// NewDigestVerifier returns a verifier that compares the written bytes
// against a passed in digest.
func NewDigestVerifier(d Digest) (Verifier, error) {
if err := d.Validate(); err != nil {
return nil, err
}
alg := d.Algorithm()
switch alg {
case "sha256", "sha384", "sha512":
return hashVerifier{
hash: alg.Hash(),
digest: d,
}, nil
default:
// Assume we have a tarsum.
version, err := tarsum.GetVersionFromTarsum(string(d))
if err != nil {
return nil, err
}
pr, pw := io.Pipe()
// TODO(stevvooe): We may actually want to ban the earlier versions of
// tarsum. That decision may not be the place of the verifier.
ts, err := tarsum.NewTarSum(pr, true, version)
if err != nil {
return nil, err
}
// TODO(sday): Ick! A goroutine per digest verification? We'll have to
// get the tarsum library to export an io.Writer variant.
go func() {
if _, err := io.Copy(ioutil.Discard, ts); err != nil {
pr.CloseWithError(err)
} else {
pr.Close()
}
}()
return &tarsumVerifier{
digest: d,
ts: ts,
pr: pr,
pw: pw,
}, nil
}
}
// FromTarArchive produces a tarsum digest from reader rd.
func FromTarArchive(rd io.Reader) (Digest, error) {
ts, err := tarsum.NewTarSum(rd, true, tarsum.Version1)
if err != nil {
return "", err
}
if _, err := io.Copy(ioutil.Discard, ts); err != nil {
return "", err
}
d, err := ParseDigest(ts.Sum(nil))
if err != nil {
return "", err
}
return d, nil
}