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Member "s-nail-14.9.10/obs-lzw.c" (25 Mar 2018, 19717 Bytes) of package /linux/misc/s-nail-14.9.10.tar.xz:


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    1 /*@ S-nail - a mail user agent derived from Berkeley Mail.
    2  *@ LZW file compression.
    3  *
    4  * Copyright (c) 2000-2004 Gunnar Ritter, Freiburg i. Br., Germany.
    5  * Copyright (c) 2012 - 2018 Steffen (Daode) Nurpmeso <sdaoden@users.sf.net>.
    6  */
    7 /*-
    8  * Copyright (c) 1985, 1986, 1992, 1993
    9  *  The Regents of the University of California.  All rights reserved.
   10  *
   11  * This code is derived from software contributed to Berkeley by
   12  * Diomidis Spinellis and James A. Woods, derived from original
   13  * work by Spencer Thomas and Joseph Orost.
   14  *
   15  * Redistribution and use in source and binary forms, with or without
   16  * modification, are permitted provided that the following conditions
   17  * are met:
   18  * 1. Redistributions of source code must retain the above copyright
   19  *    notice, this list of conditions and the following disclaimer.
   20  * 2. Redistributions in binary form must reproduce the above copyright
   21  *    notice, this list of conditions and the following disclaimer in the
   22  *    documentation and/or other materials provided with the distribution.
   23  * 4. Neither the name of the University nor the names of its contributors
   24  *    may be used to endorse or promote products derived from this software
   25  *    without specific prior written permission.
   26  *
   27  * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
   28  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
   29  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
   30  * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
   31  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
   32  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
   33  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
   34  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
   35  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
   36  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
   37  * SUCH DAMAGE.
   38  */
   39 
   40 /*  from zopen.c    8.1 (Berkeley) 6/27/93  */
   41 /*  from FreeBSD: /repoman/r/ncvs/src/usr.bin/compress/zopen.c,v
   42  *  1.5.6.1 2002/07/16 00:52:08 tjr Exp */
   43 /*  from FreeBSD: git://git.freebsd.org/freebsd,
   44  *  master:usr.bin/compress/zopen.c,
   45  *  (Fix handling of corrupt compress(1)ed data. [11:04], 2011-09-28) */
   46 
   47 /*-
   48  * lzw.c - File compression ala IEEE Computer, June 1984.
   49  *
   50  * Compress authors:
   51  *      Spencer W. Thomas   (decvax!utah-cs!thomas)
   52  *      Jim McKie       (decvax!mcvax!jim)
   53  *      Steve Davies        (decvax!vax135!petsd!peora!srd)
   54  *      Ken Turkowski       (decvax!decwrl!turtlevax!ken)
   55  *      James A. Woods      (decvax!ihnp4!ames!jaw)
   56  *      Joe Orost       (decvax!vax135!petsd!joe)
   57  *
   58  * Cleaned up and converted to library returning I/O streams by
   59  * Diomidis Spinellis <dds@doc.ic.ac.uk>.
   60  *
   61  * Adopted for Heirloom mailx by Gunnar Ritter.
   62  */
   63 #undef n_FILE
   64 #define n_FILE obs_lzw
   65 
   66 #ifndef HAVE_AMALGAMATION
   67 # include "nail.h"
   68 #endif
   69 
   70 EMPTY_FILE()
   71 #ifdef HAVE_IMAP
   72 /* Minimize differences to FreeBSDs usr.bin/compress/zopen.c */
   73 #undef u_int
   74 #define u_int       unsigned int
   75 #undef u_short
   76 #define u_short     unsigned short
   77 #undef u_char
   78 #define u_char      unsigned char
   79 #define count       cnt
   80 
   81 #define BITS        16      /* Default bits. */
   82 #define HSIZE       69001       /* 95% occupancy */
   83 
   84 /* A code_int must be able to hold 2**BITS values of type int, and also -1. */
   85 typedef long code_int;
   86 typedef long count_int;
   87 
   88 typedef u_char char_type;
   89 static char_type magic_header[] = {0x1F, 0x9D}; /* \037, \235 */
   90 
   91 #define BIT_MASK    0x1f        /* Defines for third byte of header. */
   92 #define BLOCK_MASK  0x80
   93 
   94 /*
   95  * Masks 0x40 and 0x20 are free.  I think 0x20 should mean that there is
   96  * a fourth header byte (for expansion).
