locate/code.c

   1 /* code -- bigram- and front-encode filenames for locate
   2    Copyright (C) 1994 Free Software Foundation, Inc.
   3
   4    This program is free software; you can redistribute it and/or modify
   5    it under the terms of the GNU General Public License as published by
   6    the Free Software Foundation; either version 2, or (at your option)
   7    any later version.
   8
   9    This program is distributed in the hope that it will be useful,
  10    but WITHOUT ANY WARRANTY; without even the implied warranty of
  11    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  12    GNU General Public License for more details.
  13
  14    You should have received a copy of the GNU General Public License
  15    along with this program; if not, write to the Free Software
  16    Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301,
  17    USA.
  18 */
  19
  20 /* Compress a sorted list.
  21    Works with `find' to encode a filename database to save space
  22    and search time.
  23
  24    Usage:
  25
  26    bigram < file_list > bigrams
  27    process-bigrams > most_common_bigrams
  28    code most_common_bigrams < file_list > squeezed_list
  29
  30    Uses `front compression' (see ";login:", March 1983, p. 8).
  31    The output begins with the 128 most common bigrams.
  32    After that, the output format is, for each line,
  33    an offset (from the previous line) differential count byte
  34    followed by a (partially bigram-encoded) ASCII remainder.
  35    The output lines have no terminating byte; the start of the next line
  36    is indicated by its first byte having a value <= 30.
  37
  38    The encoding of the output bytes is:
  39
  40    0-28         likeliest differential counts + offset (14) to make nonnegative
  41    30           escape code for out-of-range count to follow in next halfword
  42    128-255      bigram codes (the 128 most common, as determined by `updatedb')
  43    32-127       single character (printable) ASCII remainder
  44
  45    Written by James A. Woods <jwoods@adobe.com>.
  46    Modified by David MacKenzie <djm@gnu.org>.  */
  47
  48 #include <config.h>
  49 #include <stdio.h>
  50 #include <sys/types.h>
  51
  52 #if defined(HAVE_STRING_H) || defined(STDC_HEADERS)
  53 #include <string.h>
  54 #else
  55 #include <strings.h>
  56 #endif
  57
  58 #ifdef STDC_HEADERS
  59 #include <stdlib.h>
  60 #endif
  61
  62 #if ENABLE_NLS
  63 # include <libintl.h>
  64 # define _(Text) gettext (Text)
  65 #else
  66 # define _(Text) Text
  67 #define textdomain(Domain)
  68 #define bindtextdomain(Package, Directory)
  69 #endif
  70 #ifdef gettext_noop
  71 # define N_(String) gettext_noop (String)
  72 #else
  73 /* See locate.c for explanation as to why not use (String) */
  74 # define N_(String) String
  75 #endif
  76
  77 #include "locatedb.h"
  78 #include <getline.h>
  79 #include "closeout.h"
  80 #include "gnulib-version.h"
  81
  82 char *xmalloc PARAMS((size_t));
  83
  84 /* The name this program was run with.  */
  85 char *program_name;
  86
  87 /* The 128 most common bigrams in the file list, padded with NULs
  88    if there are fewer.  */
  89 static char bigrams[257] = {0};
  90
  91 /* Return the offset of PATTERN in STRING, or -1 if not found. */
  92
  93 static int
  94 strindex (char *string, char *pattern)
  95 {
  96   register char *s;
  97
  98   for (s = string; *s != '\0'; s++)
  99     /* Fast first char check. */
 100     if (*s == *pattern)
 101       {
 102         register char *p2 = pattern + 1, *s2 = s + 1;
 103         while (*p2 != '\0' && *p2 == *s2)
 104           p2++, s2++;
 105         if (*p2 == '\0')
 106           return s2 - strlen (pattern) - string;
 107       }
 108   return -1;
 109 }
 110
 111 /* Return the length of the longest common prefix of strings S1 and S2. */
 112
 113 static int
 114 prefix_length (char *s1, char *s2)
 115 {
 116   register char *start;
 117
 118   for (start = s1; *s1 == *s2 && *s1 != '\0'; s1++, s2++)
 119     ;
 120   return s1 - start;
 121 }
 122
 123 extern char *version_string;
 124
 125 static void
 126 usage (FILE *stream)
 127 {
 128   fprintf (stream, _("\
 129 Usage: %s [--version | --help]\n\
