cosmopolitan/libc/mem/critbit0_emplace.c

/*-*- 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                              │
│                                                                              │
│ Permission to use, copy, modify, and/or distribute this software for         │
│ any purpose with or without fee is hereby granted, provided that the         │
│ above copyright notice and this permission notice appear in all copies.      │
│                                                                              │
│ THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL                │
│ WARRANTIES WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED                │
│ WARRANTIES OF MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE             │
│ AUTHOR BE LIABLE FOR ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL         │
│ DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR        │
│ PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER               │
│ TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR             │
│ PERFORMANCE OF THIS SOFTWARE.                                                │
╚─────────────────────────────────────────────────────────────────────────────*/
#include "libc/mem/critbit0.h"
#include "libc/mem/internal.h"
#include "libc/mem/mem.h"
#include "libc/str/str.h"

static void *critbit0_dup(const void *u, size_t ulen) {
  char *res;
  if ((res = malloc(ulen + 1))) {
    if (ulen) {
      memcpy(res, u, ulen);
    }
    res[ulen] = 0;
  }
  return res;
}

/**
 * Inserts 𝑢 into 𝑡 without copying.
 *
 * @return 1 if 𝑡 was mutated, 0 if present, or -1 w/ errno
 * @note h/t djb and agl
 */
int critbit0_emplace(struct critbit0 *t, const void *u, size_t ulen) {
  unsigned char *p = t->root;
  if (!p) {
    if ((u = critbit0_dup(u, ulen))) {
      t->root = (void *)u;
      t->count = 1;
      return 1;
    } else {
      return -1;
    }
  }
  const unsigned char *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 DifferentByteFound;
    }
  }
  if (p[newbyte] != 0) {
    newotherbits = p[newbyte];
    goto DifferentByteFound;
  }
  return 0;
DifferentByteFound:
  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;
  if ((newnode = malloc(sizeof(struct CritbitNode))) &&
      (ubytes = critbit0_dup(ubytes, ulen))) {
    newnode->byte = newbyte;
    newnode->otherbits = newotherbits;
    newnode->child[1 - newdirection] = (void *)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 1;
  } else {
    free(newnode);
    return -1;
  }
}