/*
* Copyright 2016 Intel Corporation
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
#ifndef bitReader_h
#define bitReader_h
#include <stdint.h>
#include <algorithm> /*std::min*/
namespace YamiParser {
class BitReader {
public:
static const uint32_t CACHEBYTES;
BitReader(const uint8_t* data, uint32_t size);
virtual ~BitReader() {}
/* Read specified bits(<= 8*sizeof(uint32_t)) as a uint32_t to v */
/* if not enough data, it will return false, eat all data and keep v untouched */
bool read(uint32_t& v, uint32_t nbits);
/* Read specified bits(<= 8*sizeof(uint32_t)) as a uint32_t return value */
/* will return 0 if not enough data*/
uint32_t read(uint32_t nbits);
/*TODO: change to this to read, and change read to readBits */
template <class T>
inline bool readT(T& v, uint32_t nbits);
template <class T>
inline bool readT(T& v);
inline bool readT(bool& v);
/*read the next nbits bits from the bitstream but not advance the bitstream pointer*/
uint32_t peek(uint32_t nbits) const;
/* this version will check read beyond boundary */
template <class T>
bool peek(T& v, uint32_t nbits) const;
bool skip(uint32_t nbits);
/* Get the total bits that had been read from bitstream, and the return
* value also is the position of the next bit to be read. */
uint64_t getPos() const
{
return (static_cast<uint64_t>(m_loadBytes) << 3) - m_bitsInCache;
}
uint64_t getRemainingBitsCount() const
{
return m_bitsInCache + (static_cast<uint64_t>(m_size - m_loadBytes) << 3);
}
bool end() const
{
return (getPos() >= (static_cast<uint64_t>(m_size) << 3));
}
protected:
virtual void loadDataToCache(uint32_t nbytes);
const uint8_t* m_stream; /*a pointer to source data*/
uint32_t m_size; /*the size of source data in bytes*/
unsigned long int m_cache; /*the buffer which load less than or equal to 8 bytes*/
uint32_t m_loadBytes; /*the total bytes of data read from source data*/
uint32_t m_bitsInCache; /*the remaining bits in cache*/
private:
inline uint32_t extractBitsFromCache(uint32_t nbits);
inline void reload();
};
template <class T>
bool BitReader::readT(T& v, uint32_t nbits)
{
uint32_t tmp;
if (!read(tmp, nbits))
return false;
v = tmp;
return true;
}
template <class T>
bool BitReader::readT(T& v)
{
return readT(v, sizeof(v) << 3);
}
bool BitReader::readT(bool& v)
{
return readT(v, 1);
}
template <class T>
bool BitReader::peek(T& v, uint32_t nbits) const
{
BitReader tmp(*this);
return tmp.readT(v, nbits);
}
} /*namespace YamiParser*/
#endif