Add m-esr52 at 52.6.0

1 files changed, 245 insertions, 0 deletions

diff --git a/dom/bindings/DOMString.h b/dom/bindings/DOMString.h
new file mode 100644
index 000000000..72c8445ec
--- /dev/null
+++ b/dom/bindings/DOMString.h
@@ -0,0 +1,245 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set ts=8 sts=2 et sw=2 tw=80: */
+/* 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/. */
+
+#ifndef mozilla_dom_DOMString_h
+#define mozilla_dom_DOMString_h
+
+#include "nsStringGlue.h"
+#include "nsStringBuffer.h"
+#include "mozilla/Assertions.h"
+#include "mozilla/Attributes.h"
+#include "mozilla/Maybe.h"
+#include "nsDOMString.h"
+#include "nsIAtom.h"
+
+namespace mozilla {
+namespace dom {
+
+/**
+ * A class for representing string return values.  This can be either passed to
+ * callees that have an nsString or nsAString out param or passed to a callee
+ * that actually knows about this class and can work with it.  Such a callee may
+ * call SetStringBuffer or SetEphemeralStringBuffer or SetOwnedString or
+ * SetOwnedAtom on this object.  It's only OK to call
+ * SetStringBuffer/SetOwnedString/SetOwnedAtom if the caller of the method in
+ * question plans to keep holding a strong ref to the stringbuffer involved,
+ * whether it's a raw nsStringBuffer, or stored inside the string or atom being
+ * passed.  In the string/atom cases that means the caller must own the string
+ * or atom, and not mutate it (in the string case) for the lifetime of the
+ * DOMString.
+ *
+ * The proper way to store a value in this class is to either to do nothing
+ * (which leaves this as an empty string), to call
+ * SetStringBuffer/SetEphemeralStringBuffer with a non-null stringbuffer, to
+ * call SetOwnedString, to call SetOwnedAtom, to call SetNull(), or to call
+ * AsAString() and set the value in the resulting nsString.  These options are
+ * mutually exclusive! Don't do more than one of them.
+ *
+ * The proper way to extract a value is to check IsNull().  If not null, then
+ * check HasStringBuffer().  If that's true, check for a zero length, and if the
+ * length is nonzero call StringBuffer().  If the length is zero this is the
+ * empty string.  If HasStringBuffer() returns false, call AsAString() and get
+ * the value from that.
+ */
+class MOZ_STACK_CLASS DOMString {
+public:
+  DOMString()
+    : mStringBuffer(nullptr)
+    , mLength(0)
+    , mIsNull(false)
+    , mStringBufferOwned(false)
+  {}
+  ~DOMString()
+  {
+    MOZ_ASSERT(!mString || !mStringBuffer,
+               "Shouldn't have both present!");
+    if (mStringBufferOwned) {
+      MOZ_ASSERT(mStringBuffer);
+      mStringBuffer->Release();
+    }
+  }
+
+  operator nsString&()
+  {
+    return AsAString();
+  }
+
+  // It doesn't make any sense to convert a DOMString to a const nsString or
+  // nsAString reference; this class is meant for outparams only.
+  operator const nsString&() = delete;
+  operator const nsAString&() = delete;
+
+  nsString& AsAString()
+  {
+    MOZ_ASSERT(!mStringBuffer, "We already have a stringbuffer?");
+    MOZ_ASSERT(!mIsNull, "We're already set as null");
+    if (!mString) {
+      mString.emplace();
+    }
+    return *mString;
+  }
+
+  bool HasStringBuffer() const
+  {
+    MOZ_ASSERT(!mString || !mStringBuffer,
+               "Shouldn't have both present!");
+    MOZ_ASSERT(!mIsNull, "Caller should have checked IsNull() first");
+    return !mString;
+  }
+
+  // Get the stringbuffer.  This can only be called if HasStringBuffer()
+  // returned true and StringBufferLength() is nonzero.  If that's true, it will
+  // never return null.  Note that constructing a string from this
+  // nsStringBuffer with length given by StringBufferLength() might give you
+  // something that is not null-terminated.
+  nsStringBuffer* StringBuffer() const
+  {
+    MOZ_ASSERT(!mIsNull, "Caller should have checked IsNull() first");
+    MOZ_ASSERT(HasStringBuffer(),
+               "Don't ask for the stringbuffer if we don't have it");
+    MOZ_ASSERT(StringBufferLength() != 0, "Why are you asking for this?");
+    MOZ_ASSERT(mStringBuffer,
+               "If our length is nonzero, we better have a stringbuffer.");
+    return mStringBuffer;
+  }
+
+  // Get the length of the stringbuffer.  Can only be called if
+  // HasStringBuffer().
+  uint32_t StringBufferLength() const
+  {
+    MOZ_ASSERT(HasStringBuffer(), "Don't call this if there is no stringbuffer");
+    return mLength;
+  }
+
+  // Tell the DOMString to relinquish ownership of its nsStringBuffer to the
+  // caller.  Can only be called if HasStringBuffer().
