mirror of
https://github.com/klzgrad/naiveproxy.git
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134 lines
3.4 KiB
C++
134 lines
3.4 KiB
C++
// Copyright (c) 2016 The Chromium Authors. All rights reserved.
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// Use of this source code is governed by a BSD-style license that can be
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// found in the LICENSE file.
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#include "net/tools/huffman_trie/trie/trie_bit_buffer.h"
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#include "base/logging.h"
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#include "net/tools/huffman_trie/bit_writer.h"
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namespace net {
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namespace huffman_trie {
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TrieBitBuffer::TrieBitBuffer() = default;
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TrieBitBuffer::~TrieBitBuffer() = default;
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void TrieBitBuffer::WriteBit(uint8_t bit) {
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current_byte_ |= bit << (7 - used_);
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used_++;
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if (used_ == 8) {
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Flush();
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}
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}
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void TrieBitBuffer::WriteBits(uint32_t bits, uint8_t number_of_bits) {
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DCHECK(number_of_bits <= 32);
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for (uint8_t i = 1; i <= number_of_bits; i++) {
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uint8_t bit = 1 & (bits >> (number_of_bits - i));
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WriteBit(bit);
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}
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}
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void TrieBitBuffer::WritePosition(uint32_t position, int32_t* last_position) {
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if (*last_position != -1) {
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int32_t delta = position - *last_position;
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DCHECK(delta > 0) << "delta position is not positive.";
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uint8_t number_of_bits = BitLength(delta);
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DCHECK(number_of_bits <= 7 + 15) << "positive position delta too large.";
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if (number_of_bits <= 7) {
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WriteBits(0, 1);
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WriteBits(delta, 7);
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} else {
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WriteBits(1, 1);
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WriteBits(number_of_bits - 8, 4);
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WriteBits(delta, number_of_bits);
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}
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*last_position = position;
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return;
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}
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if (used_ != 0) {
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Flush();
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}
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AppendPositionElement(position);
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*last_position = position;
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}
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uint8_t TrieBitBuffer::BitLength(uint32_t input) const {
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uint8_t number_of_bits = 0;
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while (input != 0) {
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number_of_bits++;
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input >>= 1;
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}
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return number_of_bits;
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}
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void TrieBitBuffer::WriteChar(uint8_t byte,
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const HuffmanRepresentationTable& table,
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HuffmanBuilder* huffman_builder) {
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HuffmanRepresentationTable::const_iterator item;
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item = table.find(byte);
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DCHECK(item != table.end());
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if (huffman_builder) {
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huffman_builder->RecordUsage(byte);
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}
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WriteBits(item->second.bits, item->second.number_of_bits);
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}
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void TrieBitBuffer::AppendBitsElement(uint8_t bits, uint8_t number_of_bits) {
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BitsOrPosition element;
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element.bits = current_byte_;
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element.number_of_bits = used_;
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elements_.push_back(element);
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}
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void TrieBitBuffer::AppendPositionElement(uint32_t position) {
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BitsOrPosition element;
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element.position = position;
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element.number_of_bits = 0;
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elements_.push_back(element);
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}
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uint32_t TrieBitBuffer::WriteToBitWriter(BitWriter* writer) {
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Flush();
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uint32_t old_position = writer->position();
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for (auto const& element : elements_) {
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if (element.number_of_bits) {
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writer->WriteBits(element.bits >> (8 - element.number_of_bits),
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element.number_of_bits);
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} else {
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uint32_t current = old_position;
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uint32_t target = element.position;
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DCHECK(target < current) << "Reference is not backwards";
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uint32_t delta = current - target;
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uint8_t delta_number_of_bits = BitLength(delta);
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DCHECK(delta_number_of_bits < 32) << "Delta to large";
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writer->WriteBits(delta_number_of_bits, 5);
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writer->WriteBits(delta, delta_number_of_bits);
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}
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}
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return old_position;
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}
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void TrieBitBuffer::Flush() {
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if (used_) {
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AppendBitsElement(current_byte_, used_);
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used_ = 0;
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current_byte_ = 0;
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}
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}
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} // namespace huffman_trie
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} // namespace net
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