89 lines
4.0 KiB
C
89 lines
4.0 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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* Inserts 𝑢 into 𝑡 without copying.
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* @param t tree
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* @param u NUL-terminated string which must be 8+ byte aligned and
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* becomes owned by the tree afterwards
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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_emplace(struct critbit0 *t, char *u, size_t ulen) {
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unsigned char *p = t->root;
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if (!p) {
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t->root = u;
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t->count = 1;
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return true;
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}
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const unsigned char *const ubytes = (void *)u;
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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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uint32_t newbyte;
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uint32_t newotherbits;
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for (newbyte = 0; newbyte < ulen; ++newbyte) {
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if (p[newbyte] != ubytes[newbyte]) {
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newotherbits = p[newbyte] ^ ubytes[newbyte];
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goto different_byte_found;
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}
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}
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if (p[newbyte] != 0) {
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newotherbits = p[newbyte];
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goto different_byte_found;
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}
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return false;
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different_byte_found:
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newotherbits |= newotherbits >> 1;
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newotherbits |= newotherbits >> 2;
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newotherbits |= newotherbits >> 4;
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newotherbits = (newotherbits & ~(newotherbits >> 1)) ^ 255;
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unsigned char c = p[newbyte];
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int newdirection = (1 + (newotherbits | c)) >> 8;
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struct CritbitNode *newnode = malloc(sizeof(struct CritbitNode));
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newnode->byte = newbyte;
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newnode->otherbits = newotherbits;
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newnode->child[1 - newdirection] = ubytes;
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void **wherep = &t->root;
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for (;;) {
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unsigned char *wp = *wherep;
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if (!(1 & (intptr_t)wp)) break;
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struct CritbitNode *q = (void *)(wp - 1);
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if (q->byte > newbyte) break;
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if (q->byte == newbyte && q->otherbits > newotherbits) break;
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unsigned char c2 = 0;
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if (q->byte < ulen) c2 = ubytes[q->byte];
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const int direction = (1 + (q->otherbits | c2)) >> 8;
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wherep = q->child + direction;
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}
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newnode->child[newdirection] = *wherep;
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*wherep = (void *)(1 + (char *)newnode);
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t->count++;
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return true;
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}
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