compress.c

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/* compress - Reduce file size using Modified Lempel-Ziv encoding */

/*
 * 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)
 *
 *              Richard Todd            Port to MINIX
 *              Andy Tanenbaum          Cleanup
 *
 *
 * 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.
 *
 *      -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.
 */


#define AZTEC86 1

#define min(a,b)        ((a>b) ? b : a)

/*
 * 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

#define REGISTER register
#define DOTZ ".Z"

#include <limits.h>
#include <dirent.h>

/* The default for Minix is -b13, but we can do -b16 if the machine can. */
#define DEFAULTBITS 13
#if INT_MAX == 32767
# define BITS 13
#else
# define BITS 16
#endif

#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
#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


/*
 * 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 */

#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <ctype.h>
#include <signal.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include <utime.h>
#include <stdio.h>

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

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

#ifndef AZTEC86
        count_int htab [HSIZE];
        unsigned short codetab [HSIZE];
#else
        count_int *htab;
        unsigned short *codetab;
#       define HTABSIZE ((size_t)(HSIZE*sizeof(count_int)))
#       define CODETABSIZE ((size_t)(HSIZE*sizeof(unsigned short)))


#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;

_PROTOTYPE(int main, (int argc, char **argv));
_PROTOTYPE(void Usage, (void));
_PROTOTYPE(void compress, (void));
_PROTOTYPE(void onintr, (int dummy));
_PROTOTYPE(void oops, (int dummy));
_PROTOTYPE(void output, (code_int code));
_PROTOTYPE(int foreground, (void));
_PROTOTYPE(void decompress, (void));
_PROTOTYPE(code_int getcode, (void)); 
_PROTOTYPE(void writeerr, (void));
_PROTOTYPE(void copystat, (char *ifname, char *ofname));
_PROTOTYPE(int foreground, (void));
_PROTOTYPE(void cl_block , (void));
_PROTOTYPE(void cl_hash, (count_int hsize));
_PROTOTYPE(void prratio, (FILE *stream, long int num, long int den));
_PROTOTYPE(void version, (void));

void 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 = 0;          /* 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 */

#ifndef METAWARE
#ifdef AZTEC86
void
#else
int
#endif
#ifndef __STDC__
(*bgnd_flag)();
#else
(*bgnd_flag)(int);
#endif
#endif

int do_decomp = 0;


int main(argc, argv)
int argc;
char **argv;
{
    int overwrite = 0;  /* Do not overwrite unless given -f flag */
    char tempname[100];
    char **filelist, **fileptr;
    char *cp;
    struct stat statbuf;
#ifndef METAWARE
    if ( (bgnd_flag = signal ( SIGINT, SIG_IGN )) != SIG_IGN ) {
        signal ( SIGINT, onintr );
        signal ( SIGSEGV, oops );
    }
#endif
#ifdef AZTEC86
#ifdef METAWARE
        _setmode(NULL,_ALL_FILES_BINARY);
        _setmode(stdin,_BINARY);
        _setmode(stdout,_BINARY);
        _setmode(stderr,_TEXT);
#endif
        if (NULL == (htab = (count_int *)malloc(HTABSIZE)))
        {
                fprintf(stderr,"Can't allocate htab\n");
                exit(1);
        }
        if (NULL == (codetab = (unsigned short *)malloc(CODETABSIZE)))
        {
                fprintf(stderr,"Can't allocate codetab\n");
                exit(1);
        }
#endif
#ifdef COMPATIBLE
    nomagic = 1;        /* Original didn't have a magic number */
#endif /* COMPATIBLE */

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

    if((cp = strrchr(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 = 1 << maxbits;

