Detect endianess in CMakeLists.txt, get rid of most SDL_endian.h uses

.. except where SDL_Swap* is actually used (idlib/Lib.cpp).
Otherwise #if D3_IS_BIG_ENDIAN suffices, (NOT #ifdef, it's always set,
but to either 0 or 1!)

neo/CMakeLists.txt

@@ -46,6 +46,7 @@ set(DHEWM3BINARY "dhewm3")
 
 include(CheckCXXCompilerFlag)
 include(GNUInstallDirs OPTIONAL RESULT_VARIABLE GNUINSTALLDIRS)
+include(TestBigEndian)
 
 option(CORE			"Build the core" ON)
 option(BASE			"Build the base game code" ON)
@@ -313,6 +314,15 @@ unset(compiler_id_lower)
 
 endif() # not MSVC
 
+TEST_BIG_ENDIAN(is_big_endian)
+if(is_big_endian)
+	message(STATUS "Detected Big Endian architecture, setting -DD3_IS_BIG_ENDIAN=1")
+	add_definitions(-DD3_IS_BIG_ENDIAN=1)
+else()
+	message(STATUS "Detected Little Endian architecture, setting -DD3_IS_BIG_ENDIAN=0")
+	add_definitions(-DD3_IS_BIG_ENDIAN=0)
+endif()
+
 # compiler specific flags
 if(D3_COMPILER_IS_GCC_OR_CLANG)
 	add_compile_options(-pipe)

neo/d3xp/Game_local.cpp

@@ -26,8 +26,6 @@ If you have questions concerning this license or the applicable additional terms
 ===========================================================================
 */
 
-#include <SDL_endian.h>
-
 #include "sys/platform.h"
 #include "idlib/LangDict.h"
 #include "idlib/Timer.h"
@@ -527,7 +525,12 @@ void idGameLocal::SaveGame( idFile *f ) {
 	savegame.WriteString( D3_ARCH ); // CPU architecture (e.g. "x86" or "x86_64") - from CMake
 	savegame.WriteString( ENGINE_VERSION );
 	savegame.WriteShort( (short)sizeof(void*) ); // tells us if it's from a 32bit (4) or 64bit system (8)
-	savegame.WriteShort( SDL_BYTEORDER ) ; // SDL_LIL_ENDIAN or SDL_BIG_ENDIAN
+#if D3_IS_BIG_ENDIAN
+	const short byteOrder = 4321; // SDL_BIG_ENDIAN
+#else
+	const short byteOrder = 1234; // SDL_LIL_ENDIAN
+#endif
+	savegame.WriteShort( byteOrder ) ;
 	// DG end
 
 	// go through all entities and threads and add them to the object list

neo/game/Game_local.cpp

@@ -26,8 +26,6 @@ If you have questions concerning this license or the applicable additional terms
 ===========================================================================
 */
 
-#include <SDL_endian.h>
-
 #include "sys/platform.h"
 #include "idlib/LangDict.h"
 #include "idlib/Timer.h"
@@ -469,7 +467,12 @@ void idGameLocal::SaveGame( idFile *f ) {
 	savegame.WriteString( D3_ARCH ); // CPU architecture (e.g. "x86" or "x86_64") - from CMake
 	savegame.WriteString( ENGINE_VERSION );
 	savegame.WriteShort( (short)sizeof(void*) ); // tells us if it's from a 32bit (4) or 64bit system (8)
-	savegame.WriteShort( SDL_BYTEORDER ) ; // SDL_LIL_ENDIAN or SDL_BIG_ENDIAN
+#if D3_IS_BIG_ENDIAN
+	const short byteOrder = 4321; // SDL_BIG_ENDIAN
+#else
+	const short byteOrder = 1234; // SDL_LIL_ENDIAN
+#endif
+	savegame.WriteShort( byteOrder ) ;
 	// DG end
 
 	// go through all entities and threads and add them to the object list

neo/idlib/Lib.cpp

@@ -35,7 +35,32 @@ If you have questions concerning this license or the applicable additional terms
 #include <unistd.h>
 #endif
 
-#include <SDL_endian.h>
+#ifdef D3_SDL3
+  #include <SDL3/SDL_endian.h>
+  // some defines for backwards-compat with SDL2
+  #define SDL_SwapBE16(X)  SDL_Swap16BE(X)
+  #define SDL_SwapLE16(X)  SDL_Swap16LE(X)
+  #define SDL_SwapBE32(X)  SDL_Swap32BE(X)
+  #define SDL_SwapLE32(X)  SDL_Swap32LE(X)
+#else // SDL1.2 or SDL2
+  #include <SDL_endian.h>
+#endif
+
+#ifndef D3_IS_BIG_ENDIAN
+  #error "D3_IS_BIG_ENDIAN should be defined by the build system (CMake)!"
+#endif
+
+#if SDL_BYTEORDER == SDL_BIG_ENDIAN
+  #if D3_IS_BIG_ENDIAN != 1
+    #error "CMake (which sets D3_IS_BIG_ENDIAN) and SDL disagree about the endianess! CMake says little, SDL says big"
+  #endif
+#elif SDL_BYTEORDER == SDL_LIL_ENDIAN
+  #if D3_IS_BIG_ENDIAN != 0
+    #error "CMake (which sets D3_IS_BIG_ENDIAN) and SDL disagree about the endianess! CMake says big, SDL says little"
+  #endif
+#else
+  #error "According to SDL, endianess is neither Big nor Little - dhewm3 doesn't support other byteorders!"
+#endif
 
 #include "sys/platform.h"
 #include "idlib/math/Vector.h"

neo/sound/snd_decoder.cpp

@@ -26,9 +26,7 @@ If you have questions concerning this license or the applicable additional terms
 ===========================================================================
 */
 
-
-#include "SDL_endian.h"
-#if SDL_BYTEORDER == SDL_BIG_ENDIAN
+#if D3_IS_BIG_ENDIAN
   #define STB_VORBIS_BIG_ENDIAN
 #endif
 #define STB_VORBIS_NO_STDIO

neo/sound/stbvorbis_impl.c

@@ -5,8 +5,7 @@
 // (I'm doing this instead of renaming stb_vorbis.h to stb_vorbis.c so the configuration
 //  like STB_VORBIS_BIG_ENDIAN etc can be done here in code)
 
-#include "SDL_endian.h"
-#if SDL_BYTEORDER == SDL_BIG_ENDIAN
+#if D3_IS_BIG_ENDIAN
   #define STB_VORBIS_BIG_ENDIAN
 #endif
 #define STB_VORBIS_NO_STDIO