   97  */
   98 #define INIT_BITS 9         /* Initial number of bits/code. */
   99 
  100 #define MAXCODE(n_bits) ((1 << (n_bits)) - 1)
  101 
  102 struct s_zstate {
  103     FILE *zs_fp;            /* File stream for I/O */
  104     char zs_mode;           /* r or w */
  105     enum {
  106         S_START, S_MIDDLE, S_EOF
  107     } zs_state;         /* State of computation */
  108     u_int zs_n_bits;        /* Number of bits/code. */
  109     u_int zs_maxbits;       /* User settable max # bits/code. */
  110     code_int zs_maxcode;        /* Maximum code, given n_bits. */
  111     code_int zs_maxmaxcode;     /* Should NEVER generate this code. */
  112     count_int zs_htab [HSIZE];
  113     u_short zs_codetab [HSIZE];
  114     code_int zs_hsize;      /* For dynamic table sizing. */
  115     code_int zs_free_ent;       /* First unused entry. */
  116     /*
  117      * Block compression parameters -- after all codes are used up,
  118      * and compression rate changes, start over.
  119      */
  120     int zs_block_compress;
  121     int zs_clear_flg;
  122     long zs_ratio;
  123     count_int zs_checkpoint;
  124     u_int zs_offset;
  125     long zs_in_count;       /* Length of input. */
  126     long zs_bytes_out;      /* Length of compressed output. */
  127     long zs_out_count;      /* # of codes output (for debugging). */
  128     char_type zs_buf[BITS];
  129     union {
  130         struct {
  131             long zs_fcode;
  132             code_int zs_ent;
  133             code_int zs_hsize_reg;
  134             int zs_hshift;
  135         } w;            /* Write parameters */
  136         struct {
  137             char_type *zs_stackp;
  138             int zs_finchar;
  139             code_int zs_code, zs_oldcode, zs_incode;
  140             int zs_roffset, zs_size;
  141             char_type zs_gbuf[BITS];
  142         } r;            /* Read parameters */
  143     } u;
  144 };
  145 
  146 /* Definitions to retain old variable names */
  147 #define fp      zs->zs_fp
  148 #define zmode       zs->zs_mode
  149 #define state       zs->zs_state
  150 #define n_bits      zs->zs_n_bits
  151 #define maxbits     zs->zs_maxbits
  152 #define maxcode     zs->zs_maxcode
  153 #define maxmaxcode  zs->zs_maxmaxcode
  154 #define htab        zs->zs_htab
  155 #define codetab     zs->zs_codetab
  156 #define hsize       zs->zs_hsize
  157 #define free_ent    zs->zs_free_ent
  158 #define block_compress  zs->zs_block_compress
  159 #define clear_flg   zs->zs_clear_flg
  160 #define ratio       zs->zs_ratio
  161 #define checkpoint  zs->zs_checkpoint
  162 #define offset      zs->zs_offset
  163 #define in_count    zs->zs_in_count
  164 #define bytes_out   zs->zs_bytes_out
  165 #define out_count   zs->zs_out_count
  166 #define buf     zs->zs_buf
  167 #define fcode       zs->u.w.zs_fcode
  168 #define hsize_reg   zs->u.w.zs_hsize_reg
  169 #define ent     zs->u.w.zs_ent
  170 #define hshift      zs->u.w.zs_hshift
  171 #define stackp      zs->u.r.zs_stackp
  172 #define finchar     zs->u.r.zs_finchar
  173 #define code        zs->u.r.zs_code
  174 #define oldcode     zs->u.r.zs_oldcode
  175 #define incode      zs->u.r.zs_incode
  176 #define roffset     zs->u.r.zs_roffset
  177 #define size        zs->u.r.zs_size
  178 #define gbuf        zs->u.r.zs_gbuf
  179 
  180 /*
  181  * To save much memory, we overlay the table used by compress() with those
  182  * used by decompress().  The tab_prefix table is the same size and type as
  183  * the codetab.  The tab_suffix table needs 2**BITS characters.  We get this
  184  * from the beginning of htab.  The output stack uses the rest of htab, and
  185  * contains characters.  There is plenty of room for any possible stack
  186  * (stack used to be 8000 characters).
