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