unlzw.c

可以在VC6.0下编译的gzip1.24压缩源代码。

/* unlzw.c -- decompress files in LZW format.
 * The code in this file is directly derived from the public domain 'compress'
 * written by Spencer Thomas, Joe Orost, James Woods, Jim McKie, Steve Davies,
 * Ken Turkowski, Dave Mack and Peter Jannesen.
 *
 * This is a temporary version which will be rewritten in some future version
 * to accommodate in-memory decompression.
 */

#ifdef RCSID
static char rcsid[] = "$Id: unlzw.c,v 0.15 1993/06/10 13:28:35 jloup Exp $";
#endif

#include <sys/types.h>

#include "tailor.h"

#ifdef HAVE_UNISTD_H
#  include <unistd.h>
#endif
#ifndef NO_FCNTL_H
#  include <fcntl.h>
#endif

#include "gzip.h"
#include "lzw.h"

typedef	unsigned char	char_type;
typedef          long   code_int;
typedef unsigned long 	count_int;
typedef unsigned short	count_short;
typedef unsigned long 	cmp_code_int;

#define MAXCODE(n)	(1L << (n))
    
#ifndef	REGISTERS
#	define	REGISTERS	2
#endif
#define	REG1	
#define	REG2	
#define	REG3	
#define	REG4	
#define	REG5	
#define	REG6	
#define	REG7	
#define	REG8	
#define	REG9	
#define	REG10
#define	REG11	
#define	REG12	
#define	REG13
#define	REG14
#define	REG15
#define	REG16
#if REGISTERS >= 1
#	undef	REG1
#	define	REG1	register
#endif
#if REGISTERS >= 2
#	undef	REG2
#	define	REG2	register
#endif
#if REGISTERS >= 3
#	undef	REG3
#	define	REG3	register
#endif
#if REGISTERS >= 4
#	undef	REG4
#	define	REG4	register
#endif
#if REGISTERS >= 5
#	undef	REG5
#	define	REG5	register
#endif
#if REGISTERS >= 6
#	undef	REG6
#	define	REG6	register
#endif
#if REGISTERS >= 7
#	undef	REG7
#	define	REG7	register
#endif
#if REGISTERS >= 8
#	undef	REG8
#	define	REG8	register
#endif
#if REGISTERS >= 9
#	undef	REG9
#	define	REG9	register
#endif
#if REGISTERS >= 10
#	undef	REG10
#	define	REG10	register
#endif
#if REGISTERS >= 11
#	undef	REG11
#	define	REG11	register
#endif
#if REGISTERS >= 12
#	undef	REG12
#	define	REG12	register
#endif
#if REGISTERS >= 13
#	undef	REG13
#	define	REG13	register
#endif
#if REGISTERS >= 14
#	undef	REG14
#	define	REG14	register
#endif
#if REGISTERS >= 15
#	undef	REG15
#	define	REG15	register
#endif
#if REGISTERS >= 16
#	undef	REG16
#	define	REG16	register
#endif
    
#ifndef	BYTEORDER
#	define	BYTEORDER	0000
#endif
	
#ifndef	NOALLIGN
#	define	NOALLIGN	0
#endif


union	bytes {
    long  word;
    struct {
#if BYTEORDER == 4321
	char_type	b1;
	char_type	b2;
	char_type	b3;
	char_type	b4;
#else
#if BYTEORDER == 1234
	char_type	b4;
	char_type	b3;
	char_type	b2;
	char_type	b1;
#else
#	undef	BYTEORDER
	int  dummy;
#endif
#endif
    } bytes;
};

#if BYTEORDER == 4321 && NOALLIGN == 1
#  define input(b,o,c,n,m){ \
     (c) = (*(long *)(&(b)[(o)>>3])>>((o)&0x7))&(m); \
     (o) += (n); \
   }
#else
#  define input(b,o,c,n,m){ \
     REG1 char_type *p = &(b)[(o)>>3]; \
     (c) = ((((long)(p[0]))|((long)(p[1])<<8)| \
     ((long)(p[2])<<16))>>((o)&0x7))&(m); \
     (o) += (n); \
   }
#endif