  187  */
  188 
  189 #define htabof(i)   htab[i]
  190 #define codetabof(i)    codetab[i]
  191 
  192 #define tab_prefixof(i) codetabof(i)
  193 #define tab_suffixof(i) ((char_type *)(htab))[i]
  194 #define de_stack    ((char_type *)&tab_suffixof(1 << BITS))
  195 
  196 #define CHECK_GAP 10000     /* Ratio check interval. */
  197 
  198 /*
  199  * the next two codes should not be changed lightly, as they must not
  200  * lie within the contiguous general code space.
  201  */
  202 #define FIRST   257     /* First free entry. */
  203 #define CLEAR   256     /* Table clear output code. */
  204 
  205 static int  cl_block(struct s_zstate *);
  206 static void cl_hash(struct s_zstate *, count_int);
  207 static code_int getcode(struct s_zstate *);
  208 static int  output(struct s_zstate *, code_int);
  209 
  210 /*-
  211  * Algorithm from "A Technique for High Performance Data Compression",
  212  * Terry A. Welch, IEEE Computer Vol 17, No 6 (June 1984), pp 8-19.
  213  *
  214  * Algorithm:
  215  *  Modified Lempel-Ziv method (LZW).  Basically finds common
  216  * substrings and replaces them with a variable size code.  This is
  217  * deterministic, and can be done on the fly.  Thus, the decompression
  218  * procedure needs no input table, but tracks the way the table was built.
  219  */
  220 
  221 /*-
  222  * compress write
  223  *
  224  * Algorithm:  use open addressing double hashing (no chaining) on the
  225  * prefix code / next character combination.  We do a variant of Knuth's
  226  * algorithm D (vol. 3, sec. 6.4) along with G. Knott's relatively-prime
  227  * secondary probe.  Here, the modular division first probe is gives way
  228  * to a faster exclusive-or manipulation.  Also do block compression with
  229  * an adaptive reset, whereby the code table is cleared when the compression
  230  * ratio decreases, but after the table fills.  The variable-length output
  231  * codes are re-sized at this point, and a special CLEAR code is generated
  232  * for the decompressor.  Late addition:  construct the table according to
  233  * file size for noticeable speed improvement on small files.  Please direct
  234  * questions about this implementation to ames!jaw.
  235  */
  236 FL int
  237 zwrite(void *cookie, const char *wbp, int num)
  238 {
  239     code_int i;
  240     int c, disp;
  241     struct s_zstate *zs;
  242     const u_char *bp;
  243     u_char tmp;
  244     int count;
  245 
  246     if (num == 0)
  247         return (0);
  248 
  249     zs = cookie;
  250     zmode = 'w';
  251     count = num;
  252     bp = (const u_char *)wbp;
  253     if (state == S_MIDDLE)
  254         goto middle;
  255     state = S_MIDDLE;
  256 
  257     maxmaxcode = 1L << maxbits;
  258     if (fwrite(magic_header,
  259         sizeof(char), sizeof(magic_header), fp) != sizeof(magic_header))
  260         return (-1);
  261     tmp = (u_char)((maxbits) | block_compress);
  262     if (fwrite(&tmp, sizeof(char), sizeof(tmp), fp) != sizeof(tmp))
  263         return (-1);
  264 
  265     offset = 0;
  266     bytes_out = 3;      /* Includes 3-byte header mojo. */
  267     out_count = 0;
  268     clear_flg = 0;
  269     ratio = 0;
  270     in_count = 1;
  271     checkpoint = CHECK_GAP;
  272     maxcode = MAXCODE(n_bits = INIT_BITS);
  273     free_ent = ((block_compress) ? FIRST : 256);
  274 
  275     ent = *bp++;
