text: add mem{r,}chr(3) based byte search functions

These are generally implemented efficiently in libc.
While memrchr(3) is non-standard, it is a common extension.
If it is not available, we use a simple C implementation from musl.

1 files changed, 11 insertions, 0 deletions

diff --git a/util.h b/util.h
index a53deda..9048c82 100644
--- a/util.h
+++ b/util.h
@@ -23,4 +23,15 @@ static inline bool addu(size_t a, size_t b, size_t *c) {
 }
 #endif
 
+#if !HAVE_MEMRCHR
+/* MIT licensed implementation from musl libc */
+static void *memrchr(const void *m, int c, size_t n)
+{
+	const unsigned char *s = m;
+	c = (unsigned char)c;
+	while (n--) if (s[n]==c) return (void *)(s+n);
+	return 0;
+}
 #endif
+
+#endif /* UTIL_H */