fix to prevent further issues due to invalid XMB files (c.f. matt's "crash upon combat" bug report, http://www.wildfiregames.com/forum/index.php?showtopic=11703). as per philip's excellent suggestion, they are now only tagged with a header iff the file contents are valid.

details:
- add a new magic string "XMBu" to indicate an unfinished XMB file;
- header magic fields are now exclusively strings to avoid type punning;
- XMBFile::Initialize now has a return value which is checked by
ReadXMBFile;
- the XML loader re-creates the XMB if that fails.

This was SVN commit r6016.

source/ps/XML/XeroXMB.cpp

@@ -2,20 +2,25 @@
 
 #include "Xeromyces.h"
 
+#include "lib/byte_order.h"	// FOURCC_LE
 #include "ps/utf16string.h"
 
-
-
-const u32 HeaderMagic = 0x30424D58; // = "XMB0" (little-endian)
+// external linkage (also used by Xeromyces.cpp)
 const char* HeaderMagicStr = "XMB0";
+const char* UnfinishedHeaderMagicStr = "XMBu";
 
 // Warning: May contain traces of pointer abuse
 
-void XMBFile::Initialise(const char* FileData)
+bool XMBFile::Initialise(const char* FileData)
 {
 	m_Pointer = FileData;
-	u32 Header = *(u32 *)m_Pointer; m_Pointer += 4;
-	debug_assert(Header == HeaderMagic && "Invalid XMB header!");
+	char Header[5];
+	strncpy_s(Header, 5, m_Pointer, 4);
+	m_Pointer += 4;
+	// (c.f. @return documentation of this function)
+	if(!strcmp(Header, UnfinishedHeaderMagicStr))
+		return false;
+	debug_assert(!strcmp(Header, HeaderMagicStr) && "Invalid XMB header!");
 
 	int i;
 
@@ -47,6 +52,7 @@ void XMBFile::Initialise(const char* FileData)
 		m_Pointer += 4 + *(int*)m_Pointer; // skip over the string
 #endif
 
+	return true;	// success
 }
 
 std::string XMBFile::ReadZStrA()

source/ps/XML/XeroXMB.h

@@ -94,8 +94,8 @@ XMB_Text {
 #endif
 
 // File headers, to make sure it doesn't try loading anything other than an XMB
-extern const u32 HeaderMagic;
 extern const char* HeaderMagicStr;
+extern const char* UnfinishedHeaderMagicStr;
 
 class XMBElement;
 class XMBElementList;
@@ -111,7 +111,10 @@ public:
 	// Initialise from the contents of an XMB file.
 	// FileData must remain allocated and unchanged while
 	// the XMBFile is being used.
-	void Initialise(const char* FileData);
+	// @return indication of success; main cause for failure is attempting to
+	// load a partially valid XMB file (e.g. if the game was interrupted
+	// while writing it), which we detect by checking the magic string.
+	bool Initialise(const char* FileData);
 
 	// Returns the root element
 	XMBElement GetRoot() const;

source/ps/XML/Xeromyces.cpp

@@ -177,8 +177,8 @@ PSRETURN CXeromyces::Load(const VfsPath& filename)
 	{
 		if (ReadXMBFile(xmbPath))
 			return PSRETURN_OK;
-		else
-			return PSRETURN_Xeromyces_XMLOpenFailed;
+		// (no longer return PSRETURN_Xeromyces_XMLOpenFailed here because
+		// failure legitimately happens due to partially-written XMB files.)
 	}
 
 	
@@ -243,7 +243,8 @@ PSRETURN CXeromyces::Load(const VfsPath& filename)
 	XMBBuffer = writeBuffer.Data();	// add a reference
 
 	// Set up the XMBFile
-	Initialise((const char*)XMBBuffer.get());
+	const bool ok = Initialise((const char*)XMBBuffer.get());
+	debug_assert(ok);
 
 	return PSRETURN_OK;
 }
@@ -256,7 +257,8 @@ bool CXeromyces::ReadXMBFile(const VfsPath& filename)
 	debug_assert(size >= 42);	// else: invalid XMB file size. (42 bytes is the smallest possible XMB. (Well, maybe not quite, but it's a nice number.))
 
 	// Set up the XMBFile
-	Initialise((const char*)XMBBuffer.get());
+	if(!Initialise((const char*)XMBBuffer.get()))
+		return false;
 
 	return true;
 }
@@ -349,7 +351,7 @@ void XeroHandler::characters(const XMLCh* const chars, const unsigned int UNUSED
 void XeroHandler::CreateXMB()
 {
 	// Header
-	writeBuffer.Append((void*)HeaderMagicStr, 4);
+	writeBuffer.Append(UnfinishedHeaderMagicStr, 4);
 
 	std::set<std::string>::iterator it;
 	int i;
@@ -385,6 +387,9 @@ void XeroHandler::CreateXMB()
 
 	delete Root;
 	Root = NULL;
+
+	// file is now valid, so insert correct magic string
+	writeBuffer.Overwrite(HeaderMagicStr, 4, 0);
 }
 
 // Writes a whole element (recursively if it has children) into the buffer,