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The specification defines an algorithm to calculate a `ChainID`, which can be used to identify the result of subsequent applications of layers. Because this algorithm is subtle and only needs to implemented in a single place, we provide a reference implementation. For convenience, we provide functions that calculate all the chain ids and just the top-level one. It is is integrated with the distribution/digest type for safety and convenience. As part of this, the `identity` package has been introduced. For consuming code, a few helpers have been provide to ease transition as the name of the upstream package has not yet been finalized. Users of this package should employ `FromBytes`, `FromString` and `FromReader` where appropriate, which should ease the transition if these packages change. Tests are formulated based on pre-calculation of chain identifiers to ensure correctness. Signed-off-by: Stephen J Day <stephen.day@docker.com>
41 lines
1.2 KiB
Go
41 lines
1.2 KiB
Go
// Copyright 2016 The Linux Foundation
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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 identity
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import (
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_ "crypto/sha256" // side-effect to install impls, sha256
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_ "crypto/sha512" // side-effect to install impls, sha384/sh512
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"io"
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digest "github.com/opencontainers/go-digest"
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)
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// FromReader consumes the content of rd until io.EOF, returning canonical
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// digest.
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func FromReader(rd io.Reader) (digest.Digest, error) {
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return digest.Canonical.FromReader(rd)
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}
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// FromBytes digests the input and returns a Digest.
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func FromBytes(p []byte) digest.Digest {
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return digest.Canonical.FromBytes(p)
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}
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// FromString digests the input and returns a Digest.
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func FromString(s string) digest.Digest {
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return digest.Canonical.FromString(s)
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}
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