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AkihiroSudaAkihiroSuda
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add Image content converter
Go example: ```go opts := []converter.Opt{ // convert Docker media types to OCI ones converter.WithDocker2OCI(true), // convert tar.gz layers to uncompressed tar layers converter.WithLayerConvertFunc(uncompress.LayerConvertFunc), } srcRef := "example.com/foo:orig" dstRef := "example.com/foo:converted" dstImg, err = converter.Convert(ctx, client, dstRef, srcRef, opts...) fmt.Println(dstImg.Target) ``` ctr example: `ctr images convert --oci --uncompress example.com/foo:orig example.com/foo:converted` Go test: `go test -exec sudo -test.root -test.run TestConvert` The implementation is from containerd/stargz-snapshotter#224, but eStargz-specific functions are not included in this PR. eStargz converter can be specified by importing `estargz` package and using `WithLayerConvertFunc(estargz.LayerConvertFunc)` option. This converter interface will be potentially useful for converting zstd and ocicrypt layers as well. Signed-off-by: Akihiro Suda <akihiro.suda.cz@hco.ntt.co.jp>
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‎cmd/ctr/commands/images/convert.go‎

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/*
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Copyright The containerd Authors.
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Licensed under the Apache License, Version 2.0 (the "License");
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you may not use this file except in compliance with the License.
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You may obtain a copy of the License at
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http://www.apache.org/licenses/LICENSE-2.0
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Unless required by applicable law or agreed to in writing, software
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distributed under the License is distributed on an "AS IS" BASIS,
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WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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See the License for the specific language governing permissions and
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limitations under the License.
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*/
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package images
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import (
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"fmt"
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"github.com/containerd/containerd/cmd/ctr/commands"
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"github.com/containerd/containerd/images/converter"
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"github.com/containerd/containerd/images/converter/uncompress"
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"github.com/containerd/containerd/platforms"
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ocispec "github.com/opencontainers/image-spec/specs-go/v1"
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"github.com/pkg/errors"
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"github.com/urfave/cli"
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)
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var convertCommand = cli.Command{
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Name: "convert",
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Usage: "convert an image",
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ArgsUsage: "[flags] <source_ref> <target_ref>",
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Description: `Convert an image format.
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e.g., 'ctr convert --uncompress --oci example.com/foo:orig example.com/foo:converted'
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Use '--platform' to define the output platform.
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When '--all-platforms' is given all images in a manifest list must be available.
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`,
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Flags: []cli.Flag{
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// generic flags
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cli.BoolFlag{
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Name: "uncompress",
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Usage: "convert tar.gz layers to uncompressed tar layers",
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},
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cli.BoolFlag{
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Name: "oci",
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Usage: "convert Docker media types to OCI media types",
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},
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// platform flags
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cli.StringSliceFlag{
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Name: "platform",
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Usage: "Pull content from a specific platform",
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Value: &cli.StringSlice{},
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},
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cli.BoolFlag{
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Name: "all-platforms",
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Usage: "exports content from all platforms",
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},
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},
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Action: func(context *cli.Context) error {
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var convertOpts []converter.Opt
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srcRef := context.Args().Get(0)
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targetRef := context.Args().Get(1)
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if srcRef == "" || targetRef == "" {
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return errors.New("src and target image need to be specified")
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}
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if !context.Bool("all-platforms") {
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if pss := context.StringSlice("platform"); len(pss) > 0 {
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var all []ocispec.Platform
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for _, ps := range pss {
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p, err := platforms.Parse(ps)
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if err != nil {
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return errors.Wrapf(err, "invalid platform %q", ps)
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}
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all = append(all, p)
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}
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convertOpts = append(convertOpts, converter.WithPlatform(platforms.Ordered(all...)))
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} else {
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convertOpts = append(convertOpts, converter.WithPlatform(platforms.DefaultStrict()))
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}
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}
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if context.Bool("uncompress") {
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convertOpts = append(convertOpts, converter.WithLayerConvertFunc(uncompress.LayerConvertFunc))
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}
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if context.Bool("oci") {
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convertOpts = append(convertOpts, converter.WithDockerToOCI(true))
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}
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client, ctx, cancel, err := commands.NewClient(context)
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if err != nil {
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return err
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}
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defer cancel()
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newImg, err := converter.Convert(ctx, client, targetRef, srcRef, convertOpts...)
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if err != nil {
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return err
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}
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fmt.Fprintln(context.App.Writer, newImg.Target.Digest.String())
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return nil
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},
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}

‎cmd/ctr/commands/images/images.go‎

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removeCommand,
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tagCommand,
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setLabelsCommand,
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convertCommand,
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},
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}
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‎convert_test.go‎

