www.pudn.com > aacenc.rar > bitstream.c

/* 有关比特流的操作 */ 
 
/* Heavily modified since it is now only used to write bits to a buffer. */ 
 
#include  
#include  
#include  
#include  
 
#include "bitstream.h"		/* bit stream module */ 
#include "common.h"		/* common module */ 
 
 
#define BYTE_NUMBIT 8		/* bits in byte (char) */ 
#define LONG_NUMBIT 32		/* bits in unsigned long */ 
#define bit2byte(a) (((a)+BYTE_NUMBIT-1)/BYTE_NUMBIT) 
#define byte2bit(a) ((a)*BYTE_NUMBIT) 
 
 
BsBitStream *BsOpenWrite(int size) 
{ 
	BsBitStream *bs; 
 
	bs = malloc(sizeof(BsBitStream)); 
	bs->size = size; 
	bs->numBit = 0; 
	bs->currentBit = 0; 
	bs->data = malloc(bit2byte(size)); 
 
	return bs; 
} 
 
void BsClose(BsBitStream *bs) 
{ 
	free(bs->data); 
	free(bs); 
} 
 
long BsBufferNumBit (BsBitStream *bs) 
{ 
	return bs->numBit; 
} 
 
int BsWriteByte (BsBitStream *stream, 
				 unsigned long data, 
				 int numBit) 
{ 
	long numUsed,idx; 
 
	idx = (stream->currentBit / BYTE_NUMBIT) % bit2byte(stream->size); 
	numUsed = stream->currentBit % BYTE_NUMBIT; 
	if (numUsed == 0) 
		stream->data[idx] = 0; 
	stream->data[idx] |= (data & ((1<currentBit += numBit; 
	stream->numBit = stream->currentBit; 
 
	return 0; 
} 
 
int BsPutBit (BsBitStream *stream, 
			  unsigned long data, 
			  int numBit) 
{ 
	int num,maxNum,curNum; 
	unsigned long bits; 
 
	if (numBit == 0) 
		return 0; 
 
	/* write bits in packets according to buffer byte boundaries */ 
	num = 0; 
	maxNum = BYTE_NUMBIT - stream->currentBit % BYTE_NUMBIT; 
	while (num < numBit) { 
		curNum = min(numBit-num,maxNum); 
		bits = data>>numBit-num-curNum; 
		if (BsWriteByte(stream,bits,curNum)) { 
			return 1; 
		} 
		num += curNum; 
		maxNum = BYTE_NUMBIT; 
	} 
 
	return 0; 
}