[Base] Add FourCC type

- using fourcc_t = uint32_t
- make_fourcc() overloads

src/xenia/base/byte_order.h

@@ -11,6 +11,14 @@
 #define XENIA_BASE_BYTE_ORDER_H_
 
 #include <cstdint>
+#if defined __has_include
+#if __has_include(<version>)
+#include <version>
+#endif
+#endif
+#if __cpp_lib_endian
+#include <bit>
+#endif
 
 #include "xenia/base/assert.h"
 #include "xenia/base/platform.h"

src/xenia/base/memory.h

@@ -15,6 +15,7 @@
 #include <filesystem>
 #include <functional>
 #include <string>
+#include <string_view>
 
 #include "xenia/base/assert.h"
 #include "xenia/base/byte_order.h"
@@ -441,6 +442,26 @@ inline void store_and_swap<std::u16string>(void* mem,
   return store_and_swap<std::u16string_view>(mem, value);
 }
 
+using fourcc_t = uint32_t;
+
+// Get FourCC in host byte order
+// make_fourcc('a', 'b', 'c', 'd') == 0x61626364
+constexpr inline fourcc_t make_fourcc(char a, char b, char c, char d) {
+  return fourcc_t((static_cast<fourcc_t>(a) << 24) |
+                  (static_cast<fourcc_t>(b) << 16) |
+                  (static_cast<fourcc_t>(c) << 8) | static_cast<fourcc_t>(d));
+}
+
+// Get FourCC in host byte order
+// This overload requires fourcc.length() == 4
+// make_fourcc("abcd") == 'abcd' == 0x61626364 for most compilers
+constexpr inline fourcc_t make_fourcc(const std::string_view fourcc) {
+  if (fourcc.length() != 4) {
+    throw std::runtime_error("Invalid fourcc length");
+  }
+  return make_fourcc(fourcc[0], fourcc[1], fourcc[2], fourcc[3]);
+}
+
 }  // namespace xe
 
 #endif  // XENIA_BASE_MEMORY_H_