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package daemon
import (
"context"
"fmt"
"github.com/containers/image/v5/docker/internal/tarfile"
"github.com/containers/image/v5/internal/private"
"github.com/containers/image/v5/types"
)
type daemonImageSource struct {
ref daemonReference
*tarfile.Source // Implements most of types.ImageSource
}
// newImageSource returns a types.ImageSource for the specified image reference.
// The caller must call .Close() on the returned ImageSource.
//
// It would be great if we were able to stream the input tar as it is being
// sent; but Docker sends the top-level manifest, which determines which paths
// to look for, at the end, so in we will need to seek back and re-read, several times.
// (We could, perhaps, expect an exact sequence, assume that the first plaintext file
// is the config, and that the following len(RootFS) files are the layers, but that feels
// way too brittle.)
func newImageSource(ctx context.Context, sys *types.SystemContext, ref daemonReference) (private.ImageSource, error) {
c, err := newDockerClient(sys)
if err != nil {
return nil, fmt.Errorf("initializing docker engine client: %w", err)
}
defer c.Close()
// Per NewReference(), ref.StringWithinTransport() is either an image ID (config digest), or a !reference.NameOnly() reference.
// Either way ImageSave should create a tarball with exactly one image.
inputStream, err := c.ImageSave(ctx, []string{ref.StringWithinTransport()})
if err != nil {
return nil, fmt.Errorf("loading image from docker engine: %w", err)
}
defer inputStream.Close()
archive, err := tarfile.NewReaderFromStream(sys, inputStream)
if err != nil {
return nil, err
}
src := tarfile.NewSource(archive, true, ref.Transport().Name(), nil, -1)
return &daemonImageSource{
ref: ref,
Source: src,
}, nil
}
// Reference returns the reference used to set up this source, _as specified by the user_
// (not as the image itself, or its underlying storage, claims). This can be used e.g. to determine which public keys are trusted for this image.
func (s *daemonImageSource) Reference() types.ImageReference {
return s.ref
}
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