kern/string: implement strncmp

1 files changed, 23 insertions, 0 deletions

diff --git a/kern/string.c b/kern/string.c
index b77aa2f3..584030b9 100644
--- a/kern/string.c
+++ b/kern/string.c
@@ -177,6 +177,29 @@ strcmp(const char *s1, const char *s2)
 }
 #endif /* ARCH_STRING_STRCMP */
 
+#ifndef ARCH_STRING_STRNCMP
+int
+strncmp(const char *s1, const char *s2, size_t n)
+{
+    char c1, c2;
+
+    c1 = '\0';
+    c2 = '\0';
+
+    while ((n != 0) && (c1 = *s1) == (c2 = *s2)) {
+        if (c1 == '\0') {
+            return 0;
+        }
+
+        n--;
+        s1++;
+        s2++;
+    }
+
+    return (int)c1 - (int)c2;
+}
+#endif /* ARCH_STRING_STRNCMP */
+
 #ifndef ARCH_STRING_STRCHR
 char *
 strchr(const char *s, int c)