* (bug 3019) adds the cvar cl_guidServerUniq (defaults to 1). When set to

non-zero, cl_guid will be unique for each server that the client
  connects to

code/qcommon/md5.c

@@ -257,9 +257,9 @@ static void MD5Final(struct MD5Context *ctx, unsigned char *digest)
 }
 
 
-char *Com_MD5File(const char *fn, int length)
+char *Com_MD5File( const char *fn, int length, const char *prefix, int prefix_len )
 {
-	static char final[33] = {"unknown"};
+	static char final[33] = {""};
 	unsigned char digest[16] = {""}; 
 	fileHandle_t f;
 	MD5_CTX md5;
@@ -269,8 +269,15 @@ char *Com_MD5File(const char *fn, int length)
 	int r = 0;
 	int total = 0;
 
-	filelen = FS_FOpenFileRead(fn, &f, qtrue);
-	if(filelen < 1) {
+	Q_strncpyz( final, "", sizeof( final ) );
+
+	filelen = FS_SV_FOpenFileRead( fn, &f );
+
+	if( !f ) {
+		return final;
+	}
+	if( filelen < 1 ) {
+		FS_FCloseFile( f );
 		return final;
 	}
 	if(filelen < length || !length) {
@@ -278,6 +285,10 @@ char *Com_MD5File(const char *fn, int length)
 	}
 
 	MD5Init(&md5);
+
+	if( prefix_len && *prefix )
+		MD5Update(&md5 , (unsigned char *)prefix, prefix_len);
+
 	for(;;) {
 		r = FS_Read2(buffer, sizeof(buffer), f);
 		if(r < 1)

code/qcommon/qcommon.h

@@ -732,7 +732,7 @@ void 		Com_Quit_f( void );
 int			Com_EventLoop( void );
 int			Com_Milliseconds( void );	// will be journaled properly
 unsigned	Com_BlockChecksum( const void *buffer, int length );
-char		*Com_MD5File(const char *filename, int length);
+char		*Com_MD5File(const char *filename, int length, const char *prefix, int prefix_len);
 int			Com_HashKey(char *string, int maxlen);
 int			Com_Filter(char *filter, char *name, int casesensitive);
 int			Com_FilterPath(char *filter, char *name, int casesensitive);