+  void RelinquishBufferOwnership()
+  {
+    MOZ_ASSERT(HasStringBuffer(), "Don't call this if there is no stringbuffer");
+    if (mStringBufferOwned) {
+      // Just hand that ref over.
+      mStringBufferOwned = false;
+    } else {
+      // Caller should end up holding a ref.
+      mStringBuffer->AddRef();
+    }
+  }
+
+  // Initialize the DOMString to a (nsStringBuffer, length) pair.  The length
+  // does NOT have to be the full length of the (null-terminated) string in the
+  // nsStringBuffer.
+  void SetStringBuffer(nsStringBuffer* aStringBuffer, uint32_t aLength)
+  {
+    MOZ_ASSERT(mString.isNothing(), "We already have a string?");
+    MOZ_ASSERT(!mIsNull, "We're already set as null");
+    MOZ_ASSERT(!mStringBuffer, "Setting stringbuffer twice?");
+    MOZ_ASSERT(aStringBuffer, "Why are we getting null?");
+    mStringBuffer = aStringBuffer;
+    mLength = aLength;
+  }
+
+  // Like SetStringBuffer, but holds a reference to the nsStringBuffer.
+  void SetEphemeralStringBuffer(nsStringBuffer* aStringBuffer, uint32_t aLength)
+  {
+    // We rely on SetStringBuffer to ensure our state invariants.
+    SetStringBuffer(aStringBuffer, aLength);
+    aStringBuffer->AddRef();
+    mStringBufferOwned = true;
+  }
+
+  void SetOwnedString(const nsAString& aString)
+  {
+    MOZ_ASSERT(mString.isNothing(), "We already have a string?");
+    MOZ_ASSERT(!mIsNull, "We're already set as null");
+    MOZ_ASSERT(!mStringBuffer, "Setting stringbuffer twice?");
+    nsStringBuffer* buf = nsStringBuffer::FromString(aString);
+    if (buf) {
+      SetStringBuffer(buf, aString.Length());
+    } else if (aString.IsVoid()) {
+      SetNull();
+    } else if (!aString.IsEmpty()) {
+      AsAString() = aString;
+    }
+  }
+
+  enum NullHandling
+  {
+    eTreatNullAsNull,
+    eTreatNullAsEmpty,
+    eNullNotExpected
+  };
+
+  void SetOwnedAtom(nsIAtom* aAtom, NullHandling aNullHandling)
+  {
+    MOZ_ASSERT(mString.isNothing(), "We already have a string?");
+    MOZ_ASSERT(!mIsNull, "We're already set as null");
+    MOZ_ASSERT(!mStringBuffer, "Setting stringbuffer twice?");
+    MOZ_ASSERT(aAtom || aNullHandling != eNullNotExpected);
+    if (aNullHandling == eNullNotExpected || aAtom) {
+      SetStringBuffer(aAtom->GetStringBuffer(), aAtom->GetLength());
+    } else if (aNullHandling == eTreatNullAsNull) {
+      SetNull();
+    }
+  }
+
+  void SetNull()
+  {
+    MOZ_ASSERT(!mStringBuffer, "Should have no stringbuffer if null");
+    MOZ_ASSERT(mString.isNothing(), "Should have no string if null");
+    mIsNull = true;
+  }
+
+  bool IsNull() const
+  {
+    MOZ_ASSERT(!mStringBuffer || mString.isNothing(),
+               "How could we have a stringbuffer and a nonempty string?");
+    return mIsNull || (mString && mString->IsVoid());
+  }
+
+  void ToString(nsAString& aString)
+  {
+    if (IsNull()) {
+      SetDOMStringToNull(aString);
+    } else if (HasStringBuffer()) {
+      if (StringBufferLength() == 0) {
+        aString.Truncate();
+      } else {
+        // Don't share the nsStringBuffer with aString if the result would not
+        // be null-terminated.
+        nsStringBuffer* buf = StringBuffer();
+        uint32_t len = StringBufferLength();
+        auto chars = static_cast<char16_t*>(buf->Data());
+        if (chars[len] == '\0') {
+          // Safe to share the buffer.
+          buf->ToString(len, aString);
+        } else {
+          // We need to copy, unfortunately.
+          aString.Assign(chars, len);
+        }
+      }
+    } else {
+      aString = AsAString();
+    }
+  }
+
+private:
+  // We need to be able to act like a string as needed
+  Maybe<nsAutoString> mString;
+
+  // For callees that know we exist, we can be a stringbuffer/length/null-flag
+  // triple.
+  nsStringBuffer* MOZ_UNSAFE_REF("The ways in which this can be safe are "
+                                 "documented above and enforced through "
+                                 "assertions") mStringBuffer;
+  uint32_t mLength;
+  bool mIsNull;
+  bool mStringBufferOwned;
+};
+
+} // namespace dom
+} // namespace mozilla
+
+#endif // mozilla_dom_DOMString_h