Export Copier to support OCI artifacts

To support OCI artifacts in Podman, we need to export the Copier type
and create an exported constructor (NewCopier).  Additionally, the
actual copy and close methods are now exported.

Signed-off-by: Brent Baude <bbaude@redhat.com>

common/libimage/copier.go

@@ -160,8 +160,8 @@ type CopyOptions struct {
 	extendTimeoutSocket string
 }
 
-// copier is an internal helper to conveniently copy images.
-type copier struct {
+// Copier is a helper to conveniently copy images.
+type Copier struct {
 	extendTimeoutSocket string
 	imageCopyOptions    copy.Options
 	retryOptions        retry.Options
@@ -172,6 +172,13 @@ type copier struct {
 	destinationLookup LookupReferenceFunc
 }
 
+// newCopier creates a Copier based on a runtime's system context.
+// Note that fields in options *may* overwrite the counterparts of
+// the specified system context.  Please make sure to call `(*Copier).Close()`.
+func (r *Runtime) newCopier(options *CopyOptions) (*Copier, error) {
+	return NewCopier(options, r.SystemContext())
+}
+
 // storageAllowedPolicyScopes overrides the policy for local storage
 // to ensure that we can read images from it.
 var storageAllowedPolicyScopes = signature.PolicyTransportScopes{
@@ -213,12 +220,13 @@ func getDockerAuthConfig(name, passwd, creds, idToken string) (*types.DockerAuth
 	}
 }
 
-// newCopier creates a copier.  Note that fields in options *may* overwrite the
-// counterparts of the specified system context.  Please make sure to call
-// `(*copier).close()`.
-func (r *Runtime) newCopier(options *CopyOptions) (*copier, error) {
-	c := copier{extendTimeoutSocket: options.extendTimeoutSocket}
-	c.systemContext = r.systemContextCopy()
+// NewCopier creates a Copier based on a provided system context.
+// Note that fields in options *may* overwrite the counterparts of
+// the specified system context.  Please make sure to call `(*Copier).Close()`.
+func NewCopier(options *CopyOptions, sc *types.SystemContext) (*Copier, error) {
+	c := Copier{extendTimeoutSocket: options.extendTimeoutSocket}
+	sysContextCopy := *sc
+	c.systemContext = &sysContextCopy
 
 	if options.SourceLookupReferenceFunc != nil {
 		c.sourceLookup = options.SourceLookupReferenceFunc
@@ -333,14 +341,14 @@ func (r *Runtime) newCopier(options *CopyOptions) (*copier, error) {
 	return &c, nil
 }
 
-// close open resources.
-func (c *copier) close() error {
+// Close open resources.
+func (c *Copier) Close() error {
 	return c.policyContext.Destroy()
 }
 
-// copy the source to the destination.  Returns the bytes of the copied
+// Copy the source to the destination.  Returns the bytes of the copied
 // manifest which may be used for digest computation.
-func (c *copier) copy(ctx context.Context, source, destination types.ImageReference) ([]byte, error) {
+func (c *Copier) Copy(ctx context.Context, source, destination types.ImageReference) ([]byte, error) {
 	logrus.Debugf("Copying source image %s to destination image %s", source.StringWithinTransport(), destination.StringWithinTransport())
 
 	// Avoid running out of time when running inside a systemd unit by

common/libimage/import.go

@@ -108,9 +108,9 @@ func (r *Runtime) Import(ctx context.Context, path string, options *ImportOption
 	if err != nil {
 		return "", err
 	}
-	defer c.close()
+	defer c.Close()
 
