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ffmpeg/libavcodec/common.c
Michael Niedermayer 6300c80a88 dont trash table in GET_VLC 
Originally committed as revision 741 to svn://svn.ffmpeg.org/ffmpeg/trunk
2002-07-11 12:42:20 +00:00

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/*
* Common bit i/o utils
* Copyright (c) 2000, 2001 Fabrice Bellard.
*
* 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 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
*
* alternative bitstream reader & writer by Michael Niedermayer <michaelni@gmx.at>
*/
#include "avcodec.h"
void init_put_bits(PutBitContext *s,
UINT8 *buffer, int buffer_size,
void *opaque,
void (*write_data)(void *, UINT8 *, int))
{
s->buf = buffer;
s->buf_end = s->buf + buffer_size;
s->data_out_size = 0;
if(write_data!=NULL)
{
fprintf(stderr, "write Data callback is not supported\n");
}
#ifdef ALT_BITSTREAM_WRITER
s->index=0;
((uint32_t*)(s->buf))[0]=0;
// memset(buffer, 0, buffer_size);
#else
s->buf_ptr = s->buf;
s->bit_left=32;
s->bit_buf=0;
#endif
}
/* return the number of bits output */
INT64 get_bit_count(PutBitContext *s)
{
#ifdef ALT_BITSTREAM_WRITER
return s->data_out_size * 8 + s->index;
#else
return (s->buf_ptr - s->buf + s->data_out_size) * 8 + 32 - (INT64)s->bit_left;
#endif
}
void align_put_bits(PutBitContext *s)
{
#ifdef ALT_BITSTREAM_WRITER
put_bits(s,( - s->index) & 7,0);
#else
put_bits(s,s->bit_left & 7,0);
#endif
}
/* pad the end of the output stream with zeros */
void flush_put_bits(PutBitContext *s)
{
#ifdef ALT_BITSTREAM_WRITER
align_put_bits(s);
#else
s->bit_buf<<= s->bit_left;
while (s->bit_left < 32) {
/* XXX: should test end of buffer */
*s->buf_ptr++=s->bit_buf >> 24;
s->bit_buf<<=8;
s->bit_left+=8;
}
s->bit_left=32;
s->bit_buf=0;
#endif
}
/* pad the end of the output stream with zeros */
#ifndef ALT_BITSTREAM_WRITER
void jflush_put_bits(PutBitContext *s)
{
unsigned int b;
s->bit_buf<<= s->bit_left;
s->bit_buf |= ~1U >> (32 - s->bit_left); /* set all the unused bits to one */
while (s->bit_left < 32) {
b = s->bit_buf >> 24;
*s->buf_ptr++ = b;
if (b == 0xff)
*s->buf_ptr++ = 0;
s->bit_buf<<=8;
s->bit_left+=8;
}
s->bit_left=32;
s->bit_buf=0;
}
#else
void jflush_put_bits(PutBitContext *s)
{
int num= ( - s->index) & 7;
jput_bits(s, num,0xFF>>(8-num));
}
#endif
void put_string(PutBitContext * pbc, char *s)
{
while(*s){
put_bits(pbc, 8, *s);
s++;
}
put_bits(pbc, 8, 0);
}
/* bit input functions */
void init_get_bits(GetBitContext *s,
UINT8 *buffer, int buffer_size)
{
s->buffer= buffer;
s->size= buffer_size;
s->buffer_end= buffer + buffer_size;
#ifdef ALT_BITSTREAM_READER
s->index=0;
#elif defined LIBMPEG2_BITSTREAM_READER
s->buffer_ptr = buffer;
s->bit_count = 16;
s->cache = 0;
#elif defined A32_BITSTREAM_READER
s->buffer_ptr = (uint32_t*)buffer;
s->bit_count = 32;
s->cache0 = 0;
s->cache1 = 0;
#endif
{
OPEN_READER(re, s)
UPDATE_CACHE(re, s)
// UPDATE_CACHE(re, s)
CLOSE_READER(re, s)
}
#ifdef A32_BITSTREAM_READER
s->cache1 = 0;
#endif
}
void align_get_bits(GetBitContext *s)
{
int n= (-get_bits_count(s)) & 7;
if(n) skip_bits(s, n);
}
int check_marker(GetBitContext *s, char *msg)
{
int bit= get_bits1(s);
if(!bit) printf("Marker bit missing %s\n", msg);
return bit;
}
/* VLC decoding */
//#define DEBUG_VLC
#define GET_DATA(v, table, i, wrap, size) \
{\
UINT8 *ptr = (UINT8 *)table + i * wrap;\
switch(size) {\
case 1:\
v = *(UINT8 *)ptr;\
break;\
case 2:\
v = *(UINT16 *)ptr;\
break;\
default:\
v = *(UINT32 *)ptr;\
break;\
}\
}
static int alloc_table(VLC *vlc, int size)
{
int index;
index = vlc->table_size;
vlc->table_size += size;
if (vlc->table_size > vlc->table_allocated) {
vlc->table_allocated += (1 << vlc->bits);
