optimize strchrnul/strcspn not to scan string twice on no-match

[musl] / src / string / strchrnul.c

diff --git a/src/string/strchrnul.c b/src/string/strchrnul.c
index 5e0c1a1..ceae4d4 100644 (file)
--- a/src/string/strchrnul.c
+++ b/src/string/strchrnul.c
@@ -1,7 +1,27 @@
 #include <string.h>
+#include <stdlib.h>
+#include <stdint.h>
+#include <limits.h>
+#include "libc.h"
 
-char *strchrnul(const char *s, int c)
+#define ALIGN (sizeof(size_t))
+#define ONES ((size_t)-1/UCHAR_MAX)
+#define HIGHS (ONES * (UCHAR_MAX/2+1))
+#define HASZERO(x) ((x)-ONES & ~(x) & HIGHS)
+
+char *__strchrnul(const char *s, int c)
 {
-       char *p = strchr(s, c);
-       return p ? p : (char *)s + strlen(s);
+       size_t *w, k;
+
+       c = (unsigned char)c;
+       if (!c) return (char *)s + strlen(s);
+
+       for (; (uintptr_t)s % ALIGN; s++)
+               if (!*s || *(unsigned char *)s == c) return (char *)s;
+       k = ONES * c;
+       for (w = (void *)s; !HASZERO(*w) && !HASZERO(*w^k); w++);
+       for (s = (void *)w; *s && *(unsigned char *)s != c; s++);
+       return (char *)s;
 }
+
+weak_alias(__strchrnul, strchrnul);