huff.h

mp3解码源代码

/****************************************************************************/

/*
 *	huff.h -- Definition of Huffman Codes handling
 *
 *	Author  :   St閜hane TAVENARD
 *
 *	(C) Copyright 1997-1997 St閜hane TAVENARD
 *	    All Rights Reserved
 *
 *	This program is free software; you can redistribute it and/or modify
 *	it under the terms of the GNU General Public License as published by
 *	the Free Software Foundation; either version 2 of the License, or
 *	(at your option) any later version.
 *	
 *	This program 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 General Public License for more details.
 *	
 *	You should have received a copy of the GNU General Public License
 *	along with this program; if not, write to the Free Software
 *	Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
 */

/****************************************************************************/
#ifndef HUFF_H
#define HUFF_H
/****************************************************************************/

#define	HUFF_BUFFER_SIZE	4096
#define	HUFF_MAX_BITS		32

typedef struct {
	int		buffer_size;
	unsigned char	*buffer;
	int		write_index;
	int		read_index;
	unsigned long	bit_cache;
	int		cache_size;
	unsigned long	bits;
	INT16		nul_begin; // begin of last null zone
} HUFFMAN;


/*
 *	HUFF macros.
 */
#define HUFF_pos(h) \
	((((h->read_index<<3) - h->cache_size) < 0) ? \
	 (((h->read_index<<3) - h->cache_size) + (HUFF_BUFFER_SIZE<<3)) : \
	 ((h->read_index<<3) - h->cache_size))

#define HUFF_diff(s,e) \
	((s <= e) ? (e - s) : ((HUFF_BUFFER_SIZE<<3) + e - s))

#define HUFF_fill_byte(h,b) \
	(h->buffer[h->write_index++] = b, \
	 h->write_index &= HUFF_BUFFER_SIZE-1)

#define HUFF_read_bit(h) \
	((h->cache_size-- > 0) ? \
	 (h->bits = (h->bit_cache & 0x80000000) ? 1 : 0, \
	 h->bit_cache <<= 1, h->bits) : \
	 HUFF_read_bit_cache(h))

#define HUFF_read_bits(h,c) \
	(((c) <= 0) ? 0 : (h->cache_size >= (c)) ? \
	 (h->cache_size -= (c), h->bits = h->bit_cache >> (32-(c)), \
	 h->bit_cache <<= (c), h->bits) : HUFF_read_bits_cache(h, c))


/*
 *	Exported functions.
 */
extern HUFFMAN	*HUFF_open(void);
extern void	HUFF_close(HUFFMAN *h);
extern int	HUFF_reset(HUFFMAN *h);
extern void	HUFF_fill_bytes(HUFFMAN *h, unsigned int count, char *buffer);
extern int	HUFF_set_start(HUFFMAN *h, int start_pos);
extern int	HUFF_seek(HUFFMAN *h, int seek_pos);
extern int	HUFF_decode_pair(HUFFMAN *h, INT16 table, INT16 count,
			INT16 *x);
extern int	HUFF_decode_quad(HUFFMAN *h, INT16 table, INT16 max_bits,
			INT16 val_count, INT16 val_top, INT16 *x);

extern unsigned long	HUFF_read_bit_cache(HUFFMAN *h);
extern unsigned long	HUFF_read_bits_cache(HUFFMAN *h, unsigned int count);

/****************************************************************************/
#endif /* HUFF_H */