Adding diff and regctl cmds to compare manifests and blobs

Signed-off-by: Brandon Mitchell <git@bmitch.net>

cmd/regctl/blob.go

@@ -1,14 +1,21 @@
 package main
 
 import (
+	"archive/tar"
+	"encoding/json"
+	"fmt"
 	"io"
+	"io/fs"
 	"os"
+	"strings"
+	"time"
 
 	// crypto libraries included for go-digest
 	_ "crypto/sha256"
 	_ "crypto/sha512"
 
 	"github.com/opencontainers/go-digest"
+	"github.com/regclient/regclient/internal/diff"
 	"github.com/regclient/regclient/pkg/template"
 	"github.com/regclient/regclient/types"
 	"github.com/regclient/regclient/types/ref"
@@ -21,6 +28,22 @@ var blobCmd = &cobra.Command{
 	Aliases: []string{"layer"},
 	Short:   "manage image blobs/layers",
 }
+var blobDiffConfigCmd = &cobra.Command{
+	Use:       "diff-config <repository> <digest> <repository> <digest>",
+	Short:     "diff two image configs",
+	Long:      `This returns the difference between two configs, comparing the contents of each config json.`,
+	Args:      cobra.ExactArgs(4),
+	ValidArgs: []string{}, // do not auto complete repository or digest
+	RunE:      runBlobDiffConfig,
+}
+var blobDiffLayerCmd = &cobra.Command{
+	Use:       "diff-layer <repository> <digest> <repository> <digest>",
+	Short:     "diff two tar layers",
+	Long:      `This returns the difference between two layers, comparing the contents of each tar.`,
+	Args:      cobra.ExactArgs(4),
+	ValidArgs: []string{}, // do not auto complete repository or digest
+	RunE:      runBlobDiffLayer,
+}
 var blobGetCmd = &cobra.Command{
 	Use:     "get <repository> <digest>",
 	Aliases: []string{"pull"},
@@ -44,13 +67,23 @@ is the digest of the blob.`,
 }
 
 var blobOpts struct {
-	format    string
+	diffCtx        int
-	formatPut string
+	diffFullCtx    bool
-	mt        string
+	diffIgnoreTime bool
-	digest    string
+	format         string
+	formatPut      string
+	mt             string
+	digest         string
 }
 
 func init() {
+	blobDiffConfigCmd.Flags().IntVarP(&blobOpts.diffCtx, "context", "", 3, "Lines of context")
+	blobDiffConfigCmd.Flags().BoolVarP(&blobOpts.diffFullCtx, "context-full", "", false, "Show all lines of context")
+
+	blobDiffLayerCmd.Flags().IntVarP(&blobOpts.diffCtx, "context", "", 3, "Lines of context")
+	blobDiffLayerCmd.Flags().BoolVarP(&blobOpts.diffFullCtx, "context-full", "", false, "Show all lines of context")
+	blobDiffLayerCmd.Flags().BoolVarP(&blobOpts.diffIgnoreTime, "ignore-timestamp", "", false, "Ignore timestamps on files")
+
 	blobGetCmd.Flags().StringVarP(&blobOpts.format, "format", "", "{{printPretty .}}", "Format output with go template syntax")
 	blobGetCmd.Flags().StringVarP(&blobOpts.mt, "media-type", "", "", "Set the requested mediaType (deprecated)")
 	blobGetCmd.RegisterFlagCompletionFunc("format", completeArgNone)
@@ -72,11 +105,145 @@ func init() {
 	blobPutCmd.RegisterFlagCompletionFunc("digest", completeArgNone)
 	blobPutCmd.Flags().MarkHidden("content-type")
 
+	blobCmd.AddCommand(blobDiffConfigCmd)
+	blobCmd.AddCommand(blobDiffLayerCmd)
 	blobCmd.AddCommand(blobGetCmd)
 	blobCmd.AddCommand(blobPutCmd)
 	rootCmd.AddCommand(blobCmd)
 }
 