    if (*filelist != NULL) 
        {
                for (fileptr = filelist; *fileptr; fileptr++) 
                {
                    exit_stat = 0;
                    if (do_decomp != 0) 
                        {                       /* DECOMPRESSION */
                                /* Check for .Z suffix */
#ifndef PCDOS
                                if (strcmp(*fileptr + strlen(*fileptr) - 2, DOTZ) != 0) 
#else
                                if (strcmp(*fileptr + strlen(*fileptr) - 1, DOTZ) != 0) 
#endif
                                {
                                    /* No .Z: tack one on */
                                    strcpy(tempname, *fileptr);
#ifndef PCDOS
                                    strcat(tempname, DOTZ);
#else
                                        /* either tack one on or replace last character */
                                        {
                                                char *dot;
                                                if (NULL == (dot = strchr(tempname,'.')))
                                                {
                                                        strcat(tempname,".Z");
                                                }
                                                else
                                                /* if there is a dot then either tack a z on
                                                   or replace last character */
                                                {
                                                        if (strlen(dot) < 4)
                                                                strcat(tempname,DOTZ);
                                                        else
                                                                dot[3] = 'Z';
                                                }
                                        }
#endif
                                    *fileptr = tempname;
                                }
                                /* Open input file */
                                if ((freopen(*fileptr, "r", stdin)) == NULL) 
                                {
                                        perror(*fileptr); continue;
                                }
                                /* Check the magic number */
                                if (nomagic == 0) 
                                {
                                        unsigned magic1, magic2;
                                    if (((magic1 = getc(stdin)) != (magic_header[0] & 0xFF))
                                     || ((magic2 = getc(stdin)) != (magic_header[1] & 0xFF))) 
                                        {
                                                fprintf(stderr, 
                                                "%s: not in compressed format %x %x\n",
                                            *fileptr,magic1,magic2);
                                            continue;
                                    }
                                    maxbits = getc(stdin);      /* set -b from file */
                                    block_compress = maxbits & BLOCK_MASK;
                                    maxbits &= BIT_MASK;
                                    maxmaxcode = 1 << 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);
#ifndef PCDOS
                                ofname[strlen(*fileptr) - 2] = '\0';  /* Strip off .Z */
#else
                                /* kludge to handle various common three character extension */
                                {
                                        char *dot; 
                                        char fixup = '\0';
                                        /* first off, map name to upper case */
                                        for (dot = ofname; *dot; dot++)
                                                *dot = toupper(*dot);
                                        if (NULL == (dot = strchr(ofname,'.')))
                                        {
                                                fprintf(stderr,"Bad filename %s\n",ofname);
                                                exit(1);
                                        }
                                        if (strlen(dot) == 4)
                                        /* we got three letter extensions */
                                        {
                                                if (strcmp(dot,".EXZ") == 0)
                                                        fixup = 'E';
                                                else if (strcmp(dot,".COZ") == 0)
                                                        fixup = 'M';
                                                else if (strcmp(dot,".BAZ") == 0)
                                                        fixup = 'S';
                                                else if (strcmp(dot,".OBZ") == 0)
                                                        fixup = 'J';
                                                else if (strcmp(dot,".SYZ") == 0)
                                                        fixup = 'S';
                                                else if (strcmp(dot,".DOZ") == 0)
                                                        fixup = 'C';

                                        } 
                                        /* replace the Z */
                                        ofname[strlen(*fileptr) - 1] = fixup;
                                }
#endif
                    } else 
                        {                                       /* COMPRESSION */
                                if (strcmp(*fileptr + strlen(*fileptr) - 2, DOTZ) == 0) 
                                {
                                fprintf(stderr, "%s: already has .Z suffix -- no change\n",
                                    *fileptr);
                                    continue;
                                }
                                /* Open input file */
                                if ((freopen(*fileptr, "r", stdin)) == NULL) 
                                {
                                    perror(*fileptr); continue;
                                }
                                (void)stat( *fileptr, &statbuf );
                                fsize = (long) statbuf.st_size;
                                /*
                                 * tune hash table size for small files -- ad hoc,
                                 * but the sizes match earlier #defines, which
                                 * serve as upper bounds on the number of output codes. 
                                 */
                                hsize = HSIZE; /*lint -e506 -e712 */
                                if ( fsize < (1 << 12) )
                                    hsize = min ( 5003, HSIZE );
                                else if ( fsize < (1 << 13) )
                                    hsize = min ( 9001, HSIZE );
                                else if ( fsize < (1 << 14) )
                                    hsize = min ( 18013, HSIZE );
                                else if ( fsize < (1 << 15) )
                                    hsize = min ( 35023, HSIZE );
                                else if ( fsize < 47000 )
                                    hsize = min ( 50021, HSIZE ); /*lint +e506 +e712 */

                                /* Generate output filename */
                                strcpy(ofname, *fileptr);
#ifndef BSD4_2          /* Short filenames */
                                if ((cp=strrchr(ofname,'/')) != NULL)
                                        cp++;
                                else
                                        cp = ofname;
                                if (strlen(cp) >= _DIRENT_NAME_LEN-3) 
                                {
                                    fprintf(stderr,"%s: filename too long to tack on .Z\n",cp);
                                    continue;
                                }
#ifdef PCDOS
                                else
                                {
                                        /* either tack one on or replace last character */
                                        char *dot;
                                        if (NULL == (dot = strchr(cp,'.')))
                                        {
                                                strcat(cp,".Z");
                                        }
                                        else
                                        /* if there is a dot then either tack a z on
                                           or replace last character */
                                        {
                                                if (strlen(dot) < 4)
                                                        strcat(cp,DOTZ);
                                                else
                                                        dot[3] = 'Z';
                                        }
                                }
#endif
#endif  /* BSD4_2               Long filenames allowed */
#ifndef PCDOS
                        /* PCDOS takes care of this above */
                                strcat(ofname, DOTZ);
#endif
                    }
                    /* Check for overwrite of existing file */
                    if (overwrite == 0 && zcat_flg == 0) 
                        {
                                if (stat(ofname, &statbuf) == 0) 
                                {
                                    char response[2]; int fd;
                                    response[0] = 'n';
                                    fprintf(stderr, "%s already exists;", ofname);
                                    if (foreground()) 
                                        {
                                                fd = open("/dev/tty", O_RDONLY);
                                                fprintf(stderr, 
                                                " do you wish to overwrite %s (y or n)? ", ofname);
                                                fflush(stderr);
                                                (void)read(fd, response, 2);
                                                while (response[1] != '\n') 
                                                {
                                                    if (read(fd, response+1, 1) < 0) 
                                                        {       /* Ack! */
                                                                perror("stderr"); 
                                                                break;
                                                    }
                                                }
                                                close(fd);
                                    }
                                    if (response[0] != 'y') 
                                        {
                                                fprintf(stderr, "\tnot overwritten\n");
                                                continue;
                                    }
                                }
                    }
                    if(zcat_flg == 0) 
                        {               /* Open output file */
                                if (freopen(ofname, "w", stdout) == NULL) 
                                {
                                    perror(ofname);
                                    continue;
                                }
                                if(!quiet)
                                        fprintf(stderr, "%s: ", *fileptr);
                    }

