bitwise.c

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/********************************************************************
 *                                                                  *
 * THIS FILE IS PART OF THE OggVorbis SOFTWARE CODEC SOURCE CODE.   *
 * USE, DISTRIBUTION AND REPRODUCTION OF THIS LIBRARY SOURCE IS     *
 * GOVERNED BY A BSD-STYLE SOURCE LICENSE INCLUDED WITH THIS SOURCE *
 * IN 'COPYING'. PLEASE READ THESE TERMS BEFORE DISTRIBUTING.       *
 *                                                                  *
 * THE OggVorbis SOURCE CODE IS (C) COPYRIGHT 1994-2002             *
 * by the Xiph.Org Foundation http://www.xiph.org/                  *
 *                                                                  *
 ********************************************************************

  function: packing variable sized words into an octet stream
  last mod: $Id: bitwise.c 7675 2004-09-01 00:34:39Z xiphmont $

 ********************************************************************/

/* We're 'LSb' endian; if we write a word but read individual bits,
   then we'll read the lsb first */

#include <string.h>
#include <stdlib.h>
#include <ogg/ogg.h>

#define BUFFER_INCREMENT 256

static const unsigned long mask[]=
{0x00000000,0x00000001,0x00000003,0x00000007,0x0000000f,
 0x0000001f,0x0000003f,0x0000007f,0x000000ff,0x000001ff,
 0x000003ff,0x000007ff,0x00000fff,0x00001fff,0x00003fff,
 0x00007fff,0x0000ffff,0x0001ffff,0x0003ffff,0x0007ffff,
 0x000fffff,0x001fffff,0x003fffff,0x007fffff,0x00ffffff,
 0x01ffffff,0x03ffffff,0x07ffffff,0x0fffffff,0x1fffffff,
 0x3fffffff,0x7fffffff,0xffffffff };

static const unsigned int mask8B[]=
{0x00,0x80,0xc0,0xe0,0xf0,0xf8,0xfc,0xfe,0xff};

void oggpack_writeinit(oggpack_buffer *b){
  memset(b,0,sizeof(*b));
  b->ptr=b->buffer=_ogg_malloc(BUFFER_INCREMENT);
  b->buffer[0]='\0';
  b->storage=BUFFER_INCREMENT;
}

void oggpackB_writeinit(oggpack_buffer *b){
  oggpack_writeinit(b);
}

void oggpack_writetrunc(oggpack_buffer *b,long bits){
  long bytes=bits>>3;
  bits-=bytes*8;
  b->ptr=b->buffer+bytes;
  b->endbit=bits;
  b->endbyte=bytes;
  *b->ptr&=mask[bits];
}

void oggpackB_writetrunc(oggpack_buffer *b,long bits){
  long bytes=bits>>3;
  bits-=bytes*8;
  b->ptr=b->buffer+bytes;
  b->endbit=bits;
  b->endbyte=bytes;
  *b->ptr&=mask8B[bits];
}

/* Takes only up to 32 bits. */
void oggpack_write(oggpack_buffer *b,unsigned long value,int bits){
  if(b->endbyte+4>=b->storage){
    b->buffer=_ogg_realloc(b->buffer,b->storage+BUFFER_INCREMENT);
    b->storage+=BUFFER_INCREMENT;
    b->ptr=b->buffer+b->endbyte;
  }

  value&=mask[bits]; 
  bits+=b->endbit;

  b->ptr[0]|=value<<b->endbit;  
  
  if(bits>=8){
    b->ptr[1]=(unsigned char)(value>>(8-b->endbit));
    if(bits>=16){
      b->ptr[2]=(unsigned char)(value>>(16-b->endbit));
      if(bits>=24){
	b->ptr[3]=(unsigned char)(value>>(24-b->endbit));
	if(bits>=32){
	  if(b->endbit)
	    b->ptr[4]=(unsigned char)(value>>(32-b->endbit));
	  else
	    b->ptr[4]=0;
	}
      }
    }
  }

  b->endbyte+=bits/8;
  b->ptr+=bits/8;
  b->endbit=bits&7;
}

/* Takes only up to 32 bits. */
void oggpackB_write(oggpack_buffer *b,unsigned long value,int bits){
  if(b->endbyte+4>=b->storage){
    b->buffer=_ogg_realloc(b->buffer,b->storage+BUFFER_INCREMENT);
    b->storage+=BUFFER_INCREMENT;
    b->ptr=b->buffer+b->endbyte;
  }

