3 * Monoalphabetic matcher
5 * (c) 2003 Mark Wooding
8 /*----- Licensing notice --------------------------------------------------*
10 * This file is part of Anag: a simple wordgame helper.
12 * Anag is free software; you can redistribute it and/or modify
13 * it under the terms of the GNU General Public License as published by
14 * the Free Software Foundation; either version 2 of the License, or
15 * (at your option) any later version.
17 * Anag is distributed in the hope that it will be useful,
18 * but WITHOUT ANY WARRANTY; without even the implied warranty of
19 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
20 * GNU General Public License for more details.
22 * You should have received a copy of the GNU General Public License
23 * along with Anag; if not, write to the Free Software Foundation,
24 * Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
27 /*----- Header files ------------------------------------------------------*/
31 /*----- Data structures ---------------------------------------------------*/
33 typedef struct node_mono {
39 /*----- Main code ---------------------------------------------------------*/
41 /* --- Matching --- */
43 static int n_mono(node *nn, const char *p, size_t sz)
45 node_mono *n = (node_mono *)nn;
46 unsigned map[UCHAR_MAX];
47 const unsigned char *q = n->p;
51 /* Monoalphabetic substitution preserves length. */
52 if (sz != n->len) return (0);
54 /* Canonicalize this string as we did the pattern. Fail if we find a
57 memset(map, UCHAR_MAX, sizeof(map));
60 if (map[ch] >= max) map[ch] = max++;
61 if (max >= UCHAR_MAX) return (0);
62 if (*q++ != map[ch]) return (0);
67 /* --- Node creation --- */
69 node *mono(const char *const *av)
71 unsigned char map[UCHAR_MAX];
72 const char *p = av[0];
77 node_mono *n = xmalloc(sizeof(*n));
79 n->p = q = xmalloc(n->len);
82 /* Convert the string into the canonical representative of its equivalence
83 * class, specifically the lexically first string which is equivalent under
84 * monoalphabetic substitution. That is: replace the first distinct
85 * character with zero, the second with one, and so on.
87 memset(map, UCHAR_MAX, sizeof(map));
90 if (map[ch] >= max) map[ch] = max++;
91 assert(max < UCHAR_MAX);
98 /*----- That's all, folks -------------------------------------------------*/