                    /* Actually do the compression/decompression */
                    if (do_decomp == 0) 
                                compress();
#ifndef DEBUG
                    else                        
                                decompress();
#else
                    else if (debug == 0)        
                                decompress();
                    else                        
                                printcodes();
                    if (verbose)                
                                dump_tab();
#endif /* DEBUG */
                    if(zcat_flg == 0) 
                        {
                                copystat(*fileptr, ofname);     /* Copy stats */
                                if((exit_stat == 1) || (!quiet))
                                        putc('\n', stderr);
                    }
                }
    } else 
        {               /* Standard input */
                if (do_decomp == 0) 
                {
                        compress();
#ifdef DEBUG
                        if(verbose)             dump_tab();
#endif /* DEBUG */
                        if(!quiet)
                                putc('\n', stderr);
                } else 
                {
                    /* Check the magic number */
                    if (nomagic == 0) 
                        {
                                if ((getc(stdin)!=(magic_header[0] & 0xFF))
                                 || (getc(stdin)!=(magic_header[1] & 0xFF))) 
                                {
                                    fprintf(stderr, "stdin: not in compressed format\n");
                                    exit(1);
                                }
                                maxbits = getc(stdin);  /* set -b from file */
                                block_compress = maxbits & BLOCK_MASK;
                                maxbits &= BIT_MASK;
                                maxmaxcode = 1 << maxbits;
                                fsize = 100000;         /* assume stdin large for USERMEM */
                                if(maxbits > BITS) 
                                {
                                        fprintf(stderr,
                                        "stdin: compressed with %d bits, can only handle %d bits\n",
                                        maxbits, BITS);
                                        exit(1);
                                }
                    }
#ifndef DEBUG
                    decompress();
#else
                    if (debug == 0)     decompress();
                    else                printcodes();
                    if (verbose)        dump_tab();
#endif /* DEBUG */
                }
    }
    return(exit_stat);
}

static int offset;
long int in_count = 1;                  /* length of input */
long int bytes_out;                     /* length of compressed output */
long int out_count = 0;                 /* # of codes output (for debugging) */

/*
 * compress stdin to stdout
 *
 * Algorithm:  use open addressing double hashing (no chaining) on the 
 * prefix code / next character combination.  We do a variant of Knuth's
 * algorithm D (vol. 3, sec. 6.4) along with G. Knott's relatively-prime
 * secondary probe.  Here, the modular division first probe is gives way
 * to a faster exclusive-or manipulation.  Also do block compression with
 * an adaptive reset, whereby the code table is cleared when the compression
 * ratio decreases, but after the table fills.  The variable-length output
 * codes are re-sized at this point, and a special CLEAR code is generated
 * for the decompressor.  Late addition:  construct the table according to
 * file size for noticeable speed improvement on small files.  Please direct
 * questions about this implementation to ames!jaw.
 */

void compress() 
{
    REGISTER long fcode;
    REGISTER code_int i = 0;
    REGISTER int c;
    REGISTER code_int ent;
#ifdef XENIX_16
    REGISTER code_int disp;
#else   /* Normal machine */
    REGISTER int disp;
#endif
    REGISTER code_int hsize_reg;
    REGISTER int hshift;

#ifndef COMPATIBLE
    if (nomagic == 0) 
        {
                putc(magic_header[0],stdout); 
                putc(magic_header[1],stdout);
                putc((char)(maxbits | block_compress),stdout);
                if(ferror(stdout))
                        writeerr();
    }
#endif /* COMPATIBLE */

    offset = 0;
    bytes_out = 3;              /* includes 3-byte header mojo */
    out_count = 0;
    clear_flg = 0;
    ratio = 0;
    in_count = 1;
    checkpoint = CHECK_GAP;
    maxcode = MAXCODE(n_bits = INIT_BITS);
    free_ent = ((block_compress) ? FIRST : 256 );

    ent = getc(stdin);

    hshift = 0;
    for ( fcode = (long) hsize;  fcode < 65536L; fcode *= 2L )
        hshift++;
    hshift = 8 - hshift;                /* set hash code range bound */

    hsize_reg = hsize;
    cl_hash( (count_int) hsize_reg);            /* clear hash table */

