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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,
#include "chrome/common/ipc_message_utils.h"
#include "mozilla/ipc/SharedMemory.h"
namespace IPC {
static uint32_t kShmemThreshold = 64 * 1024;
MessageBufferWriter::MessageBufferWriter(MessageWriter* writer,
uint32_t full_len)
: writer_(writer) {
// NOTE: We only write out the `shmem_ok` bool if we're over kShmemThreshold
// to avoid bloating the size of messages with small buffers.
if (full_len > kShmemThreshold) {
shmem_ = new mozilla::ipc::SharedMemory();
bool shmem_ok = shmem_->Create(full_len) && shmem_->Map(full_len);
writer->WriteBool(shmem_ok);
if (shmem_ok) {
if (!shmem_->WriteHandle(writer)) {
writer->FatalError("SharedMemory::WriteHandle failed");
return;
}
buffer_ = reinterpret_cast<char*>(shmem_->Memory());
} else {
// Creating or mapping the shared memory region failed, perhaps due to FD
// exhaustion or address space fragmentation. Fall back to trying to send
// data inline.
shmem_ = nullptr;
writer->NoteLargeBufferShmemFailure(full_len);
}
}
remaining_ = full_len;
}
MessageBufferWriter::~MessageBufferWriter() {
if (remaining_ != 0) {
writer_->FatalError("didn't fully write message buffer");
}
}
bool MessageBufferWriter::WriteBytes(const void* data, uint32_t len) {
MOZ_RELEASE_ASSERT(len == remaining_ || (len % 4) == 0,
"all writes except for the final write must be a multiple "
"of 4 bytes in length due to padding");
if (len > remaining_) {
writer_->FatalError("MessageBufferWriter overrun");
return false;
}
remaining_ -= len;
// If we're serializing using a shared memory region, `buffer_` will be
// initialized to point into that region.
if (buffer_) {
memcpy(buffer_, data, len);
buffer_ += len;
return true;
}
return writer_->WriteBytes(data, len);
}
MessageBufferReader::MessageBufferReader(MessageReader* reader,
uint32_t full_len)
: reader_(reader) {
// NOTE: We only write out the `shmem_ok` bool if we're over kShmemThreshold
// to avoid bloating the size of messages with small buffers.
if (full_len > kShmemThreshold) {
bool shmem_ok = false;
if (!reader->ReadBool(&shmem_ok)) {
reader->FatalError("MessageReader::ReadBool failed!");
return;
}
if (shmem_ok) {
shmem_ = new mozilla::ipc::SharedMemory();
if (!shmem_->ReadHandle(reader)) {
reader->FatalError("SharedMemory::ReadHandle failed!");
return;
}
if (!shmem_->Map(full_len)) {
reader->FatalError("SharedMemory::Map failed");
return;
}
buffer_ = reinterpret_cast<const char*>(shmem_->Memory());
}
}
remaining_ = full_len;
}
MessageBufferReader::~MessageBufferReader() {
if (remaining_ != 0) {
reader_->FatalError("didn't fully write message buffer");
}
}
bool MessageBufferReader::ReadBytesInto(void* data, uint32_t len) {
MOZ_RELEASE_ASSERT(len == remaining_ || (len % 4) == 0,
"all reads except for the final read must be a multiple "
"of 4 bytes in length due to padding");
if (len > remaining_) {
reader_->FatalError("MessageBufferReader overrun");
return false;
}
remaining_ -= len;
// If we're serializing using a shared memory region, `buffer_` will be
// initialized to point into that region.
if (buffer_) {
memcpy(data, buffer_, len);
buffer_ += len;
return true;
}
return reader_->ReadBytesInto(data, len);
}
} // namespace IPC