Add string similarity function

libc/mem/alg.h

@@ -7,7 +7,6 @@ void *bsearch(const void *, const void *, size_t, size_t,
 void *bsearch_r(const void *, const void *, size_t, size_t,
                 int (*)(const void *, const void *, void *), void *)
     paramsnonnull((1, 2, 5)) nosideeffect;
-void djbsort(int32_t *, size_t) libcesque;
 void qsort3(void *, size_t, size_t,
             int (*)(const void *, const void *)) libcesque paramsnonnull();
 void qsort(void *, size_t, size_t,
@@ -25,8 +24,12 @@ int mergesort(void *, size_t, size_t, int (*)(const void *, const void *));
 int mergesort_r(void *, size_t, size_t,
                 int (*)(const void *, const void *, void *), void *);
 
+#ifdef _COSMO_SOURCE
+void djbsort(int32_t *, size_t) libcesque;
 int radix_sort_int32(int32_t *, size_t) libcesque;
 int radix_sort_int64(int64_t *, size_t) libcesque;
+double levenshtein(const char *, const char *) libcesque;
+#endif
 
 COSMOPOLITAN_C_END_
 #endif /* COSMOPOLITAN_LIBC_ALG_ALG_H_ */

libc/mem/levenshtein.c

@@ -0,0 +1,48 @@
+/*-*- mode:c;indent-tabs-mode:nil;c-basic-offset:2;tab-width:8;coding:utf-8 -*-│
+│ vi: set et ft=c ts=2 sts=2 sw=2 fenc=utf-8                               :vi │
+╞══════════════════════════════════════════════════════════════════════════════╡
+│ Copyright 2024 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/alg.h"
+#include "libc/mem/mem.h"
+
+#define MIN3(a, b, c) \
+  ((a) < (b) ? ((a) < (c) ? (a) : (c)) : ((b) < (c) ? (b) : (c)))
+
+/**
+ * Computes similarity between two strings.
+ */
+double levenshtein(const char *s0, const char *s1) {
+  int n0 = strlen(s0) + 1;
+  int n1 = strlen(s1) + 1;
+  int *col = (int *)malloc(n1 * sizeof(int));
+  int *pol = (int *)malloc(n1 * sizeof(int));
+  for (int i = 0; i < n1; i++)
+    pol[i] = i;
+  for (int i = 0; i < n0; i++) {
+    col[0] = i;
+    for (int j = 1; j < n1; j++)
+      col[j] = MIN3(1 + col[j - 1], 1 + pol[j],
+                    pol[j - 1] + !(i > 0 && s0[i - 1] == s1[j - 1]));
+    int *t = col;
+    col = pol;
+    pol = t;
+  }
+  int dist = pol[n1 - 1];
+  free(pol);
+  free(col);
+  return 1 - dist / ((n0 > n1 ? n0 : n1) - 1.);
+}

third_party/dlmalloc/locks.inc

@@ -34,7 +34,7 @@
 #define MLOCK_T atomic_uint
 
 static int malloc_wipe(MLOCK_T *lk) {
-  bzero(lk, sizeof(*lk));
+  atomic_store_explicit(lk, 0, memory_order_relaxed);
   return 0;
 }