#ifdef SIGNED_COMPARE_SLOW
    while ( (c = getc(stdin)) != (unsigned) EOF )
#else
    while ( (c = getc(stdin)) != EOF )
#endif
        {
                in_count++;
                fcode = (long) (((long) c << maxbits) + ent);
                i = ((c << hshift) ^ ent);      /* xor hashing */

                if ( htabof (i) == fcode ) 
                {
                    ent = codetabof (i);
                    continue;
                } else if ( (long)htabof (i) < 0 )      /* empty slot */
                    goto nomatch;
                disp = hsize_reg - i;           /* secondary hash (after G. Knott) */
                if ( i == 0 )
                    disp = 1;
probe:
                if ( (i -= disp) < 0 )
                    i += hsize_reg;

                if ( htabof (i) == fcode ) 
                {
                    ent = codetabof (i);
                    continue;
                }
                if ( (long)htabof (i) > 0 ) 
                    goto probe;
nomatch:
                output ( (code_int) ent );
                out_count++;
                ent = c;
#ifdef SIGNED_COMPARE_SLOW
                if ( (unsigned) free_ent < (unsigned) maxmaxcode)
#else
                if ( free_ent < maxmaxcode )
#endif
                {
                    codetabof (i) = free_ent++; /* code -> hashtable */
                    htabof (i) = fcode;
                }
                else if ( (count_int)in_count >= checkpoint && block_compress )
                    cl_block ();
    }
    /*
     * Put out the final code.
     */
    output( (code_int)ent );
    out_count++;
    output( (code_int)-1 );

    /*
     * Print out stats on stderr
     */
    if(zcat_flg == 0 && !quiet) 
        {
#ifdef DEBUG
                fprintf( stderr,
                "%ld chars in, %ld codes (%ld bytes) out, compression factor: ",
                in_count, out_count, bytes_out );
                prratio( stderr, in_count, bytes_out );
                fprintf( stderr, "\n");
                fprintf( stderr, "\tCompression as in compact: " );
                prratio( stderr, in_count-bytes_out, in_count );
                fprintf( stderr, "\n");
                fprintf( stderr, "\tLargest code (of last block) was %d (%d bits)\n",
                free_ent - 1, n_bits );
#else /* !DEBUG */
                fprintf( stderr, "Compression: " );
                prratio( stderr, in_count-bytes_out, in_count );
#endif /* DEBUG */
    }
    if(bytes_out > in_count)    /* exit(2) if no savings */
                exit_stat = 2;
    return;
}

/*****************************************************************
 * TAG( output )
 *
 * Output the given code.
 * Inputs:
 *      code:   A n_bits-bit integer.  If == -1, then EOF.  This assumes
 *              that n_bits =< (long)wordsize - 1.
 * Outputs:
 *      Outputs code to the file.
 * Assumptions:
 *      Chars are 8 bits long.
 * Algorithm:
 *      Maintain a BITS character long buffer (so that 8 codes will
 * fit in it exactly).  Use the VAX insv instruction to insert each
 * code in turn.  When the buffer fills up empty it and start over.
 */

static char buf[BITS];

#ifndef vax
char_type lmask[9] = {0xff, 0xfe, 0xfc, 0xf8, 0xf0, 0xe0, 0xc0, 0x80, 0x00};
char_type rmask[9] = {0x00, 0x01, 0x03, 0x07, 0x0f, 0x1f, 0x3f, 0x7f, 0xff};
#endif /* vax */
void output( code )
code_int  code;
{
#ifdef DEBUG
    static int col = 0;
#endif /* DEBUG */

    /*
     * On the VAX, it is important to have the REGISTER declarations
     * in exactly the order given, or the asm will break.
     */
    REGISTER int r_off = offset, bits= n_bits;
    REGISTER char * bp = buf;
#ifndef BREAKHIGHC
#ifdef METAWARE
        int temp;
#endif
#endif
#ifdef DEBUG
        if ( verbose )
            fprintf( stderr, "%5d%c", code,
                    (col+=6) >= 74 ? (col = 0, '\n') : ' ' );
#endif /* DEBUG */
    if ( code >= 0 ) 
        {
#ifdef vax
        /* VAX DEPENDENT!! Implementation on other machines is below.
         *
         * Translation: Insert BITS bits from the argument starting at
         * offset bits from the beginning of buf.
         */
        0;      /* Work around for pcc -O bug with asm and if stmt */
        asm( "insv      4(ap),r11,r10,(r9)" );
#else /* not a vax */
/* 
 * byte/bit numbering on the VAX is simulated by the following code
 */
        /*
         * Get to the first byte.
         */
        bp += (r_off >> 3);
        r_off &= 7;
        /*
         * Since code is always >= 8 bits, only need to mask the first
         * hunk on the left.
         */
#ifndef BREAKHIGHC
#ifdef METAWARE
        *bp &= rmask[r_off];
        temp = (code << r_off) & lmask[r_off];
        *bp |= temp;
#else
        *bp = (*bp & rmask[r_off]) | ((code << r_off) & lmask[r_off]);
#endif
#else
        *bp = (*bp & rmask[r_off]) | ((code << r_off) & lmask[r_off]);
#endif
        bp++;
        bits -= (8 - r_off);
        code >>= (8 - r_off);
        /* Get any 8 bit parts in the middle (<=1 for up to 16 bits). */
        if ( bits >= 8 ) 
        {
            *bp++ = code;
            code >>= 8;
            bits -= 8;
        }
        /* Last bits. */
        if(bits)
            *bp = code;
#endif /* vax */
        offset += n_bits;
        if ( offset == (n_bits << 3) ) 
        {
            bp = buf;
            bits = n_bits;
            bytes_out += bits;
            do
                putc(*bp++,stdout);
            while(--bits);
            offset = 0;
        }

