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