  value=(value&mask[bits])<<(32-bits); 
  bits+=b->endbit;

  b->ptr[0]|=value>>(24+b->endbit);  
  
  if(bits>=8){
    b->ptr[1]=(unsigned char)(value>>(16+b->endbit));
    if(bits>=16){
      b->ptr[2]=(unsigned char)(value>>(8+b->endbit));
      if(bits>=24){
	b->ptr[3]=(unsigned char)(value>>(b->endbit));
	if(bits>=32){
	  if(b->endbit)
	    b->ptr[4]=(unsigned char)(value<<(8-b->endbit));
	  else
	    b->ptr[4]=0;
	}
      }
    }
  }

  b->endbyte+=bits/8;
  b->ptr+=bits/8;
  b->endbit=bits&7;
}

void oggpack_writealign(oggpack_buffer *b){
  int bits=8-b->endbit;
  if(bits<8)
    oggpack_write(b,0,bits);
}

void oggpackB_writealign(oggpack_buffer *b){
  int bits=8-b->endbit;
  if(bits<8)
    oggpackB_write(b,0,bits);
}

static void oggpack_writecopy_helper(oggpack_buffer *b,
				     void *source,
				     long bits,
				     void (*w)(oggpack_buffer *,
					       unsigned long,
					       int),
				     int msb){
  unsigned char *ptr=(unsigned char *)source;

  long bytes=bits/8;
  bits-=bytes*8;

  if(b->endbit){
    int i;
    /* unaligned copy.  Do it the hard way. */
    for(i=0;i<bytes;i++)
      w(b,(unsigned long)(ptr[i]),8);    
  }else{
    /* aligned block copy */
    if(b->endbyte+bytes+1>=b->storage){
      b->storage=b->endbyte+bytes+BUFFER_INCREMENT;
      b->buffer=_ogg_realloc(b->buffer,b->storage);
      b->ptr=b->buffer+b->endbyte;
    }

    memmove(b->ptr,source,bytes);
    b->ptr+=bytes;
    b->endbyte+=bytes;
    *b->ptr=0;

  }
  if(bits){
    if(msb)
      w(b,(unsigned long)(ptr[bytes]>>(8-bits)),bits);    
    else
      w(b,(unsigned long)(ptr[bytes]),bits);    
  }
}

void oggpack_writecopy(oggpack_buffer *b,void *source,long bits){
  oggpack_writecopy_helper(b,source,bits,oggpack_write,0);
}

void oggpackB_writecopy(oggpack_buffer *b,void *source,long bits){
  oggpack_writecopy_helper(b,source,bits,oggpackB_write,1);
}

void oggpack_reset(oggpack_buffer *b){
  b->ptr=b->buffer;
  b->buffer[0]=0;
  b->endbit=b->endbyte=0;
}

void oggpackB_reset(oggpack_buffer *b){
  oggpack_reset(b);
}

void oggpack_writeclear(oggpack_buffer *b){
  _ogg_free(b->buffer);
  memset(b,0,sizeof(*b));
}

void oggpackB_writeclear(oggpack_buffer *b){
  oggpack_writeclear(b);
}

void oggpack_readinit(oggpack_buffer *b,unsigned char *buf,int bytes){
  memset(b,0,sizeof(*b));
  b->buffer=b->ptr=buf;
  b->storage=bytes;
}

void oggpackB_readinit(oggpack_buffer *b,unsigned char *buf,int bytes){
  oggpack_readinit(b,buf,bytes);
}

/* Read in bits without advancing the bitptr; bits <= 32 */
long oggpack_look(oggpack_buffer *b,int bits){
  unsigned long ret;
  unsigned long m=mask[bits];

  bits+=b->endbit;

  if(b->endbyte+4>=b->storage){
    /* not the main path */
    if(b->endbyte*8+bits>b->storage*8)return(-1);
  }
  
  ret=b->ptr[0]>>b->endbit;
  if(bits>8){
    ret|=b->ptr[1]<<(8-b->endbit);  
    if(bits>16){
      ret|=b->ptr[2]<<(16-b->endbit);  
      if(bits>24){
	ret|=b->ptr[3]<<(24-b->endbit);  
	if(bits>32 && b->endbit)
	  ret|=b->ptr[4]<<(32-b->endbit);
      }
    }
  }
  return(m&ret);
}