  276     --count;
  277 
  278     hshift = 0;
  279     for (fcode = (long)hsize; fcode < 65536L; fcode *= 2L)
  280         hshift++;
  281     hshift = 8 - hshift;    /* Set hash code range bound. */
  282 
  283     hsize_reg = hsize;
  284     cl_hash(zs, (count_int)hsize_reg);  /* Clear hash table. */
  285 
  286 middle: for (i = 0; count--;) {
  287         c = *bp++;
  288         in_count++;
  289         fcode = (long)(((long)c << maxbits) + ent);
  290         i = ((c << hshift) ^ ent);  /* Xor hashing. */
  291 
  292         if (htabof(i) == fcode) {
  293             ent = codetabof(i);
  294             continue;
  295         } else if ((long)htabof(i) < 0) /* Empty slot. */
  296             goto nomatch;
  297         disp = hsize_reg - i;   /* Secondary hash (after G. Knott). */
  298         if (i == 0)
  299             disp = 1;
  300 probe:      if ((i -= disp) < 0)
  301             i += hsize_reg;
  302 
  303         if (htabof(i) == fcode) {
  304             ent = codetabof(i);
  305             continue;
  306         }
  307         if ((long)htabof(i) >= 0)
  308             goto probe;
  309 nomatch:    if (output(zs, (code_int) ent) == -1)
  310             return (-1);
  311         out_count++;
  312         ent = c;
  313         if (free_ent < maxmaxcode) {
  314             codetabof(i) = free_ent++;  /* code -> hashtable */
  315             htabof(i) = fcode;
  316         } else if ((count_int)in_count >=
  317             checkpoint && block_compress) {
  318             if (cl_block(zs) == -1)
  319                 return (-1);
  320         }
  321     }
  322     return (num);
  323 }
  324 
  325 FL int
  326 zfree(void *cookie)
  327 {
  328     struct s_zstate *zs;
  329 
  330     zs = cookie;
  331     if (zmode == 'w') {     /* Put out the final code. */
  332         if (output(zs, (code_int) ent) == -1) {
  333             free(zs);
  334             return (-1);
  335         }
  336         out_count++;
  337         if (output(zs, (code_int) - 1) == -1) {
  338             free(zs);
  339             return (-1);
  340         }
  341     }
  342     free(zs);
  343     return (0);
  344 }
  345 
  346 /*-
  347  * Output the given code.
  348  * Inputs:
  349  *  code:   A n_bits-bit integer.  If == -1, then EOF.  This assumes
  350  *      that n_bits =< (long)wordsize - 1.
  351  * Outputs:
  352  *  Outputs code to the file.
  353  * Assumptions:
  354  *  Chars are 8 bits long.
  355  * Algorithm:
  356  *  Maintain a BITS character long buffer (so that 8 codes will
  357  * fit in it exactly).  Use the VAX insv instruction to insert each
  358  * code in turn.  When the buffer fills up empty it and start over.
  359  */
  360 
  361 static char_type lmask[9] =
  362     {0xff, 0xfe, 0xfc, 0xf8, 0xf0, 0xe0, 0xc0, 0x80, 0x00};
  363 static char_type rmask[9] =
  364     {0x00, 0x01, 0x03, 0x07, 0x0f, 0x1f, 0x3f, 0x7f, 0xff};
  365 
  366 static int
  367 output(struct s_zstate *zs, code_int ocode)
  368 {
  369     int r_off;
  370     u_int bits;
  371     char_type *bp;
  372 
  373     r_off = offset;
  374     bits = n_bits;
  375     bp = buf;
  376     if (ocode >= 0) {
  377         /* Get to the first byte. */
  378         bp += (r_off >> 3);
  379         r_off &= 7;
  380         /*
  381          * Since ocode is always >= 8 bits, only need to mask the first
  382          * hunk on the left.
