| /* $NetBSD: tsearch.c,v 1.3 1999/09/16 11:45:37 lukem Exp $ */ |
| |
| /* |
| * Tree search generalized from Knuth (6.2.2) Algorithm T just like |
| * the AT&T man page says. |
| * |
| * The node_t structure is for internal use only, lint doesn't grok it. |
| * |
| * Written by reading the System V Interface Definition, not the code. |
| * |
| * Totally public domain. |
| */ |
| |
| #ifndef _MSC_FULL_VER |
| #include <sys/cdefs.h> |
| #endif //! _MSC_FULL_VER |
| #define _SEARCH_PRIVATE |
| #include "tsearch.h" |
| #include <stdlib.h> |
| |
| /* find or insert datum into search tree */ |
| void * |
| tsearch(vkey, vrootp, compar) |
| const void *vkey; /* key to be located */ |
| void **vrootp; /* address of tree root */ |
| int (*compar)(const void *, const void *); |
| { |
| node_t *q; |
| node_t **rootp = (node_t **)vrootp; |
| |
| if (rootp == NULL) |
| return NULL; |
| |
| while (*rootp != NULL) { /* Knuth's T1: */ |
| int r; |
| |
| if ((r = (*compar)(vkey, (*rootp)->key)) == 0) /* T2: */ |
| return *rootp; /* we found it! */ |
| |
| rootp = (r < 0) ? |
| &(*rootp)->llink : /* T3: follow left branch */ |
| &(*rootp)->rlink; /* T4: follow right branch */ |
| } |
| |
| q = malloc(sizeof(node_t)); /* T5: key not found */ |
| if (q != 0) { /* make new node */ |
| *rootp = q; /* link new node to old */ |
| /* LINTED const castaway ok */ |
| q->key = (void *)vkey; /* initialize new node */ |
| q->llink = q->rlink = NULL; |
| } |
| return q; |
| } |
| |
| /* find a node, or return 0 */ |
| void * |
| tfind(vkey, vrootp, compar) |
| const void *vkey; /* key to be found */ |
| void * const *vrootp; /* address of the tree root */ |
| int (*compar)(const void *, const void *); |
| { |
| node_t **rootp = (node_t **)vrootp; |
| |
| if (rootp == NULL) |
| return NULL; |
| |
| while (*rootp != NULL) { /* T1: */ |
| int r; |
| |
| if ((r = (*compar)(vkey, (*rootp)->key)) == 0) /* T2: */ |
| return *rootp; /* key found */ |
| rootp = (r < 0) ? |
| &(*rootp)->llink : /* T3: follow left branch */ |
| &(*rootp)->rlink; /* T4: follow right branch */ |
| } |
| return NULL; |
| } |
| |
| /* |
| * delete node with given key |
| * |
| * vkey: key to be deleted |
| * vrootp: address of the root of the tree |
| * compar: function to carry out node comparisons |
| */ |
| void * |
| tdelete(const void * __restrict vkey, void ** __restrict vrootp, |
| int (*compar)(const void *, const void *)) |
| { |
| node_t **rootp = (node_t **)vrootp; |
| node_t *p, *q, *r; |
| int cmp; |
| |
| if (rootp == NULL || (p = *rootp) == NULL) |
| return NULL; |
| |
| while ((cmp = (*compar)(vkey, (*rootp)->key)) != 0) { |
| p = *rootp; |
| rootp = (cmp < 0) ? |
| &(*rootp)->llink : /* follow llink branch */ |
| &(*rootp)->rlink; /* follow rlink branch */ |
| if (*rootp == NULL) |
| return NULL; /* key not found */ |
| } |
| r = (*rootp)->rlink; /* D1: */ |
| if ((q = (*rootp)->llink) == NULL) /* Left NULL? */ |
| q = r; |
| else if (r != NULL) { /* Right link is NULL? */ |
| if (r->llink == NULL) { /* D2: Find successor */ |
| r->llink = q; |
| q = r; |
| } else { /* D3: Find NULL link */ |
| for (q = r->llink; q->llink != NULL; q = r->llink) |
| r = q; |
| r->llink = q->rlink; |
| q->llink = (*rootp)->llink; |
| q->rlink = (*rootp)->rlink; |
| } |
| } |
| free(*rootp); /* D4: Free node */ |
| *rootp = q; /* link parent to new node */ |
| return p; |
| } |
| |
| /* end of tsearch.c */ |