Merge pull request #4399 from TBBle/wcow_compare_layers_to_tar

Implement windowsDiff.Compare to allow outputting OCI images

vendor/github.com/Microsoft/hcsshim/pkg/ociwclayer/export.go

@@ -0,0 +1,86 @@
+// Package ociwclayer provides functions for importing and exporting Windows
+// container layers from and to their OCI tar representation.
+package ociwclayer
+
+import (
+	"archive/tar"
+	"context"
+	"io"
+	"path/filepath"
+
+	"github.com/Microsoft/go-winio/backuptar"
+	"github.com/Microsoft/hcsshim"
+)
+
+var driverInfo = hcsshim.DriverInfo{}
+
+// ExportLayerToTar writes an OCI layer tar stream from the provided on-disk layer.
+// The caller must specify the parent layers, if any, ordered from lowest to
+// highest layer.
+//
+// The layer will be mounted for this process, so the caller should ensure that
+// it is not currently mounted.
+func ExportLayerToTar(ctx context.Context, w io.Writer, path string, parentLayerPaths []string) error {
+	err := hcsshim.ActivateLayer(driverInfo, path)
+	if err != nil {
+		return err
+	}
+	defer hcsshim.DeactivateLayer(driverInfo, path)
+
+	// Prepare and unprepare the layer to ensure that it has been initialized.
+	err = hcsshim.PrepareLayer(driverInfo, path, parentLayerPaths)
+	if err != nil {
+		return err
+	}
+	err = hcsshim.UnprepareLayer(driverInfo, path)
+	if err != nil {
+		return err
+	}
+
+	r, err := hcsshim.NewLayerReader(driverInfo, path, parentLayerPaths)
+	if err != nil {
+		return err
+	}
+
+	err = writeTarFromLayer(ctx, r, w)
+	cerr := r.Close()
+	if err != nil {
+		return err
+	}
+	return cerr
+}
+
+func writeTarFromLayer(ctx context.Context, r hcsshim.LayerReader, w io.Writer) error {
+	t := tar.NewWriter(w)
+	for {
+		select {
+		case <-ctx.Done():
+			return ctx.Err()
+		default:
+		}
+
+		name, size, fileInfo, err := r.Next()
+		if err == io.EOF {
+			break
+		}
+		if err != nil {
+			return err
+		}
+		if fileInfo == nil {
+			// Write a whiteout file.
+			hdr := &tar.Header{
+				Name: filepath.ToSlash(filepath.Join(filepath.Dir(name), whiteoutPrefix+filepath.Base(name))),
+			}
+			err := t.WriteHeader(hdr)
+			if err != nil {
+				return err
+			}
+		} else {
+			err = backuptar.WriteTarFileFromBackupStream(t, r, name, size, fileInfo)
+			if err != nil {
+				return err
+			}
+		}
+	}
+	return t.Close()
+}

