add compatibility headers

src/util/compat/io.h

@@ -0,0 +1,48 @@
+// Copyright (c) 2025 Quinn
+// Licensed under the MIT Licence. See LICENSE for details
+#pragma once
+
+#if defined __unix__
+#include <features.h>
+#include <unistd.h>
+#elif defined _WIN32
+#include <io.h>
+#else
+#error platform not supported!
+#endif
+
+/* tests a files access with F_OK, X_OK, R_OK, W_OK OR'd together
+   returns 0 upon success. -1 when errno is set and anything else when one or more of the permissions isn't set */
+static inline int faccess(char const* restrict fname, int perms);
+
+// define the constants if they haven't been
+#ifndef F_OK
+#define F_OK 0
+#endif
+#ifndef X_OK
+#define X_OK 1
+#endif
+#ifndef W_OK
+#define W_OK 2
+#endif
+#ifndef R_OK
+#define R_OK 4
+#endif
+
+#if defined __unix__ && _POSIX_C_SOURCE >= 200809L
+#define PATH_SEP     '/' // contains the path separator as a character. Yes it is extremely annoying that this has to exist.
+#define PATH_SEP_STR "/" // contains the path separator as a string, useful for concatenation. Yes it is extremely annoying that this has to exist.
+
+int faccess(char const* restrict fname, int perms) {
+	return access(fname, perms);
+}
+#elif defined(_WIN32)
+#define PATH_SEP     '\\' // contains the path separator as a character. Yes it is extremely annoying that this has to exist.
+#define PATH_SEP_STR "\\" // contains the path separator as a string, useful for concatenation. Yes it is extremely annoying that this has to exist.
+
+int faccess(char const* restrict fname, int perms) {
+	return _access(fname, perms);
+}
+#else
+#error platform unsupported!
+#endif