// Copyright 2017 The Chromium OS 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 "puffin/src/bit_reader.h"
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#include "puffin/src/logging.h"
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namespace puffin {
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bool BufferBitReader::CacheBits(size_t nbits) {
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if ((in_size_ - index_) * 8 + in_cache_bits_ < nbits) {
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return false;
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}
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if (nbits > sizeof(in_cache_) * 8) {
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return false;
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}
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while (in_cache_bits_ < nbits) {
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in_cache_ |= in_buf_[index_++] << in_cache_bits_;
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in_cache_bits_ += 8;
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}
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return true;
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}
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uint32_t BufferBitReader::ReadBits(size_t nbits) {
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return in_cache_ & ((1U << nbits) - 1);
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}
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void BufferBitReader::DropBits(size_t nbits) {
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in_cache_ >>= nbits;
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in_cache_bits_ -= nbits;
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}
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uint8_t BufferBitReader::ReadBoundaryBits() {
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return in_cache_ & ((1 << (in_cache_bits_ & 7)) - 1);
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}
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size_t BufferBitReader::SkipBoundaryBits() {
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size_t nbits = in_cache_bits_ & 7;
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in_cache_ >>= nbits;
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in_cache_bits_ -= nbits;
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return nbits;
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}
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bool BufferBitReader::GetByteReaderFn(
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size_t length, std::function<bool(uint8_t*, size_t)>* read_fn) {
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index_ -= (in_cache_bits_ + 7) / 8;
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in_cache_ = 0;
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in_cache_bits_ = 0;
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TEST_AND_RETURN_FALSE(length <= in_size_ - index_);
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*read_fn = [this, length](uint8_t* buffer, size_t count) mutable {
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TEST_AND_RETURN_FALSE(count <= length);
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if (buffer != nullptr) {
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memcpy(buffer, &in_buf_[index_], count);
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}
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index_ += count;
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length -= count;
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return true;
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};
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return true;
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}
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size_t BufferBitReader::Offset() const {
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return index_ - in_cache_bits_ / 8;
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}
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uint64_t BufferBitReader::OffsetInBits() const {
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return (index_ * 8) - in_cache_bits_;
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}
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uint64_t BufferBitReader::BitsRemaining() const {
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return ((in_size_ - index_) * 8) + in_cache_bits_;
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}
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} // namespace puffin
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