-	if _, err := c.copy(ctx, srcRef, destRef); err != nil {
+	if _, err := c.Copy(ctx, srcRef, destRef); err != nil {
 		return "", err
 	}
 

common/libimage/manifest_list.go

@@ -796,7 +796,7 @@ func (m *ManifestList) Push(ctx context.Context, destination string, options *Ma
 	if err != nil {
 		return "", err
 	}
-	defer copier.close()
+	defer copier.Close()
 
 	pushOptions := manifests.PushOptions{
 		AddCompression:                   options.AddCompression,

common/libimage/pull.go

@@ -235,7 +235,7 @@ func (r *Runtime) copyFromDefault(ctx context.Context, ref types.ImageReference,
 	if err != nil {
 		return nil, err
 	}
-	defer c.close()
+	defer c.Close()
 
 	// Figure out a name for the storage destination.
 	var storageName, imageName string
@@ -321,7 +321,7 @@ func (r *Runtime) copyFromDefault(ctx context.Context, ref types.ImageReference,
 		return nil, fmt.Errorf("parsing %q: %w", storageName, err)
 	}
 
-	_, err = c.copy(ctx, ref, destRef)
+	_, err = c.Copy(ctx, ref, destRef)
 	return []string{imageName}, err
 }
 
@@ -391,7 +391,7 @@ func (r *Runtime) copyFromDockerArchiveReaderReference(ctx context.Context, read
 	if err != nil {
 		return nil, err
 	}
-	defer c.close()
+	defer c.Close()
 
 	// Get a slice of storage references we can copy.
 	references, destNames, err := r.storageReferencesReferencesFromArchiveReader(ctx, readerRef, reader)
@@ -401,7 +401,7 @@ func (r *Runtime) copyFromDockerArchiveReaderReference(ctx context.Context, read
 
 	// Now copy all of the images.  Use readerRef for performance.
 	for _, destRef := range references {
-		if _, err := c.copy(ctx, readerRef, destRef); err != nil {
+		if _, err := c.Copy(ctx, readerRef, destRef); err != nil {
 			return nil, err
 		}
 	}
@@ -640,7 +640,7 @@ func (r *Runtime) copySingleImageFromRegistry(ctx context.Context, imageName str
 	if err != nil {
 		return nil, err
 	}
-	defer c.close()
+	defer c.Close()
 
 	var pullErrors []error
 	for _, candidate := range resolved.PullCandidates {
@@ -678,7 +678,7 @@ func (r *Runtime) copySingleImageFromRegistry(ctx context.Context, imageName str
 			}
 		}
 		var manifestBytes []byte
-		if manifestBytes, err = c.copy(ctx, srcRef, destRef); err != nil {
+		if manifestBytes, err = c.Copy(ctx, srcRef, destRef); err != nil {
 			logrus.Debugf("Error pulling candidate %s: %v", candidateString, err)
 			pullErrors = append(pullErrors, err)
 			continue

common/libimage/push.go

@@ -114,7 +114,7 @@ func (r *Runtime) Push(ctx context.Context, source, destination string, options
 		return nil, err
 	}
 
-	defer c.close()
+	defer c.Close()
 
-	return c.copy(ctx, srcRef, destRef)
+	return c.Copy(ctx, srcRef, destRef)
 }

common/libimage/save.go

@@ -123,9 +123,9 @@ func (r *Runtime) saveSingleImage(ctx context.Context, name, format, path string
 	if err != nil {
 		return err
 	}
-	defer c.close()
+	defer c.Close()
 
-	_, err = c.copy(ctx, srcRef, destRef)
+	_, err = c.Copy(ctx, srcRef, destRef)
 	return err
 }
 
@@ -208,7 +208,7 @@ func (r *Runtime) saveDockerArchive(ctx context.Context, names []string, path st
 		if err != nil {
 			return err
 		}
-		defer c.close()
+		defer c.Close()
 
 		destRef, err := writer.NewReference(nil)
 		if err != nil {
@@ -220,7 +220,7 @@ func (r *Runtime) saveDockerArchive(ctx context.Context, names []string, path st
 			return err
 		}
 
-		if _, err := c.copy(ctx, srcRef, destRef); err != nil {
+		if _, err := c.Copy(ctx, srcRef, destRef); err != nil {
 			return err
 		}
 	}