#ifndef MAXSEG_64K
   /* DECLARE(ush, tab_prefix, (1<<BITS)); -- prefix code */
#  define tab_prefixof(i) tab_prefix[i]
#  define clear_tab_prefixof()	memzero(tab_prefix, 256);
#else
   /* DECLARE(ush, tab_prefix0, (1<<(BITS-1)); -- prefix for even codes */
   /* DECLARE(ush, tab_prefix1, (1<<(BITS-1)); -- prefix for odd  codes */
   ush *tab_prefix[2];
#  define tab_prefixof(i) tab_prefix[(i)&1][(i)>>1]
#  define clear_tab_prefixof()	\
      memzero(tab_prefix0, 128), \
      memzero(tab_prefix1, 128);
#endif
#define de_stack        ((char_type *)(&d_buf[DIST_BUFSIZE-1]))
#define tab_suffixof(i) tab_suffix[i]

int block_mode = BLOCK_MODE; /* block compress mode -C compatible with 2.0 */

/* ============================================================================
 * Decompress in to out.  This routine adapts to the codes in the
 * file building the "string" table on-the-fly; requiring no table to
 * be stored in the compressed file.
 * IN assertions: the buffer inbuf contains already the beginning of
 *   the compressed data, from offsets iptr to insize-1 included.
 *   The magic header has already been checked and skipped.
 *   bytes_in and bytes_out have been initialized.
 */
int unlzw(in, out) 
    int in, out;    /* input and output file descriptors */
{
    REG2   char_type  *stackp;
    REG3   code_int   code;
    REG4   int        finchar;
    REG5   code_int   oldcode;
    REG6   code_int   incode;
    REG7   long       inbits;
    REG8   long       posbits;
    REG9   int        outpos;
/*  REG10  int        insize; (global) */
    REG11  unsigned   bitmask;
    REG12  code_int   free_ent;
    REG13  code_int   maxcode;
    REG14  code_int   maxmaxcode;
    REG15  int        n_bits;
    REG16  int        rsize;
    
#ifdef MAXSEG_64K
    tab_prefix[0] = tab_prefix0;
    tab_prefix[1] = tab_prefix1;
#endif
    maxbits = get_byte();
    block_mode = maxbits & BLOCK_MODE;
    if ((maxbits & LZW_RESERVED) != 0) {
	WARN((stderr, "\n%s: %s: warning, unknown flags 0x%x\n",
	      progname, ifname, maxbits & LZW_RESERVED));
    }
    maxbits &= BIT_MASK;
    maxmaxcode = MAXCODE(maxbits);
    
    if (maxbits > BITS) {
	fprintf(stderr,
		"\n%s: %s: compressed with %d bits, can only handle %d bits\n",
		progname, ifname, maxbits, BITS);
	exit_code = ERROR;
	return ERROR;
    }
    rsize = insize;
    maxcode = MAXCODE(n_bits = INIT_BITS)-1;
    bitmask = (1<<n_bits)-1;
    oldcode = -1;
    finchar = 0;
    outpos = 0;
    posbits = inptr<<3;

    free_ent = ((block_mode) ? FIRST : 256);
    
    clear_tab_prefixof(); /* Initialize the first 256 entries in the table. */
    
    for (code = 255 ; code >= 0 ; --code) {
	tab_suffixof(code) = (char_type)code;
    }
    do {
	REG1 int i;
	int  e;
	int  o;
	
    resetbuf:
	e = insize-(o = (posbits>>3));
	
	for (i = 0 ; i < e ; ++i) {
	    inbuf[i] = inbuf[i+o];
	}
	insize = e;
	posbits = 0;
	
	if (insize < INBUF_EXTRA) {
	    if ((rsize = read(in, (char*)inbuf+insize, INBUFSIZ)) == EOF) {
		read_error();
	    }
	    insize += rsize;
	    bytes_in += (ulg)rsize;
	}
	inbits = ((rsize != 0) ? ((long)insize - insize%n_bits)<<3 : 
		  ((long)insize<<3)-(n_bits-1));
	
