[musl] [PATCH] strcasestr: increase performance via inlining

[musl] [PATCH] strcasestr: increase performance via inlining

[NRK]

this is a follow up to: https://www.openwall.com/lists/musl/2022/06/16/4

simply inlining the comparison has measureable performance improvement,
~10x on my system.

the algorithmic complexity is still the same as before as it's the same
exact brute force algorithm. so hopefully this is not seen as too much
code/maintainance burden while still improving the performance a tad
bit.
---
 src/string/strcasestr.c | 9 ++++++---
 1 file changed, 6 insertions(+), 3 deletions(-)

diff --git a/src/string/strcasestr.c b/src/string/strcasestr.c
index af109f36..b5e21f70 100644
--- a/src/string/strcasestr.c
+++ b/src/string/strcasestr.c
@@ -1,9 +1,12 @@
-#define _GNU_SOURCE
+#include <ctype.h>
 #include <string.h>
 
 char *strcasestr(const char *h, const char *n)
 {
-	size_t l = strlen(n);
-	for (; *h; h++) if (!strncasecmp(h, n, l)) return (char *)h;
+	size_t i, l = strlen(n);
+	for (; *h; h++) {
+		for (i = 0; i < l && tolower((unsigned char)n[i]) == tolower((unsigned char)h[i]); ++i);
+		if (i == l) return (char *)h;
+	}
 	return 0;
 }
-- 
2.35.1