text: // 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_
  