mirror of https://github.com/containers/image.git
83 lines
2.4 KiB
Go
83 lines
2.4 KiB
Go
package archive
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import (
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"io"
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"os"
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"github.com/containers/image/v5/docker/internal/tarfile"
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"github.com/containers/image/v5/docker/reference"
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"github.com/containers/image/v5/types"
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"github.com/pkg/errors"
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)
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// Writer manages a single in-progress Docker archive and allows adding images to it.
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type Writer struct {
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path string // The original, user-specified path; not the maintained temporary file, if any
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archive *tarfile.Writer
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writer io.Closer
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}
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// NewWriter returns a Writer for path.
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// The caller should call .Close() on the returned object.
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func NewWriter(sys *types.SystemContext, path string) (*Writer, error) {
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fh, err := openArchiveForWriting(path)
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if err != nil {
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return nil, err
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}
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archive := tarfile.NewWriter(fh)
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return &Writer{
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path: path,
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archive: archive,
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writer: fh,
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}, nil
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}
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// Close writes all outstanding data about images to the archive, and
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// releases state associated with the Writer, if any.
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// No more images can be added after this is called.
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func (w *Writer) Close() error {
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err := w.archive.Close()
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if err2 := w.writer.Close(); err2 != nil && err == nil {
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err = err2
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}
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return err
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}
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// NewReference returns an ImageReference that allows adding an image to Writer,
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// with an optional reference.
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func (w *Writer) NewReference(destinationRef reference.NamedTagged) (types.ImageReference, error) {
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return newReference(w.path, destinationRef, -1, nil, w.archive)
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}
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// openArchiveForWriting opens path for writing a tar archive,
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// making a few sanity checks.
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func openArchiveForWriting(path string) (*os.File, error) {
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// path can be either a pipe or a regular file
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// in the case of a pipe, we require that we can open it for write
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// in the case of a regular file, we don't want to overwrite any pre-existing file
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// so we check for Size() == 0 below (This is racy, but using O_EXCL would also be racy,
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// only in a different way. Either way, it’s up to the user to not have two writers to the same path.)
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fh, err := os.OpenFile(path, os.O_WRONLY|os.O_CREATE, 0644)
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if err != nil {
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return nil, errors.Wrapf(err, "error opening file %q", path)
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}
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succeeded := false
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defer func() {
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if !succeeded {
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fh.Close()
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}
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}()
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fhStat, err := fh.Stat()
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if err != nil {
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return nil, errors.Wrapf(err, "error statting file %q", path)
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}
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if fhStat.Mode().IsRegular() && fhStat.Size() != 0 {
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return nil, errors.New("docker-archive doesn't support modifying existing images")
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}
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succeeded = true
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return fh, nil
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}
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