cosmopolitan/libc/alg/critbit0_emplace.c

89 lines
4.0 KiB
C
Raw Blame History

This file contains ambiguous Unicode characters!

This file contains ambiguous Unicode characters that may be confused with others in your current locale. If your use case is intentional and legitimate, you can safely ignore this warning. Use the Escape button to highlight these characters.

/*-*- 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/mem/mem.h"
#include "libc/str/str.h"
/**
* Inserts 𝑢 into 𝑡 without copying.
* @param t tree
* @param u NUL-terminated string which must be 8+ byte aligned and
* becomes owned by the tree afterwards
* @return true if 𝑡 was mutated
* @note h/t djb and agl
*/
bool critbit0_emplace(struct critbit0 *t, char *u, size_t ulen) {
unsigned char *p = t->root;
if (!p) {
t->root = u;
t->count = 1;
return true;
}
const unsigned char *const ubytes = (void *)u;
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];
}
uint32_t newbyte;
uint32_t newotherbits;
for (newbyte = 0; newbyte < ulen; ++newbyte) {
if (p[newbyte] != ubytes[newbyte]) {
newotherbits = p[newbyte] ^ ubytes[newbyte];
goto different_byte_found;
}
}
if (p[newbyte] != 0) {
newotherbits = p[newbyte];
goto different_byte_found;
}
return false;
different_byte_found:
newotherbits |= newotherbits >> 1;
newotherbits |= newotherbits >> 2;
newotherbits |= newotherbits >> 4;
newotherbits = (newotherbits & ~(newotherbits >> 1)) ^ 255;
unsigned char c = p[newbyte];
int newdirection = (1 + (newotherbits | c)) >> 8;
struct CritbitNode *newnode = malloc(sizeof(struct CritbitNode));
newnode->byte = newbyte;
newnode->otherbits = newotherbits;
newnode->child[1 - newdirection] = ubytes;
void **wherep = &t->root;
for (;;) {
unsigned char *wp = *wherep;
if (!(1 & (intptr_t)wp)) break;
struct CritbitNode *q = (void *)(wp - 1);
if (q->byte > newbyte) break;
if (q->byte == newbyte && q->otherbits > newotherbits) break;
unsigned char c2 = 0;
if (q->byte < ulen) c2 = ubytes[q->byte];
const int direction = (1 + (q->otherbits | c2)) >> 8;
wherep = q->child + direction;
}
newnode->child[newdirection] = *wherep;
*wherep = (void *)(1 + (char *)newnode);
t->count++;
return true;
}