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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 R_ARM_RELATIVE relocations. |
| 6 // |
| 7 // Run-length encoded R_ARM_RELATIVE relocations consist of a large number |
| 8 // of pairs of relatively small positive integer values. Encoding these as |
| 9 // LEB128 saves space. |
| 10 // |
| 11 // For more on LEB128 see http://en.wikipedia.org/wiki/LEB128. |
| 12 |
| 13 #ifndef TOOLS_RELOCATION_PACKER_SRC_LEB128_H_ |
| 14 #define TOOLS_RELOCATION_PACKER_SRC_LEB128_H_ |
| 15 |
| 16 #include <stdint.h> |
| 17 #include <unistd.h> |
| 18 #include <vector> |
| 19 |
| 20 namespace relocation_packer { |
| 21 |
| 22 // Encode packed words as a LEB128 byte stream. |
| 23 class Leb128Encoder { |
| 24 public: |
| 25 // Add a value to the encoding stream. |
| 26 // |value| is the unsigned int to add. |
| 27 void Enqueue(uint32_t value); |
| 28 |
| 29 // Add a vector of values to the encoding stream. |
| 30 // |values| is the vector of unsigned ints to add. |
| 31 void EnqueueAll(const std::vector<uint32_t>& values); |
| 32 |
| 33 // Retrieve the encoded representation of the values. |
| 34 // |encoding| is the returned vector of encoded data. |
| 35 void GetEncoding(std::vector<uint8_t>* encoding) { *encoding = encoding_; } |
| 36 |
| 37 private: |
| 38 // Growable vector holding the encoded LEB128 stream. |
| 39 std::vector<uint8_t> encoding_; |
| 40 }; |
| 41 |
| 42 // Decode a LEB128 byte stream to produce packed words. |
| 43 class Leb128Decoder { |
| 44 public: |
| 45 // Create a new decoder for the given encoded stream. |
| 46 // |encoding| is the vector of encoded data. |
| 47 explicit Leb128Decoder(const std::vector<uint8_t>& encoding) |
| 48 : encoding_(encoding), cursor_(0) { } |
| 49 |
| 50 // Retrieve the next value from the encoded stream. |
| 51 uint32_t Dequeue(); |
| 52 |
| 53 // Retrieve all remaining values from the encoded stream. |
| 54 // |values| is the vector of decoded data. |
| 55 void DequeueAll(std::vector<uint32_t>* values); |
| 56 |
| 57 private: |
| 58 // Encoded LEB128 stream. |
| 59 std::vector<uint8_t> encoding_; |
| 60 |
| 61 // Cursor indicating the current stream retrieval point. |
| 62 size_t cursor_; |
| 63 }; |
| 64 |
| 65 } // namespace relocation_packer |
| 66 |
| 67 #endif // TOOLS_RELOCATION_PACKER_SRC_LEB128_H_ |
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