79 lines
3 KiB
C++
79 lines
3 KiB
C++
/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
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/* vim: set ts=8 sts=2 et sw=2 tw=80: */
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/* This Source Code Form is subject to the terms of the Mozilla Public
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* License, v. 2.0. If a copy of the MPL was not distributed with this file,
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* You can obtain one at http://mozilla.org/MPL/2.0/. */
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#include "mozilla/ipc/SerializedStructuredCloneBuffer.h"
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#include "js/StructuredClone.h"
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namespace IPC {
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void ParamTraits<JSStructuredCloneData>::Write(MessageWriter* aWriter,
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const paramType& aParam) {
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MOZ_ASSERT(!(aParam.Size() % sizeof(uint64_t)));
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// We can only construct shared memory regions up to 4Gb in size, making that
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// the maximum possible JSStructuredCloneData size.
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mozilla::CheckedUint32 size = aParam.Size();
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if (!size.isValid()) {
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aWriter->FatalError("JSStructuredCloneData over 4Gb in size");
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return;
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}
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WriteParam(aWriter, size.value());
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MessageBufferWriter bufWriter(aWriter, size.value());
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aParam.ForEachDataChunk([&](const char* aData, size_t aSize) {
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return bufWriter.WriteBytes(aData, aSize);
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});
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}
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bool ParamTraits<JSStructuredCloneData>::Read(MessageReader* aReader,
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paramType* aResult) {
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uint32_t length = 0;
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if (!ReadParam(aReader, &length)) {
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aReader->FatalError("JSStructuredCloneData length read failed");
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return false;
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}
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MOZ_ASSERT(!(length % sizeof(uint64_t)));
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// Borrowing is not suitable to use for IPC to hand out data because we often
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// want to store the data somewhere for processing after IPC has released the
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// underlying buffers.
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//
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// This deserializer previously used a mechanism to transfer ownership over
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// the underlying buffers from IPC into the JSStructuredCloneData. This was
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// removed when support for serializing over shared memory was added, as the
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// benefit for avoiding copies was limited due to it only functioning for
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// buffers under 64k in size (as larger buffers would be serialized using
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// shared memory), and it added substantial complexity to the BufferList type
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// and the IPC serialization layer due to things like buffer alignment. This
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// can be revisited in the future if it turns out to be a noticable
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// performance regression. (bug 1783242)
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mozilla::BufferList<js::SystemAllocPolicy> buffers(0, 0, 4096);
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MessageBufferReader bufReader(aReader, length);
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uint32_t read = 0;
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while (read < length) {
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size_t bufLen;
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char* buf = buffers.AllocateBytes(length - read, &bufLen);
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if (!buf) {
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// Would be nice to allow actor to control behaviour here (bug 1784307)
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NS_ABORT_OOM(length - read);
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return false;
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}
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if (!bufReader.ReadBytesInto(buf, bufLen)) {
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aReader->FatalError("JSStructuredCloneData ReadBytesInto failed");
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return false;
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}
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read += bufLen;
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}
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MOZ_ASSERT(read == length);
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*aResult = JSStructuredCloneData(
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std::move(buffers), JS::StructuredCloneScope::DifferentProcess,
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OwnTransferablePolicy::IgnoreTransferablesIfAny);
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return true;
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}
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} // namespace IPC
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