libc.

Author: ncruces

sqlite3/strings.c

@@ -0,0 +1,87 @@
+#include <limits.h>
+#include <stddef.h>
+#include <stdint.h>
+
+#if defined(__wasm_bulk_memory__)
+#define memset __builtin_memset
+#define memcpy __builtin_memcpy
+#define memmove __builtin_memmove
+#endif
+
+#define ONES (~(uintmax_t)(0) / UCHAR_MAX)
+#define HIGHS (ONES * (UCHAR_MAX / 2 + 1))
+#define HASZERO(x) ((x) - (typeof(x))(ONES) & ~(x) & (typeof(x))(HIGHS))
+#define UNALIGNED(x) ((uintptr_t)(x) & (sizeof(*x) - 1))
+
+int memcmp(const void *v1, const void *v2, size_t n) {
+  typedef uint64_t __attribute__((__may_alias__)) word;
+
+  const word *w1 = v1;
+  const word *w2 = v2;
+  if (!(UNALIGNED(w1) | UNALIGNED(w2))) {
+    while (n >= sizeof(word) && *w1 == *w2) {
+      n -= sizeof(word);
+      w1++;
+      w2++;
+    }
+  }
+
+  const unsigned char *u1 = (const void *)w1;
+  const unsigned char *u2 = (const void *)w2;
+  while (n--) {
+    if (*u1 != *u2) return *u1 - *u2;
+    u1++;
+    u2++;
+  }
+  return 0;
+}
+
+int strcmp(const char *c1, const char *c2) {
+  typedef uintptr_t __attribute__((__may_alias__)) word;
+
+  const word *w1 = (const void *)c1;
+  const word *w2 = (const void *)c2;
+  if (!(UNALIGNED(w1) | UNALIGNED(w2))) {
+    while (*w1 == *w2) {
+      if (HASZERO(*w1)) return 0;
+      w1++;
+      w2++;
+    }
+    c1 = (const void *)w1;
+    c2 = (const void *)w2;
+  }
+
+  while (*c1 == *c2 && *c1) {
+    c1++;
+    c2++;
+  }
+  return *(unsigned char *)c1 - *(unsigned char *)c2;
+}
+
+int strncmp(const char *c1, const char *c2, size_t n) {
+  typedef uintptr_t __attribute__((__may_alias__)) word;
+
+  const word *w1 = (const void *)c1;
+  const word *w2 = (const void *)c2;
+  if (!(UNALIGNED(w1) | UNALIGNED(w2))) {
+    while (n >= sizeof(word) && *w1 == *w2) {
+      if ((n -= sizeof(word)) == 0 || HASZERO(*w1)) return 0;
+      w1++;
+      w2++;
+    }
+    c1 = (const void *)w1;
+    c2 = (const void *)w2;
+  }
+
+  while (n-- && *c1 == *c2) {
+    if (n == 0 || *c1 == 0) return 0;
+    c1++;
+    c2++;
+  }
+  return *(unsigned char *)c1 - *(unsigned char *)c2;
+}
+
+#undef UNALIGNED
+#undef HASZERO
+#undef HIGHS
+#undef ONES