forked from cilium/cilium
/
sha1.go
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/
sha1.go
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// Copyright 2019 Authors of Cilium
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
package sha1
import (
"crypto/sha1"
"encoding"
"encoding/hex"
"fmt"
"hash"
)
// ResumableHash is the intefrace for a hash that can be stored and copied.
//
// Unlike hash implementations in the standard library, it does not implement
// the encoding.BinaryMarshaler and encoding.BinaryUnmarshaler interfaces;
// however, it does provide a method for creating a copy of the underlying
// hash. This allows the hash to be stored, duplicated, and resumed at a later
// time. For convenience, it also provides a standard method for converting
// the hash into a string.
type ResumableHash interface {
hash.Hash
fmt.Stringer
Copy() (ResumableHash, error)
}
// digest is a wrapper for the standard sha1 library which implements
// ResumableHash.
type digest struct {
hash.Hash
}
// New returns a new ResumableHash computing the SHA1 checksum.
func New() ResumableHash {
return &digest{
sha1.New(),
}
}
// Copy duplicates the hash and returns the copy.
func (d *digest) Copy() (ResumableHash, error) {
newHash := hash.Hash(sha1.New())
state, err := d.Hash.(encoding.BinaryMarshaler).MarshalBinary()
if err != nil {
return nil, err
}
if err := newHash.(encoding.BinaryUnmarshaler).UnmarshalBinary(state); err != nil {
return nil, err
}
return &digest{
newHash,
}, nil
}
// String returns a string representation of the underlying hash.
func (d *digest) String() string {
return hex.EncodeToString(d.Sum(nil))
}