vendor/github.com/Microsoft/hcsshim/pkg/ociwclayer/import.go

@@ -0,0 +1,148 @@
+package ociwclayer
+
+import (
+	"archive/tar"
+	"bufio"
+	"context"
+	"io"
+	"os"
+	"path"
+	"path/filepath"
+	"strings"
+
+	winio "github.com/Microsoft/go-winio"
+	"github.com/Microsoft/go-winio/backuptar"
+	"github.com/Microsoft/hcsshim"
+)
+
+const whiteoutPrefix = ".wh."
+
+var (
+	// mutatedFiles is a list of files that are mutated by the import process
+	// and must be backed up and restored.
+	mutatedFiles = map[string]string{
+		"UtilityVM/Files/EFI/Microsoft/Boot/BCD":      "bcd.bak",
+		"UtilityVM/Files/EFI/Microsoft/Boot/BCD.LOG":  "bcd.log.bak",
+		"UtilityVM/Files/EFI/Microsoft/Boot/BCD.LOG1": "bcd.log1.bak",
+		"UtilityVM/Files/EFI/Microsoft/Boot/BCD.LOG2": "bcd.log2.bak",
+	}
+)
+
+// ImportLayerFromTar  reads a layer from an OCI layer tar stream and extracts it to the
+// specified path. The caller must specify the parent layers, if any, ordered
+// from lowest to highest layer.
+//
+// The caller must ensure that the thread or process has acquired backup and
+// restore privileges.
+//
+// This function returns the total size of the layer's files, in bytes.
+func ImportLayerFromTar(ctx context.Context, r io.Reader, path string, parentLayerPaths []string) (int64, error) {
+	err := os.MkdirAll(path, 0)
+	if err != nil {
+		return 0, err
+	}
+	w, err := hcsshim.NewLayerWriter(hcsshim.DriverInfo{}, path, parentLayerPaths)
+	if err != nil {
+		return 0, err
+	}
+	n, err := writeLayerFromTar(ctx, r, w, path)
+	cerr := w.Close()
+	if err != nil {
+		return 0, err
+	}
+	if cerr != nil {
+		return 0, cerr
+	}
+	return n, nil
+}
+
+func writeLayerFromTar(ctx context.Context, r io.Reader, w hcsshim.LayerWriter, root string) (int64, error) {
+	t := tar.NewReader(r)
+	hdr, err := t.Next()
+	totalSize := int64(0)
+	buf := bufio.NewWriter(nil)
+	for err == nil {
+		select {
+		case <-ctx.Done():
+			return 0, ctx.Err()
+		default:
+		}
+
+		base := path.Base(hdr.Name)
+		if strings.HasPrefix(base, whiteoutPrefix) {
+			name := path.Join(path.Dir(hdr.Name), base[len(whiteoutPrefix):])
+			err = w.Remove(filepath.FromSlash(name))
+			if err != nil {
+				return 0, err
+			}
+			hdr, err = t.Next()
+		} else if hdr.Typeflag == tar.TypeLink {
+			err = w.AddLink(filepath.FromSlash(hdr.Name), filepath.FromSlash(hdr.Linkname))
+			if err != nil {
+				return 0, err
+			}
+			hdr, err = t.Next()
+		} else {
+			var (
+				name     string
+				size     int64
+				fileInfo *winio.FileBasicInfo
+			)
+			name, size, fileInfo, err = backuptar.FileInfoFromHeader(hdr)
+			if err != nil {
+				return 0, err
+			}
+			err = w.Add(filepath.FromSlash(name), fileInfo)
+			if err != nil {
+				return 0, err
+			}
+			hdr, err = writeBackupStreamFromTarAndSaveMutatedFiles(buf, w, t, hdr, root)
+			totalSize += size
+		}
+	}
+	if err != io.EOF {
+		return 0, err
+	}
+	return totalSize, nil
+}
+
+// writeBackupStreamFromTarAndSaveMutatedFiles reads data from a tar stream and
+// writes it to a backup stream, and also saves any files that will be mutated
+// by the import layer process to a backup location.
+func writeBackupStreamFromTarAndSaveMutatedFiles(buf *bufio.Writer, w io.Writer, t *tar.Reader, hdr *tar.Header, root string) (nextHdr *tar.Header, err error) {
+	var bcdBackup *os.File
+	var bcdBackupWriter *winio.BackupFileWriter
+	if backupPath, ok := mutatedFiles[hdr.Name]; ok {
+		bcdBackup, err = os.Create(filepath.Join(root, backupPath))
+		if err != nil {
+			return nil, err
+		}
+		defer func() {
+			cerr := bcdBackup.Close()
+			if err == nil {
+				err = cerr
+			}
+		}()
+
+		bcdBackupWriter = winio.NewBackupFileWriter(bcdBackup, false)
+		defer func() {
+			cerr := bcdBackupWriter.Close()
+			if err == nil {
+				err = cerr
+			}
+		}()
+
+		buf.Reset(io.MultiWriter(w, bcdBackupWriter))
+	} else {
+		buf.Reset(w)
+	}
+
+	defer func() {
+		ferr := buf.Flush()
+		if err == nil {
+			err = ferr
+		}
+	}()
+
+	return backuptar.WriteBackupStreamFromTarFile(buf, t, hdr)
+}