/* 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 "amiga.h"
#include "audio.h"
#include "getbits.h"

#define HUFFMAN
#include "huffman.h"

static 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 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 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 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;
}