Add SDK/CRT string routines and headers

SDK/CRT/STRING/str.c

@@ -0,0 +1,45 @@
+/*++
+
+Copyright (c) 2024, Quinn Stephens.
+Provided under the BSD 3-Clause license.
+
+Module Name:
+
+   str.c
+
+Abstract:
+
+   Provides string manipulation routines.
+
+--*/
+
+#include <string.h>
+
+size_t
+strlen (
+    const char *str
+    )
+
+{
+    const char *ptr;
+
+    ptr = str;
+    while (*ptr++);
+
+    return ptr - str - sizeof(char);
+}
+
+size_t
+strnlen (
+    const char *str,
+    size_t maxlen
+    )
+
+{
+    size_t len;
+
+    len = 0;
+    while (len < maxlen && str[len++]);
+
+    return len - sizeof(char);
+}