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56 lines
2.2 KiB
56 lines
2.2 KiB
// Copyright 2017 Docker, 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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// https://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 digest provides a generalized type to opaquely represent message |
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// digests and their operations within the registry. The Digest type is |
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// designed to serve as a flexible identifier in a content-addressable system. |
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// More importantly, it provides tools and wrappers to work with |
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// hash.Hash-based digests with little effort. |
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// |
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// Basics |
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// |
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// The format of a digest is simply a string with two parts, dubbed the |
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// "algorithm" and the "digest", separated by a colon: |
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// |
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// <algorithm>:<digest> |
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// |
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// An example of a sha256 digest representation follows: |
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// |
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// sha256:7173b809ca12ec5dee4506cd86be934c4596dd234ee82c0662eac04a8c2c71dc |
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// |
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// In this case, the string "sha256" is the algorithm and the hex bytes are |
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// the "digest". |
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// |
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// Because the Digest type is simply a string, once a valid Digest is |
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// obtained, comparisons are cheap, quick and simple to express with the |
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// standard equality operator. |
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// |
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// Verification |
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// |
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// The main benefit of using the Digest type is simple verification against a |
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// given digest. The Verifier interface, modeled after the stdlib hash.Hash |
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// interface, provides a common write sink for digest verification. After |
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// writing is complete, calling the Verifier.Verified method will indicate |
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// whether or not the stream of bytes matches the target digest. |
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// |
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// Missing Features |
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// |
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// In addition to the above, we intend to add the following features to this |
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// package: |
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// |
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// 1. A Digester type that supports write sink digest calculation. |
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// |
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// 2. Suspend and resume of ongoing digest calculations to support efficient digest verification in the registry. |
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// |
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package digest
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