mirror of
https://github.com/scratchfoundation/bgfx.git
synced 2024-11-25 09:08:22 -05:00
125 lines
3.7 KiB
C++
125 lines
3.7 KiB
C++
/*
|
|
Copyright (c) 2014, Conor Stokes
|
|
All rights reserved.
|
|
|
|
Redistribution and use in source and binary forms, with or without
|
|
modification, are permitted provided that the following conditions are met:
|
|
|
|
1. Redistributions of source code must retain the above copyright notice, this
|
|
list of conditions and the following disclaimer.
|
|
2. Redistributions in binary form must reproduce the above copyright notice,
|
|
this list of conditions and the following disclaimer in the documentation
|
|
and/or other materials provided with the distribution.
|
|
|
|
THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND
|
|
ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
|
|
WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
|
|
DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR
|
|
ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
|
|
(INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
|
|
LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
|
|
ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
|
|
(INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
|
|
SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
|
|
*/
|
|
#ifndef READ_BIT_STREAM_H__
|
|
#define READ_BIT_STREAM_H__
|
|
#pragma once
|
|
|
|
#include <stdint.h>
|
|
|
|
#ifdef _MSC_VER
|
|
|
|
#define RBS_INLINE __forceinline
|
|
|
|
#else
|
|
|
|
#define RBS_INLINE __attribute__((always_inline))
|
|
|
|
#endif
|
|
|
|
// Very simple reader bitstream, note it does not do any overflow checking, etc.
|
|
class ReadBitstream
|
|
{
|
|
public:
|
|
|
|
// Construct the bitstream with a fixed byte buffer (which should be padded out to multiples of 8 bytes, as we read in 8 byte chunks).
|
|
ReadBitstream( const uint8_t* buffer, size_t bufferSize );
|
|
|
|
~ReadBitstream() {}
|
|
|
|
// Read a number of bits
|
|
uint32_t Read( uint32_t bitcount );
|
|
|
|
// Get the buffer size of this in bytes
|
|
size_t Size() const { return m_bufferSize; }
|
|
|
|
private:
|
|
|
|
uint64_t m_bitBuffer;
|
|
|
|
const uint8_t* m_buffer;
|
|
const uint8_t* m_cursor;
|
|
|
|
size_t m_bufferSize;
|
|
uint32_t m_bitsLeft;
|
|
|
|
};
|
|
|
|
inline ReadBitstream::ReadBitstream( const uint8_t* buffer, size_t bufferSize )
|
|
{
|
|
m_cursor =
|
|
m_buffer = buffer;
|
|
m_bufferSize = bufferSize;
|
|
|
|
if ( bufferSize >= 8 )
|
|
{
|
|
m_bitBuffer = m_cursor[ 0 ];
|
|
m_bitBuffer |= static_cast< uint64_t >( m_cursor[ 1 ] ) << 8;
|
|
m_bitBuffer |= static_cast< uint64_t >( m_cursor[ 2 ] ) << 16;
|
|
m_bitBuffer |= static_cast< uint64_t >( m_cursor[ 3 ] ) << 24;
|
|
m_bitBuffer |= static_cast< uint64_t >( m_cursor[ 4 ] ) << 32;
|
|
m_bitBuffer |= static_cast< uint64_t >( m_cursor[ 5 ] ) << 40;
|
|
m_bitBuffer |= static_cast< uint64_t >( m_cursor[ 6 ] ) << 48;
|
|
m_bitBuffer |= static_cast< uint64_t >( m_cursor[ 7 ] ) << 56;
|
|
|
|
m_cursor += 8;
|
|
m_bitsLeft = 64;
|
|
}
|
|
else
|
|
{
|
|
m_bitsLeft = 0;
|
|
}
|
|
}
|
|
|
|
|
|
RBS_INLINE uint32_t ReadBitstream::Read( uint32_t bitCount )
|
|
{
|
|
uint64_t mask = ( 1 << bitCount ) - 1;
|
|
uint32_t result = static_cast< uint32_t >( ( m_bitBuffer >> ( 64 - m_bitsLeft ) ) & mask );
|
|
|
|
if ( m_bitsLeft < bitCount )
|
|
{
|
|
m_bitBuffer = m_cursor[ 0 ];
|
|
m_bitBuffer |= static_cast< uint64_t >( m_cursor[ 1 ] ) << 8;
|
|
m_bitBuffer |= static_cast< uint64_t >( m_cursor[ 2 ] ) << 16;
|
|
m_bitBuffer |= static_cast< uint64_t >( m_cursor[ 3 ] ) << 24;
|
|
m_bitBuffer |= static_cast< uint64_t >( m_cursor[ 4 ] ) << 32;
|
|
m_bitBuffer |= static_cast< uint64_t >( m_cursor[ 5 ] ) << 40;
|
|
m_bitBuffer |= static_cast< uint64_t >( m_cursor[ 6 ] ) << 48;
|
|
m_bitBuffer |= static_cast< uint64_t >( m_cursor[ 7 ] ) << 56;
|
|
|
|
m_cursor += 8;
|
|
|
|
result |= static_cast< uint32_t >( m_bitBuffer << m_bitsLeft ) & mask;
|
|
m_bitsLeft = 64 - ( bitCount - m_bitsLeft );
|
|
}
|
|
else
|
|
{
|
|
m_bitsLeft -= bitCount;
|
|
}
|
|
|
|
return result;
|
|
}
|
|
|
|
#endif // -- READ_BIT_STREAM_H__
|