libc: add strnlen()

Sometimes handy.

Signed-off-by: Oliver O'Halloran <oohall@gmail.com>
Signed-off-by: Stewart Smith <stewart@linux.vnet.ibm.com>

2 files changed, 14 insertions, 0 deletions

diff --git a/libc/include/string.h b/libc/include/string.h
index e4b4fac..2172bdc 100644
--- a/libc/include/string.h
+++ b/libc/include/string.h
@@ -25,6 +25,7 @@ int strncasecmp(const char *s1, const char *s2, size_t n);
 char *strchr(const char *s, int c);
 char *strrchr(const char *s, int c);
 size_t strlen(const char *s);
+size_t strnlen(const char *s, size_t n);
 char *strstr(const char *hay, const char *needle);
 char *strtok(char *src, const char *pattern);
 char *strdup(const char *src);
diff --git a/libc/string/strlen.c b/libc/string/strlen.c
index 95b99d2..5b408e7 100644
--- a/libc/string/strlen.c
+++ b/libc/string/strlen.c
@@ -25,3 +25,16 @@ strlen(const char *s)
 	return len;
 }
 
+size_t
+strnlen(const char *s, size_t n)
+{
+	size_t len = 0;
+
+	while (*s != 0 && n) {
+		len += 1;
+		s += 1;
+		n--;
+	}
+
+	return len;
+}