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/* Copyright (C) 2002 Jean-Marc Valin
File: bits.c
Handles bit packing/unpacking
This library is free software; you can redistribute it and/or
modify it under the terms of the GNU Lesser General Public
License as published by the Free Software Foundation; either
version 2.1 of the License, or (at your option) any later version.
This library is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
Lesser General Public License for more details.
You should have received a copy of the GNU Lesser General Public
License along with this library; if not, write to the Free Software
Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
*/
#include "bits.h"
#include <stdio.h>
#include <stdlib.h>
void frame_bits_init(FrameBits *bits)
{
int i;
for (i=0;i<MAX_BYTES_PER_FRAME;i++)
bits->bytes[i]=0;
bits->nbBits=0;
bits->bytePtr=0;
bits->bitPtr=0;
}
void frame_bits_destroy(FrameBits *bits)
{
/* Will do something once the allocation is dynamic */
}
void frame_bits_reset(FrameBits *bits)
{
int i;
for (i=0;i<MAX_BYTES_PER_FRAME;i++)
bits->bytes[i]=0;
bits->nbBits=0;
bits->bytePtr=0;
bits->bitPtr=0;
}
void frame_bits_rewind(FrameBits *bits)
{
bits->bytePtr=0;
bits->bitPtr=0;
}
void frame_bits_init_from(FrameBits *bits, char *bytes, int len)
{
int i;
if (len > MAX_BYTES_PER_FRAME)
{
fprintf (stderr, "Trying to init frame with too many bits");
exit(1);
}
for (i=0;i<len;i++)
bits->bytes[i]=bytes[i];
bits->nbBits=len<<3;
bits->bytePtr=0;
bits->bitPtr=0;
}
int frame_bits_write(FrameBits *bits, char *bytes, int max_len)
{
int i;
if (max_len > ((bits->nbBits+7)>>3))
max_len = ((bits->nbBits+7)>>3);
for (i=0;i<max_len;i++)
bytes[i]=bits->bytes[i];
return max_len;
}
int frame_bits_write_whole_bytes(FrameBits *bits, char *bytes, int max_len)
{
int i;
if (max_len > ((bits->nbBits)>>3))
max_len = ((bits->nbBits)>>3);
for (i=0;i<max_len;i++)
bytes[i]=bits->bytes[i];
bits->bytes[0]=bits->bytes[max_len];
bits->bytePtr=0;
bits->nbBits-=((bits->nbBits)>>3)<<3;
return max_len;
}
void frame_bits_pack(FrameBits *bits, int data, int nbBits)
{
unsigned int d=data;
while(nbBits)
{
int bit;
bit = (d>>(nbBits-1))&1;
bits->bytes[bits->bytePtr] |= bit<<(7-bits->bitPtr);
bits->bitPtr++;
/*fprintf(stderr, "%d %d\n", nbBits, bit);*/
if (bits->bitPtr==8)
{
bits->bitPtr=0;
bits->bytePtr++;
}
bits->nbBits++;
nbBits--;
}
}
int frame_bits_unpack_signed(FrameBits *bits, int nbBits)
{
unsigned int d=frame_bits_unpack_unsigned(bits,nbBits);
/* If number is negative */
if (d>>(nbBits-1))
{
d |= (-1)<<nbBits;
}
return d;
}
unsigned int frame_bits_unpack_unsigned(FrameBits *bits, int nbBits)
{
unsigned int d=0;
while(nbBits)
{
d<<=1;
d |= (bits->bytes[bits->bytePtr]>>(7-bits->bitPtr))&1;
bits->bitPtr++;
if (bits->bitPtr==8)
{
bits->bitPtr=0;
bits->bytePtr++;
}
nbBits--;
}
return d;
}
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