsISupports**) array;
+            for (uint32_t i = 0; i < initedCount; i++) {
+                nsISupports* p = a[i];
+                NS_IF_RELEASE(p);
+            }
+        } else if (cleanupMode == fr) {
+            void** a = (void**) array;
+            for (uint32_t i = 0; i < initedCount; i++) {
+                void* p = a[i];
+                if (p) free(p);
+            }
+        }
+        free(array);
+    }
+
+    return false;
+
+#undef POPULATE
+}
+
+// static
+bool
+XPCConvert::NativeStringWithSize2JS(MutableHandleValue d, const void* s,
+                                    const nsXPTType& type,
+                                    uint32_t count,
+                                    nsresult* pErr)
+{
+    NS_PRECONDITION(s, "bad param");
+
+    AutoJSContext cx;
+    if (pErr)
+        *pErr = NS_ERROR_XPC_BAD_CONVERT_NATIVE;
+
+    switch (type.TagPart()) {
+        case nsXPTType::T_PSTRING_SIZE_IS:
+        {
+            char* p = *((char**)s);
+            if (!p)
+                break;
+            JSString* str;
+            if (!(str = JS_NewStringCopyN(cx, p, count)))
+                return false;
+            d.setString(str);
+            break;
+        }
+        case nsXPTType::T_PWSTRING_SIZE_IS:
+        {
+            char16_t* p = *((char16_t**)s);
+            if (!p)
+                break;
+            JSString* str;
+            if (!(str = JS_NewUCStringCopyN(cx, p, count)))
+                return false;
+            d.setString(str);
+            break;
+        }
+        default:
+            XPC_LOG_ERROR(("XPCConvert::NativeStringWithSize2JS : unsupported type"));
+            return false;
+    }
+    return true;
+}
+
+// static
+bool
+XPCConvert::JSStringWithSize2Native(void* d, HandleValue s,
+                                    uint32_t count, const nsXPTType& type,
+                                    nsresult* pErr)
+{
+    NS_PRECONDITION(!s.isNull(), "bad param");
+    NS_PRECONDITION(d, "bad param");
+
+    AutoJSContext cx;
+    uint32_t len;
+
+    if (pErr)
+        *pErr = NS_ERROR_XPC_BAD_CONVERT_NATIVE;
+
+    switch (type.TagPart()) {
+        case nsXPTType::T_PSTRING_SIZE_IS:
+        {
+            if (s.isUndefined() || s.isNull()) {
+                if (0 != count) {
+                    if (pErr)
+                        *pErr = NS_ERROR_XPC_NOT_ENOUGH_CHARS_IN_STRING;
+                    return false;
+                }
+                if (0 != count) {
+                    len = (count + 1) * sizeof(char);
+                    if (!(*((void**)d) = moz_xmalloc(len)))
+                        return false;
+                    return true;
+                }
+                // else ...
+
+                *((char**)d) = nullptr;
+                return true;
+            }
+
+            JSString* str = ToString(cx, s);
+            if (!str) {
+                return false;
+            }
+
+            size_t length = JS_GetStringEncodingLength(cx, str);
+            if (length == size_t(-1)) {
+                return false;
+            }
+            if (length > count) {
+                if (pErr)
+                    *pErr = NS_ERROR_XPC_NOT_ENOUGH_CHARS_IN_STRING;
+                return false;
+            }
+            len = uint32_t(length);
+
+            if (len < count)
+                len = count;
+
+            uint32_t alloc_len = (len + 1) * sizeof(char);
+            char* buffer = static_cast<char*>(moz_xmalloc(alloc_len));
+            if (!buffer) {
+                return false;
+            }
+            JS_EncodeStringToBuffer(cx, str, buffer, len);
+            buffer[len] = '\0';
+            *((char**)d) = buffer;
+
+            return true;
+        }
+
+        case nsXPTType::T_PWSTRING_SIZE_IS:
+        {
+            JSString* str;
+
+            if (s.isUndefined() || s.isNull()) {
+                if (0 != count) {
+                    if (pErr)
+                        *pErr = NS_ERROR_XPC_NOT_ENOUGH_CHARS_IN_STRING;
+                    return false;
+                }
+
+                if (0 != count) {
+                    len = (count + 1) * sizeof(char16_t);
+                    if (!(*((void**)d) = moz_xmalloc(len)))
+                        return false;
+                    return true;
+                }
+
+                // else ...
+                *((const char16_t**)d) = nullptr;
+                return true;
+            }
+
+            if (!(str = ToString(cx, s))) {
+                return false;
+            }
+
+            len = JS_GetStringLength(str);
+            if (len > count) {
+                if (pErr)
+                    *pErr = NS_ERROR_XPC_NOT_ENOUGH_CHARS_IN_STRING;
+                return false;
+            }
+
+            len = count;
+
+            uint32_t alloc_len = (len + 1) * sizeof(char16_t);
+            if (!(*((void**)d) = moz_xmalloc(alloc_len))) {
+                // XXX should report error
+                return false;
+            }
+            mozilla::Range<char16_t> destChars(*((char16_t**)d), len + 1);
+            if (!JS_CopyStringChars(cx, destChars, str))
+                return false;
+            destChars[count] = 0;
+
+            return true;
+        }
+        default:
+            XPC_LOG_ERROR(("XPCConvert::JSStringWithSize2Native : unsupported type"));
+            return false;
+    }
+}