+func runBlobDiffConfig(cmd *cobra.Command, args []string) error {
+	diffOpts := []diff.Opt{}
+	if blobOpts.diffCtx > 0 {
+		diffOpts = append(diffOpts, diff.WithContext(blobOpts.diffCtx, blobOpts.diffCtx))
+	}
+	if blobOpts.diffFullCtx {
+		diffOpts = append(diffOpts, diff.WithFullContext())
+	}
+	ctx := cmd.Context()
+	r1, err := ref.New(args[0])
+	if err != nil {
+		return err
+	}
+	r2, err := ref.New(args[2])
+	if err != nil {
+		return err
+	}
+	rc := newRegClient()
+
+	// open both configs, and output each as formatted json
+	d1, err := digest.Parse(args[1])
+	if err != nil {
+		return err
+	}
+	c1, err := rc.BlobGetOCIConfig(ctx, r1, types.Descriptor{Digest: d1})
+	if err != nil {
+		return err
+	}
+	c1Json, err := json.MarshalIndent(c1, "", "  ")
+	if err != nil {
+		return err
+	}
+
+	d2, err := digest.Parse(args[3])
+	if err != nil {
+		return err
+	}
+	c2, err := rc.BlobGetOCIConfig(ctx, r2, types.Descriptor{Digest: d2})
+	if err != nil {
+		return err
+	}
+	c2Json, err := json.MarshalIndent(c2, "", "  ")
+	if err != nil {
+		return err
+	}
+
+	cDiff := diff.Diff(strings.Split(string(c1Json), "\n"), strings.Split(string(c2Json), "\n"), diffOpts...)
+
+	_, err = fmt.Fprintln(os.Stdout, strings.Join(cDiff, "\n"))
+	return err
+	// TODO: support templating
+	// return template.Writer(os.Stdout, blobOpts.format, cDiff)
+}
+
+func runBlobDiffLayer(cmd *cobra.Command, args []string) error {
+	diffOpts := []diff.Opt{}
+	if blobOpts.diffCtx > 0 {
+		diffOpts = append(diffOpts, diff.WithContext(blobOpts.diffCtx, blobOpts.diffCtx))
+	}
+	if blobOpts.diffFullCtx {
+		diffOpts = append(diffOpts, diff.WithFullContext())
+	}
+	ctx := cmd.Context()
+	r1, err := ref.New(args[0])
+	if err != nil {
+		return err
+	}
+	r2, err := ref.New(args[2])
+	if err != nil {
+		return err
+	}
+	rc := newRegClient()
+
+	// open both blobs, and generate reports of each content
+	d1, err := digest.Parse(args[1])
+	if err != nil {
+		return err
+	}
+	b1, err := rc.BlobGet(ctx, r1, types.Descriptor{Digest: d1})
+	if err != nil {
+		return err
+	}
+	defer b1.Close()
+	btr1, err := b1.ToTarReader()
+	if err != nil {
+		return err
+	}
+	tr1, err := btr1.GetTarReader()
+	if err != nil {
+		return err
+	}
+	rep1, err := blobReportLayer(tr1)
+	if err != nil {
+		return err
+	}
+	err = btr1.Close()
+	if err != nil {
+		return err
+	}
+
+	d2, err := digest.Parse(args[3])
+	if err != nil {
+		return err
+	}
+	b2, err := rc.BlobGet(ctx, r2, types.Descriptor{Digest: d2})
+	if err != nil {
+		return err
+	}
+	defer b2.Close()
+	btr2, err := b2.ToTarReader()
+	if err != nil {
+		return err
+	}
+	tr2, err := btr2.GetTarReader()
+	if err != nil {
+		return err
+	}
+	rep2, err := blobReportLayer(tr2)
+	if err != nil {
+		return err
+	}
+	err = btr2.Close()
+	if err != nil {
+		return err
+	}
+
+	// run diff and output result
+	lDiff := diff.Diff(rep1, rep2, diffOpts...)
+	_, err = fmt.Fprintln(os.Stdout, strings.Join(lDiff, "\n"))
+	return err
+}
+
 func runBlobGet(cmd *cobra.Command, args []string) error {
 	ctx := cmd.Context()
 	r, err := ref.New(args[0])
@@ -155,3 +322,37 @@ func runBlobPut(cmd *cobra.Command, args []string) error {
 
 	return template.Writer(os.Stdout, blobOpts.formatPut, result)
 }
+
+func blobReportLayer(tr *tar.Reader) ([]string, error) {
+	report := []string{}
+	if tr == nil {
+		return report, nil
+	}
+	for {
+		th, err := tr.Next()
+		if err != nil {
+			if err == io.EOF {
+				break
+			}
+			return report, err
+		}
+		line := fmt.Sprintf("%s %d/%d %8d", fs.FileMode(th.Mode).String(), th.Uid, th.Gid, th.Size)
+		if !blobOpts.diffIgnoreTime {
+			line += " " + th.ModTime.Format(time.RFC3339)
+		}
+		line += fmt.Sprintf(" %-40s", th.Name)
+		if th.Size > 0 {
+			d := digest.Canonical.Digester()
+			size, err := io.Copy(d.Hash(), tr)
+			if err != nil {
+				return report, fmt.Errorf("failed to read %s: %w", th.Name, err)
+			}
+			if size != th.Size {
+				return report, fmt.Errorf("size mismatch for %s, expected %d, read %d", th.Name, th.Size, size)
+			}
+			line += " " + d.Digest().String()
+		}
+		report = append(report, line)
+	}
+	return report, nil
+}

cmd/regctl/manifest.go

@@ -2,12 +2,14 @@ package main
 
 import (
 	"context"
+	"encoding/json"
 	"fmt"
 	"io/ioutil"
 	"os"
 	"strings"
 
