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| 1 // Copyright 2014 The Chromium Authors. All rights reserved. | 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 | 2 // Use of this source code is governed by a BSD-style license that can be |
| 3 // found in the LICENSE file. | 3 // found in the LICENSE file. |
| 4 | 4 |
| 5 // LEB128 encoder and decoder for packed relative relocations. | 5 // LEB128 encoder and decoder for packed relative relocations. |
| 6 // | 6 // |
| 7 // Run-length encoded relative relocations consist of a large number | 7 // Run-length encoded relative relocations consist of a large number |
| 8 // of pairs of relatively small positive integer values. Encoding these as | 8 // of pairs of relatively small positive integer values. Encoding these as |
| 9 // LEB128 saves space. | 9 // LEB128 saves space. |
| 10 // | 10 // |
| 11 // For more on LEB128 see http://en.wikipedia.org/wiki/LEB128. | 11 // For more on LEB128 see http://en.wikipedia.org/wiki/LEB128. |
| 12 | 12 |
| 13 #ifndef TOOLS_RELOCATION_PACKER_SRC_LEB128_H_ | 13 #ifndef TOOLS_RELOCATION_PACKER_SRC_LEB128_H_ |
| 14 #define TOOLS_RELOCATION_PACKER_SRC_LEB128_H_ | 14 #define TOOLS_RELOCATION_PACKER_SRC_LEB128_H_ |
| 15 | 15 |
| 16 #include <stdint.h> | 16 #include <stdint.h> |
| 17 #include <vector> | 17 #include <vector> |
| 18 | 18 |
| 19 #include "elf_traits.h" | 19 #include "elf_traits.h" |
| 20 | 20 |
| 21 namespace relocation_packer { | 21 namespace relocation_packer { |
| 22 | 22 |
| 23 // Encode packed words as a LEB128 byte stream. | 23 // Encode packed words as a LEB128 byte stream. |
| 24 template <typename uint_t> |
| 24 class Leb128Encoder { | 25 class Leb128Encoder { |
| 25 public: | 26 public: |
| 26 // Explicit (but empty) constructor and destructor, for chromium-style. | 27 // Explicit (but empty) constructor and destructor, for chromium-style. |
| 27 Leb128Encoder(); | 28 Leb128Encoder(); |
| 28 ~Leb128Encoder(); | 29 ~Leb128Encoder(); |
| 29 | 30 |
| 30 // Add a value to the encoding stream. | 31 // Add a value to the encoding stream. |
| 31 // |value| is the unsigned int to add. | 32 // |value| is the unsigned int to add. |
| 32 void Enqueue(ELF::Xword value); | 33 void Enqueue(uint_t value); |
| 33 | 34 |
| 34 // Add a vector of values to the encoding stream. | 35 // Add a vector of values to the encoding stream. |
| 35 // |values| is the vector of unsigned ints to add. | 36 // |values| is the vector of unsigned ints to add. |
| 36 void EnqueueAll(const std::vector<ELF::Xword>& values); | 37 void EnqueueAll(const std::vector<uint_t>& values); |
| 37 | 38 |
| 38 // Retrieve the encoded representation of the values. | 39 // Retrieve the encoded representation of the values. |
| 39 // |encoding| is the returned vector of encoded data. | 40 // |encoding| is the returned vector of encoded data. |
| 40 void GetEncoding(std::vector<uint8_t>* encoding) { *encoding = encoding_; } | 41 void GetEncoding(std::vector<uint8_t>* encoding) { *encoding = encoding_; } |
| 41 | 42 |
| 42 private: | 43 private: |
| 43 // Growable vector holding the encoded LEB128 stream. | 44 // Growable vector holding the encoded LEB128 stream. |
| 44 std::vector<uint8_t> encoding_; | 45 std::vector<uint8_t> encoding_; |
| 45 }; | 46 }; |
| 46 | 47 |
| 47 // Decode a LEB128 byte stream to produce packed words. | 48 // Decode a LEB128 byte stream to produce packed words. |
| 49 template <typename uint_t> |
| 48 class Leb128Decoder { | 50 class Leb128Decoder { |
| 49 public: | 51 public: |
| 50 // Create a new decoder for the given encoded stream. | 52 // Create a new decoder for the given encoded stream. |
| 51 // |encoding| is the vector of encoded data. | 53 // |encoding| is the vector of encoded data. |
| 52 explicit Leb128Decoder(const std::vector<uint8_t>& encoding); | 54 explicit Leb128Decoder(const std::vector<uint8_t>& encoding, size_t start_with
); |
| 53 | 55 |
| 54 // Explicit (but empty) destructor, for chromium-style. | 56 // Explicit (but empty) destructor, for chromium-style. |
| 55 ~Leb128Decoder(); | 57 ~Leb128Decoder(); |
| 56 | 58 |
| 57 // Retrieve the next value from the encoded stream. | 59 // Retrieve the next value from the encoded stream. |
| 58 ELF::Xword Dequeue(); | 60 uint_t Dequeue(); |
| 59 | 61 |
| 60 // Retrieve all remaining values from the encoded stream. | 62 // Retrieve all remaining values from the encoded stream. |
| 61 // |values| is the vector of decoded data. | 63 // |values| is the vector of decoded data. |
| 62 void DequeueAll(std::vector<ELF::Xword>* values); | 64 void DequeueAll(std::vector<uint_t>* values); |
| 63 | 65 |
| 64 private: | 66 private: |
| 65 // Encoded LEB128 stream. | 67 // Encoded LEB128 stream. |
| 66 std::vector<uint8_t> encoding_; | 68 std::vector<uint8_t> encoding_; |
| 67 | 69 |
| 68 // Cursor indicating the current stream retrieval point. | 70 // Cursor indicating the current stream retrieval point. |
| 69 size_t cursor_; | 71 size_t cursor_; |
| 70 }; | 72 }; |
| 71 | 73 |
| 72 } // namespace relocation_packer | 74 } // namespace relocation_packer |
| 73 | 75 |
| 74 #endif // TOOLS_RELOCATION_PACKER_SRC_LEB128_H_ | 76 #endif // TOOLS_RELOCATION_PACKER_SRC_LEB128_H_ |
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