man_hash.c

   1 /*      $Id: man_hash.c,v 1.29 2014/12/01 08:05:52 schwarze Exp $ */
   2 /*
   3  * Copyright (c) 2008, 2009, 2010 Kristaps Dzonsons <kristaps@bsd.lv>
   4  *
   5  * Permission to use, copy, modify, and distribute this software for any
   6  * purpose with or without fee is hereby granted, provided that the above
   7  * copyright notice and this permission notice appear in all copies.
   8  *
   9  * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
  10  * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
  11  * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
  12  * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
  13  * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
  14  * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
  15  * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
  16  */
  17 #include "config.h"
  18
  19 #include <sys/types.h>
  20
  21 #include <assert.h>
  22 #include <ctype.h>
  23 #include <limits.h>
  24 #include <string.h>
  25
  26 #include "man.h"
  27 #include "libman.h"
  28
  29 #define HASH_DEPTH       6
  30
  31 #define HASH_ROW(x) do { \
  32                 if (isupper((unsigned char)(x))) \
  33                         (x) -= 65; \
  34                 else \
  35                         (x) -= 97; \
  36                 (x) *= HASH_DEPTH; \
  37         } while (/* CONSTCOND */ 0)
  38
  39 /*
  40  * Lookup table is indexed first by lower-case first letter (plus one
  41  * for the period, which is stored in the last row), then by lower or
  42  * uppercase second letter.  Buckets correspond to the index of the
  43  * macro (the integer value of the enum stored as a char to save a bit
  44  * of space).
  45  */
  46 static  unsigned char    table[26 * HASH_DEPTH];
  47
  48
  49 /*
  50  * XXX - this hash has global scope, so if intended for use as a library
  51  * with multiple callers, it will need re-invocation protection.
  52  */
  53 void
  54 man_hash_init(void)
  55 {
  56         int              i, j, x;
  57
  58         memset(table, UCHAR_MAX, sizeof(table));
  59
  60         assert(MAN_MAX < UCHAR_MAX);
  61
  62         for (i = 0; i < (int)MAN_MAX; i++) {
  63                 x = man_macronames[i][0];
  64
  65                 assert(isalpha((unsigned char)x));
  66
  67                 HASH_ROW(x);
  68
  69                 for (j = 0; j < HASH_DEPTH; j++)
  70                         if (UCHAR_MAX == table[x + j]) {
  71                                 table[x + j] = (unsigned char)i;
  72                                 break;
  73                         }
  74
  75                 assert(j < HASH_DEPTH);
  76         }
  77 }
  78
  79 enum mant
  80 man_hash_find(const char *tmp)
  81 {
  82         int              x, y, i;
  83         enum mant        tok;
  84
  85         if ('\0' == (x = tmp[0]))
  86                 return(MAN_MAX);
  87         if ( ! (isalpha((unsigned char)x)))
  88                 return(MAN_MAX);
  89
  90         HASH_ROW(x);
  91
  92         for (i = 0; i < HASH_DEPTH; i++) {
  93                 if (UCHAR_MAX == (y = table[x + i]))
  94                         return(MAN_MAX);
  95
  96                 tok = (enum mant)y;
  97                 if (0 == strcmp(tmp, man_macronames[tok]))
  98                         return(tok);
  99         }
 100
 101         return(MAN_MAX);
 102 }