 	"github.com/regclient/regclient"
+	"github.com/regclient/regclient/internal/diff"
 	"github.com/regclient/regclient/pkg/template"
 	"github.com/regclient/regclient/types"
 	"github.com/regclient/regclient/types/manifest"
@@ -36,6 +38,14 @@ layers (blobs) separately or not at all. See also the "tag delete" command.`,
 	RunE:      runManifestDelete,
 }
 
+var manifestDiffCmd = &cobra.Command{
+	Use:               "diff <image_ref> <image_ref>",
+	Short:             "compare manifests",
+	Args:              cobra.ExactArgs(2),
+	ValidArgsFunction: completeArgTag,
+	RunE:              runManifestDiff,
+}
+
 var manifestDigestCmd = &cobra.Command{
 	Use:               "digest <image_ref>",
 	Short:             "retrieve digest of manifest",
@@ -67,6 +77,8 @@ var manifestPutCmd = &cobra.Command{
 var manifestOpts struct {
 	byDigest      bool
 	contentType   string
+	diffCtx       int
+	diffFullCtx   bool
 	forceTagDeref bool
 	format        string
 	formatPut     string
@@ -78,6 +90,9 @@ var manifestOpts struct {
 func init() {
 	manifestDeleteCmd.Flags().BoolVarP(&manifestOpts.forceTagDeref, "force-tag-dereference", "", false, "Dereference the a tag to a digest, this is unsafe")
 
+	manifestDiffCmd.Flags().IntVarP(&manifestOpts.diffCtx, "context", "", 3, "Lines of context")
+	manifestDiffCmd.Flags().BoolVarP(&manifestOpts.diffFullCtx, "context-full", "", false, "Show all lines of context")
+
 	manifestDigestCmd.Flags().BoolVarP(&manifestOpts.list, "list", "", true, "Do not resolve platform from manifest list (enabled by default)")
 	manifestDigestCmd.Flags().StringVarP(&manifestOpts.platform, "platform", "p", "", "Specify platform (e.g. linux/amd64 or local)")
 	manifestDigestCmd.Flags().BoolVarP(&manifestOpts.requireList, "require-list", "", false, "Fail if manifest list is not received")
@@ -98,6 +113,7 @@ func init() {
 	manifestPutCmd.Flags().StringVarP(&manifestOpts.formatPut, "format", "", "", "Format output with go template syntax")
 
 	manifestCmd.AddCommand(manifestDeleteCmd)
+	manifestCmd.AddCommand(manifestDiffCmd)
 	manifestCmd.AddCommand(manifestDigestCmd)
 	manifestCmd.AddCommand(manifestGetCmd)
 	manifestCmd.AddCommand(manifestPutCmd)
@@ -214,6 +230,57 @@ func runManifestDelete(cmd *cobra.Command, args []string) error {
 	return nil
 }
 
+func runManifestDiff(cmd *cobra.Command, args []string) error {
+	diffOpts := []diff.Opt{}
+	if manifestOpts.diffCtx > 0 {
+		diffOpts = append(diffOpts, diff.WithContext(manifestOpts.diffCtx, manifestOpts.diffCtx))
+	}
+	if manifestOpts.diffFullCtx {
+		diffOpts = append(diffOpts, diff.WithFullContext())
+	}
+	ctx := cmd.Context()
+	r1, err := ref.New(args[0])
+	if err != nil {
+		return err
+	}
+	r2, err := ref.New(args[1])
+	if err != nil {
+		return err
+	}
+
+	rc := newRegClient()
+
+	log.WithFields(logrus.Fields{
+		"ref1": r1.CommonName(),
+		"ref2": r2.CommonName(),
+	}).Debug("Manifest diff")
+
+	m1, err := rc.ManifestGet(ctx, r1)
+	if err != nil {
+		return err
+	}
+	m2, err := rc.ManifestGet(ctx, r2)
+	if err != nil {
+		return err
+	}
+
+	m1Json, err := json.MarshalIndent(m1, "", "  ")
+	if err != nil {
+		return err
+	}
+	m2Json, err := json.MarshalIndent(m2, "", "  ")
+	if err != nil {
+		return err
+	}
+
+	mDiff := diff.Diff(strings.Split(string(m1Json), "\n"), strings.Split(string(m2Json), "\n"), diffOpts...)
+
+	_, err = fmt.Fprintln(os.Stdout, strings.Join(mDiff, "\n"))
+	return err
+	// TODO: support templating
+	// return template.Writer(os.Stdout, manifestOpts.format, mDiff)
+}
+
 func runManifestDigest(cmd *cobra.Command, args []string) error {
 	ctx := cmd.Context()
 	if manifestOpts.platform != "" && !flagChanged(cmd, "list") {

docs/README.md

@@ -1,6 +1,6 @@
 # regclient Documentation
 
-- [Project Specific Documentation](#project-dpecific-documentation)
+- [Project Specific Documentation](#project-specific-documentation)
 - [Schemes](#schemes)
 - [Template Functions](#template-functions)
 - [FAQ](#faq)

docs/regctl.md

@@ -162,6 +162,7 @@ Usage:
 
