1 | /* $NetBSD: tdelete.c,v 1.2 1999/09/16 11:45:37 lukem Exp $ */ |
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2 | |
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3 | /* |
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4 | * Tree search generalized from Knuth (6.2.2) Algorithm T just like |
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5 | * the AT&T man page says. |
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6 | * |
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7 | * The node_t structure is for internal use only, lint doesn't grok it. |
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8 | * |
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9 | * Written by reading the System V Interface Definition, not the code. |
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10 | * |
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11 | * Totally public domain. |
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12 | */ |
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13 | |
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14 | #include <sys/cdefs.h> |
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15 | #if 0 |
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16 | #if defined(LIBC_SCCS) && !defined(lint) |
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17 | __RCSID("$NetBSD: tdelete.c,v 1.2 1999/09/16 11:45:37 lukem Exp $"); |
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18 | #endif /* LIBC_SCCS and not lint */ |
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19 | #endif |
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20 | |
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21 | #include <assert.h> |
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22 | #define _SEARCH_PRIVATE |
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23 | #include <search.h> |
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24 | #include <stdlib.h> |
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25 | |
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26 | |
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27 | /* delete node with given key */ |
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28 | void * |
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29 | tdelete (const void *__restrict vkey, /* key to be deleted */ |
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30 | void **__restrict vrootp, /* address of the root of tree */ |
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31 | int (*compar)(const void *, const void *)) |
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32 | { |
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33 | node_t **rootp = (node_t **)vrootp; |
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34 | node_t *p, *q, *r; |
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35 | int cmp; |
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36 | |
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37 | if (rootp == NULL || (p = *rootp) == NULL) |
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38 | return NULL; |
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39 | |
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40 | while ((cmp = (*compar)(vkey, (*rootp)->key)) != 0) { |
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41 | p = *rootp; |
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42 | rootp = (cmp < 0) ? |
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43 | &(*rootp)->llink : /* follow llink branch */ |
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44 | &(*rootp)->rlink; /* follow rlink branch */ |
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45 | if (*rootp == NULL) |
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46 | return NULL; /* key not found */ |
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47 | } |
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48 | r = (*rootp)->rlink; /* D1: */ |
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49 | if ((q = (*rootp)->llink) == NULL) /* Left NULL? */ |
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50 | q = r; |
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51 | else if (r != NULL) { /* Right link is NULL? */ |
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52 | if (r->llink == NULL) { /* D2: Find successor */ |
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53 | r->llink = q; |
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54 | q = r; |
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55 | } else { /* D3: Find NULL link */ |
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56 | for (q = r->llink; q->llink != NULL; q = r->llink) |
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57 | r = q; |
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58 | r->llink = q->rlink; |
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59 | q->llink = (*rootp)->llink; |
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60 | q->rlink = (*rootp)->rlink; |
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61 | } |
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62 | } |
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63 | free(*rootp); /* D4: Free node */ |
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64 | *rootp = q; /* link parent to new node */ |
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65 | return p; |
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66 | } |
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