Fixed loading utf8-bom Lua scripts

Originally committed to SVN as r688.

aegisub/auto4_lua.cpp

@@ -38,6 +38,7 @@
 #include "ass_style.h"
 #include "ass_file.h"
 #include "ass_override.h"
+#include "text_file_reader.h"
 #include <lualib.h>
 #include <lauxlib.h>
 #include <wx/msgdlg.h>
@@ -93,13 +94,89 @@ namespace Automation4 {
 #endif
 
 
+	// LuaScriptReader
+	struct LuaScriptReader {
+		FILE *f;
+		bool first;
+		char *databuf;
+		static const size_t bufsize = 512;
+		LuaScriptReader(const wxString &filename)
+		{
+#ifdef WIN32
+			f = _tfopen(filename.c_str(), _T("rb"));
+#else
+			f = fopen(filename.c_str(), _T("rb"));
+#endif
+			first = true;
+			databuf = new char[bufsize];
+		}
+		~LuaScriptReader()
+		{
+			if (databuf)
+				delete databuf;
+			fclose(f);
+		}
+
+		static const char* reader_func(lua_State *L, void *data, size_t *size)
+		{
+			LuaScriptReader *self = (LuaScriptReader*)(data);
+			unsigned char *b = (unsigned char *)self->databuf;
+			FILE *f = self->f;
+
+			if (feof(f)) {
+				*size = 0;
+				return 0;
+			}
+
+			if (self->first) {
+				// check if file is sensible and maybe skip bom
+				if ((*size = fread(b, 1, 4, f)) == 4) {
+					if (b[0] == 0xEF && b[1] == 0xBB && b[2] == 0xBF) {
+						// got an utf8 file with bom
+						// nothing further to do, already skipped the bom
+						fseek(f, -1, SEEK_CUR);
+					} else {
+						// oops, not utf8 with bom
+						// check if there is some other BOM in place and complain if there is...
+						if ((b[0] == 0xFF && b[1] == 0xFE && b[2] == 0x00 && b[3] == 0x00) || // utf32be
+							(b[0] == 0x00 && b[1] == 0x00 && b[2] == 0xFE && b[3] == 0xFF) || // utf32le
+							(b[0] == 0xFF && b[1] == 0xFE) || // utf16be
+							(b[0] == 0xFE && b[1] == 0xFF) || // utf16le
+							(b[0] == 0x2B && b[1] == 0x2F && b[2] == 0x76) || // utf7
+							(b[0] == 0x00 && b[2] == 0x00) || // looks like utf16be
+							(b[1] == 0x00 && b[3] == 0x00)) { // looks like utf16le
+								throw _T("The script file uses an unsupported character set. Only UTF-8 is supported.");
+						}
+						// assume utf8 without bom, and rewind file
+						fseek(f, 0, SEEK_SET);
+					}
+				} else {
+					// hmm, rather short file this...
+					// doesn't have a bom, assume it's just ascii/utf8 without bom
+					return self->databuf; // *size is already set
+				}
+				self->first = false;
+			}
+
+			*size = fread(b, 1, bufsize, f);
+
+			return self->databuf;
+		}
+	};
+
+
 	// LuaScript
 
 	LuaScript::LuaScript(const wxString &filename)
 		: Script(filename)
 		, L(0)
 	{
-		Create();
+		try {
+			Create();
+		}
+		catch (wxChar *e) {
+			description = e;
+		}
 	}
 
 	LuaScript::~LuaScript()
@@ -160,7 +237,9 @@ namespace Automation4 {
 			_stackcheck.check(0);
 
 			// load user script
-			if (luaL_loadfile(L, GetFilename().mb_str(wxConvUTF8))) {
+			LuaScriptReader script_reader(GetFilename());
+			if (lua_load(L, script_reader.reader_func, &script_reader, GetFilename().mb_str(wxConvUTF8))) {
+			//if (luaL_loadfile(L, GetFilename().mb_str(wxConvUTF8))) {
 				wxString *err = new wxString(lua_tostring(L, -1), wxConvUTF8);
 				err->Prepend(_T("An error occurred loading the Lua script file \"") + GetFilename() + _T("\":\n\n"));
 				throw err->c_str();