Add an osd_truncate call to truncate files [O. Galibert]

src/osd/osdcore.h

@@ -166,6 +166,23 @@ file_error osd_read(osd_file *file, void *buffer, UINT64 offset, UINT32 length,
 file_error osd_write(osd_file *file, const void *buffer, UINT64 offset, UINT32 length, UINT32 *actual);
 
 
+/*-----------------------------------------------------------------------------
+    osd_truncate: change the size of an open file
+
+    Parameters:
+
+        file - handle to a file previously opened via osd_open
+
+        offset - future size of the file
+
+    Return value:
+
+        a file_error describing any error that occurred while writing to
+        the file, or FILERR_NONE if no error occurred
+-----------------------------------------------------------------------------*/
+file_error osd_truncate(osd_file *file, UINT64 offset);
+
+
 /*-----------------------------------------------------------------------------
     osd_rmfile: deletes a file
 

src/osd/sdl/sdlfile.c

@@ -359,6 +359,29 @@ file_error osd_write(osd_file *file, const void *buffer, UINT64 offset, UINT32 c
 }
 
 
+//============================================================
+//  osd_truncate
+//============================================================
+
+file_error osd_truncate(osd_file *file, UINT64 offset)
+{
+	UINT32 result;
+
+	switch (file->type)
+	{
+		case SDLFILE_FILE:
+			result = ftruncate(file->handle, offset);
+			if (!result)
+				return error_to_file_error(errno);
+			return FILERR_NONE;
+			break;
+
+		default:
+			return FILERR_FAILURE;
+	}
+}
+
+
 //============================================================
 //  osd_close
 //============================================================

src/osd/windows/winfile.c

@@ -238,6 +238,43 @@ file_error osd_write(osd_file *file, const void *buffer, UINT64 offset, UINT32 l
 }
 
 
+//============================================================
+//  osd_truncate
+//============================================================
+
+file_error osd_truncate(osd_file *file, UINT64 offset)
+{
+	DWORD result;
+	LONG upper = offset >> 32;
+
+	switch (file->type)
+	{
+		case WINFILE_FILE:
+			// attempt to set the file pointer
+			result = SetFilePointer(file->handle, (UINT32)offset, &upper, FILE_BEGIN);
+			if (result == INVALID_SET_FILE_POINTER)
+			{
+				DWORD error = GetLastError();
+				if (error != NO_ERROR)
+					return win_error_to_mame_file_error(error);
+			}
+
+			// then perform the truncation
+			if (!SetEndOfFile(file->handle))
+				return win_error_to_mame_file_error(GetLastError());
+			break;
+		case WINFILE_SOCKET:
+			return FILERR_FAILURE;
+			break;
+		case WINFILE_PTTY:
+			return FILERR_FAILURE;
+			break;
+
+	}
+	return FILERR_NONE;
+}
+
+
 //============================================================
 //  osd_close
 //============================================================