157 lines
4.4 KiB
Go
157 lines
4.4 KiB
Go
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package hcsshim
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import (
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"io"
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"io/ioutil"
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"os"
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"syscall"
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"github.com/Microsoft/go-winio"
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"github.com/sirupsen/logrus"
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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(info DriverInfo, layerId string, exportFolderPath string, parentLayerPaths []string) error {
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title := "hcsshim::ExportLayer "
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logrus.Debugf(title+"flavour %d layerId %s folder %s", info.Flavour, layerId, exportFolderPath)
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// Generate layer descriptors
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layers, err := layerPathsToDescriptors(parentLayerPaths)
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if err != nil {
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return err
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}
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// Convert info to API calling convention
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infop, err := convertDriverInfo(info)
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if err != nil {
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logrus.Error(err)
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return err
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}
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err = exportLayer(&infop, layerId, exportFolderPath, layers)
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if err != nil {
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err = makeErrorf(err, title, "layerId=%s flavour=%d folder=%s", layerId, info.Flavour, exportFolderPath)
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logrus.Error(err)
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return err
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}
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logrus.Debugf(title+"succeeded flavour=%d layerId=%s folder=%s", info.Flavour, layerId, exportFolderPath)
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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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// FilterLayerReader provides an interface for extracting the contents of an on-disk layer.
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type FilterLayerReader struct {
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context uintptr
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}
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// Next reads the next available file from a layer, ensuring that parent directories are always read
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// before child files and directories.
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//
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// Next returns the file's relative path, size, and basic file metadata. Read() should be used to
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// extract a Win32 backup stream with the remainder of the metadata and the data.
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func (r *FilterLayerReader) Next() (string, int64, *winio.FileBasicInfo, error) {
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var fileNamep *uint16
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fileInfo := &winio.FileBasicInfo{}
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var deleted uint32
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var fileSize int64
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err := exportLayerNext(r.context, &fileNamep, fileInfo, &fileSize, &deleted)
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if err != nil {
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if err == syscall.ERROR_NO_MORE_FILES {
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err = io.EOF
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} else {
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err = makeError(err, "ExportLayerNext", "")
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}
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return "", 0, nil, err
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}
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fileName := convertAndFreeCoTaskMemString(fileNamep)
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if deleted != 0 {
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fileInfo = nil
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}
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if fileName[0] == '\\' {
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fileName = fileName[1:]
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}
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return fileName, fileSize, fileInfo, nil
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}
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// Read reads from the current file's Win32 backup stream.
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func (r *FilterLayerReader) Read(b []byte) (int, error) {
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var bytesRead uint32
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err := exportLayerRead(r.context, b, &bytesRead)
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if err != nil {
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return 0, makeError(err, "ExportLayerRead", "")
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}
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if bytesRead == 0 {
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return 0, io.EOF
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}
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return int(bytesRead), nil
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}
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// Close frees resources associated with the layer reader. It will return an
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// error if there was an error while reading the layer or of the layer was not
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// completely read.
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func (r *FilterLayerReader) Close() (err error) {
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if r.context != 0 {
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err = exportLayerEnd(r.context)
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if err != nil {
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err = makeError(err, "ExportLayerEnd", "")
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}
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r.context = 0
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}
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return
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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(info DriverInfo, layerID string, parentLayerPaths []string) (LayerReader, error) {
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if procExportLayerBegin.Find() != nil {
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// The new layer reader is not available on this Windows build. Fall back to the
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// legacy export code path.
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path, 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(info, layerID, path, parentLayerPaths)
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if err != nil {
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os.RemoveAll(path)
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return nil, err
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}
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return &legacyLayerReaderWrapper{newLegacyLayerReader(path)}, nil
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}
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layers, err := layerPathsToDescriptors(parentLayerPaths)
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if err != nil {
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return nil, err
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}
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infop, err := convertDriverInfo(info)
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if err != nil {
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return nil, err
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}
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r := &FilterLayerReader{}
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err = exportLayerBegin(&infop, layerID, layers, &r.context)
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if err != nil {
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return nil, makeError(err, "ExportLayerBegin", "")
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}
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return r, err
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}
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type legacyLayerReaderWrapper struct {
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*legacyLayerReader
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}
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func (r *legacyLayerReaderWrapper) Close() error {
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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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