usr: sdk: Add strcmp() to sdk/string.h + sources

Signed-off-by: Ian Moffett <ian@osmora.org>

2 files changed, 30 insertions, 0 deletions

diff --git a/usr/sdk/common/string/strcmp.c b/usr/sdk/common/string/strcmp.c
new file mode 100644
index 0000000..cb47cfb
--- /dev/null
+++ b/usr/sdk/common/string/strcmp.c
@@ -0,0 +1,19 @@
+/*
+ * Copyright (c) 2025, Ian Moffett.
+ * Provided under the BSD-3 clause.
+ */
+
+#include <sdk/string.h>
+#include <sdk/types.h>
+
+int
+strcmp(const char *s1, const char *s2)
+{
+    while (*s1 == *s2++) {
+        if (*s1++ == 0) {
+            return (0);
+        }
+    }
+
+    return (*(UBYTE *)s1 - *(UBYTE *)--s2);
+}
diff --git a/usr/sdk/inc/sdk/string.h b/usr/sdk/inc/sdk/string.h
index 965f66a..9e648d9 100644
--- a/usr/sdk/inc/sdk/string.h
+++ b/usr/sdk/inc/sdk/string.h
@@ -29,6 +29,17 @@ USIZE strlen(const char *str);
 void *memcpy(void *dest, const void *src, USIZE count);
 
 /*
+ * Compare two strings to see if they are equal.
+ *
+ * @s1: First string
+ * @s2: Second string
+ *
+ * Returns the differences between the two string, zero if
+ * equal.
+ */
+int strcmp(const char *s1, const char *s2);
+
+/*
  * Convert a given value into a string based on a
  * specific radix/base
  *