vlc->table = realloc(vlc->table,
sizeof(VLC_TYPE) * 2 * vlc->table_allocated);
if (!vlc->table)
return -1;
}
return index;
}
static int build_table(VLC *vlc, int table_nb_bits,
int nb_codes,
const void *bits, int bits_wrap, int bits_size,
const void *codes, int codes_wrap, int codes_size,
UINT32 code_prefix, int n_prefix)
{
int i, j, k, n, table_size, table_index, nb, n1, index;
UINT32 code;
VLC_TYPE (*table)[2];
table_size = 1 << table_nb_bits;
table_index = alloc_table(vlc, table_size);
#ifdef DEBUG_VLC
printf("new table index=%d size=%d code_prefix=%x n=%d\n",
table_index, table_size, code_prefix, n_prefix);
#endif
if (table_index < 0)
return -1;
table = &vlc->table[table_index];
for(i=0;i<table_size;i++) {
table[i][1] = 0; //bits
table[i][0] = -1; //codes
}
/* first pass: map codes and compute auxillary table sizes */
for(i=0;i<nb_codes;i++) {
GET_DATA(n, bits, i, bits_wrap, bits_size);
GET_DATA(code, codes, i, codes_wrap, codes_size);
/* we accept tables with holes */
if (n <= 0)
continue;
#if defined(DEBUG_VLC) && 0
printf("i=%d n=%d code=0x%x\n", i, n, code);
#endif
/* if code matches the prefix, it is in the table */
n -= n_prefix;
if (n > 0 && (code >> n) == code_prefix) {
if (n <= table_nb_bits) {
/* no need to add another table */
j = (code << (table_nb_bits - n)) & (table_size - 1);
nb = 1 << (table_nb_bits - n);
for(k=0;k<nb;k++) {
#ifdef DEBUG_VLC
printf("%4x: code=%d n=%d\n",
j, i, n);
#endif
if (table[j][1] /*bits*/ != 0) {
fprintf(stderr, "incorrect codes\n");
exit(1);
}
table[j][1] = n; //bits
table[j][0] = i; //code
j++;
}
} else {
n -= table_nb_bits;
j = (code >> n) & ((1 << table_nb_bits) - 1);
#ifdef DEBUG_VLC
printf("%4x: n=%d (subtable)\n",
j, n);
#endif
/* compute table size */
n1 = -table[j][1]; //bits
if (n > n1)
n1 = n;
table[j][1] = -n1; //bits
}
}
}
/* second pass : fill auxillary tables recursively */
for(i=0;i<table_size;i++) {
n = table[i][1]; //bits
if (n < 0) {
n = -n;
if (n > table_nb_bits) {
n = table_nb_bits;
table[i][1] = -n; //bits
}
index = build_table(vlc, n, nb_codes,
bits, bits_wrap, bits_size,
codes, codes_wrap, codes_size,
(code_prefix << table_nb_bits) | i,
n_prefix + table_nb_bits);
if (index < 0)
return -1;
/* note: realloc has been done, so reload tables */
table = &vlc->table[table_index];
table[i][0] = index; //code
}
}
return table_index;
}
/* Build VLC decoding tables suitable for use with get_vlc().
'nb_bits' set thee decoding table size (2^nb_bits) entries. The
bigger it is, the faster is the decoding. But it should not be too
big to save memory and L1 cache. '9' is a good compromise.
'nb_codes' : number of vlcs codes
'bits' : table which gives the size (in bits) of each vlc code.
'codes' : table which gives the bit pattern of of each vlc code.
'xxx_wrap' : give the number of bytes between each entry of the
'bits' or 'codes' tables.
'xxx_size' : gives the number of bytes of each entry of the 'bits'
or 'codes' tables.
'wrap' and 'size' allows to use any memory configuration and types
(byte/word/long) to store the 'bits' and 'codes' tables.
*/
int init_vlc(VLC *vlc, int nb_bits, int nb_codes,
const void *bits, int bits_wrap, int bits_size,
const void *codes, int codes_wrap, int codes_size)
{
vlc->bits = nb_bits;
vlc->table = NULL;
vlc->table_allocated = 0;
vlc->table_size = 0;
#ifdef DEBUG_VLC
printf("build table nb_codes=%d\n", nb_codes);
#endif
if (build_table(vlc, nb_bits, nb_codes,
bits, bits_wrap, bits_size,
codes, codes_wrap, codes_size,
0, 0) < 0) {
av_free(vlc->table);
return -1;
}
return 0;
}
void free_vlc(VLC *vlc)
{
av_free(vlc->table);
}
int ff_gcd(int a, int b){
if(b) return ff_gcd(b, a%b);
else return a;
}
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