/* 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"


/* huffman_decode() is supposed to be faster now
 * decodes one codeword and returns no. of bits
 */
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;
}