62 lines
2.9 KiB
C
62 lines
2.9 KiB
C
/*-*- mode:c;indent-tabs-mode:nil;c-basic-offset:2;tab-width:8;coding:utf-8 -*-│
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│vi: set net ft=c ts=2 sts=2 sw=2 fenc=utf-8 :vi│
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╞══════════════════════════════════════════════════════════════════════════════╡
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│ Copyright 2020 Justine Alexandra Roberts Tunney │
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│ │
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│ This program is free software; you can redistribute it and/or modify │
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│ it under the terms of the GNU General Public License as published by │
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│ the Free Software Foundation; version 2 of the License. │
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│ │
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│ This program is distributed in the hope that it will be useful, but │
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│ WITHOUT ANY WARRANTY; without even the implied warranty of │
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│ MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU │
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│ General Public License for more details. │
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│ │
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│ You should have received a copy of the GNU General Public License │
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│ along with this program; if not, write to the Free Software │
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│ Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA │
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│ 02110-1301 USA │
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╚─────────────────────────────────────────────────────────────────────────────*/
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#include "libc/alg/alg.h"
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#include "libc/alg/internal.h"
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#include "libc/mem/mem.h"
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#include "libc/str/str.h"
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/**
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* Removes 𝑢 from 𝑡.
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* @param t tree
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* @param u NUL-terminated string
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* @return true if 𝑡 was mutated
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* @note h/t djb and agl
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*/
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bool critbit0_delete(struct critbit0 *t, const char *u) {
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const unsigned char *ubytes = (void *)u;
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const size_t ulen = strlen(u);
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unsigned char *p = t->root;
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void **wherep = &t->root;
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void **whereq = 0;
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struct CritbitNode *q = 0;
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int direction = 0;
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if (!p) return false;
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while (1 & (intptr_t)p) {
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whereq = wherep;
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q = (void *)(p - 1);
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unsigned char c = 0;
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if (q->byte < ulen) c = ubytes[q->byte];
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direction = (1 + (q->otherbits | c)) >> 8;
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wherep = q->child + direction;
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p = *wherep;
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}
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if (0 != strcmp(u, (const char *)p)) return false;
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free(p), p = NULL;
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if (!whereq) {
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t->root = NULL;
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t->count = 0;
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return true;
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}
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*whereq = q->child[1 - direction];
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free(q), q = NULL;
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t->count--;
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return true;
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}
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