        /*
         * If the next entry is going to be too big for the code size,
         * then increase it, if possible.
         */
        if ( free_ent > maxcode || (clear_flg > 0))
        {
            /*
             * Write the whole buffer, because the input side won't
             * discover the size increase until after it has read it.
             */
            if ( offset > 0 ) 
                {
                        if( fwrite( buf, (size_t)1, (size_t)n_bits, stdout ) != n_bits)
                                writeerr();
                        bytes_out += n_bits;
            }
            offset = 0;

            if ( clear_flg ) 
                {
                maxcode = MAXCODE (n_bits = INIT_BITS);
                        clear_flg = 0;
            }
            else 
                {
                n_bits++;
                if ( n_bits == maxbits )
                            maxcode = maxmaxcode;
                else
                            maxcode = MAXCODE(n_bits);
            }
#ifdef DEBUG
            if ( debug ) 
                {
                        fprintf( stderr, "\nChange to %d bits\n", n_bits );
                        col = 0;
            }
#endif /* DEBUG */
        }
    } else 
        {
        /*
         * At EOF, write the rest of the buffer.
         */
        if ( offset > 0 )
            fwrite( buf, (size_t)1, (size_t)(offset + 7) / 8, stdout );
        bytes_out += (offset + 7) / 8;
        offset = 0;
        fflush( stdout );
#ifdef DEBUG
        if ( verbose )
            fprintf( stderr, "\n" );
#endif /* DEBUG */
        if( ferror( stdout ) )
                writeerr();
    }
}
/*
 * Decompress stdin to stdout.  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.  The tables used herein are shared
 * with those of the compress() routine.  See the definitions above.
 */

void decompress() {
    REGISTER char_type *stackp;
    REGISTER int finchar;
    REGISTER code_int code, oldcode, incode;

    /*
     * As above, initialize the first 256 entries in the table.
     */
    maxcode = MAXCODE(n_bits = INIT_BITS);
    for ( code = 255; code >= 0; code-- ) {
        tab_prefixof(code) = 0;
        tab_suffixof(code) = (char_type)code;
    }
    free_ent = ((block_compress) ? FIRST : 256 );

    finchar = oldcode = getcode();
    if(oldcode == -1)   /* EOF already? */
        return;                 /* Get out of here */
    putc( (char)finchar,stdout );               /* first code must be 8 bits = char */
    if(ferror(stdout))          /* Crash if can't write */
        writeerr();
    stackp = de_stack;

    while ( (code = getcode()) > -1 ) {

        if ( (code == CLEAR) && block_compress ) {
            for ( code = 255; code >= 0; code-- )
                tab_prefixof(code) = 0;
            clear_flg = 1;
            free_ent = FIRST - 1;
            if ( (code = getcode ()) == -1 )    /* O, untimely death! */
                break;
        }
        incode = code;
        /*
         * Special case for KwKwK string.
         */
        if ( code >= free_ent ) {
            *stackp++ = finchar;
            code = oldcode;
        }

        /*
         * Generate output characters in reverse order
         */
#ifdef SIGNED_COMPARE_SLOW
        while ( ((unsigned long)code) >= ((unsigned long)256) ) {
#else
        while ( code >= 256 ) {
#endif
            *stackp++ = tab_suffixof(code);
            code = tab_prefixof(code);
        }
        *stackp++ = finchar = tab_suffixof(code);

        /*
         * And put them out in forward order
         */
        do
            putc ( *--stackp ,stdout);
        while ( stackp > de_stack );

        /*
         * Generate the new entry.
         */
        if ( (code=free_ent) < maxmaxcode ) 
        {
            tab_prefixof(code) = (unsigned short)oldcode;
            tab_suffixof(code) = finchar;
            free_ent = code+1;
        } 
        /*
         * Remember previous code.
         */
        oldcode = incode;
    }
    fflush( stdout );
    if(ferror(stdout))
        writeerr();
}

