kraken

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// Copyright (c) 2016-2019 Uber Technologies, Inc.
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//
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// Licensed under the Apache License, Version 2.0 (the "License");
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// you may not use this file except in compliance with the License.
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// You may obtain a copy of the License at
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//
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//     http://www.apache.org/licenses/LICENSE-2.0
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//
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// Unless required by applicable law or agreed to in writing, software
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// distributed under the License is distributed on an "AS IS" BASIS,
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// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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// See the License for the specific language governing permissions and
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// limitations under the License.
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package core
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import (
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	"crypto"
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	"encoding/hex"
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	"hash"
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	"io"
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)
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const (
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	// SHA256 is the only algorithm supported.
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	SHA256 = "sha256"
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)
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// Digester calculates the digest of data stream.
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type Digester struct {
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	hash hash.Hash
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}
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// NewDigester instantiates and returns a new Digester object.
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func NewDigester() *Digester {
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	return &Digester{
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		hash: crypto.SHA256.New(),
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	}
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}
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// Digest returns the digest of existing data.
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func (d *Digester) Digest() Digest {
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	digest, err := NewSHA256DigestFromHex(hex.EncodeToString(d.hash.Sum(nil)))
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	if err != nil {
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		// This should never fail.
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		panic(err)
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	}
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	return digest
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}
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// FromReader returns the digest of data from reader.
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func (d Digester) FromReader(rd io.Reader) (Digest, error) {
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	if _, err := io.Copy(d.hash, rd); err != nil {
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		return Digest{}, err
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	}
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	return d.Digest(), nil
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}
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// FromBytes digests the input and returns a Digest.
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func (d Digester) FromBytes(p []byte) (Digest, error) {
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	if _, err := d.hash.Write(p); err != nil {
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		return Digest{}, err
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	}
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	return d.Digest(), nil
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}
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// Tee allows d to calculate a digest of r while the caller reads from the
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// returned reader.
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func (d Digester) Tee(r io.Reader) io.Reader {
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	return io.TeeReader(r, d.hash)
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}
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