Golang camlistore-org-pkg-blobref.SeekFetcher类(方法)实例源码

// NewFileReader returns a new FileReader reading the contents of fileBlobRef,
// fetching blobs from fetcher.  The fileBlobRef must be of a "bytes" or "file"
// schema blob.
//
// The caller should call Close on the FileReader when done reading.
func NewFileReader(fetcher blobref.SeekFetcher, fileBlobRef *blobref.BlobRef) (*FileReader, error) {
	// TODO(bradfitz): make this take a blobref.FetcherAt instead?
	// TODO(bradfitz): rename this into bytes reader? but for now it's still
	//                 named FileReader, but can also read a "bytes" schema.
	if fileBlobRef == nil {
		return nil, errors.New("schema/filereader: NewFileReader blobref was nil")
	}
	rsc, _, err := fetcher.Fetch(fileBlobRef)
	if err != nil {
		return nil, fmt.Errorf("schema/filereader: fetching file schema blob: %v", err)
	}
	defer rsc.Close()
	ss, err := ParseSuperset(rsc)
	if err != nil {
		return nil, fmt.Errorf("schema/filereader: decoding file schema blob: %v", err)
	}
	if ss.Type != "file" && ss.Type != "bytes" {
		return nil, fmt.Errorf("schema/filereader: expected \"file\" or \"bytes\" schema blob, got %q", ss.Type)
	}
	fr, err := ss.NewFileReader(fetcher)
	if err != nil {
		return nil, fmt.Errorf("schema/filereader: creating FileReader for %s: %v", fileBlobRef, err)
	}
	return fr, nil
}

func (ss *Superset) setFromBlobRef(fetcher blobref.SeekFetcher, blobRef *blobref.BlobRef) error {
	if blobRef == nil {
		return errors.New("schema/filereader: blobref was nil")
	}
	ss.BlobRef = blobRef
	rsc, _, err := fetcher.Fetch(blobRef)
	if err != nil {
		return fmt.Errorf("schema/filereader: fetching schema blob %s: %v", blobRef, err)
	}
	if err = json.NewDecoder(rsc).Decode(ss); err != nil {
		return fmt.Errorf("schema/filereader: decoding schema blob %s: %v", blobRef, err)
	}
	return nil
}

// TODO(bradfitz): make this take a blobref.FetcherAt instead?
// TODO(bradfitz): rename this into bytes reader? but for now it's still
//                 named FileReader, but can also read a "bytes" schema.
func NewFileReader(fetcher blobref.SeekFetcher, fileBlobRef *blobref.BlobRef) (*FileReader, error) {
	if fileBlobRef == nil {
		return nil, errors.New("schema/filereader: NewFileReader blobref was nil")
	}
	ss := new(Superset)
	rsc, _, err := fetcher.Fetch(fileBlobRef)
	if err != nil {
		return nil, fmt.Errorf("schema/filereader: fetching file schema blob: %v", err)
	}
	if err = json.NewDecoder(rsc).Decode(ss); err != nil {
		return nil, fmt.Errorf("schema/filereader: decoding file schema blob: %v", err)
	}
	if ss.Type != "file" && ss.Type != "bytes" {
		return nil, fmt.Errorf("schema/filereader: expected \"file\" or \"bytes\" schema blob, got %q", ss.Type)
	}
	fr, err := ss.NewFileReader(fetcher)
	if err != nil {
		return nil, fmt.Errorf("schema/filereader: creating FileReader for %s: %v", fileBlobRef, err)
	}
	return fr, nil
}