cannam@125: /*
cannam@125:  * Copyright (c) 2011 Apple Inc. All rights reserved.
cannam@125:  *
cannam@125:  * @APPLE_APACHE_LICENSE_HEADER_START@
cannam@125:  *
cannam@125:  * Licensed under the Apache License, Version 2.0 (the "License") ;
cannam@125:  * you may not use this file except in compliance with the License.
cannam@125:  * You may obtain a copy of the License at
cannam@125:  *
cannam@125:  *	 http://www.apache.org/licenses/LICENSE-2.0
cannam@125:  *
cannam@125:  * Unless required by applicable law or agreed to in writing, software
cannam@125:  * distributed under the License is distributed on an "AS IS" BASIS,
cannam@125:  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
cannam@125:  * See the License for the specific language governing permissions and
cannam@125:  * limitations under the License.
cannam@125:  *
cannam@125:  * @APPLE_APACHE_LICENSE_HEADER_END@
cannam@125:  */
cannam@125: 
cannam@125: /*=============================================================================
cannam@125: 	File:		ALACBitUtilities.c
cannam@125: 
cannam@125: 	$NoKeywords: $
cannam@125: =============================================================================*/
cannam@125: 
cannam@125: #include <stdio.h>
cannam@125: #include "ALACBitUtilities.h"
cannam@125: 
cannam@125: #define PRAGMA_MARK 0
cannam@125: 
cannam@125: // BitBufferInit
cannam@125: //
cannam@125: void BitBufferInit (BitBuffer * bits, uint8_t * buffer, uint32_t byteSize)
cannam@125: {
cannam@125: 	bits->cur		= buffer ;
cannam@125: 	bits->end		= bits->cur + byteSize ;
cannam@125: 	bits->bitIndex	= 0 ;
cannam@125: 	bits->byteSize	= byteSize ;
cannam@125: }
cannam@125: 
cannam@125: // BitBufferRead
cannam@125: //
cannam@125: uint32_t BitBufferRead (BitBuffer * bits, uint8_t numBits)
cannam@125: {
cannam@125: 	uint32_t		returnBits ;
cannam@125: 
cannam@125: 	//Assert (numBits <= 16) ;
cannam@125: 
cannam@125: 	returnBits = ((uint32_t) bits->cur [0] << 16) | ((uint32_t) bits->cur [1] << 8) | ((uint32_t) bits->cur [2]) ;
cannam@125: 	returnBits = returnBits << bits->bitIndex ;
cannam@125: 	returnBits &= 0x00FFFFFF ;
cannam@125: 
cannam@125: 	bits->bitIndex += numBits ;
cannam@125: 
cannam@125: 	returnBits = returnBits >> (24 - numBits) ;
cannam@125: 
cannam@125: 	bits->cur		+= (bits->bitIndex >> 3) ;
cannam@125: 	bits->bitIndex	&= 7 ;
cannam@125: 
cannam@125: 	//Assert (bits->cur <= bits->end) ;
cannam@125: 
cannam@125: 	return returnBits ;
cannam@125: }
cannam@125: 
cannam@125: // BitBufferReadSmall
cannam@125: //
cannam@125: // Reads up to 8 bits
cannam@125: uint8_t BitBufferReadSmall (BitBuffer * bits, uint8_t numBits)
cannam@125: {
cannam@125: 	uint16_t		returnBits ;
cannam@125: 
cannam@125: 	//Assert (numBits <= 8) ;
cannam@125: 
cannam@125: 	returnBits = (bits->cur [0] << 8) | bits->cur [1] ;
cannam@125: 	returnBits = returnBits << bits->bitIndex ;
cannam@125: 
cannam@125: 	bits->bitIndex += numBits ;