  383          */
  384         *bp = (*bp & rmask[r_off]) | ((ocode << r_off) & lmask[r_off]);
  385         bp++;
  386         bits -= (8 - r_off);
  387         ocode >>= 8 - r_off;
  388         /* Get any 8 bit parts in the middle (<=1 for up to 16 bits). */
  389         if (bits >= 8) {
  390             *bp++ = ocode;
  391             ocode >>= 8;
  392             bits -= 8;
  393         }
  394         /* Last bits. */
  395         if (bits)
  396             *bp = ocode;
  397         offset += n_bits;
  398         if (offset == (n_bits << 3)) {
  399             bp = buf;
  400             bits = n_bits;
  401             bytes_out += bits;
  402             if (fwrite(bp, sizeof(char), bits, fp) != bits)
  403                 return (-1);
  404             bp += bits;
  405             bits = 0;
  406             offset = 0;
  407         }
  408         /*
  409          * If the next entry is going to be too big for the ocode size,
  410          * then increase it, if possible.
  411          */
  412         if (free_ent > maxcode || (clear_flg > 0)) {
  413                /*
  414             * Write the whole buffer, because the input side won't
  415             * discover the size increase until after it has read it.
  416             */
  417             if (offset > 0) {
  418                 if (fwrite(buf, 1, n_bits, fp) != n_bits)
  419                     return (-1);
  420                 bytes_out += n_bits;
  421             }
  422             offset = 0;
  423 
  424             if (clear_flg) {
  425                 maxcode = MAXCODE(n_bits = INIT_BITS);
  426                 clear_flg = 0;
  427             } else {
  428                 n_bits++;
  429                 if (n_bits == maxbits)
  430                     maxcode = maxmaxcode;
  431                 else
  432                     maxcode = MAXCODE(n_bits);
  433             }
  434         }
  435     } else {
  436         /* At EOF, write the rest of the buffer. */
  437         if (offset > 0) {
  438             offset = (offset + 7) / 8;
  439             if (fwrite(buf, 1, offset, fp) != offset)
  440                 return (-1);
  441             bytes_out += offset;
  442         }
  443         offset = 0;
  444     }
  445     return (0);
  446 }
  447 
  448 /*
  449  * Decompress read.  This routine adapts to the codes in the file building
  450  * the "string" table on-the-fly; requiring no table to be stored in the
  451  * compressed file.  The tables used herein are shared with those of the
  452  * compress() routine.  See the definitions above.
  453  */
  454 FL int
  455 zread(void *cookie, char *rbp, int num)
  456 {
  457     u_int count;
  458     struct s_zstate *zs;
  459     u_char *bp, header[3];
  460 
  461     if (num == 0)
  462         return (0);
  463 
  464     zs = cookie;
  465     count = num;
  466     bp = (u_char *)rbp;
  467     switch (state) {
  468     case S_START:
  469         state = S_MIDDLE;
  470         break;
  471     case S_MIDDLE:
  472         goto middle;
  473     case S_EOF:
  474         goto eof;
  475     }
  476 
  477     /* Check the magic number */
  478     if (fread(header,
  479         sizeof(char), sizeof(header), fp) != sizeof(header) ||
  480         memcmp(header, magic_header, sizeof(magic_header)) != 0) {
  481         return (-1);
  482     }
  483     maxbits = header[2];    /* Set -b from file. */
  484     block_compress = maxbits & BLOCK_MASK;
  485     maxbits &= BIT_MASK;
  486     maxmaxcode = 1L << maxbits;
  487     if (maxbits > BITS || maxbits < 12) {
  488         return (-1);
  489     }
  490     /* As above, initialize the first 256 entries in the table. */
  491     maxcode = MAXCODE(n_bits = INIT_BITS);
  492     for (code = 255; code >= 0; code--) {
  493         tab_prefixof(code) = 0;
  494         tab_suffixof(code) = (char_type) code;
  495     }
  496     free_ent = block_compress ? FIRST : 256;
  497 
  498     finchar = oldcode = getcode(zs);
  499     if (oldcode == -1)  /* EOF already? */
  500         return (0); /* Get out of here */
  501 
  502     /* First code must be 8 bits = char. */
  503     *bp++ = (u_char)finchar;
  504     count--;
  505     stackp = de_stack;
  506 
  507     while ((code = getcode(zs)) > -1) {
  508 
  509         if ((code == CLEAR) && block_compress) {
  510             for (code = 255; code >= 0; code--)
  511                 tab_prefixof(code) = 0;
  512             clear_flg = 1;
  513             free_ent = FIRST;
  514             oldcode = -1;
  515             continue;
  516         }
  517         incode = code;
  518 
  519         /* Special case for kWkWk string. */
  520         if (code >= free_ent) {
  521             if (code > free_ent || oldcode == -1) {
  522                 return (-1);
  523             }
  524             *stackp++ = finchar;
  525             code = oldcode;
  526         }
  527         /*
  528          * The above condition ensures that code < free_ent.