 Available Commands:
   delete      delete a manifest
+  diff        compare manifests
   digest      retrieve digest of manifest
   get         retrieve manifest or manifest list
   put         push manifest or manifest list
@@ -172,6 +173,9 @@ This will impact all tags pointing to the same manifest and requires a digest to
 Using `--force-tag-dereference` will automatically lookup the digest for a specific tag, and will delete the underlying image which will delete any other tags pointing to the same image.
 Use `tag delete` to remove a single tag.
 
+The `diff` command compares two manifests and shows what has changed between these manifests.
+See also the `blob diff-config` and `blob diff-layer` commands.
+
 The `digest` command is useful to pin the image used within your deployment to an immutable sha256 checksum.
 
 The `get` command retrieves the manifest from the registry, showing individual components of an image.
@@ -191,10 +195,38 @@ Usage:
   regctl blob [command]
 
 Available Commands:
+  diff-config diff two image configs
+  diff-layer  diff two tar layers
   get         download a blob/layer
   put         upload a blob/layer
 ```
 
+The `diff-config` command compares two config blobs, showing the differences between the configs.
+
+The `diff-layer` command compares two layer blobs, showing exactly what changed in the filesystem between the two layers.
+
+Example usage:
+
+```shell
+$ regctl blob diff-layer --context 0 --ignore-timestamp \
+    alpine sha256:627fad6f28f79c3907ad18a4399be4d810c0e1bb503fe3712217145c555b9d2f \
+    alpine sha256:decfdc335d9bae9ca06166e1a4fc2cdf8c2344a42d85c8a1d3f964aab59ecff5
+@@ -6,1 +6,1 @@
+- -rwxr-xr-x 0/0   824904 bin/busybox                              sha256:4a1876b4899ce26853ec5f5eb75248e5a2d9e07369c4435c8d41e83393e04a9b
++ -rwxr-xr-x 0/0   829000 bin/busybox                              sha256:d15929a78a86065c41dd274f2f3f058986b6f5eee4a4c881c83d4fa4179e58ee
+@@ -85,1 +85,1 @@
+- -rw-r--r-- 0/0        8 etc/alpine-release                       sha256:9fa33d932bbf6e5784f15b467a9a10e4ce43993c2341ee742f23ce0196fd73e9
++ -rw-r--r-- 0/0        7 etc/alpine-release                       sha256:922fe0c3de073b01988e23348ea184456161678c5e329e6f34be89be24383f93
+@@ -95,1 +95,1 @@
+- -rw-r--r-- 0/0      103 etc/apk/repositories                     sha256:e44b25ef011171afece2ff51a206b732f84c7f3ddc8291c6dc50cb1572c0ae1c
++ -rw-r--r-- 0/0      103 etc/apk/repositories                     sha256:7b5dba82c50baee0b4aee54038ca2265df42d1f873d1601934bb45daf17311b4
+@@ -101,1 +101,1 @@
+- -rw-r--r-- 0/0      682 etc/group                                sha256:412af628e00706d3c90a5d465d59cc422ff68d79eeb8870c4f33ed6df04b2871
++ -rw-r--r-- 0/0      697 etc/group                                sha256:0632d55a68081065097472fe7bc7c66f0785f3b78f39fb23f622d24a7e09be9f
+@@ -106,1 +106,1 @@
+...
+```
+
 The `get` command will pull a specific sha256 blob from the registry and returns it to stdout.
 If you are requesting a tar layer, be sure to direct this to a file or command that parses the content.
 For json blobs, it's useful to redirect this to a command like `jq`.

internal/diff/diff.go

@@ -0,0 +1,112 @@
+// Package diff computes the efficient set of changes (insert/delete) between two arrays of strings
+package diff
+
+import "fmt"
+
+// opKind is used to denote the type of operation a line represents.
+type opKind int
+
+const (
+	// OpDelete is the operation kind for a line that is present in the input
+	// but not in the output.
+	OpDelete opKind = iota
+	// OpInsert is the operation kind for a line that is new in the output.
+	OpInsert
+)
+
+type operation struct {
+	Kind   opKind
+	X1, X2 int // indices of the line in a
