containerd/content/helpers.go

54 lines
1.2 KiB
Go
Raw Normal View History

package content
import (
"io"
"os"
"github.com/docker/distribution/digest"
"github.com/pkg/errors"
)
// OpenBlob opens the blob for reading identified by dgst.
//
// The opened blob may also implement seek. Callers can detect with io.Seeker.
func OpenBlob(cs *ContentStore, dgst digest.Digest) (io.ReadCloser, error) {
path, err := cs.GetPath(dgst)
if err != nil {
return nil, err
}
fp, err := os.Open(path)
return fp, err
}
// WriteBlob writes data with the expected digest into the content store. If
// expected already exists, the method returns immediately and the reader will
// not be consumed.
//
// This is useful when the digest and size are known beforehand.
//
// Copy is buffered, so no need to wrap reader in buffered io.
func WriteBlob(cs *ContentStore, r io.Reader, size int64, expected digest.Digest) error {
cw, err := cs.Begin(expected.Hex())
if err != nil {
return err
}
buf := bufPool.Get().([]byte)
defer bufPool.Put(buf)
nn, err := io.CopyBuffer(cw, r, buf)
if err != nil {
return err
}
if nn != size {
return errors.Errorf("failed size verification: %v != %v", nn, size)
}
if err := cw.Commit(size, expected); err != nil {
return err
}
return nil
}