From bf1a7ec34836c44ff7c0b670ec95f3e40455d51a Mon Sep 17 00:00:00 2001
From: Ian Moffett <ian@osmora.org>
Date: Wed, 15 Oct 2025 14:51:01 -0400
Subject: libc: string: Add memcmp() function

Signed-off-by: Ian Moffett <ian@osmora.org>
---
 src/lib/libc/include/string.h    |  9 ++++++++
 src/lib/libc/src/string/memcmp.c | 45 ++++++++++++++++++++++++++++++++++++++++
 2 files changed, 54 insertions(+)
 create mode 100644 src/lib/libc/src/string/memcmp.c

(limited to 'src/lib/libc')

diff --git a/src/lib/libc/include/string.h b/src/lib/libc/include/string.h
index 1572400..360af12 100644
--- a/src/lib/libc/include/string.h
+++ b/src/lib/libc/include/string.h
@@ -93,4 +93,13 @@ void *memset(void *s, int c, size_t n);
  */
 char *itoa(int64_t value, char *buf, int base);
 
+/*
+ * Compare two byte streams
+ *
+ * @s1: Stream one
+ * @s2: Stream two
+ * @n: Max bytes to compare
+ */
+int memcmp(const void *s1, const void *s2, size_t n);
+
 #endif  /* _STRING_H */
diff --git a/src/lib/libc/src/string/memcmp.c b/src/lib/libc/src/string/memcmp.c
new file mode 100644
index 0000000..2dab02d
--- /dev/null
+++ b/src/lib/libc/src/string/memcmp.c
@@ -0,0 +1,45 @@
+/*
+ * Copyright (c) 2025 Ian Marco Moffett and L5 engineers
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are met:
+ *
+ * 1. Redistributions of source code must retain the above copyright notice,
+ *    this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in the
+ *    documentation and/or other materials provided with the distribution.
+ * 3. Neither the name of the project nor the names of its
+ *    contributors may be used to endorse or promote products derived from
+ *    this software without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
+ * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+ * ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE
+ * LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
+ * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
+ * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
+ * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
+ * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
+ * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
+ * POSSIBILITY OF SUCH DAMAGE.
+ */
+
+#include <string.h>
+
+int
+memcmp(const void *s1, const void *s2, size_t n)
+{
+    if (n != 0) {
+        const unsigned char *p1 = s1, *p2 = s2;
+
+        do {
+            if (*p1++ != *p2++) {
+                return (*--p1 - *--p2);
+            }
+        } while (--n != 0);
+    }
+    return 0;
+}
-- 
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