+	Y1, Y2 int // indices of the line in b
+}
+
+type Opt func(*conf)
+
+type conf struct {
+	contextA    int
+	contextB    int
+	contextFull bool
+}
+
+func WithContext(a, b int) func(*conf) {
+	return func(c *conf) {
+		c.contextA = a
+		c.contextB = b
+	}
+}
+
+func WithFullContext() func(*conf) {
+	return func(c *conf) {
+		c.contextFull = true
+	}
+}
+
+// Diff returns the difference between two strings
+func Diff(a, b []string, opts ...Opt) []string {
+	c := conf{}
+	for _, fn := range opts {
+		fn(&c)
+	}
+
+	diffLines := []string{}
+	setLines := []string{}
+	ops := myersOperations(a, b)
+	sX1, sX2, sY1, sY2 := -1, -1, -1, -1
+	addSet := func() {
+		if len(setLines) == 0 {
+			return
+		}
+		// calculate how many lines of context to add
+		cA, cB := c.contextA, c.contextB
+		if sX1-cA < 0 || c.contextFull {
+			cA = sX1
+		}
+		if sX2+cB > len(a) || c.contextFull {
+			cB = len(a) - sX2
+		}
+		// add header
+		diffLines = append(diffLines, fmt.Sprintf("@@ -%d,%d +%d,%d @@", sX1-cA+1, sX2+cA+cB-sX1, sY1-cA+1, sY2+cA+cB-sY1))
+		// add context before, the change set, and context after
+		if cA > 0 {
+			for _, line := range a[sX1-cA : sX1] {
+				diffLines = append(diffLines, "  "+line)
+			}
+		}
+		diffLines = append(diffLines, setLines...)
+		setLines = []string{} // reset the setLines to a new array
+		if cB > 0 {
+			for _, line := range a[sX2 : sX2+cB] {
+				diffLines = append(diffLines, "  "+line)
+			}
+		}
+	}
+	for _, op := range ops {
+		// compare from last set
+		dX, dY := op.X1-sX2, op.Y1-sY2
+		if dX != dY || (dX > c.contextA && dX > c.contextB && !c.contextFull) {
+			// unexpected diff lines or gap exceeds context limits, create a new set
+			addSet()
+			sX1, sY1 = op.X1, op.Y1
+		} else if dX > 0 {
+			// add common lines between two diffs
+			for _, line := range a[sX2+1 : op.X1] {
+				setLines = append(setLines, "  "+line)
+			}
+		}
+		// add entries to this set, either delete or add
+		switch op.Kind {
+		case OpDelete:
+			for _, line := range a[op.X1:op.X2] {
+				setLines = append(setLines, "- "+line)
+			}
+		case OpInsert:
+			for _, line := range b[op.Y1:op.Y2] {
+				setLines = append(setLines, "+ "+line)
+			}
+		}
+		// update end of set
+		sX2, sY2 = op.X2, op.Y2
+	}
+	addSet()
+	return diffLines
+}

internal/diff/diff_test.go

@@ -0,0 +1,146 @@
+package diff
+
+import "testing"
+
+func TestDiff(t *testing.T) {
+	tests := []struct {
+		name         string
+		a, b, expect []string
+		opts         []Opt
+	}{
+		{
+			name: "empty",
+		},
+		{
+			name: "deletes",
+			a:    []string{"a", "b", "c"},
+			expect: []string{
+				"@@ -1,3 +1,0 @@",
+				"- a",
+				"- b",
+				"- c",
+			},
+		},
+		{
+			name: "inserts",
+			b:    []string{"a", "b", "c"},
+			expect: []string{
+				"@@ -1,0 +1,3 @@",
+				"+ a",
+				"+ b",
+				"+ c",
+			},
+		},
+		{
+			name: "equal",
+			a:    []string{"a", "b", "c"},
+			b:    []string{"a", "b", "c"},
+		},
+		{
+			name: "myers",
+			a:    []string{"a", "b", "c", "a", "b", "b", "a"},
+			b:    []string{"c", "b", "a", "b", "a", "c"},
+			expect: []string{
+				"@@ -1,2 +1,0 @@",
+				"- a",
+				"- b",
+				"@@ -4,0 +2,1 @@",
+				"+ b",
+				"@@ -6,1 +5,0 @@",
+				"- b",
+				"@@ -8,0 +6,1 @@",
+				"+ c",
+			},
+		},
+		{
+			name: "replace",
+			a:    []string{"a", "b", "c"},
+			b:    []string{"d", "e", "f"},
+			expect: []string{
+				"@@ -1,3 +1,3 @@",
+				"- a",
+				"- b",
+				"- c",
+				"+ d",
+				"+ e",
+				"+ f",
+			},
+		},
+		{
+			name: "change one",
+			a:    []string{"a", "b", "c", "d"},
+			b:    []string{"a", "e", "f", "d"},
+			expect: []string{
+				"@@ -2,2 +2,2 @@",
+				"- b",
+				"- c",
+				"+ e",
+				"+ f",
+			},
+		},
