From a8aeb1a3c57d0b8a5fcb3f80f4c3bb3d801a3fc0 Mon Sep 17 00:00:00 2001
From: Ali Mashtizadeh <mashti@cs.stanford.edu>
Date: Tue, 14 Oct 2014 14:07:55 -0700
Subject: [PATCH] Implement strncmp

---
 include/string.h |  1 +
 sys/kern/libc.c  | 21 +++++++++++++++++++++
 2 files changed, 22 insertions(+)

diff --git a/include/string.h b/include/string.h
index 8e87086..c4a93bd 100644
--- a/include/string.h
+++ b/include/string.h
@@ -12,6 +12,7 @@ char *strchr(const char *s, int c);
 int strcmp(const char *s1, const char *s2);
 char *strcpy(char *to, const char *from);
 size_t strlen(const char *str);
+int strncmp(const char *s1, const char *s2, size_t len);
 char *strncpy(char *to, const char *from, size_t len);
 
 #endif /* __STRING_H__ */
diff --git a/sys/kern/libc.c b/sys/kern/libc.c
index 16b4336..ec3730b 100644
--- a/sys/kern/libc.c
+++ b/sys/kern/libc.c
@@ -53,6 +53,27 @@ strcmp(const char *s1, const char *s2)
     return (*(const uint8_t *)s1 - *(const uint8_t *)(s2 - 1));
 }
 
+int
+strncmp(const char *s1, const char *s2, size_t len)
+{
+    if (len == 0)
+	return 0;
+
+    while (*s1 == *s2) {
+	if (*s1 == 0)
+	    return 0;
+
+	s1++;
+	s2++;
+
+	len--;
+	if (len == 0)
+	    return 0;
+    }
+
+    return (*(const uint8_t *)s1 - *(const uint8_t *)s2);
+}
+
 size_t
 strlen(const char *str)
 {