// newFileWriter returns a prepared fileWriter for the driver and path. This
// could be considered similar to an "open" call on a regular filesystem.
func newFileWriter(ctx context.Context, driver storagedriver.StorageDriver, path string) (*bufferedFileWriter, error) {
fw := fileWriter{
driver: driver,
path: path,
ctx: ctx,
}
if fi, err := driver.Stat(ctx, path); err != nil {
switch err := err.(type) {
case storagedriver.PathNotFoundError:
// ignore, offset is zero
default:
return nil, err
}
} else {
if fi.IsDir() {
return nil, fmt.Errorf("cannot write to a directory")
}
fw.size = fi.Size()
}
buffered := bufferedFileWriter{
fileWriter: fw,
}
buffered.bw = bufio.NewWriterSize(&buffered.fileWriter, fileWriterBufferSize)
return &buffered, nil
}
// Exists provides a utility method to test whether or not a path exists in
// the given driver.
func exists(ctx context.Context, drv driver.StorageDriver, path string) (bool, error) {
if _, err := drv.Stat(ctx, path); err != nil {
switch err := err.(type) {
case driver.PathNotFoundError:
return false, nil
default:
return false, err
}
}
return true, nil
}
