Function newRWFileHandle

vfs/read_write.go:43–77

(d *Dir, f *File, flags int)

}

func newRWFileHandle(d *Dir, f *File, flags int) (fh *RWFileHandle, err error) {
	defer log.Trace(f.Path(), "")("err=%v", &err)
	// get an item to represent this from the cache
	item := d.vfs.cache.Item(f.CachePath())

	exists := f.exists() || (item.Exists() && !item.WrittenBack())

	// if O_CREATE and O_EXCL are set and if path already exists, then return EEXIST
	if flags&(os.O_CREATE|os.O_EXCL) == os.O_CREATE|os.O_EXCL && exists {
		return nil, EEXIST
	}

	fh = &RWFileHandle{
		file:  f,
		d:     d,
		flags: flags,
		item:  item,
	}

	// truncate immediately if O_TRUNC is set or O_CREATE is set and file doesn't exist
	if !fh.readOnly() && (fh.flags&os.O_TRUNC != 0 || (fh.flags&os.O_CREATE != 0 && !exists)) {
		err = fh.Truncate(0)
		if err != nil {
			return nil, fmt.Errorf("cache open with O_TRUNC: failed to truncate: %w", err)
		}
		// we definitely need to write back the item even if we don't write to it
		item.Dirty()
	}

	if !fh.readOnly() {
		fh.file.addWriter(fh)
	}

	return fh, nil
}

// readOnly returns whether flags say fh is read only
func (fh *RWFileHandle) readOnly() bool {