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/* this file is a part of amp software, (C) tomislav uzelac 1996,1997
*/
/* huffman.c huffman decoding
*
* Created by: tomislav uzelac Mar,Apr 1996
* Last modified by: tomislav uzelac Mar 8 97
*/
#include "audio.h"
#include "getbits.h"
#define HUFFMAN
#include "huffman.h"
static inline unsigned int viewbits(int n)
{
unsigned int pos,ret_value;
pos = data >> 3;
ret_value = buffer[pos] << 24 |
buffer[pos+1] << 16 |
buffer[pos+2] << 8 |
buffer[pos+3];
ret_value <<= data & 7;
ret_value >>= 32 - n;
return ret_value;
}
static inline void sackbits(int n)
{
data += n;
data &= 8*BUFFER_SIZE-1;
}
/* huffman_decode() is supposed to be faster now
* decodes one codeword and returns no. of bits
*/
static inline int huffman_decode(int tbl,int *x,int *y)
{
unsigned int chunk;
register unsigned int *h_tab;
register unsigned int lag;
register unsigned int half_lag;
int len;
h_tab=tables[tbl];
chunk=viewbits(19);
h_tab += h_cue[tbl][chunk >> (19-NC_O)];
len=(*h_tab>>8)&0x1f;
/* check for an immediate hit, so we can decode those short codes very fast
*/
if ((*h_tab>>(32-len)) != (chunk>>(19-len))) {
if (chunk >> (19-NC_O) < N_CUE-1)
lag=(h_cue[tbl][(chunk >> (19-NC_O))+1] -
h_cue[tbl][chunk >> (19-NC_O)]);
else {
/* we strongly depend on h_cue[N_CUE-1] to point to
* the last entry in the huffman table, so we should
* not get here anyway. if it didn't, we'd have to
* have another table with huffman tables lengths, and
* it would be a mess. just in case, scream&shout.
*/
printf(" h_cue clobbered. this is a bug. blip.\n");
exit (-1);
}
chunk <<= 32-19;
chunk |= 0x1ff;
half_lag = lag >> 1;
h_tab += half_lag;
lag -= half_lag;
while (lag > 1) {
half_lag = lag >> 1;
if (*h_tab < chunk)
h_tab += half_lag;
else
h_tab -= half_lag;
lag -= half_lag;
}
len=(*h_tab>>8)&0x1f;
if ((*h_tab>>(32-len)) != (chunk>>(32-len))) {
if (*h_tab > chunk)
h_tab--;
else
h_tab++;
len=(*h_tab>>8)&0x1f;
}
}
sackbits(len);
*x=(*h_tab>>4)&0xf;
*y=*h_tab&0xf;
return len;
}
static inline int _qsign(int x,int *q)
{
int ret_value=0,i;
for (i=3;i>=0;i--)
if ((x>>i) & 1) {
if (getbits(1)) *q++=-1;
else *q++=1;
ret_value++;
}
else *q++=0;
return ret_value;
}
int decode_huffman_data(struct SIDE_INFO *info,int gr,int ch,int ssize)
{
int l,i,cnt,x,y;
int q[4],r[3],linbits[3],tr[4]={0,0,0,0};
int big_value = info->big_values[gr][ch] << 1;
for (l=0;l<3;l++) {
tr[l]=info->table_select[gr][ch][l];
linbits[l]=t_linbits[info->table_select[gr][ch][l]];
}
tr[3]=32+info->count1table_select[gr][ch];
/* we have to be careful here because big_values are not necessarily
* aligned with sfb boundaries
*/
if (!info->window_switching_flag[gr][ch] && info->block_type[gr][ch]==0) {
/* this code needed some cleanup
*/
r[0]=t_l[info->region0_count[gr][ch]] + 1;
if (r[0] > big_value)
r[0]=r[1]=big_value;
else {
r[1]=t_l[ info->region0_count[gr][ch] + info->region1_count[gr][ch] + 1 ] + 1;
if (r[1] > big_value)
r[1]=big_value;
}
r[2]=big_value;
} else {
if (info->block_type[gr][ch]==2 && info->mixed_block_flag[gr][ch]==0)
r[0]=3*(t_s[2]+1);
else
r[0]=t_l[7]+1;
if (r[0] > big_value)
r[0]=big_value;
r[1]=r[2]=big_value;
}
l=0; cnt=0;
for (i=0;i<3;i++) {
for (;l<r[i];l+=2) {
int j = linbits[i];
cnt+=huffman_decode(tr[i],&x,&y);
if (x==15 && j>0) {
x+=getbits(j);
cnt+=j;
}
if (x) {
if (getbits(1)) x=-x;
cnt++;
}
if (y==15 && j>0) {
y+=getbits(j);
cnt+=j;
}
if (y) {
if (getbits(1)) y=-y;
cnt++;
}
is[ch][l]=x;
is[ch][l+1]=y;
}
}
while ((cnt < info->part2_3_length[gr][ch]-ssize) && (l<576)) {
cnt+=huffman_decode(tr[3],&x,&y);
cnt+=_qsign(x,q);
for (i=0;i<4;i++) is[ch][l+i]=q[i]; /* ziher je ziher, is[578]*/
l+=4;
}
/* set position to start of the next gr/ch
*/
if (cnt != info->part2_3_length[gr][ch] - ssize ) {
data-=cnt-(info->part2_3_length[gr][ch] - ssize);
data&= 8*BUFFER_SIZE - 1;
}
if (l<576) non_zero[ch]=l;
else non_zero[ch]=576;
/* zero out everything else
*/
for (;l<576;l++) is[ch][l]=0;
return 1;
}
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