132 lines
3.2 KiB
Go
132 lines
3.2 KiB
Go
package digest
|
|
|
|
import (
|
|
"crypto"
|
|
"hash"
|
|
"io"
|
|
)
|
|
|
|
// Algorithm identifies and implementation of a digester by an identifier.
|
|
// Note the that this defines both the hash algorithm used and the string
|
|
// encoding.
|
|
type Algorithm string
|
|
|
|
// supported digest types
|
|
const (
|
|
SHA256 Algorithm = "sha256" // sha256 with hex encoding
|
|
SHA384 Algorithm = "sha384" // sha384 with hex encoding
|
|
SHA512 Algorithm = "sha512" // sha512 with hex encoding
|
|
|
|
// Canonical is the primary digest algorithm used with the distribution
|
|
// project. Other digests may be used but this one is the primary storage
|
|
// digest.
|
|
Canonical = SHA256
|
|
)
|
|
|
|
var (
|
|
// TODO(stevvooe): Follow the pattern of the standard crypto package for
|
|
// registration of digests. Effectively, we are a registerable set and
|
|
// common symbol access.
|
|
|
|
// algorithms maps values to hash.Hash implementations. Other algorithms
|
|
// may be available but they cannot be calculated by the digest package.
|
|
algorithms = map[Algorithm]crypto.Hash{
|
|
SHA256: crypto.SHA256,
|
|
SHA384: crypto.SHA384,
|
|
SHA512: crypto.SHA512,
|
|
}
|
|
)
|
|
|
|
// Available returns true if the digest type is available for use. If this
|
|
// returns false, New and Hash will return nil.
|
|
func (a Algorithm) Available() bool {
|
|
h, ok := algorithms[a]
|
|
if !ok {
|
|
return false
|
|
}
|
|
|
|
// check availability of the hash, as well
|
|
return h.Available()
|
|
}
|
|
|
|
func (a Algorithm) String() string {
|
|
return string(a)
|
|
}
|
|
|
|
// Size returns number of bytes returned by the hash.
|
|
func (a Algorithm) Size() int {
|
|
h, ok := algorithms[a]
|
|
if !ok {
|
|
return 0
|
|
}
|
|
return h.Size()
|
|
}
|
|
|
|
// Set implemented to allow use of Algorithm as a command line flag.
|
|
func (a *Algorithm) Set(value string) error {
|
|
if value == "" {
|
|
*a = Canonical
|
|
} else {
|
|
// just do a type conversion, support is queried with Available.
|
|
*a = Algorithm(value)
|
|
}
|
|
|
|
return nil
|
|
}
|
|
|
|
// New returns a new digester for the specified algorithm. If the algorithm
|
|
// does not have a digester implementation, nil will be returned. This can be
|
|
// checked by calling Available before calling New.
|
|
func (a Algorithm) New() Digester {
|
|
return &digester{
|
|
alg: a,
|
|
hash: a.Hash(),
|
|
}
|
|
}
|
|
|
|
// Hash returns a new hash as used by the algorithm. If not available, nil is
|
|
// returned. Make sure to check Available before calling.
|
|
func (a Algorithm) Hash() hash.Hash {
|
|
if !a.Available() {
|
|
return nil
|
|
}
|
|
|
|
return algorithms[a].New()
|
|
}
|
|
|
|
// FromReader returns the digest of the reader using the algorithm.
|
|
func (a Algorithm) FromReader(rd io.Reader) (Digest, error) {
|
|
digester := a.New()
|
|
|
|
if _, err := io.Copy(digester.Hash(), rd); err != nil {
|
|
return "", err
|
|
}
|
|
|
|
return digester.Digest(), nil
|
|
}
|
|
|
|
// TODO(stevvooe): Allow resolution of verifiers using the digest type and
|
|
// this registration system.
|
|
|
|
// 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
|
|
}
|
|
|
|
// digester provides a simple digester definition that embeds a hasher.
|
|
type digester struct {
|
|
alg Algorithm
|
|
hash hash.Hash
|
|
}
|
|
|
|
func (d *digester) Hash() hash.Hash {
|
|
return d.hash
|
|
}
|
|
|
|
func (d *digester) Digest() Digest {
|
|
return NewDigest(d.alg, d.hash)
|
|
}
|