+		{
+			name: "context one",
+			a:    []string{"a", "b", "c", "d", "e"},
+			b:    []string{"a", "b", "f", "d", "e"},
+			opts: []Opt{WithContext(1, 1)},
+			expect: []string{
+				"@@ -2,3 +2,3 @@",
+				"  b",
+				"- c",
+				"+ f",
+				"  d",
+			},
+		},
+		{
+			name: "context three",
+			a:    []string{"a", "b", "c", "d", "e"},
+			b:    []string{"a", "b", "f", "d", "e"},
+			opts: []Opt{WithContext(3, 3)},
+			expect: []string{
+				"@@ -1,5 +1,5 @@",
+				"  a",
+				"  b",
+				"- c",
+				"+ f",
+				"  d",
+				"  e",
+			},
+		},
+		{
+			name: "context full",
+			a:    []string{"a", "b", "c", "d", "e"},
+			b:    []string{"a", "b", "f", "d", "e"},
+			opts: []Opt{WithFullContext()},
+			expect: []string{
+				"@@ -1,5 +1,5 @@",
+				"  a",
+				"  b",
+				"- c",
+				"+ f",
+				"  d",
+				"  e",
+			},
+		},
+	}
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			result := Diff(tt.a, tt.b, tt.opts...)
+			if !strSliceEq(tt.expect, result) {
+				t.Errorf("mismatch, expected %v, received %v", tt.expect, result)
+			}
+		})
+	}
+
+}
+
+func strSliceEq(a, b []string) bool {
+	if len(a) != len(b) {
+		return false
+	}
+	for i := range a {
+		if a[i] != b[i] {
+			return false
+		}
+	}
+	return true
+}

internal/diff/myers.go

@@ -0,0 +1,155 @@
+package diff
+
+// Recommended reading:
+// https://blog.jcoglan.com/2017/02/17/the-myers-diff-algorithm-part-3/
+// https://www.codeproject.com/Articles/42279/%2FArticles%2F42279%2FInvestigating-Myers-diff-algorithm-Part-1-of-2
+// https://cs.opensource.google/go/x/tools/+/refs/tags/v0.1.11:internal/lsp/diff/myers/diff.go;l=19
+
+// myersOperations returns the list of operations to convert a into b.
+// This consolidates operations for multiple lines and skips equal lines.
+func myersOperations(a, b []string) []*operation {
+	if len(a) == 0 && len(b) == 0 {
+		return nil
+	}
+	trace, offset := myersShortestSeq(a, b)
+	snakes := myersBacktrack(trace, len(a), len(b), offset)
+	M, N := len(a), len(b)
+	var i int
+	solution := make([]*operation, len(a)+len(b))
+	add := func(op *operation, x2, y2 int) {
+		if op == nil {
+			return
+		}
+		if i > 0 && solution[i-1].Kind == op.Kind && solution[i-1].X2 == op.X1 && solution[i-1].Y2 == op.Y1 {
+			// extend add/delete from previous entry
+			solution[i-1].X2 = x2
+			solution[i-1].Y2 = y2
+		} else {
+			// add a new operation
+			op.X2 = x2
+			op.Y2 = y2
+			solution[i] = op
+			i++
+		}
+	}
+	x, y := 0, 0
+	for _, snake := range snakes {
+		if len(snake) < 2 {
+			continue
+		}
+		if snake[0]-snake[1] > x-y {
+			// delete (horizontal)
+			op := &operation{
+				Kind: OpDelete,
+				X1:   x,
+				Y1:   y,
+			}
+			x++
+			if x <= M {
+				add(op, x, y)
+			}
+		} else if snake[0]-snake[1] < x-y {
+			// insert (vertical)
+			op := &operation{
+				Kind: OpInsert,
+				X1:   x,
+				Y1:   y,
+			}
+			y++
+			if y <= N {
+				add(op, x, y)
+			}
+		}
+		// equal (diagonal)
+		for x < snake[0] {
+			x++
+			y++
+		}
+		if x >= M && y >= N {
+			break
+		}
+	}
+	return solution[:i]
+}
+
+// myersBacktrack returns a list of "snakes" for a given trace.
+// A "snake" is a single deletion or insertion followed by zero or more diagonals.
+// snakes[d] is the x,y coordinate of the best position on the best path at distance d.
+func myersBacktrack(trace [][]int, x, y, offset int) [][]int {
+	snakes := make([][]int, len(trace))
+	d := len(trace) - 1
+	for ; x >= 0 && y >= 0 && d > 0; d-- {
+		V := trace[d]
+		if len(V) == 0 {
+			continue
+		}
+		snakes[d] = []int{x, y}
+
+		k := x - y
+
+		var kPrev int
+		if k == -d || (k != d && V[k-1+offset] < V[k+1+offset]) {
+			kPrev = k + 1
+		} else {
+			kPrev = k - 1
+		}
+
+		x = V[kPrev+offset]
