poke/alac/codec/ALACBitUtilities.c
2023-02-12 09:14:46 +00:00

260 lines
5.4 KiB
C

/*
* Copyright (c) 2011 Apple Inc. All rights reserved.
*
* @APPLE_APACHE_LICENSE_HEADER_START@
*
* 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.
*
* @APPLE_APACHE_LICENSE_HEADER_END@
*/
/*=============================================================================
File: ALACBitUtilities.c
$NoKeywords: $
=============================================================================*/
#include <stdio.h>
#include "ALACBitUtilities.h"
// BitBufferInit
//
void BitBufferInit( BitBuffer * bits, uint8_t * buffer, uint32_t byteSize )
{
bits->cur = buffer;
bits->end = bits->cur + byteSize;
bits->bitIndex = 0;
bits->byteSize = byteSize;
}
// BitBufferRead
//
uint32_t BitBufferRead( BitBuffer * bits, uint8_t numBits )
{
uint32_t returnBits;
//Assert( numBits <= 16 );
returnBits = ((uint32_t)bits->cur[0] << 16) | ((uint32_t)bits->cur[1] << 8) | ((uint32_t)bits->cur[2]);
returnBits = returnBits << bits->bitIndex;
returnBits &= 0x00FFFFFF;
bits->bitIndex += numBits;
returnBits = returnBits >> (24 - numBits);
bits->cur += (bits->bitIndex >> 3);
bits->bitIndex &= 7;
//Assert( bits->cur <= bits->end );
return returnBits;
}
// BitBufferReadSmall
//
// Reads up to 8 bits
uint8_t BitBufferReadSmall( BitBuffer * bits, uint8_t numBits )
{
uint16_t returnBits;
//Assert( numBits <= 8 );
returnBits = (bits->cur[0] << 8) | bits->cur[1];
returnBits = returnBits << bits->bitIndex;
bits->bitIndex += numBits;
returnBits = returnBits >> (16 - numBits);
bits->cur += (bits->bitIndex >> 3);
bits->bitIndex &= 7;
//Assert( bits->cur <= bits->end );
return (uint8_t)returnBits;
}
// BitBufferReadOne
//
// Reads one byte
uint8_t BitBufferReadOne( BitBuffer * bits )
{
uint8_t returnBits;
returnBits = (bits->cur[0] >> (7 - bits->bitIndex)) & 1;
bits->bitIndex++;
bits->cur += (bits->bitIndex >> 3);
bits->bitIndex &= 7;
//Assert( bits->cur <= bits->end );
return returnBits;
}
// BitBufferPeek
//
uint32_t BitBufferPeek( BitBuffer * bits, uint8_t numBits )
{
return ((((((uint32_t) bits->cur[0] << 16) | ((uint32_t) bits->cur[1] << 8) |
((uint32_t) bits->cur[2])) << bits->bitIndex) & 0x00FFFFFF) >> (24 - numBits));
}
// BitBufferPeekOne
//
uint32_t BitBufferPeekOne( BitBuffer * bits )
{
return ((bits->cur[0] >> (7 - bits->bitIndex)) & 1);
}
// BitBufferUnpackBERSize
//
uint32_t BitBufferUnpackBERSize( BitBuffer * bits )
{
uint32_t size;
uint8_t tmp;
for ( size = 0, tmp = 0x80u; tmp &= 0x80u; size = (size << 7u) | (tmp & 0x7fu) )
tmp = (uint8_t) BitBufferReadSmall( bits, 8 );
return size;
}
// BitBufferGetPosition
//
uint32_t BitBufferGetPosition( BitBuffer * bits )
{
uint8_t * begin;
begin = bits->end - bits->byteSize;
return ((uint32_t)(bits->cur - begin) * 8) + bits->bitIndex;
}
// BitBufferByteAlign
//
void BitBufferByteAlign( BitBuffer * bits, int32_t addZeros )
{
// align bit buffer to next byte boundary, writing zeros if requested
if ( bits->bitIndex == 0 )
return;
if ( addZeros )
BitBufferWrite( bits, 0, 8 - bits->bitIndex );
else
BitBufferAdvance( bits, 8 - bits->bitIndex );
}
// BitBufferAdvance
//
void BitBufferAdvance( BitBuffer * bits, uint32_t numBits )
{
if ( numBits )
{
bits->bitIndex += numBits;
bits->cur += (bits->bitIndex >> 3);
bits->bitIndex &= 7;
}
}
// BitBufferRewind
//
void BitBufferRewind( BitBuffer * bits, uint32_t numBits )
{
uint32_t numBytes;
if ( numBits == 0 )
return;
if ( bits->bitIndex >= numBits )
{
bits->bitIndex -= numBits;
return;
}
numBits -= bits->bitIndex;
bits->bitIndex = 0;
numBytes = numBits / 8;
numBits = numBits % 8;
bits->cur -= numBytes;
if ( numBits > 0 )
{
bits->bitIndex = 8 - numBits;
bits->cur--;
}
if ( bits->cur < (bits->end - bits->byteSize) )
{
//DebugCMsg("BitBufferRewind: Rewound too far.");
bits->cur = (bits->end - bits->byteSize);
bits->bitIndex = 0;
}
}
// BitBufferWrite
//
void BitBufferWrite( BitBuffer * bits, uint32_t bitValues, uint32_t numBits )
{
uint32_t invBitIndex;
RequireAction( bits != nil, return; );
RequireActionSilent( numBits > 0, return; );
invBitIndex = 8 - bits->bitIndex;
while ( numBits > 0 )
{
uint32_t tmp;
uint8_t shift;
uint8_t mask;
uint32_t curNum;
curNum = MIN( invBitIndex, numBits );
tmp = bitValues >> (numBits - curNum);
shift = (uint8_t)(invBitIndex - curNum);
mask = 0xffu >> (8 - curNum); // must be done in two steps to avoid compiler sequencing ambiguity
mask <<= shift;
bits->cur[0] = (bits->cur[0] & ~mask) | (((uint8_t) tmp << shift) & mask);
numBits -= curNum;
// increment to next byte if need be
invBitIndex -= curNum;
if ( invBitIndex == 0 )
{
invBitIndex = 8;
bits->cur++;
}
}
bits->bitIndex = 8 - invBitIndex;
}
void BitBufferReset( BitBuffer * bits )
//void BitBufferInit( BitBuffer * bits, uint8_t * buffer, uint32_t byteSize )
{
bits->cur = bits->end - bits->byteSize;
bits->bitIndex = 0;
}
#if PRAGMA_MARK
#pragma mark -
#endif