compress.c

早期freebsd实现

#ifdef SCCSID
static char	*SccsId = "@(#)compress.c	1.14	9/24/87";
#endif /* SCCSID */
static char rcs_ident[] = "Based on compress.c,v 4.0 85/07/30 12:50:00 joe Release";

/* 
 * Compress - data compression program 
 */
#define	min(a,b)	((a>b) ? b : a)

/*
 * machine variants which require cc -Dmachine:  pdp11, z8000, pcxt
 */

/*
 * Set USERMEM to the maximum amount of physical user memory available
 * in bytes.  USERMEM is used to determine the maximum BITS that can be used
 * for compression.
 *
 * SACREDMEM is the amount of physical memory saved for others; compress
 * will hog the rest.
 */
#ifndef SACREDMEM
#define SACREDMEM	0
#endif

#ifndef USERMEM
# define USERMEM 	450000	/* default user memory */
#endif

#ifdef interdata		/* (Perkin-Elmer) */
#define SIGNED_COMPARE_SLOW	/* signed compare is slower than unsigned */
#endif

#ifdef pdp11
# define BITS 	12	/* max bits/code for 16-bit machine */
# define NO_UCHAR	/* also if "unsigned char" functions as signed char */
# undef USERMEM 
#endif /* pdp11 */	/* don't forget to compile with -i */

#ifdef z8000
# define BITS 	12
# undef vax		/* weird preprocessor */
# undef USERMEM 
#endif /* z8000 */

#ifdef pcxt
# define BITS   12
# undef USERMEM
#endif /* pcxt */

#ifdef USERMEM
# if USERMEM >= (433484+SACREDMEM)
#  define PBITS	16
# else
#  if USERMEM >= (229600+SACREDMEM)
#   define PBITS	15
#  else
#   if USERMEM >= (127536+SACREDMEM)
#    define PBITS	14
#   else
#    if USERMEM >= (73464+SACREDMEM)
#     define PBITS	13
#    else
#     define PBITS	12
#    endif
#   endif
#  endif
# endif
# undef USERMEM
#endif /* USERMEM */

#ifdef PBITS		/* Preferred BITS for this memory size */
# ifndef BITS
#  define BITS PBITS
# endif /* BITS */
#endif /* PBITS */

#if BITS == 16
# define HSIZE	69001		/* 95% occupancy */
#endif
#if BITS == 15
# define HSIZE	35023		/* 94% occupancy */
#endif
#if BITS == 14
# define HSIZE	18013		/* 91% occupancy */
#endif
#if BITS == 13
# define HSIZE	9001		/* 91% occupancy */
#endif
#if BITS <= 12
# define HSIZE	5003		/* 80% occupancy */
#endif

#ifdef M_XENIX			/* Stupid compiler can't handle arrays with */
# if BITS == 16			/* more than 65535 bytes - so we fake it */
#  define XENIX_16
# else
#  if BITS > 13			/* Code only handles BITS = 12, 13, or 16 */
#   define BITS	13
#  endif
# endif
#endif

/*
 * a code_int must be able to hold 2**BITS values of type int, and also -1
 */
#if BITS > 15
typedef long int	code_int;
#else
typedef int		code_int;
#endif

#ifdef SIGNED_COMPARE_SLOW
typedef unsigned long int count_int;
typedef unsigned short int count_short;
#else
typedef long int	  count_int;
#endif

#ifdef NO_UCHAR
 typedef char	char_type;
#else
 typedef	unsigned char	char_type;
#endif /* UCHAR */
char_type magic_header[] = { "\037\235" };	/* 1F 9D */

/* Defines for third byte of header */
#define BIT_MASK	0x1f
#define BLOCK_MASK	0x80
/* Masks 0x40 and 0x20 are free.  I think 0x20 should mean that there is
   a fourth header byte (for expansion).
*/
#define INIT_BITS 9			/* initial number of bits/code */

/*
 * compress.c - File compression ala IEEE Computer, June 1984.
 *
 * Authors:	Spencer W. Thomas	(decvax!harpo!utah-cs!utah-gr!thomas)
 *		Jim McKie		(decvax!mcvax!jim)
 *		Steve Davies		(decvax!vax135!petsd!peora!srd)
 *		Ken Turkowski		(decvax!decwrl!turtlevax!ken)
 *		James A. Woods		(decvax!ihnp4!ames!jaw)
 *		Joe Orost		(decvax!vax135!petsd!joe)
 *
 */

#include <stdio.h>
#include <ctype.h>
#include <signal.h>
#include <sys/types.h>
#include <sys/stat.h>

#define ARGVAL() (*++(*argv) || (--argc && *++argv))

int n_bits;				/* number of bits/code */
int maxbits = BITS;			/* user settable max # bits/code */
code_int maxcode;			/* maximum code, given n_bits */
code_int maxmaxcode = 1L << BITS;	/* should NEVER generate this code */
#ifdef COMPATIBLE		/* But wrong! */
# define MAXCODE(n_bits)	(1L << (n_bits) - 1)
#else
# define MAXCODE(n_bits)	((1L << (n_bits)) - 1)
#endif /* COMPATIBLE */

