Common C++ classes and routines used by my applications such as argument parser, IO and conversion utilities
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#ifndef IOUTILITIES_BITREADER_H
#define IOUTILITIES_BITREADER_H
#include "../conversion/types.h"
#include "../application/global.h"
#include <ios>
#include <iostream>
namespace IoUtilities {
class LIB_EXPORT BitReader
{
public:
BitReader(const char *buffer, std::size_t bufferSize);
BitReader(const char *buffer, const char *end);
template<typename intType> intType readBits(byte bitCount);
byte readBit();
template<typename intType> intType showBits(byte bitCount);
void skipBits(std::size_t bitCount);
void align();
std::size_t bitsAvailable();
void reset(const char *buffer, std::size_t bufferSize);
void reset(const char *buffer, const char *end);
private:
const byte *m_buffer;
const byte *m_end;
byte m_bitsAvail;
};
/*!
* \brief Constructs a new BitReader.
* \remarks
* - Does not take ownership over the specified \a buffer.
* - bufferSize must be equal or greather than 1.
*/
inline BitReader::BitReader(const char *buffer, std::size_t bufferSize) :
BitReader(buffer, buffer + bufferSize)
{}
/*!
* \brief Constructs a new BitReader.
* \remarks
* - Does not take ownership over the specified \a buffer.
* - \a end must be greather than \a buffer.
*/
inline BitReader::BitReader(const char *buffer, const char *end) :
m_buffer(reinterpret_cast<const byte *>(buffer)),
m_end(reinterpret_cast<const byte *>(end)),
m_bitsAvail(8)
{}
/*!
* \brief Reads the specified number of bits from the buffer advancing the current position by \a bitCount bits.
* \param bitCount Specifies the number of bits read.
* \tparam intType Specifies the type of the returned value.
* \remarks Does not check whether intType is big enough to hold result.
* \throws Throws ios_base::failure if the end of the buffer is exceeded.
* The reader becomes invalid in that case.
*/
template<typename intType>
intType BitReader::readBits(byte bitCount)
{
intType val = 0;
for(byte readAtOnce; bitCount; bitCount -= readAtOnce) {
if(!m_bitsAvail) {
if(++m_buffer >= m_end) {
throw std::ios_base::failure("end of buffer exceeded");
}
m_bitsAvail = 8;
}
readAtOnce = std::min(bitCount, m_bitsAvail);
val = (val << readAtOnce) | (((*m_buffer) >> (m_bitsAvail -= readAtOnce)) & (0xFF >> (0x08 - readAtOnce)));
}
return val;
}
/*!
* \brief Reads the one bit from the buffer advancing the current position by one bit.
* \throws Throws ios_base::failure if the end of the buffer is exceeded.
* The reader becomes invalid in that case.
*/
inline byte BitReader::readBit()
{
return readBits<byte>(1) == 1;
}
/*!
* \brief Reads the specified number of bits from the buffer without advancing the current position.
*/
template<typename intType>
intType BitReader::showBits(byte bitCount)
{
auto tmp = *this;
return tmp.readBits<intType>(bitCount);
}
/*!
* \brief Returns the number of bits which are still available to read.
*/
inline std::size_t BitReader::bitsAvailable()
{
return ((m_end - m_buffer) * 8) + m_bitsAvail;
}
/*!
* \brief Resets the reader.
* - Does not take ownership over the specified \a buffer.
* - bufferSize must be equal or greather than 1.
*/
inline void BitReader::reset(const char *buffer, size_t bufferSize)
{
m_buffer = reinterpret_cast<const byte *>(buffer);
m_end = reinterpret_cast<const byte *>(buffer + bufferSize);
m_bitsAvail = 8;
}
/*!
* \brief Resets the reader.
* - Does not take ownership over the specified \a buffer.
* - \a end must be greather than \a buffer.
*/
inline void BitReader::reset(const char *buffer, const char *end)
{
m_buffer = reinterpret_cast<const byte *>(buffer);
m_end = reinterpret_cast<const byte *>(end);
m_bitsAvail = 8;
}
/*!
* \brief Re-establishes alignment.
*/
inline void BitReader::align()
{
skipBits(m_bitsAvail);
}
} // namespace IoUtilities
#endif // IOUTILITIES_BITREADER_H