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// Copyright 2014 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.
// SLEB128 encoder and decoder for packed relative relocations.
//
// Delta encoded relative relocations consist of a large number
// of pairs signed integer values, many with small values. Encoding these
// as signed LEB128 saves space.
//
// For more on LEB128 see http://en.wikipedia.org/wiki/LEB128.
#ifndef TOOLS_RELOCATION_PACKER_SRC_SLEB128_H_
#define TOOLS_RELOCATION_PACKER_SRC_SLEB128_H_
#include <stdint.h>
#include <unistd.h>
#include <vector>
#include "elf_traits.h"
namespace relocation_packer {
// Encode packed words as a signed LEB128 byte stream.
class Sleb128Encoder {
public:
// Explicit (but empty) constructor and destructor, for chromium-style.
Sleb128Encoder();
~Sleb128Encoder();
// Add a value to the encoding stream.
// |value| is the signed int to add.
void Enqueue(ELF::Sxword value);
// Add a vector of values to the encoding stream.
// |values| is the vector of signed ints to add.
void EnqueueAll(const std::vector<ELF::Sxword>& values);
// Retrieve the encoded representation of the values.
// |encoding| is the returned vector of encoded data.
void GetEncoding(std::vector<uint8_t>* encoding) { *encoding = encoding_; }
private:
// Growable vector holding the encoded LEB128 stream.
std::vector<uint8_t> encoding_;
};
// Decode a LEB128 byte stream to produce packed words.
class Sleb128Decoder {
public:
// Create a new decoder for the given encoded stream.
// |encoding| is the vector of encoded data.
explicit Sleb128Decoder(const std::vector<uint8_t>& encoding);
// Explicit (but empty) destructor, for chromium-style.
~Sleb128Decoder();
// Retrieve the next value from the encoded stream.
ELF::Sxword Dequeue();
// Retrieve all remaining values from the encoded stream.
// |values| is the vector of decoded data.
void DequeueAll(std::vector<ELF::Sxword>* values);
private:
// Encoded LEB128 stream.
std::vector<uint8_t> encoding_;
// Cursor indicating the current stream retrieval point.
size_t cursor_;
};
} // namespace relocation_packer
#endif // TOOLS_RELOCATION_PACKER_SRC_SLEB128_H_
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