storage/storage_image.go
func (s *storageImageDestination) PutBlob(ctx context.Context, stream io.Reader, blobinfo types.BlobInfo, cache types.BlobInfoCache, isConfig bool) (types.BlobInfo, error) {
	// Stores a layer or data blob in our temporary directory, checking that any information
	// in the blobinfo matches the incoming data.
	errorBlobInfo := types.BlobInfo{
		Digest: "",
		Size:   -1,
	}
	// Set up to digest the blob and count its size while saving it to a file.
	hasher := digest.Canonical.Digester()
	if blobinfo.Digest.Validate() == nil {
		if a := blobinfo.Digest.Algorithm(); a.Available() {
			hasher = a.Digester()
		}
	}
	diffID := digest.Canonical.Digester()
	filename := s.computeNextBlobCacheFile()
	file, err := os.OpenFile(filename, os.O_CREATE|os.O_TRUNC|os.O_WRONLY|os.O_EXCL, 0600)
	if err != nil {
		return errorBlobInfo, errors.Wrapf(err, "error creating temporary file %q", filename)
	}
	defer file.Close()
	counter := ioutils.NewWriteCounter(hasher.Hash())
	reader := io.TeeReader(io.TeeReader(stream, counter), file)
	decompressed, err := archive.DecompressStream(reader)
	if err != nil {
		return errorBlobInfo, errors.Wrap(err, "error setting up to decompress blob")
	}
	// Copy the data to the file.
	// TODO: This can take quite some time, and should ideally be cancellable using ctx.Done().
	_, err = io.Copy(diffID.Hash(), decompressed)
	decompressed.Close()
	if err != nil {
		return errorBlobInfo, errors.Wrapf(err, "error storing blob to file %q", filename)
	}
	// Ensure that any information that we were given about the blob is correct.
	if blobinfo.Digest.Validate() == nil && blobinfo.Digest != hasher.Digest() {
		return errorBlobInfo, ErrBlobDigestMismatch
	}
	if blobinfo.Size >= 0 && blobinfo.Size != counter.Count {
		return errorBlobInfo, ErrBlobSizeMismatch
	}
	// Record information about the blob.
	s.putBlobMutex.Lock()
	s.blobDiffIDs[hasher.Digest()] = diffID.Digest()
	s.fileSizes[hasher.Digest()] = counter.Count
	s.filenames[hasher.Digest()] = filename
	s.putBlobMutex.Unlock()
	blobDigest := blobinfo.Digest
	if blobDigest.Validate() != nil {
		blobDigest = hasher.Digest()
	}
	blobSize := blobinfo.Size
	if blobSize < 0 {
		blobSize = counter.Count
	}
	// This is safe because we have just computed both values ourselves.
	cache.RecordDigestUncompressedPair(blobDigest, diffID.Digest())
	return types.BlobInfo{
		Digest:    blobDigest,
		Size:      blobSize,
		MediaType: blobinfo.MediaType,
	}, nil
}
func (s *storageImageDestination) PutBlob(ctx context.Context, stream io.Reader, blobinfo types.BlobInfo, cache types.BlobInfoCache, isConfig bool) (types.BlobInfo, error) {
	// Stores a layer or data blob in our temporary directory, checking that any information
	// in the blobinfo matches the incoming data.
	errorBlobInfo := types.BlobInfo{
		Digest: "",
		Size:   -1,
	}
	// Set up to digest the blob and count its size while saving it to a file.
	hasher := digest.Canonical.Digester()
	if blobinfo.Digest.Validate() == nil {
		if a := blobinfo.Digest.Algorithm(); a.Available() {
			hasher = a.Digester()
		}
	}
	diffID := digest.Canonical.Digester()
	filename := s.computeNextBlobCacheFile()
	file, err := os.OpenFile(filename, os.O_CREATE|os.O_TRUNC|os.O_WRONLY|os.O_EXCL, 0600)
	if err != nil {
		return errorBlobInfo, errors.Wrapf(err, "error creating temporary file %q", filename)
	}
	defer file.Close()
	counter := ioutils.NewWriteCounter(hasher.Hash())
	reader := io.TeeReader(io.TeeReader(stream, counter), file)
	decompressed, err := archive.DecompressStream(reader)
	if err != nil {
		return errorBlobInfo, errors.Wrap(err, "error setting up to decompress blob")
	}
	// Copy the data to the file.
	// TODO: This can take quite some time, and should ideally be cancellable using ctx.Done().
	_, err = io.Copy(diffID.Hash(), decompressed)
	decompressed.Close()
	if err != nil {
		return errorBlobInfo, errors.Wrapf(err, "error storing blob to file %q", filename)
	}
	// Ensure that any information that we were given about the blob is correct.
	if blobinfo.Digest.Validate() == nil && blobinfo.Digest != hasher.Digest() {
		return errorBlobInfo, ErrBlobDigestMismatch
	}
	if blobinfo.Size >= 0 && blobinfo.Size != counter.Count {
		return errorBlobInfo, ErrBlobSizeMismatch
	}
	// Record information about the blob.
	s.putBlobMutex.Lock()
	s.blobDiffIDs[hasher.Digest()] = diffID.Digest()
	s.fileSizes[hasher.Digest()] = counter.Count
	s.filenames[hasher.Digest()] = filename
	s.putBlobMutex.Unlock()
	blobDigest := blobinfo.Digest
	if blobDigest.Validate() != nil {
		blobDigest = hasher.Digest()
	}
	blobSize := blobinfo.Size
	if blobSize < 0 {
		blobSize = counter.Count
	}
	// This is safe because we have just computed both values ourselves.
	cache.RecordDigestUncompressedPair(blobDigest, diffID.Digest())
	return types.BlobInfo{
		Digest:    blobDigest,
		Size:      blobSize,
		MediaType: blobinfo.MediaType,
	}, 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.