/*****************************************************************
 * TAG( getcode )
 *
 * Read one code from the standard input.  If EOF, return -1.
 * Inputs:
 *      stdin
 * Outputs:
 *      code or -1 is returned.
 */

code_int
getcode() 
{
    /*
     * On the VAX, it is important to have the REGISTER declarations
     * in exactly the order given, or the asm will break.
     */
    REGISTER code_int code;
    static int offset = 0, size = 0;
    static char_type buf[BITS];
    REGISTER int r_off, bits;
    REGISTER char_type *bp = buf;

    if ( clear_flg > 0 || offset >= size || free_ent > maxcode ) 
        {
                /*
                 * If the next entry will be too big for the current code
                 * size, then we must increase the size.  This implies reading
                 * a new buffer full, too.
                 */
                if ( free_ent > maxcode ) 
                {
                    n_bits++;
                    if ( n_bits == maxbits )
                                maxcode = maxmaxcode;   /* won't get any bigger now */
                    else
                                maxcode = MAXCODE(n_bits);
                }
                if ( clear_flg > 0) 
                {
            maxcode = MAXCODE (n_bits = INIT_BITS);
                    clear_flg = 0;
                }
                size = fread( buf, (size_t)1, (size_t)n_bits, stdin );
                if ( size <= 0 )
                    return -1;                  /* end of file */
                offset = 0;
                /* Round size down to integral number of codes */
                size = (size << 3) - (n_bits - 1);
    }
    r_off = offset;
    bits = n_bits;
#ifdef vax
    asm( "extzv   r10,r9,(r8),r11" );
#else /* not a vax */
        /*
         * Get to the first byte.
         */
        bp += (r_off >> 3);
        r_off &= 7;
        /* Get first part (low order bits) */
#ifdef NO_UCHAR
        code = ((*bp++ >> r_off) & rmask[8 - r_off]) & 0xff;
#else
        code = (*bp++ >> r_off);
#endif /* NO_UCHAR */
        bits -= (8 - r_off);
        r_off = 8 - r_off;              /* now, offset into code word */
        /* Get any 8 bit parts in the middle (<=1 for up to 16 bits). */
        if ( bits >= 8 ) 
        {
#ifdef NO_UCHAR
            code |= (*bp++ & 0xff) << r_off;
#else
            code |= *bp++ << r_off;
#endif /* NO_UCHAR */
            r_off += 8;
            bits -= 8;
        }
        /* high order bits. */
        code |= (*bp & rmask[bits]) << r_off;
#endif /* vax */
    offset += n_bits;

    return code;
}

#ifndef AZTEC86
char *
strrchr(s, c)           /* For those who don't have it in libc.a */
REGISTER char *s, c;
{
        char *p;
        for (p = NULL; *s; s++)
            if (*s == c)
                p = s;
        return(p);
}
#endif


#ifndef METAWARE
#ifdef DEBUG
printcodes()
{
    /*
     * Just print out codes from input file.  For debugging.
     */
    code_int code;
    int col = 0, bits;

    bits = n_bits = INIT_BITS;
    maxcode = MAXCODE(n_bits);
    free_ent = ((block_compress) ? FIRST : 256 );
    while ( ( code = getcode() ) >= 0 ) {
        if ( (code == CLEAR) && block_compress ) {
            free_ent = FIRST - 1;
            clear_flg = 1;
        }
        else if ( free_ent < maxmaxcode )
            free_ent++;
        if ( bits != n_bits ) {
            fprintf(stderr, "\nChange to %d bits\n", n_bits );
            bits = n_bits;
            col = 0;
        }
        fprintf(stderr, "%5d%c", code, (col+=6) >= 74 ? (col = 0, '\n') : ' ' );
    }
    putc( '\n', stderr );
    exit( 0 );
}
#ifdef DEBUG2
code_int sorttab[1<<BITS];      /* sorted pointers into htab */
#define STACK_SIZE      500
static char stack[STACK_SIZE];
/* dumptab doesn't use main stack now -prevents distressing crashes */
dump_tab()      /* dump string table */
{
    REGISTER int i, first;
    REGISTER ent;
    int stack_top = STACK_SIZE;
    REGISTER c;

    if(do_decomp == 0) {        /* compressing */
        REGISTER int flag = 1;

        for(i=0; i<hsize; i++) {        /* build sort pointers */
                if((long)htabof(i) >= 0) {
                        sorttab[codetabof(i)] = i;
                }
        }
        first = block_compress ? FIRST : 256;
        for(i = first; i < free_ent; i++) {
                fprintf(stderr, "%5d: \"", i);
                stack[--stack_top] = '\n';
                stack[--stack_top] = '"'; /* " */
                stack_top = in_stack((int)(htabof(sorttab[i])>>maxbits)&0xff, 
                                     stack_top);
                for(ent=htabof(sorttab[i]) & ((1<<maxbits)-1);
                    ent > 256;
                    ent=htabof(sorttab[ent]) & ((1<<maxbits)-1)) {
                        stack_top = in_stack((int)(htabof(sorttab[ent]) >> maxbits),
                                                stack_top);
                }
                stack_top = in_stack(ent, stack_top);
                fwrite( &stack[stack_top], (size_t)1, (size_t)(STACK_SIZE-stack_top), stderr);
                stack_top = STACK_SIZE;
        }
   } else if(!debug) {  /* decompressing */

