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/* -*- 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 */
/* A type that can be sent without needing to make a copy during
* serialization. In addition the receiver can take ownership of the
* data to avoid having to make an additional copy. */
#ifndef mozilla_ipc_ByteBufUtils_h
#define mozilla_ipc_ByteBufUtils_h
#include "mozilla/ipc/ByteBuf.h"
#include "mozilla/CheckedInt.h"
#include "mozilla/mozalloc_oom.h"
#include "ipc/IPCMessageUtils.h"
namespace IPC {
template <>
struct ParamTraits<mozilla::ipc::ByteBuf> {
typedef mozilla::ipc::ByteBuf paramType;
// this is where we transfer the memory from the ByteBuf to IPDL, avoiding a
// copy
static void Write(MessageWriter* aWriter, paramType&& aParam) {
// We need to send the length as a 32-bit value, not a size_t, because on
// ARM64 Windows we end up with a 32-bit GMP process sending a ByteBuf to
// a 64-bit parent process. WriteBytesZeroCopy takes a uint32_t as an
// argument, so it would end up getting truncated anyways. See bug 1757534.
mozilla::CheckedInt<uint32_t> length = aParam.mLen;
WriteParam(aWriter, length.value());
// hand over ownership of the buffer to the Message
aWriter->WriteBytesZeroCopy(aParam.mData, length.value(), aParam.mCapacity);
aParam.mData = nullptr;
aParam.mCapacity = 0;
aParam.mLen = 0;
static bool Read(MessageReader* aReader, paramType* aResult) {
// We make a copy from the BufferList so that we get a contigous result.
uint32_t length;
if (!ReadParam(aReader, &length)) return false;
if (!aResult->Allocate(length)) {
return false;
return aReader->ReadBytesInto(aResult->mData, length);
} // namespace IPC
#endif // ifndef mozilla_ipc_ByteBufUtils_h