	while (inbits > posbits) {
	    if (free_ent > maxcode) {
		posbits = ((posbits-1) +
			   ((n_bits<<3)-(posbits-1+(n_bits<<3))%(n_bits<<3)));
		++n_bits;
		if (n_bits == maxbits) {
		    maxcode = maxmaxcode;
		} else {
		    maxcode = MAXCODE(n_bits)-1;
		}
		bitmask = (1<<n_bits)-1;
		goto resetbuf;
	    }
	    input(inbuf,posbits,code,n_bits,bitmask);
	    Tracev((stderr, "%d ", code));

	    if (oldcode == -1) {
		if (code >= 256) error("corrupt input.");
		outbuf[outpos++] = (char_type)(finchar = (int)(oldcode=code));
		continue;
	    }
	    if (code == CLEAR && block_mode) {
		clear_tab_prefixof();
		free_ent = FIRST - 1;
		posbits = ((posbits-1) +
			   ((n_bits<<3)-(posbits-1+(n_bits<<3))%(n_bits<<3)));
		maxcode = MAXCODE(n_bits = INIT_BITS)-1;
		bitmask = (1<<n_bits)-1;
		goto resetbuf;
	    }
	    incode = code;
	    stackp = de_stack;
	    
	    if (code >= free_ent) { /* Special case for KwKwK string. */
		if (code > free_ent) {
#ifdef DEBUG		    
		    char_type *p;

		    posbits -= n_bits;
		    p = &inbuf[posbits>>3];
		    fprintf(stderr,
			    "code:%ld free_ent:%ld n_bits:%d insize:%u\n",
			    code, free_ent, n_bits, insize);
		    fprintf(stderr,
			    "posbits:%ld inbuf:%02X %02X %02X %02X %02X\n",
			    posbits, p[-1],p[0],p[1],p[2],p[3]);
#endif
		    if (!test && outpos > 0) {
			write_buf(out, (char*)outbuf, outpos);
			bytes_out += (ulg)outpos;
		    }
		    error(to_stdout ? "corrupt input." :
			  "corrupt input. Use zcat to recover some data.");
		}
		*--stackp = (char_type)finchar;
		code = oldcode;
	    }

	    while ((cmp_code_int)code >= (cmp_code_int)256) {
		/* Generate output characters in reverse order */
		*--stackp = tab_suffixof(code);
		code = tab_prefixof(code);
	    }
	    *--stackp =	(char_type)(finchar = tab_suffixof(code));
	    
	    /* And put them out in forward order */
	    {
		REG1 int	i;
	    
		if (outpos+(i = (de_stack-stackp)) >= OUTBUFSIZ) {
		    do {
			if (i > OUTBUFSIZ-outpos) i = OUTBUFSIZ-outpos;

			if (i > 0) {
			    memcpy(outbuf+outpos, stackp, i);
			    outpos += i;
			}
			if (outpos >= OUTBUFSIZ) {
			    if (!test) {
				write_buf(out, (char*)outbuf, outpos);
				bytes_out += (ulg)outpos;
			    }
			    outpos = 0;
			}
			stackp+= i;
		    } while ((i = (de_stack-stackp)) > 0);
		} else {
		    memcpy(outbuf+outpos, stackp, i);
		    outpos += i;
		}
	    }

	    if ((code = free_ent) < maxmaxcode) { /* Generate the new entry. */

		tab_prefixof(code) = (unsigned short)oldcode;
		tab_suffixof(code) = (char_type)finchar;
		free_ent = code+1;
	    } 
	    oldcode = incode;	/* Remember previous code.	*/
	}
    } while (rsize != 0);
    
    if (!test && outpos > 0) {
	write_buf(out, (char*)outbuf, outpos);
	bytes_out += (ulg)outpos;
    }
    return OK;
}