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// Copyright 2012 the V8 project authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.
#ifndef V8_SNAPSHOT_SNAPSHOT_SOURCE_SINK_H_
#define V8_SNAPSHOT_SNAPSHOT_SOURCE_SINK_H_
#include <utility>
#include "src/base/logging.h"
#include "src/snapshot/serializer-common.h"
#include "src/utils/utils.h"
namespace v8 {
namespace internal {
/**
* Source to read snapshot and builtins files from.
*
* Note: Memory ownership remains with callee.
*/
class SnapshotByteSource final {
public:
SnapshotByteSource(const char* data, int length)
: data_(reinterpret_cast<const byte*>(data)),
length_(length),
position_(0) {}
explicit SnapshotByteSource(Vector<const byte> payload)
: data_(payload.begin()), length_(payload.length()), position_(0) {}
~SnapshotByteSource() = default;
bool HasMore() { return position_ < length_; }
byte Get() {
DCHECK(position_ < length_);
return data_[position_++];
}
void Advance(int by) { position_ += by; }
void CopyRaw(void* to, int number_of_bytes) {
memcpy(to, data_ + position_, number_of_bytes);
position_ += number_of_bytes;
}
inline int GetInt() {
// This way of decoding variable-length encoded integers does not
// suffer from branch mispredictions.
DCHECK(position_ + 3 < length_);
uint32_t answer = data_[position_];
answer |= data_[position_ + 1] << 8;
answer |= data_[position_ + 2] << 16;
answer |= data_[position_ + 3] << 24;
int bytes = (answer & 3) + 1;
Advance(bytes);
uint32_t mask = 0xffffffffu;
mask >>= 32 - (bytes << 3);
answer &= mask;
answer >>= 2;
return answer;
}
int GetIntSlow() {
// Unlike GetInt, this reads only up to the end of the blob, even if less
// than 4 bytes are remaining.
// TODO(jgruber): Remove once the use in MakeFromScriptsSource is gone.
DCHECK(position_ < length_);
uint32_t answer = data_[position_];
if (position_ + 1 < length_) answer |= data_[position_ + 1] << 8;
if (position_ + 2 < length_) answer |= data_[position_ + 2] << 16;
if (position_ + 3 < length_) answer |= data_[position_ + 3] << 24;
int bytes = (answer & 3) + 1;
Advance(bytes);
uint32_t mask = 0xffffffffu;
mask >>= 32 - (bytes << 3);
answer &= mask;
answer >>= 2;
return answer;
}
// Returns length.
int GetBlob(const byte** data);
int position() { return position_; }
void set_position(int position) { position_ = position; }
uint32_t GetChecksum() const {
return Checksum(Vector<const byte>(data_, length_));
}
private:
const byte* data_;
int length_;
int position_;
DISALLOW_COPY_AND_ASSIGN(SnapshotByteSource);
};
/**
* Sink to write snapshot files to.
*
* Subclasses must implement actual storage or i/o.
*/
class SnapshotByteSink {
public:
SnapshotByteSink() = default;
explicit SnapshotByteSink(int initial_size) : data_(initial_size) {}
~SnapshotByteSink() = default;
void Put(byte b, const char* description) { data_.push_back(b); }
void PutSection(int b, const char* description) {
DCHECK_LE(b, kMaxUInt8);
Put(static_cast<byte>(b), description);
}
void PutInt(uintptr_t integer, const char* description);
void PutRaw(const byte* data, int number_of_bytes, const char* description);
void Append(const SnapshotByteSink& other);
int Position() const { return static_cast<int>(data_.size()); }
const std::vector<byte>* data() const { return &data_; }
private:
std::vector<byte> data_;
};
} // namespace internal
} // namespace v8
#endif // V8_SNAPSHOT_SNAPSHOT_SOURCE_SINK_H_
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