| 1 | /* ternary.c - Ternary Search Trees |
| 2 | Copyright (C) 2001 Free Software Foundation, Inc. |
| 3 | |
| 4 | Contributed by Daniel Berlin (dan@cgsoftware.com) |
| 5 | |
| 6 | This program is free software; you can redistribute it and/or modify it |
| 7 | under the terms of the GNU General Public License as published by the |
| 8 | Free Software Foundation; either version 2, or (at your option) any |
| 9 | later version. |
| 10 | |
| 11 | This program is distributed in the hope that it will be useful, |
| 12 | but WITHOUT ANY WARRANTY; without even the implied warranty of |
| 13 | MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the |
| 14 | GNU General Public License for more details. |
| 15 | |
| 16 | You should have received a copy of the GNU General Public License |
| 17 | along with this program; if not, write to the Free Software |
| 18 | Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, |
| 19 | USA. */ |
| 20 | #ifdef HAVE_CONFIG_H |
| 21 | #include "config.h" |
| 22 | #endif |
| 23 | |
| 24 | #ifdef HAVE_STDLIB_H |
| 25 | #include <stdlib.h> |
| 26 | #endif |
| 27 | |
| 28 | #include <stdio.h> |
| 29 | |
| 30 | #include "libiberty.h" |
| 31 | #include "ternary.h" |
| 32 | |
| 33 | /* Non-recursive so we don't waste stack space/time on large |
| 34 | insertions. */ |
| 35 | |
| 36 | PTR |
| 37 | ternary_insert (ternary_tree *root, const char *s, PTR data, int replace) |
| 38 | { |
| 39 | int diff; |
| 40 | ternary_tree curr, *pcurr; |
| 41 | |
| 42 | /* Start at the root. */ |
| 43 | pcurr = root; |
| 44 | /* Loop until we find the right position */ |
| 45 | while ((curr = *pcurr)) |
| 46 | { |
| 47 | /* Calculate the difference */ |
| 48 | diff = *s - curr->splitchar; |
| 49 | /* Handle current char equal to node splitchar */ |
| 50 | if (diff == 0) |
| 51 | { |
| 52 | /* Handle the case of a string we already have */ |
| 53 | if (*s++ == 0) |
| 54 | { |
| 55 | if (replace) |
| 56 | curr->eqkid = (ternary_tree) data; |
| 57 | return (PTR) curr->eqkid; |
| 58 | } |
| 59 | pcurr = &(curr->eqkid); |
| 60 | } |
| 61 | /* Handle current char less than node splitchar */ |
| 62 | else if (diff < 0) |
| 63 | { |
| 64 | pcurr = &(curr->lokid); |
| 65 | } |
| 66 | /* Handle current char greater than node splitchar */ |
| 67 | else |
| 68 | { |
| 69 | pcurr = &(curr->hikid); |
| 70 | } |
| 71 | } |
| 72 | /* It's not a duplicate string, and we should insert what's left of |
| 73 | the string, into the tree rooted at curr */ |
| 74 | for (;;) |
| 75 | { |
| 76 | /* Allocate the memory for the node, and fill it in */ |
| 77 | *pcurr = (ternary_tree) xmalloc (sizeof (ternary_node)); |
| 78 | curr = *pcurr; |
| 79 | curr->splitchar = *s; |
| 80 | curr->lokid = curr->hikid = curr->eqkid = 0; |
| 81 | |
| 82 | /* Place nodes until we hit the end of the string. |
| 83 | When we hit it, place the data in the right place, and |
| 84 | return. |
| 85 | */ |
| 86 | if (*s++ == 0) |
| 87 | { |
| 88 | curr->eqkid = (ternary_tree) data; |
| 89 | return data; |
| 90 | } |
| 91 | pcurr = &(curr->eqkid); |
| 92 | } |
| 93 | } |
| 94 | |
| 95 | /* Free the ternary search tree rooted at p. */ |
| 96 | void |
| 97 | ternary_cleanup (ternary_tree p) |
| 98 | { |
| 99 | if (p) |
| 100 | { |
| 101 | ternary_cleanup (p->lokid); |
| 102 | if (p->splitchar) |
| 103 | ternary_cleanup (p->eqkid); |
| 104 | ternary_cleanup (p->hikid); |
| 105 | free (p); |
| 106 | } |
| 107 | } |
| 108 | |
| 109 | /* Non-recursive find of a string in the ternary tree */ |
| 110 | PTR |
| 111 | ternary_search (const ternary_node *p, const char *s) |
| 112 | { |
| 113 | const ternary_node *curr; |
| 114 | int diff, spchar; |
| 115 | spchar = *s; |
| 116 | curr = p; |
| 117 | /* Loop while we haven't hit a NULL node or returned */ |
| 118 | while (curr) |
| 119 | { |
| 120 | /* Calculate the difference */ |
| 121 | diff = spchar - curr->splitchar; |
| 122 | /* Handle the equal case */ |
| 123 | if (diff == 0) |
| 124 | { |
| 125 | if (spchar == 0) |
| 126 | return (PTR) curr->eqkid; |
| 127 | spchar = *++s; |
| 128 | curr = curr->eqkid; |
| 129 | } |
| 130 | /* Handle the less than case */ |
| 131 | else if (diff < 0) |
| 132 | curr = curr->lokid; |
| 133 | /* All that's left is greater than */ |
| 134 | else |
| 135 | curr = curr->hikid; |
| 136 | } |
| 137 | return NULL; |
| 138 | } |
| 139 | |
| 140 | /* For those who care, the recursive version of the search. Useful if |
| 141 | you want a starting point for pmsearch or nearsearch. */ |
| 142 | static PTR |
| 143 | ternary_recursivesearch (const ternary_node *p, const char *s) |
| 144 | { |
| 145 | if (!p) |
| 146 | return 0; |
| 147 | if (*s < p->splitchar) |
| 148 | return ternary_recursivesearch (p->lokid, s); |
| 149 | else if (*s > p->splitchar) |
| 150 | return ternary_recursivesearch (p->hikid, s); |
| 151 | else |
| 152 | { |
| 153 | if (*s == 0) |
| 154 | return (PTR) p->eqkid; |
| 155 | return ternary_recursivesearch (p->eqkid, ++s); |
| 156 | } |
| 157 | } |