 130 or     %s most_common_bigrams < file-list > locate-database\n"),
 131            program_name, program_name);
 132   fputs (_("\nReport bugs to <bug-findutils@gnu.org>.\n"), stream);
 133 }
 134
 135
 136 int
 137 main (int argc, char **argv)
 138 {
 139   char *path;                   /* The current input entry.  */
 140   char *oldpath;                /* The previous input entry.  */
 141   size_t pathsize, oldpathsize; /* Amounts allocated for them.  */
 142   int count, oldcount, diffcount; /* Their prefix lengths & the difference. */
 143   char bigram[3];               /* Bigram to search for in table.  */
 144   int code;                     /* Index of `bigram' in bigrams table.  */
 145   FILE *fp;                     /* Most common bigrams file.  */
 146   int line_len;                 /* Length of input line.  */
 147
 148   program_name = argv[0];
 149   atexit (close_stdout);
 150
 151   bigram[2] = '\0';
 152
 153   if (argc != 2)
 154     {
 155       usage(stderr);
 156       return 2;
 157     }
 158
 159   if (0 == strcmp(argv[1], "--help"))
 160     {
 161       usage(stdout);
 162       return 0;
 163     }
 164   else if (0 == strcmp(argv[1], "--version"))
 165     {
 166       printf (_("GNU findutils version %s\n"), version_string);
 167       printf (_("Built using GNU gnulib version %s\n"), gnulib_version);
 168       return 0;
 169     }
 170
 171   fp = fopen (argv[1], "r");
 172   if (fp == NULL)
 173     {
 174       fprintf (stderr, "%s: ", argv[0]);
 175       perror (argv[1]);
 176       return 1;
 177     }
 178
 179   pathsize = oldpathsize = 1026; /* Increased as necessary by getline.  */
 180   path = xmalloc (pathsize);
 181   oldpath = xmalloc (oldpathsize);
 182
 183   /* Set to empty string, to force the first prefix count to 0.  */
 184   oldpath[0] = '\0';
 185   oldcount = 0;
 186
 187   /* Copy the list of most common bigrams to the output,
 188      padding with NULs if there are <128 of them.  */
 189   fgets (bigrams, 257, fp);
 190   fwrite (bigrams, 1, 256, stdout);
 191   fclose (fp);
 192
 193   while ((line_len = getline (&path, &pathsize, stdin)) > 0)
 194     {
 195       char *pp;
 196
 197       path[line_len - 1] = '\0'; /* Remove newline. */
 198
 199       /* Squelch unprintable chars in path so as not to botch decoding.  */
 200       for (pp = path; *pp != '\0'; pp++)
 201         {
 202           if (!(*pp >= 040 && *pp < 0177))
 203             *pp = '?';
 204         }
 205
 206       count = prefix_length (oldpath, path);
 207       diffcount = count - oldcount;
 208       oldcount = count;
 209       /* If the difference is small, it fits in one byte;
 210          otherwise, two bytes plus a marker noting that fact.  */
 211       if (diffcount < -LOCATEDB_OLD_OFFSET || diffcount > LOCATEDB_OLD_OFFSET)
 212         {
 213           putc (LOCATEDB_OLD_ESCAPE, stdout);
 214           putw (diffcount + LOCATEDB_OLD_OFFSET, stdout);
 215         }
 216       else
 217         putc (diffcount + LOCATEDB_OLD_OFFSET, stdout);
 218
 219       /* Look for bigrams in the remainder of the path.  */
 220       for (pp = path + count; *pp != '\0'; pp += 2)
 221         {
 222           if (pp[1] == '\0')
 223             {
 224               /* No bigram is possible; only one char is left.  */
 225               putchar (*pp);
 226               break;
 227             }
 228           bigram[0] = *pp;
 229           bigram[1] = pp[1];
 230           /* Linear search for specific bigram in string table. */
 231           code = strindex (bigrams, bigram);
 232           if (code % 2 == 0)
 233             putchar ((code / 2) | 0200); /* It's a common bigram.  */
 234           else
 235             fputs (bigram, stdout); /* Write the text as printable ASCII.  */
 236         }
 237
 238       {
 239         /* Swap path and oldpath and their sizes.  */
 240         char *tmppath = oldpath;
 241         size_t tmppathsize = oldpathsize;
 242         oldpath = path;
 243         oldpathsize = pathsize;
 244         path = tmppath;
 245         pathsize = tmppathsize;
 246       }
 247     }
 248
 249   free (path);
 250   free (oldpath);
 251
 252   return 0;
 253 }