95 lines
2.7 KiB
Go
95 lines
2.7 KiB
Go
package wclayer
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import (
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"context"
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"io/ioutil"
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"os"
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"strings"
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"github.com/Microsoft/go-winio"
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"github.com/Microsoft/hcsshim/internal/hcserror"
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"github.com/Microsoft/hcsshim/internal/oc"
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"go.opencensus.io/trace"
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)
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// ExportLayer will create a folder at exportFolderPath and fill that folder with
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// the transport format version of the layer identified by layerId. This transport
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// format includes any metadata required for later importing the layer (using
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// ImportLayer), and requires the full list of parent layer paths in order to
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// perform the export.
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func ExportLayer(ctx context.Context, path string, exportFolderPath string, parentLayerPaths []string) (err error) {
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title := "hcsshim::ExportLayer"
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ctx, span := trace.StartSpan(ctx, title)
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defer span.End()
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defer func() { oc.SetSpanStatus(span, err) }()
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span.AddAttributes(
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trace.StringAttribute("path", path),
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trace.StringAttribute("exportFolderPath", exportFolderPath),
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trace.StringAttribute("parentLayerPaths", strings.Join(parentLayerPaths, ", ")))
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// Generate layer descriptors
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layers, err := layerPathsToDescriptors(ctx, parentLayerPaths)
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if err != nil {
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return err
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}
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err = exportLayer(&stdDriverInfo, path, exportFolderPath, layers)
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if err != nil {
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return hcserror.New(err, title+" - failed", "")
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}
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return nil
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}
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type LayerReader interface {
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Next() (string, int64, *winio.FileBasicInfo, error)
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Read(b []byte) (int, error)
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Close() error
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}
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// NewLayerReader returns a new layer reader for reading the contents of an on-disk layer.
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// The caller must have taken the SeBackupPrivilege privilege
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// to call this and any methods on the resulting LayerReader.
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func NewLayerReader(ctx context.Context, path string, parentLayerPaths []string) (_ LayerReader, err error) {
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ctx, span := trace.StartSpan(ctx, "hcsshim::NewLayerReader")
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defer func() {
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if err != nil {
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oc.SetSpanStatus(span, err)
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span.End()
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}
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}()
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span.AddAttributes(
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trace.StringAttribute("path", path),
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trace.StringAttribute("parentLayerPaths", strings.Join(parentLayerPaths, ", ")))
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exportPath, err := ioutil.TempDir("", "hcs")
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if err != nil {
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return nil, err
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}
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err = ExportLayer(ctx, path, exportPath, parentLayerPaths)
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if err != nil {
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os.RemoveAll(exportPath)
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return nil, err
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}
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return &legacyLayerReaderWrapper{
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ctx: ctx,
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s: span,
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legacyLayerReader: newLegacyLayerReader(exportPath),
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}, nil
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}
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type legacyLayerReaderWrapper struct {
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ctx context.Context
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s *trace.Span
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*legacyLayerReader
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}
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func (r *legacyLayerReaderWrapper) Close() (err error) {
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defer r.s.End()
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defer func() { oc.SetSpanStatus(r.s, err) }()
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err = r.legacyLayerReader.Close()
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os.RemoveAll(r.root)
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return err
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}
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