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registry/storage: clean up zero-length blob comments

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A previous inspection of the code surrounding zero-length blobs led to
some interesting question. After inspection, it was found that the hash
was indeed for the empty string (""), and not an empty tar, so the code
was correct. The variable naming and comments have been updated
accordingly.

Signed-off-by: Stephen J Day <stephen.day@docker.com>
This commit is contained in:
Stephen J Day 2017-01-27 14:47:45 -08:00
parent 545102ea07
commit 7f565ed65a
No known key found for this signature in database
GPG key ID: 67B3DED84EDC823F
2 changed files with 6 additions and 6 deletions
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2
registry/storage/blob_test.go
View file

@ -530,7 +530,7 @@ func TestLayerUploadZeroLength(t *testing.T) {
}
bs := repository.Blobs(ctx)
simpleUpload(t, bs, []byte{}, digestSha256EmptyTar)
simpleUpload(t, bs, []byte{}, digestSha256Empty)
}
func simpleUpload(t *testing.T, bs distribution.BlobIngester, blob []byte, expectedDigest digest.Digest) {

10
registry/storage/blobwriter.go
View file

@ -19,8 +19,8 @@ var (
)
const (
// DigestSha256EmptyTar is the canonical sha256 digest of empty data
digestSha256EmptyTar = "sha256:e3b0c44298fc1c149afbf4c8996fb92427ae41e4649b934ca495991b7852b855"
// digestSha256Empty is the canonical sha256 digest of empty data
digestSha256Empty = "sha256:e3b0c44298fc1c149afbf4c8996fb92427ae41e4649b934ca495991b7852b855"
)
// blobWriter is used to control the various aspects of resumable
@ -314,7 +314,7 @@ func (bw *blobWriter) moveBlob(ctx context.Context, desc distribution.Descriptor
// If no data was received, we may not actually have a file on disk. Check
// the size here and write a zero-length file to blobPath if this is the
// case. For the most part, this should only ever happen with zero-length
// tars.
// blobs.
if _, err := bw.blobStore.driver.Stat(ctx, bw.path); err != nil {
switch err := err.(type) {
case storagedriver.PathNotFoundError:
@ -322,8 +322,8 @@ func (bw *blobWriter) moveBlob(ctx context.Context, desc distribution.Descriptor
// get a hash, then the underlying file is deleted, we risk moving
// a zero-length blob into a nonzero-length blob location. To
// prevent this horrid thing, we employ the hack of only allowing
// to this happen for the digest of an empty tar.
if desc.Digest == digestSha256EmptyTar {
// to this happen for the digest of an empty blob.
if desc.Digest == digestSha256Empty {
return bw.blobStore.driver.PutContent(ctx, blobPath, []byte{})
}