ostree/ostree_dest.go
func (d *ostreeImageDestination) PutBlob(ctx context.Context, stream io.Reader, inputInfo types.BlobInfo, cache types.BlobInfoCache, isConfig bool) (types.BlobInfo, error) {
	tmpDir, err := ioutil.TempDir(d.tmpDirPath, "blob")
	if err != nil {
		return types.BlobInfo{}, err
	}

	blobPath := filepath.Join(tmpDir, "content")
	blobFile, err := os.Create(blobPath)
	if err != nil {
		return types.BlobInfo{}, err
	}
	defer blobFile.Close()

	digester := digest.Canonical.Digester()
	tee := io.TeeReader(stream, digester.Hash())

	// TODO: This can take quite some time, and should ideally be cancellable using ctx.Done().
	size, err := io.Copy(blobFile, tee)
	if err != nil {
		return types.BlobInfo{}, err
	}
	computedDigest := digester.Digest()
	if inputInfo.Size != -1 && size != inputInfo.Size {
		return types.BlobInfo{}, errors.Errorf("Size mismatch when copying %s, expected %d, got %d", computedDigest, inputInfo.Size, size)
	}
	if err := blobFile.Sync(); err != nil {
		return types.BlobInfo{}, err
	}

	hash := computedDigest.Hex()
	d.blobs[hash] = &blobToImport{Size: size, Digest: computedDigest, BlobPath: blobPath}
	return types.BlobInfo{Digest: computedDigest, Size: size}, nil
}
func (d *ostreeImageDestination) PutBlob(ctx context.Context, stream io.Reader, inputInfo types.BlobInfo, cache types.BlobInfoCache, isConfig bool) (types.BlobInfo, error) {
	tmpDir, err := ioutil.TempDir(d.tmpDirPath, "blob")
	if err != nil {
		return types.BlobInfo{}, err
	}

	blobPath := filepath.Join(tmpDir, "content")
	blobFile, err := os.Create(blobPath)
	if err != nil {
		return types.BlobInfo{}, err
	}
	defer blobFile.Close()

	digester := digest.Canonical.Digester()
	tee := io.TeeReader(stream, digester.Hash())

	// TODO: This can take quite some time, and should ideally be cancellable using ctx.Done().
	size, err := io.Copy(blobFile, tee)
	if err != nil {
		return types.BlobInfo{}, err
	}
	computedDigest := digester.Digest()
	if inputInfo.Size != -1 && size != inputInfo.Size {
		return types.BlobInfo{}, errors.Errorf("Size mismatch when copying %s, expected %d, got %d", computedDigest, inputInfo.Size, size)
	}
	if err := blobFile.Sync(); err != nil {
		return types.BlobInfo{}, err
	}

	hash := computedDigest.Hex()
	d.blobs[hash] = &blobToImport{Size: size, Digest: computedDigest, BlobPath: blobPath}
	return types.BlobInfo{Digest: computedDigest, Size: size}, nil
}
// PutBlob writes contents of stream and returns data representing the result.
// inputInfo.Digest can be optionally provided if known; it is not mandatory for the implementation to verify it.
// inputInfo.Size is the expected length of stream, if known.
// inputInfo.MediaType describes the blob format, if known.
// May update cache.
// WARNING: The contents of stream are being verified on the fly.  Until stream.Read() returns io.EOF, the contents of the data SHOULD NOT be available
// to any other readers for download using the supplied digest.
// If stream.Read() at any time, ESPECIALLY at end of input, returns an error, PutBlob MUST 1) fail, and 2) delete any data stored so far.