       for ( i = 0; i < free_ent; i++ ) {
           ent = i;
           c = tab_suffixof(ent);
           if ( isascii(c) && isprint(c) )
               fprintf( stderr, "%5d: %5d/'%c'  \"",
                           ent, tab_prefixof(ent), c );
           else
               fprintf( stderr, "%5d: %5d/\\%03o \"",
                           ent, tab_prefixof(ent), c );
           stack[--stack_top] = '\n';
           stack[--stack_top] = '"'; /* " */
           for ( ; ent != NULL;
                   ent = (ent >= FIRST ? tab_prefixof(ent) : NULL) ) {
               stack_top = in_stack(tab_suffixof(ent), stack_top);
           }
           fwrite( &stack[stack_top], (size_t)1, (size_t)(STACK_SIZE - stack_top), stderr );
           stack_top = STACK_SIZE;
       }
    }
}

int
in_stack(c, stack_top)
        REGISTER int c, stack_top;
{
        if ( (isascii(c) && isprint(c) && c != '\\') || c == ' ' ) {
            stack[--stack_top] = c;
        } else {
            switch( c ) {
            case '\n': stack[--stack_top] = 'n'; break;
            case '\t': stack[--stack_top] = 't'; break;
            case '\b': stack[--stack_top] = 'b'; break;
            case '\f': stack[--stack_top] = 'f'; break;
            case '\r': stack[--stack_top] = 'r'; break;
            case '\\': stack[--stack_top] = '\\'; break;
            default:
                stack[--stack_top] = '0' + c % 8;
                stack[--stack_top] = '0' + (c / 8) % 8;
                stack[--stack_top] = '0' + c / 64;
                break;
            }
            stack[--stack_top] = '\\';
        }
        if (stack_top<0) {
            fprintf(stderr,"dump_tab stack overflow!!!\n");
            exit(1);
        }
        return stack_top;
}
#else
dump_tab() {}
#endif /* DEBUG2 */
#endif /* DEBUG */
#endif /* METAWARE */

void writeerr()
{
    perror ( ofname );
    unlink ( ofname );
    exit ( 1 );
}

void copystat(ifname, ofname)
char *ifname, *ofname;
{
    struct stat statbuf;
    int mode;
#ifndef AZTEC86
    time_t timep[2];
#else
        unsigned long timep[2];
#endif
    fflush(stdout);
    close(fileno(stdout));
    if (stat(ifname, &statbuf)) 
        {               /* Get stat on input file */
                perror(ifname);
                return;
    }
#ifndef PCDOS
    /* meddling with UNIX-style file modes */
    if ((statbuf.st_mode & S_IFMT/*0170000*/) != S_IFREG/*0100000*/) 
        {
                if(quiet)
                fprintf(stderr, "%s: ", ifname);
                fprintf(stderr, " -- not a regular file: unchanged");
                exit_stat = 1;
    } else if (statbuf.st_nlink > 1) 
        {
                if(quiet)
                fprintf(stderr, "%s: ", ifname);
                fprintf(stderr, " -- has %d other links: unchanged",
                statbuf.st_nlink - 1);
                exit_stat = 1;
    } else 
#endif
        if (exit_stat == 2 && (!force)) 
        { /* No compression: remove file.Z */
                if(!quiet)
                        fprintf(stderr, " -- file unchanged");
    } else 
        {                       /* ***** Successful Compression ***** */
                exit_stat = 0;
#ifndef PCDOS
                mode = statbuf.st_mode & 07777;
#else
                mode = statbuf.st_attr & 07777;
#endif
                if (chmod(ofname, mode))                /* Copy modes */
                    perror(ofname);
#ifndef PCDOS
                chown(ofname, statbuf.st_uid, statbuf.st_gid);  /* Copy ownership */
                timep[0] = statbuf.st_atime;
                timep[1] = statbuf.st_mtime;
#else
                timep[0] = statbuf.st_mtime;
                timep[1] = statbuf.st_mtime;
#endif
                utime(ofname, (struct utimbuf *)timep); /* Update last accessed and modified times */
/*
                if (unlink(ifname))
                    perror(ifname);
*/
                if(!quiet)
                    if(do_decomp == 0)
                        fprintf(stderr, " -- compressed to %s", ofname);
                    else
                        fprintf(stderr, " -- decompressed to %s", ofname);
                return;         /* Successful return */
    }

