Add an ErrorString utility which converts the code from GetLastError() into a human readable std::string.

Originally committed to SVN as r4345.

aegisub/build/libaegisub_vs2008/libaegisub_vs2008.vcproj

@@ -211,6 +211,10 @@
 				RelativePath="..\..\libaegisub\include\libaegisub\util.h"
 				>
 			</File>
+			<File
+				RelativePath="..\..\libaegisub\include\libaegisub\util_win.h"
+				>
+			</File>
 			<File
 				RelativePath="..\..\libaegisub\include\libaegisub\validator.h"
 				>

aegisub/libaegisub/include/libaegisub/util_win.h

@@ -0,0 +1,33 @@
+// Copyright (c) 2010, Amar Takhar <verm@aegisub.org>
+//
+// Permission to use, copy, modify, and distribute this software for any
+// purpose with or without fee is hereby granted, provided that the above
+// copyright notice and this permission notice appear in all copies.
+//
+// THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
+// WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
+// MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
+// ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
+// WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
+// ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
+// OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
+//
+// $Id$
+
+/// @file util.h
+/// @brief Public interface for Windows utilities.
+/// @ingroup libaegisub windows
+
+#ifndef LAGI_PRE
+#include <string>
+#include <windows.h>
+#endif
+
+namespace agi {
+	namespace util {
+
+	std::string ErrorString(DWORD error);
+
+
+	} // namespace util
+} // namespace agi

aegisub/libaegisub/windows/util.cpp

@@ -28,6 +28,7 @@
 
 #include <string.h>
 #include "libaegisub/util.h"
+#include "libaegisub/util_win.h"
 
 namespace agi {
 	namespace util {
@@ -55,5 +56,20 @@ void Rename(const std::string& from, const std::string& to) {
 	MoveFileExA(from.c_str(), to.c_str(), MOVEFILE_REPLACE_EXISTING);
 }
 
+std::string ErrorString(DWORD error) {
+	LPSTR lpstr = NULL;
+
+	if(FormatMessageA(FORMAT_MESSAGE_ALLOCATE_BUFFER | FORMAT_MESSAGE_FROM_SYSTEM, NULL, error, 0, (LPSTR)&lpstr, 0, NULL) == 0) {
+		/// @todo Return the actual 'unknown error' string from windows.
+		std::string str("Unknown Error");		
+		return str;
+	}
+
+	std::string str(lpstr);
+	LocalFree(lpstr);
+	return str;
+}
+
+
 	} // namespace io
 } // namespace agi