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| 1 // Copyright 2014 The Chromium Authors. All rights reserved. | |
| 2 // Use of this source code is governed by a BSD-style license that can be | |
| 3 // found in the LICENSE file. | |
| 4 | |
| 5 // LEB128 encoder and decoder for packed relative relocations. | |
| 6 // | |
| 7 // Packed relocations consist of a large number of relatively small | |
| 8 // integer values. Encoding these as LEB128 saves space. | |
| 9 // | |
| 10 // For more on LEB128 see http://en.wikipedia.org/wiki/LEB128. | |
| 11 | |
| 12 #ifndef TOOLS_RELOCATION_PACKER_SRC_LEB128_H_ | |
| 13 #define TOOLS_RELOCATION_PACKER_SRC_LEB128_H_ | |
| 14 | |
| 15 #include <stdint.h> | |
| 16 #include <vector> | |
| 17 | |
| 18 #include "elf_traits.h" | |
| 19 | |
| 20 namespace relocation_packer { | |
| 21 | |
| 22 // Encode packed words as a LEB128 byte stream. | |
| 23 template <typename uint_t> | |
| 24 class Leb128Encoder { | |
| 25 public: | |
| 26 // Explicit (but empty) constructor and destructor, for chromium-style. | |
| 27 Leb128Encoder(); | |
| 28 ~Leb128Encoder(); | |
| 29 | |
| 30 // Add a value to the encoding stream. | |
| 31 // |value| is the unsigned int to add. | |
| 32 void Enqueue(uint_t value); | |
| 33 | |
| 34 // Add a vector of values to the encoding stream. | |
| 35 // |values| is the vector of unsigned ints to add. | |
| 36 void EnqueueAll(const std::vector<uint_t>& values); | |
| 37 | |
| 38 // Retrieve the encoded representation of the values. | |
| 39 // |encoding| is the returned vector of encoded data. | |
| 40 void GetEncoding(std::vector<uint8_t>* encoding) { *encoding = encoding_; } | |
| 41 | |
| 42 private: | |
| 43 // Growable vector holding the encoded LEB128 stream. | |
| 44 std::vector<uint8_t> encoding_; | |
| 45 }; | |
| 46 | |
| 47 // Decode a LEB128 byte stream to produce packed words. | |
| 48 template <typename uint_t> | |
| 49 class Leb128Decoder { | |
| 50 public: | |
| 51 // Create a new decoder for the given encoded stream. | |
| 52 // |encoding| is the vector of encoded data. | |
| 53 explicit Leb128Decoder(const std::vector<uint8_t>& encoding, size_t start_with
); | |
| 54 | |
| 55 // Explicit (but empty) destructor, for chromium-style. | |
| 56 ~Leb128Decoder(); | |
| 57 | |
| 58 // Retrieve the next value from the encoded stream. | |
| 59 uint_t Dequeue(); | |
| 60 | |
| 61 // Retrieve all remaining values from the encoded stream. | |
| 62 // |values| is the vector of decoded data. | |
| 63 void DequeueAll(std::vector<uint_t>* values); | |
| 64 | |
| 65 private: | |
| 66 // Encoded LEB128 stream. | |
| 67 std::vector<uint8_t> encoding_; | |
| 68 | |
| 69 // Cursor indicating the current stream retrieval point. | |
| 70 size_t cursor_; | |
| 71 }; | |
| 72 | |
| 73 } // namespace relocation_packer | |
| 74 | |
| 75 #endif // TOOLS_RELOCATION_PACKER_SRC_LEB128_H_ | |
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