core: mirror fopen() behavior

docs/changelog.rst

@@ -5,6 +5,10 @@ Changelog
 ------
 *DD MMM YYYY*
 
+**Data Compiler**
+
+* Windows: fixed garbage data written past EOF in some circumnstances.
+
 0.42.0
 ------
 *05 Mar 2021*

src/core/filesystem/filesystem_disk.cpp

@@ -55,7 +55,7 @@ struct FileDisk : public File
 			, (mode == FileOpenMode::READ) ? GENERIC_READ : GENERIC_WRITE
 			, 0
 			, NULL
-			, OPEN_ALWAYS
+			, (mode == FileOpenMode::READ) ? OPEN_EXISTING : CREATE_ALWAYS
 			, FILE_ATTRIBUTE_NORMAL
 			, NULL
 			);