#ifdef XENIX_16
count_int htab0[8192];
count_int htab1[8192];
count_int htab2[8192];
count_int htab3[8192];
count_int htab4[8192];
count_int htab5[8192];
count_int htab6[8192];
count_int htab7[8192];
count_int htab8[HSIZE-65536];
count_int * htab[9] = {
	htab0, htab1, htab2, htab3, htab4, htab5, htab6, htab7, htab8 };

#define htabof(i)	(htab[(i) >> 13][(i) & 0x1fff])
unsigned short code0tab[16384];
unsigned short code1tab[16384];
unsigned short code2tab[16384];
unsigned short code3tab[16384];
unsigned short code4tab[16384];
unsigned short * codetab[5] = {
	code0tab, code1tab, code2tab, code3tab, code4tab };

#define codetabof(i)	(codetab[(i) >> 14][(i) & 0x3fff])

#else	/* Normal machine */
# ifdef sel
/* support gould base register problems */
/*NOBASE*/
count_int htab [HSIZE];
unsigned short codetab [HSIZE];
/*NOBASE*/
# else /* !gould */
count_int htab [HSIZE];
unsigned short codetab [HSIZE];
# endif /* !gould */
#define htabof(i)	htab[i]
#define codetabof(i)	codetab[i]
#endif	/* !XENIX_16 */
code_int hsize = HSIZE;			/* for dynamic table sizing */
count_int fsize;

/*
 * To save much memory, we overlay the table used by compress() with those
 * used by decompress().  The tab_prefix table is the same size and type
 * as the codetab.  The tab_suffix table needs 2**BITS characters.  We
 * get this from the beginning of htab.  The output stack uses the rest
 * of htab, and contains characters.  There is plenty of room for any
 * possible stack (stack used to be 8000 characters).
 */

#define tab_prefixof(i)	codetabof(i)
#ifdef XENIX_16
# define tab_suffixof(i)	((char_type *)htab[(i)>>15])[(i) & 0x7fff]
# define de_stack		((char_type *)(htab2))
#else	/* Normal machine */
# define tab_suffixof(i)	((char_type *)(htab))[i]
# define de_stack		((char_type *)&tab_suffixof(1<<BITS))
#endif	/* XENIX_16 */

code_int free_ent = 0;			/* first unused entry */
int exit_stat = 0;

code_int getcode();

Usage() {
#ifdef DEBUG
fprintf(stderr,"Usage: compress [-dDVfc] [-b maxbits] [file ...]\n");
}
int debug = 0;
#else
fprintf(stderr,"Usage: compress [-dfvcV] [-b maxbits] [file ...]\n");
}
#endif /* DEBUG */
int nomagic = 0;	/* Use a 3-byte magic number header, unless old file */
int zcat_flg = 0;	/* Write output on stdout, suppress messages */
int quiet = 1;		/* don't tell me about compression */

/*
 * block compression parameters -- after all codes are used up,
 * and compression rate changes, start over.
 */
int block_compress = BLOCK_MASK;
int clear_flg = 0;
long int ratio = 0;
#define CHECK_GAP 10000	/* ratio check interval */
count_int checkpoint = CHECK_GAP;
/*
 * the next two codes should not be changed lightly, as they must not
 * lie within the contiguous general code space.
 */ 
#define FIRST	257	/* first free entry */
#define	CLEAR	256	/* table clear output code */

int force = 0;
char ofname [100];
#ifdef DEBUG
int verbose = 0;
#endif /* DEBUG */
int (*bgnd_flag)();

int do_decomp = 0;

/*****************************************************************
 * TAG( main )
 *
 * Algorithm from "A Technique for High Performance Data Compression",
 * Terry A. Welch, IEEE Computer Vol 17, No 6 (June 1984), pp 8-19.
 *
 * Usage: compress [-dfvc] [-b bits] [file ...]
 * Inputs:
 *	-d:	    If given, decompression is done instead.
 *
 *      -c:         Write output on stdout, don't remove original.
 *
 *      -b:         Parameter limits the max number of bits/code.
 *
 *	-f:	    Forces output file to be generated, even if one already
 *		    exists, and even if no space is saved by compressing.
 *		    If -f is not used, the user will be prompted if stdin is
 *		    a tty, otherwise, the output file will not be overwritten.
 *
 *      -v:	    Write compression statistics
 *
 * 	file ...:   Files to be compressed.  If none specified, stdin
 *		    is used.
 * Outputs:
 *	file.Z:	    Compressed form of file with same mode, owner, and utimes
 * 	or stdout   (if stdin used as input)
 *
 * Assumptions:
 *	When filenames are given, replaces with the compressed version
 *	(.Z suffix) only if the file decreases in size.
 * Algorithm:
 * 	Modified Lempel-Ziv method (LZW).  Basically finds common
 * substrings and replaces them with a variable size code.  This is
 * deterministic, and can be done on the fly.  Thus, the decompression
 * procedure needs no input table, but tracks the way the table was built.
 */

main( argc, argv )
register int argc; char **argv;
{
    int overwrite = 0;	/* Do not overwrite unless given -f flag */
    char tempname[100];
    char **filelist, **fileptr;
    char *cp, *rindex(), *malloc();
    struct stat statbuf;
    extern onintr(), oops();


    if ( (bgnd_flag = signal ( SIGINT, SIG_IGN )) != SIG_IGN ) {
	signal ( SIGINT, onintr );
	signal ( SIGSEGV, oops );
    }

