www.pudn.com > av3dec_20050318.zip > sam_bitbuffer.c

/* 
*********************************************************************** 
* COPYRIGHT AND WARRANTY INFORMATION 
* 
* Copyright 2004,  Audio Video Coding Standard, Part III 
* 
* This software module was originally developed by 
* 
* JungHoe Kim (kjh94@samsung.com), Samsung AIT 
* 
* edited by 
* 
* Lei Miao (win.miaolei@samsung.com), Samsung AIT 
* 
* DISCLAIMER OF WARRANTY 
* 
* These software programs are available to the users without any 
* license fee or royalty on an "as is" basis. The AVS disclaims 
* any and all warranties, whether express, implied, or statutory, 
* including any implied warranties of merchantability or of fitness 
* for a particular purpose. In no event shall the contributors or  
* the AVS be liable for any incidental, punitive, or consequential 
* damages of any kind whatsoever arising from the use of this program. 
* 
* This disclaimer of warranty extends to the user of this program 
* and user's customers, employees, agents, transferees, successors, 
* and assigns. 
* 
* The AVS does not represent or warrant that the program furnished 
* hereunder are free of infringement of any third-party patents. 
* Commercial implementations of AVS, including shareware, may be 
* subject to royalty fees to patent holders. Information regarding 
* the AVS patent policy is available from the AVS Web site at 
* http://www.avs.org.cn 
* 
* THIS IS NOT A GRANT OF PATENT RIGHTS - SEE THE AVS PATENT POLICY. 
************************************************************************ 
*/ 
 
#include  
#include  
#include  
#include  
#include "sam_cbc_dec.h" 
 
#define  MINIMUM    3 
#define  MAX_LENGTH  32 
#define  ALIGNING  8 
 
static unsigned char bs_buf[4096];  /* bit stream buffer */ 
static int  bs_buf_size;            /* size of buffer (in number of bytes) */ 
static long  bs_totbit;             /* bit counter of bit stream */ 
static int  bs_buf_byte_idx;        /* pointer to top byte in buffer */ 
static int  bs_buf_bit_idx;         /* pointer to top bit of top byte in buffer */ 
static int  bs_eob;                 /* end of buffer index */ 
static int  bs_eobs;                /* end of bit stream flag */ 
 
 
/* open the device to read the bit stream from it */ 
void init_layer_buf() 
{ 
  int i; 
  bs_buf_byte_idx=4095; 
  bs_buf_bit_idx=0; 
  bs_totbit=0; 
  bs_eob = FALSE; 
  bs_eobs = FALSE; 
  bs_buf_size = 4096; 
  for(i = 0; i < bs_buf_size; i++) 
    bs_buf[i] = 0; 
} 
 
void setRBitBufPos(int pos) 
{ 
	bs_buf_byte_idx = pos / 8; 
	bs_buf_bit_idx  = 8 - (pos % 8); 
} 
 
static int putmask[9]={0x0, 0x1, 0x3, 0x7, 0xf, 0x1f, 0x3f, 0x7f, 0xff}; 
static int mask[8]={0x1, 0x2, 0x4, 0x8, 0x10, 0x20, 0x40, 0x80}; 
 
/*read N bit from the bit stream */ 
unsigned int getbitsfrombuf(int N) 
{ 
  unsigned long val=0; 
  register int i; 
  register int j = N; 
  register int k, tmp; 
 
  if(N <= 0) return 0; 
 
  if (N > MAX_LENGTH) 
    printf("Cannot read or write more than %d bits at a time.\n", MAX_LENGTH); 
 
  bs_totbit += N; 
  while (j > 0) { 
    if (!bs_buf_bit_idx) { 
      bs_buf_bit_idx = 8; 
      bs_buf_byte_idx++; 
      if ((bs_buf_byte_idx >= (bs_buf_size - MINIMUM)) || (bs_buf_byte_idx == bs_eob)) { 
        if (bs_eob) { 
          bs_eobs = TRUE; 
          return 0; 
        } 
		else { 
          for (i=bs_buf_byte_idx; i> (bs_buf_bit_idx-k)) << (j-k); 
    bs_buf_bit_idx -= k; 
    j -= k; 
  } 
  return(val); 
} 
 
/*write N bits into the bit stream */ 
int putbits2buf( unsigned int val, int N) 
{ 
 register int j = N; 
 register int k, tmp; 
 
 if (N < 1) 
	return 0; 
 if (N > MAX_LENGTH) { 
    printf("Cannot read or write more than %d bits[%d] at a time.\n", MAX_LENGTH, val); 
    return 0; 
 } 
 
 while (j > 0) { 
   k = (j < bs_buf_bit_idx) ? j : bs_buf_bit_idx; 
   tmp = val >> (j-k); 
   bs_buf[bs_buf_byte_idx] |= (tmp&putmask[k]) << (bs_buf_bit_idx-k); 
   bs_buf_bit_idx -= k; 
   if (!bs_buf_bit_idx) { 
       bs_buf_bit_idx = 8; 
       bs_buf_byte_idx++; 
       if (bs_buf_byte_idx > bs_buf_size-1) { 
		fprintf(stderr, "SAM: bitstream buffer overflow!\n"); 
	   } 
   } 
   j -= k; 
 } 
 return N; 
}