bitstr.h

这是一个自己开发的键盘驱动代码

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

/*
 *	bitstr.h -- C Definition of BitStream files handling
 *
 *	Author  :   St閜hane TAVENARD
 *
 *	(C) Copyright 1997-1998 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 BITSTR_H
#define BITSTR_H
/****************************************************************************/

/*
 *	Endianess optimizations.
 */
#ifndef LITTLE_ENDIAN
#define BSTR_MSBF
#endif

#ifdef BSTR_MSBF
// This target is MSB first, so faster
#define BSTR_BUFF unsigned int
#else
#define BSTR_BUFF unsigned char
#endif

/*
 *	File stream access:
 *
 *	open:  open the bitstream, should return the file handle or NULL
 *	       if failed
 *	close: close the bitstream
 *	read:  read bytes from bitstream, return # of bytes read or <=0 if EOF
 *	seek:  seek to an absolute byte position inside the bitstream,
 *	       return 0 if Ok
 */
typedef struct {
	long	(*open)(char *stream_name, long buffer_size, long *stream_size);
	void	(*close)(long handle);
	long	(*read)(long handle, void *buffer, long num_bytes);
	int	(*seek)(long handle, long abs_byte_seek_pos);
} BITSTREAM_ACCESS;

typedef struct {
	BITSTREAM_ACCESS baccess;
	long		file_handle;
	long		buffer_size;
	BSTR_BUFF	*buffer;
	BSTR_BUFF	*buffer_ptr;
	long		remain_bytes;
	long		bitstream_size;
	int		end_of_stream;
	unsigned int	bit_cache;
	int		cache_size;
	unsigned int	bits;
	long		buffer_len;
	long		buffer_pos;
} BITSTREAM;

#define BSTR_MAX_BITS	32

extern BITSTREAM	*BSTR_open(BITSTREAM_ACCESS *bs_access,
				char *filename, long buffer_size);
extern unsigned long	BSTR_read_byte(BITSTREAM *b);
extern unsigned int	BSTR_read_bytes(BITSTREAM *b, unsigned int count,
				char *buffer);
extern unsigned long	BSTR_read_bit_cache(BITSTREAM *bitstream);
extern unsigned long	BSTR_read_bits_cache(BITSTREAM *bitstream,
				unsigned int bit_count);
extern void		BSTR_close(BITSTREAM *bitstream);
extern int		BSTR_seek( BITSTREAM *bitstream, long seek_byte_pos );
extern long		BSTR_pos( BITSTREAM *bitstream );

#define BSTR_end(b)	b->end_of_stream

#define BSTR_read_bit(b) \
	((b->cache_size-- > 0) ? \
	 (b->bits = (b->bit_cache & 0x80000000) ? 1 : 0, \
	 b->bit_cache <<= 1, b->bits) : \
	 BSTR_read_bit_cache(b))

#define BSTR_read_bits(b,c) \
	((b->cache_size >= (c)) ? \
	 (b->cache_size -= c, b->bits = b->bit_cache >> (32-(c)), \
	 b->bit_cache <<= c, b->bits) : \
	 BSTR_read_bits_cache(b,c))

/****************************************************************************/
#endif /* BITSTR_H */