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// 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.
#include "leb128.h"
#include <stdint.h>
#include <vector>
#include "elf_traits.h"
namespace relocation_packer {
// Empty constructor and destructor to silence chromium-style.
template <typename uint_t>
Leb128Encoder<uint_t>::Leb128Encoder() { }
template <typename uint_t>
Leb128Encoder<uint_t>::~Leb128Encoder() { }
// Add a single value to the encoding. Values are encoded with variable
// length. The least significant 7 bits of each byte hold 7 bits of data,
// and the most significant bit is set on each byte except the last.
template <typename uint_t>
void Leb128Encoder<uint_t>::Enqueue(uint_t value) {
uint_t uvalue = static_cast<uint_t>(value);
do {
const uint8_t byte = uvalue & 127;
uvalue >>= 7;
encoding_.push_back((uvalue ? 128 : 0) | byte);
} while (uvalue);
}
// Add a vector of values to the encoding.
template <typename uint_t>
void Leb128Encoder<uint_t>::EnqueueAll(const std::vector<uint_t>& values) {
for (size_t i = 0; i < values.size(); ++i) {
Enqueue(values[i]);
}
}
// Create a new decoder for the given encoded stream.
template <typename uint_t>
Leb128Decoder<uint_t>::Leb128Decoder(const std::vector<uint8_t>& encoding, size_t start_with) {
encoding_ = encoding;
cursor_ = start_with;
}
// Empty destructor to silence chromium-style.
template <typename uint_t>
Leb128Decoder<uint_t>::~Leb128Decoder() { }
// Decode and retrieve a single value from the encoding. Read forwards until
// a byte without its most significant bit is found, then read the 7 bit
// fields of the bytes spanned to re-form the value.
template <typename uint_t>
uint_t Leb128Decoder<uint_t>::Dequeue() {
uint_t value = 0;
size_t shift = 0;
uint8_t byte;
// Loop until we reach a byte with its high order bit clear.
do {
byte = encoding_[cursor_++];
value |= static_cast<uint_t>(byte & 127) << shift;
shift += 7;
} while (byte & 128);
return value;
}
// Decode and retrieve all remaining values from the encoding.
template <typename uint_t>
void Leb128Decoder<uint_t>::DequeueAll(std::vector<uint_t>* values) {
while (cursor_ < encoding_.size()) {
values->push_back(Dequeue());
}
}
template class Leb128Encoder<uint32_t>;
template class Leb128Encoder<uint64_t>;
template class Leb128Decoder<uint32_t>;
template class Leb128Decoder<uint64_t>;
} // namespace relocation_packer
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