cannam@125: 
cannam@125: 	returnBits = returnBits >> (16 - numBits) ;
cannam@125: 
cannam@125: 	bits->cur		+= (bits->bitIndex >> 3) ;
cannam@125: 	bits->bitIndex	&= 7 ;
cannam@125: 
cannam@125: 	//Assert (bits->cur <= bits->end) ;
cannam@125: 
cannam@125: 	return (uint8_t) returnBits ;
cannam@125: }
cannam@125: 
cannam@125: // BitBufferReadOne
cannam@125: //
cannam@125: // Reads one byte
cannam@125: uint8_t BitBufferReadOne (BitBuffer * bits)
cannam@125: {
cannam@125: 	uint8_t		returnBits ;
cannam@125: 
cannam@125: 	returnBits = (bits->cur [0] >> (7 - bits->bitIndex)) & 1 ;
cannam@125: 
cannam@125: 	bits->bitIndex++ ;
cannam@125: 
cannam@125: 	bits->cur		+= (bits->bitIndex >> 3) ;
cannam@125: 	bits->bitIndex	&= 7 ;
cannam@125: 
cannam@125: 	//Assert (bits->cur <= bits->end) ;
cannam@125: 
cannam@125: 	return returnBits ;
cannam@125: }
cannam@125: 
cannam@125: // BitBufferPeek
cannam@125: //
cannam@125: uint32_t BitBufferPeek (BitBuffer * bits, uint8_t numBits)
cannam@125: {
cannam@125: 	return ((((((uint32_t) bits->cur [0] << 16) | ((uint32_t) bits->cur [1] << 8) |
cannam@125: 			((uint32_t) bits->cur [2])) << bits->bitIndex) & 0x00FFFFFF) >> (24 - numBits)) ;
cannam@125: }
cannam@125: 
cannam@125: // BitBufferPeekOne
cannam@125: //
cannam@125: uint32_t BitBufferPeekOne (BitBuffer * bits)
cannam@125: {
cannam@125: 	return ((bits->cur [0] >> (7 - bits->bitIndex)) & 1) ;
cannam@125: }
cannam@125: 
cannam@125: // BitBufferUnpackBERSize
cannam@125: //
cannam@125: uint32_t BitBufferUnpackBERSize (BitBuffer * bits)
cannam@125: {
cannam@125: 	uint32_t		size ;
cannam@125: 	uint8_t		tmp ;
cannam@125: 
cannam@125: 	for (size = 0, tmp = 0x80u ; tmp &= 0x80u ; size = (size << 7u) | (tmp & 0x7fu))
cannam@125: 		tmp = (uint8_t) BitBufferReadSmall (bits, 8) ;
cannam@125: 
cannam@125: 	return size ;
cannam@125: }
cannam@125: 
cannam@125: // BitBufferGetPosition
cannam@125: //
cannam@125: uint32_t BitBufferGetPosition (BitBuffer * bits)
cannam@125: {
cannam@125: 	uint8_t *		begin ;
cannam@125: 
cannam@125: 	begin = bits->end - bits->byteSize ;
cannam@125: 
cannam@125: 	return ((uint32_t) (bits->cur - begin) * 8) + bits->bitIndex ;
cannam@125: }
cannam@125: 
cannam@125: // BitBufferByteAlign
cannam@125: //
cannam@125: void BitBufferByteAlign (BitBuffer * bits, int32_t addZeros)
cannam@125: {
cannam@125: 	// align bit buffer to next byte boundary, writing zeros if requested
cannam@125: 	if (bits->bitIndex == 0)
cannam@125: 		return ;
cannam@125: 
cannam@125: 	if (addZeros)
cannam@125: 		BitBufferWrite (bits, 0, 8 - bits->bitIndex) ;
cannam@125: 	else
cannam@125: 		BitBufferAdvance (bits, 8 - bits->bitIndex) ;
cannam@125: }
cannam@125: 
cannam@125: // BitBufferAdvance
cannam@125: //
cannam@125: void BitBufferAdvance (BitBuffer * bits, uint32_t numBits)
cannam@125: {
cannam@125: 	if (numBits)
cannam@125: 	{
cannam@125: 		bits->bitIndex += numBits ;
