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Refactor specification of supported digests

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To make the definition of supported digests more clear, we have refactored the
digest package to have a special Algorithm type. This represents the digest's
prefix and we associated various supported hash implementations through
function calls.

Signed-off-by: Stephen J Day <stephen.day@docker.com>
This commit is contained in:
Stephen J Day 2015-05-21 18:44:08 -07:00
parent eee6cad2cf
commit 44da954565
14 changed files with 109 additions and 66 deletions
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16
digest/digest.go
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@ -2,7 +2,6 @@ package digest
import (
"bytes"
"crypto"
"fmt"
"hash"
"io"
@ -19,9 +18,6 @@ const (
// DigestSha256EmptyTar is the canonical sha256 digest of empty data
DigestSha256EmptyTar = "sha256:e3b0c44298fc1c149afbf4c8996fb92427ae41e4649b934ca495991b7852b855"
CanonicalAlgorithm = "sha256"
CanonicalHash = crypto.SHA256 // main digest algorithm used through distribution
)
// Digest allows simple protection of hex formatted digest strings, prefixed
@ -43,7 +39,7 @@ const (
type Digest string
// NewDigest returns a Digest from alg and a hash.Hash object.
func NewDigest(alg string, h hash.Hash) Digest {
func NewDigest(alg Algorithm, h hash.Hash) Digest {
return Digest(fmt.Sprintf("%s:%x", alg, h.Sum(nil)))
}
@ -76,7 +72,7 @@ func ParseDigest(s string) (Digest, error) {
// FromReader returns the most valid digest for the underlying content.
func FromReader(rd io.Reader) (Digest, error) {
digester := NewCanonicalDigester()
digester := Canonical.New()
if _, err := io.Copy(digester.Hash(), rd); err != nil {
return "", err
@ -135,8 +131,8 @@ func (d Digest) Validate() error {
return ErrDigestInvalidFormat
}
switch s[:i] {
case "sha256", "sha384", "sha512":
switch Algorithm(s[:i]) {
case SHA256, SHA384, SHA512:
break
default:
return ErrDigestUnsupported
@ -147,8 +143,8 @@ func (d Digest) Validate() error {
// Algorithm returns the algorithm portion of the digest. This will panic if
// the underlying digest is not in a valid format.
func (d Digest) Algorithm() string {
return string(d[:d.sepIndex()])
func (d Digest) Algorithm() Algorithm {
return Algorithm(d[:d.sepIndex()])
}
// Hex returns the hex digest portion of the digest. This will panic if the