  529          * The construction of tab_prefixof in turn guarantees that
  530          * each iteration decreases code and therefore stack usage is
  531          * bound by 1 << BITS - 256.
  532          */
  533 
  534         /* Generate output characters in reverse order. */
  535         while (code >= 256) {
  536             *stackp++ = tab_suffixof(code);
  537             code = tab_prefixof(code);
  538         }
  539         *stackp++ = finchar = tab_suffixof(code);
  540 
  541         /* And put them out in forward order.  */
  542 middle:     do {
  543             if (count-- == 0)
  544                 return (num);
  545             *bp++ = *--stackp;
  546         } while (stackp > de_stack);
  547 
  548         /* Generate the new entry. */
  549         if ((code = free_ent) < maxmaxcode && oldcode != -1) {
  550             tab_prefixof(code) = (u_short) oldcode;
  551             tab_suffixof(code) = finchar;
  552             free_ent = code + 1;
  553         }
  554 
  555         /* Remember previous code. */
  556         oldcode = incode;
  557     }
  558     state = S_EOF;
  559 eof:    return (num - count);
  560 }
  561 
  562 /*-
  563  * Read one code from the standard input.  If EOF, return -1.
  564  * Inputs:
  565  *  stdin
  566  * Outputs:
  567  *  code or -1 is returned.
  568  */
  569 static code_int
  570 getcode(struct s_zstate *zs)
  571 {
  572     code_int gcode;
  573     int r_off, bits;
  574     char_type *bp;
  575 
  576     bp = gbuf;
  577     if (clear_flg > 0 || roffset >= size || free_ent > maxcode) {
  578         /*
  579          * If the next entry will be too big for the current gcode
  580          * size, then we must increase the size.  This implies reading
  581          * a new buffer full, too.
  582          */
  583         if (free_ent > maxcode) {
  584             n_bits++;
  585             if (n_bits == maxbits)  /* Won't get any bigger now. */
  586                 maxcode = maxmaxcode;
  587             else
  588                 maxcode = MAXCODE(n_bits);
  589         }
  590         if (clear_flg > 0) {
  591             maxcode = MAXCODE(n_bits = INIT_BITS);
  592             clear_flg = 0;
  593         }
  594         size = fread(gbuf, 1, n_bits, fp);
  595         if (size <= 0)          /* End of file. */
  596             return (-1);
  597         roffset = 0;
  598         /* Round size down to integral number of codes. */
  599         size = (size << 3) - (n_bits - 1);
  600     }
  601     r_off = roffset;
  602     bits = n_bits;
  603 
  604     /* Get to the first byte. */
  605     bp += (r_off >> 3);
  606     r_off &= 7;
  607 
  608     /* Get first part (low order bits). */
  609     gcode = (*bp++ >> r_off);
  610     bits -= (8 - r_off);
  611     r_off = 8 - r_off;  /* Now, roffset into gcode word. */
  612 
  613     /* Get any 8 bit parts in the middle (<=1 for up to 16 bits). */
  614     if (bits >= 8) {
  615         gcode |= *bp++ << r_off;
  616         r_off += 8;
  617         bits -= 8;
  618     }
  619 
  620     /* High order bits. */
  621     gcode |= (*bp & rmask[bits]) << r_off;
  622     roffset += n_bits;
  623 
  624     return (gcode);
  625 }
  626 
  627 static int
  628 cl_block(struct s_zstate *zs)       /* Table clear for block compress. */
  629 {
  630     long rat;
  631 
  632     checkpoint = in_count + CHECK_GAP;
  633 
