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Justine Tunney 2020-06-15 07:18:57 -07:00
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libc/alg/critbit0_allprefixed.c Normal file
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/*-*- mode:c;indent-tabs-mode:nil;c-basic-offset:2;tab-width:8;coding:utf-8 -*-│
│vi: set net ft=c ts=2 sts=2 sw=2 fenc=utf-8 :vi│
╞══════════════════════════════════════════════════════════════════════════════╡
│ Copyright 2020 Justine Alexandra Roberts Tunney │
│ │
│ This program is free software; you can redistribute it and/or modify │
│ it under the terms of the GNU General Public License as published by │
│ the Free Software Foundation; version 2 of the License. │
│ │
│ This program is distributed in the hope that it will be useful, but │
│ WITHOUT ANY WARRANTY; without even the implied warranty of │
│ MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU │
│ General Public License for more details. │
│ │
│ You should have received a copy of the GNU General Public License │
│ along with this program; if not, write to the Free Software │
│ Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA │
│ 02110-1301 USA │
╚─────────────────────────────────────────────────────────────────────────────*/
#include "libc/alg/alg.h"
#include "libc/alg/internal.h"
#include "libc/str/str.h"
static intptr_t allprefixed_traverse(unsigned char *top,
intptr_t (*callback)(const char *, void *),
void *arg) {
if (1 & (intptr_t)top) {
struct CritbitNode *q = (void *)(top - 1);
for (int direction = 0; direction < 2; ++direction) {
intptr_t rc = allprefixed_traverse(q->child[direction], callback, arg);
if (rc) return rc;
}
return 0;
}
return callback((const char *)top, arg);
}
/**
* Invokes callback for all items with prefix.
*
* @return 0 unless iteration was halted by CALLBACK returning
* nonzero, in which case that value is returned
* @note h/t djb and agl
*/
intptr_t critbit0_allprefixed(struct critbit0 *t, const char *prefix,
intptr_t (*callback)(const char *elem, void *arg),
void *arg) {
const unsigned char *ubytes = (void *)prefix;
const size_t ulen = strlen(prefix);
unsigned char *p = t->root;
unsigned char *top = p;
if (!p) return 0;
while (1 & (intptr_t)p) {
struct CritbitNode *q = (void *)(p - 1);
unsigned char c = 0;
if (q->byte < ulen) c = ubytes[q->byte];
const int direction = (1 + (q->otherbits | c)) >> 8;
p = q->child[direction];
if (q->byte < ulen) top = p;
}
for (size_t i = 0; i < ulen; ++i) {
if (p[i] != ubytes[i]) return 0;
}
return allprefixed_traverse(top, callback, arg);
}