+		y = x - kPrev
+	}
+	if x < 0 || y < 0 {
+		return snakes
+	}
+	snakes[d] = []int{x, y}
+	return snakes
+}
+
+// myersShortestSeq returns the shortest edit sequence that converts a into b.
+// M and N, length of a and b respectively.
+// x: index of a, x+1 moves right, indicating deletion from a.
+// y: index of b, y+1 moves down, indicating insertion from b.
+// k: diagonals represented by the equation y = x - k. If inserts==deletes, k=0.
+// V[k]=x: best values of x for each k diagonal.
+// d: distance, sum of inserts/deletes.
+// trace[d]=V, best values for x for each k diagonal and distance d.
+// return is the trace and offset
+func myersShortestSeq(a, b []string) ([][]int, int) {
+	M, N := len(a), len(b)
+	V := make([]int, 2*(N+M)+1)
+	offset := N + M
+	trace := make([][]int, N+M+1)
+	// iterate up to the maximum possible length
+	for d := 0; d <= N+M; d++ {
+		newV := make([]int, len(V))
+		// move in increments of 2 because end points for even d are on even k lines
+		for k := -d; k <= d; k += 2 {
+			// At each point, we either go down or to the right.
+			// We go down if k == -d, and we go to the right if k == d.
+			// We also prioritize the maximum x value, because we prefer deletions to insertions.
+			var x int
+			if k == -d || (k != d && V[k-1+offset] < V[k+1+offset]) {
+				x = V[k+1+offset] // down
+			} else {
+				x = V[k-1+offset] + 1 // right
+			}
+			y := x - k
+			// Diagonal moves while we have equal contents.
+			for x < M && y < N && a[x] == b[y] {
+				x++
+				y++
+			}
+			V[k+offset] = x
+			// Return if we've exceeded the maximum values.
+			if x == M && y == N {
+				// Makes sure to save the state of the array before returning.
+				copy(newV, V)
+				trace[d] = newV
+				return trace, offset
+			}
+		}
+		// Save the state of the array.
+		copy(newV, V)
+		trace[d] = newV
+	}
+	return nil, 0
+}

types/blob/blob_test.go

@@ -7,6 +7,7 @@ import (
 	"fmt"
 	"io"
 	"net/http"
+	"os"
 	"testing"
 
 	"github.com/opencontainers/go-digest"
@@ -234,6 +235,7 @@ func TestReader(t *testing.T) {
 		if b.GetDescriptor().Size != exLen {
 			t.Errorf("length mismatch, expected %d, received %d", exLen, b.GetDescriptor().Size)
 		}
+
 	})
 
 	t.Run("ociconfig", func(t *testing.T) {
@@ -379,6 +381,96 @@ func TestOCI(t *testing.T) {
 	})
 }
 
+func TestTarReader(t *testing.T) {
+	fh, err := os.Open("../../testdata/layer.tar")
+	if err != nil {
+		t.Errorf("failed to open test data: %v", err)
+		return
+	}
+	digger := digest.Canonical.Digester()
+	fhSize, err := io.Copy(digger.Hash(), fh)
+	if err != nil {
+		t.Errorf("failed to build digest on test data: %v", err)
+		return
+	}
+	fh.Close()
+	dig := digger.Digest()
+
+	tests := []struct {
+		name     string
+		opts     []Opts
+		errClose bool
+	}{
+		{
+			name: "no desc",
+			opts: []Opts{},
+		},
+		{
+			name: "good desc",
+			opts: []Opts{
+				WithDesc(types.Descriptor{
+					MediaType: types.MediaTypeOCI1Layer,
+					Size:      fhSize,
+					Digest:    dig,
+				}),
+			},
+		},
+		{
+			name: "bad desc",
+			opts: []Opts{
+				WithDesc(types.Descriptor{
+					MediaType: types.MediaTypeOCI1Layer,
+					Size:      fhSize,
+					Digest:    digest.FromString("bad digest"),
+				}),
+			},
+		},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			fh, err := os.Open("../../testdata/layer.tar")
+			if err != nil {
+				t.Errorf("failed to open test data: %v", err)
+				return
+			}
+			opts := append(tt.opts, WithReader(fh))
+			btr := NewTarReader(opts...)
+			tr, err := btr.GetTarReader()
+			if err != nil {
+				t.Errorf("failed to get tar reader: %v", err)
+				return
+			}
+			for {
+				th, err := tr.Next()
+				if err != nil {
+					if err != io.EOF {