cannam@125: 		bits->cur += (bits->bitIndex >> 3) ;
cannam@125: 		bits->bitIndex &= 7 ;
cannam@125: 	}
cannam@125: }
cannam@125: 
cannam@125: // BitBufferRewind
cannam@125: //
cannam@125: void BitBufferRewind (BitBuffer * bits, uint32_t numBits)
cannam@125: {
cannam@125: 	uint32_t	numBytes ;
cannam@125: 
cannam@125: 	if (numBits == 0)
cannam@125: 		return ;
cannam@125: 
cannam@125: 	if (bits->bitIndex >= numBits)
cannam@125: 	{
cannam@125: 		bits->bitIndex -= numBits ;
cannam@125: 		return ;
cannam@125: 	}
cannam@125: 
cannam@125: 	numBits -= bits->bitIndex ;
cannam@125: 	bits->bitIndex = 0 ;
cannam@125: 
cannam@125: 	numBytes	= numBits / 8 ;
cannam@125: 	numBits		= numBits % 8 ;
cannam@125: 
cannam@125: 	bits->cur -= numBytes ;
cannam@125: 
cannam@125: 	if (numBits > 0)
cannam@125: 	{
cannam@125: 		bits->bitIndex = 8 - numBits ;
cannam@125: 		bits->cur-- ;
cannam@125: 	}
cannam@125: 
cannam@125: 	if (bits->cur < (bits->end - bits->byteSize))
cannam@125: 	{
cannam@125: 		//DebugCMsg ("BitBufferRewind: Rewound too far.") ;
cannam@125: 
cannam@125: 		bits->cur		= (bits->end - bits->byteSize) ;
cannam@125: 		bits->bitIndex	= 0 ;
cannam@125: 	}
cannam@125: }
cannam@125: 
cannam@125: // BitBufferWrite
cannam@125: //
cannam@125: void BitBufferWrite (BitBuffer * bits, uint32_t bitValues, uint32_t numBits)
cannam@125: {
cannam@125: 	uint32_t				invBitIndex ;
cannam@125: 
cannam@125: 	RequireAction (bits != NULL, return ;) ;
cannam@125: 	RequireActionSilent (numBits > 0, return ;) ;
cannam@125: 
cannam@125: 	invBitIndex = 8 - bits->bitIndex ;
cannam@125: 
cannam@125: 	while (numBits > 0)
cannam@125: 	{
cannam@125: 		uint32_t		tmp ;
cannam@125: 		uint8_t		shift ;
cannam@125: 		uint8_t		mask ;
cannam@125: 		uint32_t		curNum ;
cannam@125: 
cannam@125: 		curNum = MIN (invBitIndex, numBits) ;
cannam@125: 
cannam@125: 		tmp = bitValues >> (numBits - curNum) ;
cannam@125: 
cannam@125: 		shift = (uint8_t) (invBitIndex - curNum) ;
cannam@125: 		mask = 0xffu >> (8 - curNum) ;		// must be done in two steps to avoid compiler sequencing ambiguity
cannam@125: 		mask <<= shift ;
cannam@125: 
cannam@125: 		bits->cur [0] = (bits->cur [0] & ~mask) | (((uint8_t) tmp << shift) & mask) ;
cannam@125: 		numBits -= curNum ;
cannam@125: 
cannam@125: 		// increment to next byte if need be
cannam@125: 		invBitIndex -= curNum ;
cannam@125: 		if (invBitIndex == 0)
cannam@125: 		{
cannam@125: 			invBitIndex = 8 ;
cannam@125: 			bits->cur++ ;
cannam@125: 		}
cannam@125: 	}
cannam@125: 
cannam@125: 	bits->bitIndex = 8 - invBitIndex ;
cannam@125: }
cannam@125: 
cannam@125: void	BitBufferReset (BitBuffer * bits)
cannam@125: //void BitBufferInit (BitBuffer * bits, uint8_t * buffer, uint32_t byteSize)
cannam@125: {
cannam@125: 	bits->cur = bits->end - bits->byteSize ;
cannam@125: 	bits->bitIndex = 0 ;
cannam@125: }
cannam@125: 
cannam@125: #if PRAGMA_MARK
cannam@125: #pragma mark -
cannam@125: #endif