  634     if (in_count > 0x007fffff) {    /* Shift will overflow. */
  635         rat = bytes_out >> 8;
  636         if (rat == 0)       /* Don't divide by zero. */
  637             rat = 0x7fffffff;
  638         else
  639             rat = in_count / rat;
  640     } else
  641         rat = (in_count << 8) / bytes_out;  /* 8 fractional bits. */
  642     if (rat > ratio)
  643         ratio = rat;
  644     else {
  645         ratio = 0;
  646         cl_hash(zs, (count_int) hsize);
  647         free_ent = FIRST;
  648         clear_flg = 1;
  649         if (output(zs, (code_int) CLEAR) == -1)
  650             return (-1);
  651     }
  652     return (0);
  653 }
  654 
  655 static void
  656 cl_hash(struct s_zstate *zs, count_int cl_hsize)    /* Reset code table. */
  657 {
  658     count_int *htab_p;
  659     long i, m1;
  660 
  661     m1 = -1;
  662     htab_p = htab + cl_hsize;
  663     i = cl_hsize - 16;
  664     do {            /* Might use Sys V memset(3) here. */
  665         *(htab_p - 16) = m1;
  666         *(htab_p - 15) = m1;
  667         *(htab_p - 14) = m1;
  668         *(htab_p - 13) = m1;
  669         *(htab_p - 12) = m1;
  670         *(htab_p - 11) = m1;
  671         *(htab_p - 10) = m1;
  672         *(htab_p - 9) = m1;
  673         *(htab_p - 8) = m1;
  674         *(htab_p - 7) = m1;
  675         *(htab_p - 6) = m1;
  676         *(htab_p - 5) = m1;
  677         *(htab_p - 4) = m1;
  678         *(htab_p - 3) = m1;
  679         *(htab_p - 2) = m1;
  680         *(htab_p - 1) = m1;
  681         htab_p -= 16;
  682     } while ((i -= 16) >= 0);
  683     for (i += 16; i > 0; i--)
  684         *--htab_p = m1;
  685 }
  686 
  687 #undef fp
  688 FL void *
  689 zalloc(FILE *fp)
  690 {
  691 #define bits    BITS
  692     struct s_zstate *zs;
  693 
  694     zs = scalloc(1, sizeof *zs);
  695     maxbits = bits ? bits : BITS;   /* User settable max # bits/code. */
  696     maxmaxcode = 1L << maxbits; /* Should NEVER generate this code. */
  697     hsize = HSIZE;          /* For dynamic table sizing. */
  698     free_ent = 0;           /* First unused entry. */
  699     block_compress = BLOCK_MASK;
  700     clear_flg = 0;
  701     ratio = 0;
  702     checkpoint = CHECK_GAP;
  703     in_count = 1;           /* Length of input. */
  704     out_count = 0;          /* # of codes output (for debugging). */
  705     state = S_START;
  706     roffset = 0;
  707     size = 0;
  708     zs->zs_fp = fp;
  709     return zs;
  710 }
  711 
  712 #undef u_int
  713 #undef u_short
  714 #undef u_char
  715 #undef count
  716 #undef BITS
  717 #undef HSIZE
  718 #undef BIT_MASK
  719 #undef BLOCK_MASK
  720 #undef INIT_BITS
  721 #undef MAXCODE
  722 #undef fp
  723 #undef zmode
  724 #undef state
  725 #undef n_bits
  726 #undef maxbits
  727 #undef maxcode
  728 #undef maxmaxcode
  729 #undef htab
  730 #undef codetab
  731 #undef hsize
  732 #undef free_ent
  733 #undef block_compress
  734 #undef clear_flg
  735 #undef ratio
  736 #undef checkpoint
  737 #undef offset
  738 #undef in_count
  739 #undef bytes_out
  740 #undef out_count
  741 #undef buf
  742 #undef fcode
  743 #undef hsize_reg
  744 #undef ent
  745 #undef hshift
  746 #undef stackp
  747 #undef finchar
  748 #undef code
  749 #undef oldcode
  750 #undef incode
  751 #undef roffset
  752 #undef size
  753 #undef gbuf
  754 #endif /* ndef HAVE_IMAP */