+						t.Errorf("failed to read tar: %v", err)
+						return
+					}
+					break
+				}
+				if th.Size != 0 {
+					b, err := io.ReadAll(tr)
+					if err != nil {
+						t.Errorf("failed to read content: %v", err)
+						break
+					}
+					if int64(len(b)) != th.Size {
+						t.Errorf("content size mismatch, expected %d, received %d", th.Size, len(b))
+					}
+				}
+			}
+			err = btr.Close()
+			if !tt.errClose && err != nil {
+				t.Errorf("failed to close tar reader: %v", err)
+			} else if tt.errClose && err == nil {
+				t.Errorf("close did not fail")
+			}
+		})
+	}
+}
+
 func cmpSliceString(a, b []string) bool {
 	if len(a) != len(b) {
 		return false

types/blob/reader.go

@@ -18,6 +18,7 @@ type Reader interface {
 	Blob
 	io.ReadCloser
 	ToOCIConfig() (OCIConfig, error)
+	ToTarReader() (TarReader, error)
 }
 
 // reader is the internal struct implementing BlobReader
@@ -163,3 +164,19 @@ func (b *reader) ToOCIConfig() (OCIConfig, error) {
 		WithResp(b.resp),
 	), nil
 }
+
+func (b *reader) ToTarReader() (TarReader, error) {
+	if !b.blobSet {
+		return nil, fmt.Errorf("blob is not defined")
+	}
+	if b.readBytes != 0 {
+		return nil, fmt.Errorf("unable to convert after read has been performed")
+	}
+	return NewTarReader(
+		WithDesc(b.desc),
+		WithHeader(b.rawHeader),
+		WithRef(b.r),
+		WithResp(b.resp),
+		WithReader(b.reader),
+	), nil
+}

types/blob/tar.go

@@ -0,0 +1,102 @@
+package blob
+
+import (
+	"archive/tar"
+	"fmt"
+	"io"
+	"io/ioutil"
+
+	"github.com/opencontainers/go-digest"
+	"github.com/regclient/regclient/pkg/archive"
+)
+
+// TarReader reads or writes to a blob with tar contents and optional compression
+type TarReader interface {
+	Blob
+	io.Closer
+	GetTarReader() (*tar.Reader, error)
+}
+
+type tarReader struct {
+	common
+	origRdr  io.Reader
+	reader   io.Reader
+	digester digest.Digester
+	tr       *tar.Reader
+}
+
+// NewTarReader creates a TarReader
+func NewTarReader(opts ...Opts) TarReader {
+	bc := blobConfig{}
+	for _, opt := range opts {
+		opt(&bc)
+	}
+	c := common{
+		desc:      bc.desc,
+		r:         bc.r,
+		rawHeader: bc.header,
+		resp:      bc.resp,
+	}
+	tr := tarReader{
+		common:  c,
+		origRdr: bc.rdr,
+	}
+	if bc.rdr != nil {
+		tr.blobSet = true
+		tr.digester = digest.Canonical.Digester()
+		tr.reader = io.TeeReader(bc.rdr, tr.digester.Hash())
+	}
+	return &tr
+}
+
+// Close attempts to close the reader and populates/validates the digest
+func (tr *tarReader) Close() error {
+	var err error
+	if tr.digester != nil {
+		dig := tr.digester.Digest()
+		tr.digester = nil
+		if tr.desc.Digest.String() != "" && dig != tr.desc.Digest {
+			err = fmt.Errorf("digest mismatch, expected %s, received %s", tr.desc.Digest.String(), dig.String())
+		}
+		tr.desc.Digest = dig
+	}
+	if tr.origRdr == nil {
+		return err
+	}
+	// attempt to close if available in original reader
+	if trc, ok := tr.origRdr.(io.Closer); ok {
+		return trc.Close()
+	}
+	return err
+}
+
+// GetTarReader returns the tar.Reader for the blob
+func (tr *tarReader) GetTarReader() (*tar.Reader, error) {
+	if tr.reader == nil {
+		return nil, fmt.Errorf("blob has no reader defined")
+	}
+	if tr.tr == nil {
+		dr, err := archive.Decompress(tr.reader)
+		if err != nil {
+			return nil, err
+		}
+		tr.tr = tar.NewReader(dr)
+	}
+	return tr.tr, nil
+}
+
+// RawBody returns the original body from the request
+func (tr *tarReader) RawBody() ([]byte, error) {
+	if !tr.blobSet {
+		return []byte{}, fmt.Errorf("Blob is not defined")
+	}
+	if tr.tr != nil {
+		return []byte{}, fmt.Errorf("RawBody cannot be returned after TarReader returned")
+	}
+	b, err := ioutil.ReadAll(tr.reader)
+	if err != nil {
+		return b, err
+	}
+	err = tr.Close()
+	return b, err
+}