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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 // TODO(simonb): Extend for 64-bit target libraries. |
| 6 |
| 7 #include "relocation_packer_leb128.h" |
| 8 |
| 9 #include <stdint.h> |
| 10 #include <vector> |
| 11 |
| 12 namespace relocation_packer { |
| 13 |
| 14 // Add a single value to the encoding. Values are encoded with variable |
| 15 // length. The least significant 7 bits of each byte hold 7 bits of data, |
| 16 // and the most significant bit is set on each byte except the last. |
| 17 void Leb128Encoder::Enqueue(uint32_t value) { |
| 18 while (value > 127) { |
| 19 encoding_.push_back((1 << 7) | (value & 127)); |
| 20 value >>= 7; |
| 21 } |
| 22 encoding_.push_back(value); |
| 23 } |
| 24 |
| 25 // Add a vector of values to the encoding. |
| 26 void Leb128Encoder::Enqueue(const std::vector<uint32_t>& values) { |
| 27 for (size_t i = 0; i < values.size(); ++i) |
| 28 Enqueue(values[i]); |
| 29 } |
| 30 |
| 31 // Decode and retrieve a single value from the encoding. Read forwards until |
| 32 // a byte without its most significant bit is found, then read the 7 bit |
| 33 // fields of the bytes spanned to re-form the value. |
| 34 uint32_t Leb128Decoder::Dequeue() { |
| 35 size_t extent = cursor_; |
| 36 while (encoding_[extent] >> 7) |
| 37 extent++; |
| 38 |
| 39 uint32_t value = 0; |
| 40 for (size_t i = extent; i > cursor_; --i) { |
| 41 value = (value << 7) | (encoding_[i] & 127); |
| 42 } |
| 43 value = (value << 7) | (encoding_[cursor_] & 127); |
| 44 |
| 45 cursor_ = extent + 1; |
| 46 return value; |
| 47 } |
| 48 |
| 49 // Decode and retrieve all remaining values from the encoding. |
| 50 void Leb128Decoder::Dequeue(std::vector<uint32_t>* values) { |
| 51 while (cursor_ < encoding_.size()) |
| 52 values->push_back(Dequeue()); |
| 53 } |
| 54 |
| 55 } // namespace relocation_packer |
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