libc: Implement case-insensitive string comparison functions

lib/xboxrt/libc_extensions/string_ext_.c

@@ -1,3 +1,6 @@
+#include <assert.h>
+#include <errno.h>
+#include <ctype.h>
 #include <string.h>
 #include <stdlib.h>
 
@@ -14,3 +17,45 @@ char *strdup (const char *s)
 
     return new_s;
 }
+
+int _strnicmp (const char *s1, const char *s2, size_t n)
+{
+    assert(s1);
+    assert(s2);
+
+    if (!s1 || !s2) {
+        errno = EINVAL;
+        return _NLSCMPERROR;
+    }
+
+    while (n && *s1 && (tolower(*s1) == tolower(*s2))) {
+        ++s1;
+        ++s2;
+        --n;
+    }
+
+    if (n == 0) {
+        return 0;
+    } else {
+        return (tolower(*(unsigned char *)s1) - tolower(*(unsigned char *)s2));
+    }
+}
+
+int _stricmp (const char *s1, const char *s2)
+{
+    assert(s1);
+    assert(s2);
+
+    if (!s1 || !s2) {
+        errno = EINVAL;
+        return _NLSCMPERROR;
+    }
+
+    while (*s1 && (tolower(*s1) == tolower(*s2))) {
+        ++s1;
+        ++s2;
+    }
+
+    return (tolower(*(unsigned char *)s1) - tolower(*(unsigned char *)s2));
+}
+

lib/xboxrt/libc_extensions/string_ext_.h

@@ -9,6 +9,27 @@ static char *_strdup (const char *s)
     return strdup(s);
 }
 
+// Compared to their Win32 counterparts, these functions currently don't invoke
+// an invalid parameter handler routine as described in the MSDN, and instead
+// behave as if the invalid parameter handler allowed to continue execution.
+int _strnicmp (const char *s1, const char *s2, size_t n);
+int _stricmp (const char *s1, const char *s2);
+
+__attribute__((deprecated)) static int strnicmp (const char *s1, const char *s2, size_t n)
+{
+    return _strnicmp(s1, s2, n);
+}
+
+__attribute__((deprecated)) static int stricmp (const char *s1, const char *s2)
+{
+    return _stricmp(s1, s2);
+}
+
+#ifndef NLSCMP_DEFINED
+#define _NLSCMPERROR 0x7FFFFFFF
+#define _NLSCMP_DEFINED
+#endif
+
 #ifdef __cplusplus
 }
 #endif