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// Copyright 2015 The Chromium Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.
#include "mojo/public/cpp/bindings/lib/pickle_buffer.h"
#include <stddef.h>
#include <stdint.h>
#include <stdlib.h>
#include "base/logging.h"
#include "base/macros.h"
#include "base/pickle.h"
#include "mojo/public/cpp/bindings/lib/bindings_serialization.h"
namespace mojo {
namespace internal {
class PickleBuffer::Storage : public base::Pickle {
public:
explicit Storage(size_t num_bytes);
~Storage() override {}
size_t available_capacity() const {
return capacity_after_header() - payload_size();
}
void* GetData() { return static_cast<void*>(mutable_payload()); }
void* Claim(size_t num_bytes) { return ClaimBytes(num_bytes); }
private:
// TODO(rockot): Stop wasting 8 bytes per buffer.
//
// We don't use Pickle's header at all, but its base header type consumes 4
// bytes. We waste another 4 bytes to keep our actual buffer aligned to an
// 8-byte boundary.
//
// The reason we don't use base::Pickle's header is that it stores payload
// length in the first 4 bytes. Mojo Messages are packed like mojom structs,
// where the first 4 bytes are header size rather than payload size.
struct PaddedHeader : public base::Pickle::Header {
uint32_t padding;
};
static_assert(sizeof(PaddedHeader) % 8 == 0,
"PickleBuffer requires a Pickle header size with 8-byte alignment.");
DISALLOW_COPY_AND_ASSIGN(Storage);
};
PickleBuffer::Storage::Storage(size_t num_bytes)
: base::Pickle(sizeof(PaddedHeader)) {
headerT<PaddedHeader>()->padding = 0;
Resize(num_bytes);
}
PickleBuffer::PickleBuffer(size_t num_bytes, bool zero_initialized)
: storage_(new Storage(num_bytes)) {
if (zero_initialized)
memset(storage_->GetData(), 0, num_bytes);
}
PickleBuffer::~PickleBuffer() {
}
const void* PickleBuffer::data() const { return storage_->GetData(); }
size_t PickleBuffer::data_num_bytes() const { return storage_->payload_size(); }
base::Pickle* PickleBuffer::pickle() const {
return storage_.get();
}
void* PickleBuffer::Allocate(size_t num_bytes) {
DCHECK(storage_);
// The last allocation may terminate in between 8-byte boundaries. Pad the
// front of this allocation if that's the case.
size_t padded_capacity = Align(storage_->payload_size());
DCHECK_GE(padded_capacity, storage_->payload_size());
size_t padding_bytes = padded_capacity - storage_->payload_size();
size_t allocation_size = padding_bytes + num_bytes;
const void* previous_data_location = storage_->GetData();
if (storage_->available_capacity() < allocation_size) {
NOTREACHED() <<
"Message buffers must be fully allocated before serialization.";
return nullptr;
}
char* p = static_cast<char*>(storage_->Claim(allocation_size));
DCHECK_EQ(storage_->GetData(), previous_data_location);
return p + padding_bytes;
}
PickleBuffer* PickleBuffer::AsPickleBuffer() { return this; }
} // namespace internal
} // namespace mojo
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