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Remove digest package's dependency on external sha implementation

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The change relies on a refactor of the upstream resumable sha256/sha512 package
that opts to register implementations with the standard library. This allows
the resumable support to be detected where it matters, avoiding unnecessary and
complex code. It also ensures that consumers of the digest package don't need
to depend on the forked sha implementations.

We also get an optimization with this change. If the size of data written to a
digester is the same as the file size, we check to see if the digest has been
verified. This works if the blob is written and committed in a single request.

Signed-off-by: Stephen J Day <stephen.day@docker.com>
This commit is contained in:
Stephen J Day 2015-05-20 23:44:08 -07:00
parent 07ff029506
commit eee6cad2cf
32 changed files with 431 additions and 459 deletions
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54
digest/digester.go
View file

@ -1,54 +1,40 @@
package digest
import (
"crypto/sha256"
"hash"
)
import "hash"
// Digester calculates the digest of written data. It is functionally
// equivalent to hash.Hash but provides methods for returning the Digest type
// rather than raw bytes.
type Digester struct {
alg string
hash.Hash
// Digester calculates the digest of written data. Writes should go directly
// to the return value of Hash, while calling Digest will return the current
// value of the digest.
type Digester interface {
Hash() hash.Hash // provides direct access to underlying hash instance.
Digest() Digest
}
// NewDigester create a new Digester with the given hashing algorithm and instance
// of that algo's hasher.
// NewDigester create a new Digester with the given hashing algorithm and
// instance of that algo's hasher.
func NewDigester(alg string, h hash.Hash) Digester {
return Digester{
return &digester{
alg: alg,
Hash: h,
hash: h,
}
}
// NewCanonicalDigester is a convenience function to create a new Digester with
// our default settings.
func NewCanonicalDigester() Digester {
return NewDigester("sha256", sha256.New())
return NewDigester(CanonicalAlgorithm, CanonicalHash.New())
}
// Digest returns the current digest for this digester.
func (d *Digester) Digest() Digest {
return NewDigest(d.alg, d.Hash)
// digester provides a simple digester definition that embeds a hasher.
type digester struct {
alg string
hash hash.Hash
}
// ResumableHash is the common interface implemented by all resumable hash
// functions.
type ResumableHash interface {
// ResumableHash is a superset of hash.Hash
hash.Hash
// Len returns the number of bytes written to the Hash so far.
Len() uint64
// State returns a snapshot of the state of the Hash.
State() ([]byte, error)
// Restore resets the Hash to the given state.
Restore(state []byte) error
func (d *digester) Hash() hash.Hash {
return d.hash
}
// ResumableDigester is a digester that can export its internal state and be
// restored from saved state.
type ResumableDigester interface {
ResumableHash
Digest() Digest
func (d *digester) Digest() Digest {
return NewDigest(d.alg, d.Hash())
}