/* Read in bits without advancing the bitptr; bits <= 32 */
long oggpackB_look(oggpack_buffer *b,int bits){
  unsigned long ret;
  int m=32-bits;

  bits+=b->endbit;

  if(b->endbyte+4>=b->storage){
    /* not the main path */
    if(b->endbyte*8+bits>b->storage*8)return(-1);
  }
  
  ret=b->ptr[0]<<(24+b->endbit);
  if(bits>8){
    ret|=b->ptr[1]<<(16+b->endbit);  
    if(bits>16){
      ret|=b->ptr[2]<<(8+b->endbit);  
      if(bits>24){
	ret|=b->ptr[3]<<(b->endbit);  
	if(bits>32 && b->endbit)
	  ret|=b->ptr[4]>>(8-b->endbit);
      }
    }
  }
  return ((ret&0xffffffff)>>(m>>1))>>((m+1)>>1);
}

long oggpack_look1(oggpack_buffer *b){
  if(b->endbyte>=b->storage)return(-1);
  return((b->ptr[0]>>b->endbit)&1);
}

long oggpackB_look1(oggpack_buffer *b){
  if(b->endbyte>=b->storage)return(-1);
  return((b->ptr[0]>>(7-b->endbit))&1);
}

void oggpack_adv(oggpack_buffer *b,int bits){
  bits+=b->endbit;
  b->ptr+=bits/8;
  b->endbyte+=bits/8;
  b->endbit=bits&7;
}

void oggpackB_adv(oggpack_buffer *b,int bits){
  oggpack_adv(b,bits);
}

void oggpack_adv1(oggpack_buffer *b){
  if(++(b->endbit)>7){
    b->endbit=0;
    b->ptr++;
    b->endbyte++;
  }
}

void oggpackB_adv1(oggpack_buffer *b){
  oggpack_adv1(b);
}

/* bits <= 32 */
long oggpack_read(oggpack_buffer *b,int bits){
  long ret;
  unsigned long m=mask[bits];

  bits+=b->endbit;

  if(b->endbyte+4>=b->storage){
    /* not the main path */
    ret=-1L;
    if(b->endbyte*8+bits>b->storage*8)goto overflow;
  }
  
  ret=b->ptr[0]>>b->endbit;
  if(bits>8){
    ret|=b->ptr[1]<<(8-b->endbit);  
    if(bits>16){
      ret|=b->ptr[2]<<(16-b->endbit);  
      if(bits>24){
	ret|=b->ptr[3]<<(24-b->endbit);  
	if(bits>32 && b->endbit){
	  ret|=b->ptr[4]<<(32-b->endbit);
	}
      }
    }
  }
  ret&=m;
  
 overflow:

  b->ptr+=bits/8;
  b->endbyte+=bits/8;
  b->endbit=bits&7;
  return(ret);
}

/* bits <= 32 */
long oggpackB_read(oggpack_buffer *b,int bits){
  long ret;
  long m=32-bits;
  
  bits+=b->endbit;

  if(b->endbyte+4>=b->storage){
    /* not the main path */
    ret=-1L;
    if(b->endbyte*8+bits>b->storage*8)goto overflow;
  }
  
  ret=b->ptr[0]<<(24+b->endbit);
  if(bits>8){
    ret|=b->ptr[1]<<(16+b->endbit);  
    if(bits>16){
      ret|=b->ptr[2]<<(8+b->endbit);  
      if(bits>24){
	ret|=b->ptr[3]<<(b->endbit);  
	if(bits>32 && b->endbit)
	  ret|=b->ptr[4]>>(8-b->endbit);
      }
    }
  }
  ret=((ret&0xffffffffUL)>>(m>>1))>>((m+1)>>1);
  
 overflow:

  b->ptr+=bits/8;
  b->endbyte+=bits/8;
  b->endbit=bits&7;
  return(ret);
}

long oggpack_read1(oggpack_buffer *b){
  long ret;
  
  if(b->endbyte>=b->storage){
    /* not the main path */
    ret=-1L;
    goto overflow;
  }

  ret=(b->ptr[0]>>b->endbit)&1;
  
 overflow: