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., 59 Temple Place - Suite 330, Boston, MA 02111-1307,
  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.ai.mit.edu>.  */
  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
  80 char *xmalloc PARAMS((size_t));
  81
  82 /* The name this program was run with.  */
  83 char *program_name;
  84
  85 /* The 128 most common bigrams in the file list, padded with NULs
  86    if there are fewer.  */
  87 static char bigrams[257] = {0};
  88
  89 /* Return the offset of PATTERN in STRING, or -1 if not found. */
  90
  91 static int
  92 strindex (char *string, char *pattern)
  93 {
  94   register char *s;
  95
  96   for (s = string; *s != '\0'; s++)
  97     /* Fast first char check. */
  98     if (*s == *pattern)
  99       {
 100         register char *p2 = pattern + 1, *s2 = s + 1;
 101         while (*p2 != '\0' && *p2 == *s2)
 102           p2++, s2++;
 103         if (*p2 == '\0')
 104           return s2 - strlen (pattern) - string;
 105       }
 106   return -1;
 107 }
 108
 109 /* Return the length of the longest common prefix of strings S1 and S2. */
 110
 111 static int
 112 prefix_length (char *s1, char *s2)
 113 {
 114   register char *start;
 115
 116   for (start = s1; *s1 == *s2 && *s1 != '\0'; s1++, s2++)
 117     ;
 118   return s1 - start;
 119 }
 120
 121 extern char *version_string;
 122
 123 static void
 124 usage (stream)
 125      FILE *stream;
 126 {
 127   fprintf (stream, _("\
 128 Usage: %s [--version | --help]\n\
 129 or     %s most_common_bigrams < file-list > locate-database\n"),
 130            program_name, program_name);
 131   fputs (_("\nReport bugs to <bug-findutils@gnu.org>.\n"), stream);
 132 }
 133
 134
 135 int
 136 main (int argc, char **argv)
 137 {
 138   char *path;                   /* The current input entry.  */
 139   char *oldpath;                /* The previous input entry.  */
 140   size_t pathsize, oldpathsize; /* Amounts allocated for them.  */
 141   int count, oldcount, diffcount; /* Their prefix lengths & the difference. */
 142   char bigram[3];               /* Bigram to search for in table.  */
 143   int code;                     /* Index of `bigram' in bigrams table.  */
 144   FILE *fp;                     /* Most common bigrams file.  */
 145   int line_len;                 /* Length of input line.  */
 146
 147   program_name = argv[0];
 148
 149   bigram[2] = '\0';
 150
 151   if (argc != 2)
 152     {
 153       usage(stderr);
 154       return 2;
 155     }
 156
 157   if (0 == strcmp(argv[1], "--help"))
 158     {
 159       usage(stdout);
 160       return 0;
 161     }
 162   else if (0 == strcmp(argv[1], "--version"))
 163     {
 164       printf (_("GNU findutils version %s\n"), version_string);
 165       return 0;
 166     }
 167
 168   fp = fopen (argv[1], "r");
 169   if (fp == NULL)
 170     {
 171       fprintf (stderr, "%s: ", argv[0]);
 172       perror (argv[1]);
 173       return 1;
 174     }
 175
 176   pathsize = oldpathsize = 1026; /* Increased as necessary by getline.  */
 177   path = xmalloc (pathsize);
 178   oldpath = xmalloc (oldpathsize);
 179
 180   /* Set to anything not starting with a slash, to force the first
 181      prefix count to 0.  */
 182   strcpy (oldpath, " ");
 183   oldcount = 0;
 184
 185   /* Copy the list of most common bigrams to the output,
 186      padding with NULs if there are <128 of them.  */
 187   fgets (bigrams, 257, fp);
 188   fwrite (bigrams, 1, 256, stdout);
 189   fclose (fp);
 190
 191   while ((line_len = getline (&path, &pathsize, stdin)) > 0)
 192     {
 193       char *pp;
 194
 195       path[line_len - 1] = '\0'; /* Remove newline. */
 196
 197       /* Squelch unprintable chars in path so as not to botch decoding.  */
 198       for (pp = path; *pp != '\0'; pp++)
 199         {
 200           if (!(*pp >= 040 && *pp < 0177))
 201             *pp = '?';
 202         }
 203
 204       count = prefix_length (oldpath, path);
 205       diffcount = count - oldcount;
 206       oldcount = count;
 207       /* If the difference is small, it fits in one byte;
 208          otherwise, two bytes plus a marker noting that fact.  */
 209       if (diffcount < -LOCATEDB_OLD_OFFSET || diffcount > LOCATEDB_OLD_OFFSET)
 210         {
 211           putc (LOCATEDB_OLD_ESCAPE, stdout);
 212           putw (diffcount + LOCATEDB_OLD_OFFSET, stdout);
 213         }
 214       else
 215         putc (diffcount + LOCATEDB_OLD_OFFSET, stdout);
 216
 217       /* Look for bigrams in the remainder of the path.  */
 218       for (pp = path + count; *pp != '\0'; pp += 2)
 219         {
 220           if (pp[1] == '\0')
 221             {
 222               /* No bigram is possible; only one char is left.  */
 223               putchar (*pp);
 224               break;
 225             }
 226           bigram[0] = *pp;
 227           bigram[1] = pp[1];
 228           /* Linear search for specific bigram in string table. */
 229           code = strindex (bigrams, bigram);
 230           if (code % 2 == 0)
 231             putchar ((code / 2) | 0200); /* It's a common bigram.  */
 232           else
 233             fputs (bigram, stdout); /* Write the text as printable ASCII.  */
 234         }
 235
 236       {
 237         /* Swap path and oldpath and their sizes.  */
 238         char *tmppath = oldpath;
 239         size_t tmppathsize = oldpathsize;
 240         oldpath = path;
 241         oldpathsize = pathsize;
 242         path = tmppath;
 243         pathsize = tmppathsize;
 244       }
 245     }
 246
 247   free (path);
 248   free (oldpath);
 249
 250   return 0;
 251 }