#ifdef COMPATIBLE
    nomagic = 1;	/* Original didn't have a magic number */
#endif /* COMPATIBLE */

    filelist = fileptr = (char **)(malloc(argc * sizeof(*argv)));
    *filelist = NULL;

    if((cp = rindex(argv[0], '/')) != 0) {
	cp++;
    } else {
	cp = argv[0];
    }
    if(strcmp(cp, "uncompress") == 0) {
	do_decomp = 1;
    } else if(strcmp(cp, "zcat") == 0) {
	do_decomp = 1;
	zcat_flg = 1;
    }

#ifdef BSD4_2
    /* 4.2BSD dependent - take it out if not */
    setlinebuf( stderr );
#endif /* BSD4_2 */

    /* Argument Processing
     * All flags are optional.
     * -D => debug
     * -V => print Version; debug verbose
     * -d => do_decomp
     * -v => unquiet
     * -f => force overwrite of output file
     * -n => no header: useful to uncompress old files
     * -b maxbits => maxbits.  If -b is specified, then maxbits MUST be
     *	    given also.
     * -c => cat all output to stdout
     * -C => generate output compatible with compress 2.0.
     * if a string is left, must be an input filename.
     */
    for (argc--, argv++; argc > 0; argc--, argv++) {
	if (**argv == '-') {	/* A flag argument */
	    while (*++(*argv)) {	/* Process all flags in this arg */
		switch (**argv) {
#ifdef DEBUG
		    case 'D':
			debug = 1;
			break;
		    case 'V':
			verbose = 1;
			version();
			break;
#else
		    case 'V':
			version();
			break;
#endif /* DEBUG */
		    case 'v':
			quiet = 0;
			break;
		    case 'd':
			do_decomp = 1;
			break;
		    case 'f':
		    case 'F':
			overwrite = 1;
			force = 1;
			break;
		    case 'n':
			nomagic = 1;
			break;
		    case 'C':
			block_compress = 0;
			break;
		    case 'b':
			if (!ARGVAL()) {
			    fprintf(stderr, "Missing maxbits\n");
			    Usage();
			    exit(1);
			}
			maxbits = atoi(*argv);
			goto nextarg;
		    case 'c':
			zcat_flg = 1;
			break;
		    case 'q':
			quiet = 1;
			break;
		    default:
			fprintf(stderr, "Unknown flag: '%c'; ", **argv);
			Usage();
			exit(1);
		}
	    }
	}
	else {		/* Input file name */
	    *fileptr++ = *argv;	/* Build input file list */
	    *fileptr = NULL;
	    /* process nextarg; */
	}
	nextarg: continue;
    }

    if(maxbits < INIT_BITS) maxbits = INIT_BITS;
    if (maxbits > BITS) maxbits = BITS;
    maxmaxcode = 1L << maxbits;

    if (*filelist != NULL) {
	for (fileptr = filelist; *fileptr; fileptr++) {
	    exit_stat = 0;
	    if (do_decomp != 0) {			/* DECOMPRESSION */
		/* Check for .Z suffix */
		if (strcmp(*fileptr + strlen(*fileptr) - 2, ".Z") != 0) {
		    /* No .Z: tack one on */
		    strcpy(tempname, *fileptr);
		    strcat(tempname, ".Z");
		    *fileptr = tempname;
		}
		/* Open input file */
		if ((freopen(*fileptr, "r", stdin)) == NULL) {
			perror(*fileptr); continue;
		}
		/* Check the magic number */
		if (nomagic == 0) {
		    if ((getchar() != (magic_header[0] & 0xFF))
		     || (getchar() != (magic_header[1] & 0xFF))) {
			fprintf(stderr, "%s: not in compressed format\n",
			    *fileptr);
		    continue;
		    }
		    maxbits = getchar();	/* set -b from file */
		    block_compress = maxbits & BLOCK_MASK;
		    maxbits &= BIT_MASK;
		    maxmaxcode = 1L << maxbits;
		    if(maxbits > BITS) {
			fprintf(stderr,
			"%s: compressed with %d bits, can only handle %d bits\n",
			*fileptr, maxbits, BITS);
			continue;
		    }
		}
		/* Generate output filename */
		strcpy(ofname, *fileptr);
		ofname[strlen(*fileptr) - 2] = '\0';  /* Strip off .Z */
	    } else {					/* COMPRESSION */
		if (strcmp(*fileptr + strlen(*fileptr) - 2, ".Z") == 0) {
		    	fprintf(stderr, "%s: already has .Z suffix -- no change\n",
			    *fileptr);
		    continue;
		}
		/* Open input file */
		if ((freopen(*fileptr, "r", stdin)) == NULL) {