45 lines
2.6 KiB
C
45 lines
2.6 KiB
C
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/*-*- 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/str/str.h"
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/**
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* Returns first item in 𝑡 with prefix 𝑢.
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* @param t tree
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* @param u NUL-terminated string
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* @return item or NULL if not found
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* @note h/t djb and agl
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*/
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char *critbit0_get(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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if (!p) return 0;
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while (1 & (intptr_t)p) {
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struct CritbitNode *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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const int direction = (1 + (q->otherbits | c)) >> 8;
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p = q->child[direction];
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}
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return strncmp(u, (const char *)p, ulen) == 0 ? (const char *)p : NULL;
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}
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