Пример #1
0
// rangeReader calls ioutil.ReadAll on the given byte range [start, n). It uses
// optimizations for different kinds of VFSs.
func rangeReader(fs rwvfs.FileSystem, name string, f io.ReadSeeker, start, n int64) (io.Reader, error) {
	if fs, ok := fs.(rwvfs.FetcherOpener); ok {
		// Clone f so we can parallelize it.
		var err error
		f, err = fs.OpenFetcher(name)
		if err != nil {
			return nil, err
		}
		if err := f.(rwvfs.Fetcher).Fetch(start, start+n); err != nil {
			return nil, err
		}
	}
	if _, err := f.Seek(start, 0); err != nil {
		return nil, err
	}
	return f, nil
}