    /* Unsuccessful return -- one of the tests failed */
    if (unlink(ofname))
                perror(ofname);
}
/*
 * This routine returns 1 if we are running in the foreground and stderr
 * is a tty.
 */
int foreground()
{
#ifndef METAWARE
        if(bgnd_flag) { /* background? */
                return(0);
        } else {                        /* foreground */
#endif
                if(isatty(2)) {         /* and stderr is a tty */
                        return(1);
                } else {
                        return(0);
                }
#ifndef METAWARE
        }
#endif
}
#ifndef METAWARE
void onintr (dummy)
int dummy; /* to keep the compiler happy */
{
        (void)signal(SIGINT,SIG_IGN);
    unlink ( ofname );
    exit ( 1 );
}

void oops (dummy)       /* wild pointer -- assume bad input */
int dummy; /* to keep the compiler happy */
{
        (void)signal(SIGSEGV,SIG_IGN);
    if ( do_decomp == 1 ) 
        fprintf ( stderr, "uncompress: corrupt input\n" );
    unlink ( ofname );
    exit ( 1 );
}
#endif
void cl_block ()                /* table clear for block compress */
{
    REGISTER long int rat;

    checkpoint = in_count + CHECK_GAP;
#ifdef DEBUG
        if ( debug ) {
                fprintf ( stderr, "count: %ld, ratio: ", in_count );
                prratio ( stderr, in_count, bytes_out );
                fprintf ( stderr, "\n");
        }
#endif /* DEBUG */

    if(in_count > 0x007fffff) { /* shift will overflow */
        rat = bytes_out >> 8;
        if(rat == 0) {          /* Don't divide by zero */
            rat = 0x7fffffff;
        } else {
            rat = in_count / rat;
        }
    } else {
        rat = (in_count << 8) / bytes_out;      /* 8 fractional bits */
    }
    if ( rat > ratio ) {
        ratio = rat;
    } else {
        ratio = 0;
#ifdef DEBUG
        if(verbose)
                dump_tab();     /* dump string table */
#endif
        cl_hash ( (count_int) hsize );
        free_ent = FIRST;
        clear_flg = 1;
        output ( (code_int) CLEAR );
#ifdef DEBUG
        if(debug)
                fprintf ( stderr, "clear\n" );
#endif /* DEBUG */
    }
}

void cl_hash(hsize)             /* reset code table */
        REGISTER count_int hsize;
{
#ifdef AZTEC86
#ifdef PCDOS
        /* This function only in PC-DOS lib, not in MINIX lib */
        memset(htab,-1, hsize * sizeof(count_int));
#else
/* MINIX and all non-PC machines do it this way */      
#ifndef XENIX_16        /* Normal machine */
        REGISTER count_int *htab_p = htab+hsize;
#else
        REGISTER j;
        REGISTER long k = hsize;
        REGISTER count_int *htab_p;
#endif
        REGISTER long i;
        REGISTER long m1 = -1;

#ifdef XENIX_16
    for(j=0; j<=8 && k>=0; j++,k-=8192) 
        {
                i = 8192;
                if(k < 8192) 
                {
                        i = k;
                }
                htab_p = &(htab[j][i]);
                i -= 16;
                if(i > 0) 
                {
#else
        i = hsize - 16;
#endif
                do 
                {                               /* might use Sys V memset(3) here */
                        *(htab_p-16) = m1;
                        *(htab_p-15) = m1;
                        *(htab_p-14) = m1;
                        *(htab_p-13) = m1;
                        *(htab_p-12) = m1;
                        *(htab_p-11) = m1;
                        *(htab_p-10) = m1;
                        *(htab_p-9) = m1;
                        *(htab_p-8) = m1;
                        *(htab_p-7) = m1;
                        *(htab_p-6) = m1;
                        *(htab_p-5) = m1;
                        *(htab_p-4) = m1;
                        *(htab_p-3) = m1;
                        *(htab_p-2) = m1;
                        *(htab_p-1) = m1;
                        htab_p -= 16;
                } while ((i -= 16) >= 0);
#ifdef XENIX_16
                }
    }
#endif
        for ( i += 16; i > 0; i-- )
                *--htab_p = m1;
#endif
#endif
}

void prratio(stream, num, den)
FILE *stream;
long int num;
long int den;
{
        REGISTER int q;                 /* Doesn't need to be long */
        if(num > 214748L) 
        {               /* 2147483647/10000 */
                q = (int)(num / (den / 10000L));
        } else 
        {
                q = (int)(10000L * num / den);          /* Long calculations, though */
        }
        if (q < 0) 
        {
                putc('-', stream);
                q = -q;
        }
        fprintf(stream, "%d.%02d%c", q / 100, q % 100, '%');
}

void version()
{
        fprintf(stderr, "compress 4.1\n");
        fprintf(stderr, "Options: ");
#ifdef vax
        fprintf(stderr, "vax, ");
#endif
#ifdef _MINIX
        fprintf(stderr, "MINIX, ");
#endif
#ifdef NO_UCHAR
        fprintf(stderr, "NO_UCHAR, ");
#endif
#ifdef SIGNED_COMPARE_SLOW
        fprintf(stderr, "SIGNED_COMPARE_SLOW, ");
#endif
#ifdef XENIX_16
        fprintf(stderr, "XENIX_16, ");
#endif
#ifdef COMPATIBLE
        fprintf(stderr, "COMPATIBLE, ");
#endif
#ifdef DEBUG
        fprintf(stderr, "DEBUG, ");
#endif
#ifdef BSD4_2
        fprintf(stderr, "BSD4_2, ");
#endif
        fprintf(stderr, "BITS = %d\n", BITS);
}
/* End of text from uok.UUCP:net.sources */

---