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/*
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Copyright The containerd Authors.
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Licensed under the Apache License, Version 2.0 (the "License");
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you may not use this file except in compliance with the License.
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You may obtain a copy of the License at
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http://www.apache.org/licenses/LICENSE-2.0
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Unless required by applicable law or agreed to in writing, software
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distributed under the License is distributed on an "AS IS" BASIS,
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WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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See the License for the specific language governing permissions and
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limitations under the License.
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*/
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package containerd
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import (
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"testing"
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"github.com/containerd/containerd/images"
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"github.com/containerd/containerd/images/converter"
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"github.com/containerd/containerd/images/converter/uncompress"
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"github.com/containerd/containerd/platforms"
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ocispec "github.com/opencontainers/image-spec/specs-go/v1"
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"gotest.tools/v3/assert"
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)
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// TestConvert creates an image from testImage, with the following conversion:
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// - Media type: Docker -> OCI
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// - Layer type: tar.gz -> tar
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// - Arch: Multi -> Single
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func TestConvert(t *testing.T) {
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if testing.Short() {
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t.Skip()
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}
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ctx, cancel := testContext(t)
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defer cancel()
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client, err := New(address)
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if err != nil {
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t.Fatal(err)
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}
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defer client.Close()
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_, err = client.Fetch(ctx, testImage)
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if err != nil {
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t.Fatal(err)
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}
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dstRef := testImage + "-testconvert"
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defPlat := platforms.DefaultStrict()
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opts := []converter.Opt{
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converter.WithDockerToOCI(true),
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converter.WithLayerConvertFunc(uncompress.LayerConvertFunc),
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converter.WithPlatform(defPlat),
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}
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dstImg, err := converter.Convert(ctx, client, dstRef, testImage, opts...)
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if err != nil {
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t.Fatal(err)
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}
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defer func() {
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if deleteErr := client.ImageService().Delete(ctx, dstRef); deleteErr != nil {
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t.Fatal(deleteErr)
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}
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}()
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cs := client.ContentStore()
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plats, err := images.Platforms(ctx, cs, dstImg.Target)
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if err != nil {
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t.Fatal(err)
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}
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// Assert that the image does not have any extra arch.
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assert.Equal(t, 1, len(plats))
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assert.Check(t, defPlat.Match(plats[0]))
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// Assert that the media type is converted to OCI and also uncompressed
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mani, err := images.Manifest(ctx, cs, dstImg.Target, defPlat)
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if err != nil {
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t.Fatal(err)
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}
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for _, l := range mani.Layers {
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if plats[0].OS == "windows" {
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assert.Equal(t, ocispec.MediaTypeImageLayerNonDistributable, l.MediaType)
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} else {
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assert.Equal(t, ocispec.MediaTypeImageLayer, l.MediaType)
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}
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}
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}

‎images/converter/converter.go‎

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/*
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Copyright The containerd Authors.
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Licensed under the Apache License, Version 2.0 (the "License");
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you may not use this file except in compliance with the License.
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You may obtain a copy of the License at
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http://www.apache.org/licenses/LICENSE-2.0
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Unless required by applicable law or agreed to in writing, software
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distributed under the License is distributed on an "AS IS" BASIS,
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WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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See the License for the specific language governing permissions and
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limitations under the License.
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*/
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// Package converter provides image converter
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package converter
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import (
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"context"
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"github.com/containerd/containerd/content"
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"github.com/containerd/containerd/images"
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"github.com/containerd/containerd/leases"
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"github.com/containerd/containerd/platforms"
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)
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type convertOpts struct {
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layerConvertFunc ConvertFunc
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docker2oci bool
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indexConvertFunc ConvertFunc
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platformMC platforms.MatchComparer
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}
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// Opt is an option for Convert()
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type Opt func(*convertOpts) error
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// WithLayerConvertFunc specifies the function that converts layers.
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func WithLayerConvertFunc(fn ConvertFunc) Opt {
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return func(copts *convertOpts) error {
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copts.layerConvertFunc = fn
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return nil
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}
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}
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// WithDockerToOCI converts Docker media types into OCI ones.
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func WithDockerToOCI(v bool) Opt {
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return func(copts *convertOpts) error {
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copts.docker2oci = true
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return nil
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}
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}
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// WithPlatform specifies the platform.
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// Defaults to all platforms.
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func WithPlatform(p platforms.MatchComparer) Opt {
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return func(copts *convertOpts) error {
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copts.platformMC = p
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return nil
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}
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}
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// WithIndexConvertFunc specifies the function that converts manifests and index (manifest lists).
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// Defaults to DefaultIndexConvertFunc.
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func WithIndexConvertFunc(fn ConvertFunc) Opt {
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return func(copts *convertOpts) error {
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copts.indexConvertFunc = fn
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return nil
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}
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}
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// Client is implemented by *containerd.Client .
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type Client interface {
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WithLease(ctx context.Context, opts ...leases.Opt) (context.Context, func(context.Context) error, error)
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ContentStore() content.Store
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ImageService() images.Store
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}
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// Convert converts an image.
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func Convert(ctx context.Context, client Client, dstRef, srcRef string, opts ...Opt) (*images.Image, error) {
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var copts convertOpts
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for _, o := range opts {
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if err := o(&copts); err != nil {
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return nil, err
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}
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}
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if copts.platformMC == nil {
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copts.platformMC = platforms.All
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}
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if copts.indexConvertFunc == nil {
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copts.indexConvertFunc = DefaultIndexConvertFunc(copts.layerConvertFunc, copts.docker2oci, copts.platformMC)
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}
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ctx, done, err := client.WithLease(ctx)
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if err != nil {
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return nil, err
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}
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defer done(ctx)
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cs := client.ContentStore()
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is := client.ImageService()
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srcImg, err := is.Get(ctx, srcRef)
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if err != nil {
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return nil, err
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}
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dstDesc, err := copts.indexConvertFunc(ctx, cs, srcImg.Target)
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if err != nil {
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return nil, err
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}
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dstImg := srcImg
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dstImg.Name = dstRef
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if dstDesc != nil {
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dstImg.Target = *dstDesc
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}
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var res images.Image
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if dstRef != srcRef {
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_ = is.Delete(ctx, dstRef)
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res, err = is.Create(ctx, dstImg)
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} else {
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res, err = is.Update(ctx, dstImg)
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}
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return &res, err
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}

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