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Merge pull request #486 from stevvooe/chainid-implementation
identity: add implementation of ChainID
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package: github.com/opencontainers/image-spec | ||
import: | ||
- package: github.com/pkg/errors | ||
version: ">=0.7.0" | ||
version: '>=0.7.0' | ||
- package: github.com/xeipuuv/gojsonschema | ||
version: d5336c75940ef31c9ceeb0ae64cf92944bccb4ee | ||
- package: github.com/russross/blackfriday | ||
version: ~v1.4 | ||
- package: github.com/shurcooL/sanitized_anchor_name | ||
version: 10ef21a441db47d8b13ebcc5fd2310f636973c77 | ||
- package: github.com/opencontainers/go-digest |
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// Copyright 2016 The Linux Foundation | ||
// | ||
// 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. | ||
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// Package identity provides implementations of subtle calculations pertaining | ||
// to image and layer identity. The primary item present here is the ChainID | ||
// calculation used in identifying the result of subsequent layer applications. | ||
// | ||
// Helpers are also provided here to ease transition to the | ||
// github.com/opencontainers/go-digest package, but that package may be used | ||
// directly. | ||
package identity | ||
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import "github.com/opencontainers/go-digest" | ||
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// ChainID takes a slice of digests and returns the ChainID corresponding to | ||
// the last entry. Typically, these are a list of layer DiffIDs, with the | ||
// result providing the ChainID identifying the result of sequential | ||
// application of the preceding layers. | ||
func ChainID(dgsts []digest.Digest) digest.Digest { | ||
chainIDs := make([]digest.Digest, len(dgsts)) | ||
copy(chainIDs, dgsts) | ||
ChainIDs(chainIDs) | ||
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if len(chainIDs) == 0 { | ||
return "" | ||
} | ||
return chainIDs[len(chainIDs)-1] | ||
} | ||
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// ChainIDs calculates the recursively applied chain id for each identifier in | ||
// the slice. The result is written direcly back into the slice such that the | ||
// ChainID for each item will be in the respective position. | ||
// | ||
// By definition of ChainID, the zeroth element will always be the same before | ||
// and after the call. | ||
// | ||
// As an example, given the chain of ids `[A, B, C]`, the result `[A, | ||
// ChainID(A|B), ChainID(A|B|C)]` will be written back to the slice. | ||
// | ||
// The input is provided as a return value for convenience. | ||
// | ||
// Typically, these are a list of layer DiffIDs, with the | ||
// result providing the ChainID for each the result of each layer application | ||
// sequentially. | ||
func ChainIDs(dgsts []digest.Digest) []digest.Digest { | ||
if len(dgsts) < 2 { | ||
return dgsts | ||
} | ||
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parent := digest.FromBytes([]byte(dgsts[0] + " " + dgsts[1])) | ||
next := dgsts[1:] | ||
next[0] = parent | ||
ChainIDs(next) | ||
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return dgsts | ||
} |
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// Copyright 2016 The Linux Foundation | ||
// | ||
// 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. | ||
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package identity | ||
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import ( | ||
_ "crypto/sha256" // required to install sha256 digest support | ||
"reflect" | ||
"testing" | ||
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"github.com/opencontainers/go-digest" | ||
) | ||
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func TestChainID(t *testing.T) { | ||
// To provide a good testing base, we define the individual links in a | ||
// chain recursively, illustrating the calculations for each chain. | ||
// | ||
// Note that we use invalid digests for the unmodified identifiers here to | ||
// make the computation more readable. | ||
chainDigestAB := digest.FromString("sha256:a" + " " + "sha256:b") // chain for A|B | ||
chainDigestABC := digest.FromString(chainDigestAB.String() + " " + "sha256:c") // chain for A|B|C | ||
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for _, testcase := range []struct { | ||
Name string | ||
Digests []digest.Digest | ||
Expected []digest.Digest | ||
}{ | ||
{ | ||
Name: "nil", | ||
}, | ||
{ | ||
Name: "empty", | ||
Digests: []digest.Digest{}, | ||
Expected: []digest.Digest{}, | ||
}, | ||
{ | ||
Name: "identity", | ||
Digests: []digest.Digest{"sha256:a"}, | ||
Expected: []digest.Digest{"sha256:a"}, | ||
}, | ||
{ | ||
Name: "two", | ||
Digests: []digest.Digest{"sha256:a", "sha256:b"}, | ||
Expected: []digest.Digest{"sha256:a", chainDigestAB}, | ||
}, | ||
{ | ||
Name: "three", | ||
Digests: []digest.Digest{"sha256:a", "sha256:b", "sha256:c"}, | ||
Expected: []digest.Digest{"sha256:a", chainDigestAB, chainDigestABC}, | ||
}, | ||
} { | ||
t.Run(testcase.Name, func(t *testing.T) { | ||
t.Log("before", testcase.Digests) | ||
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var ids []digest.Digest | ||
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if testcase.Digests != nil { | ||
ids = make([]digest.Digest, len(testcase.Digests)) | ||
copy(ids, testcase.Digests) | ||
} | ||
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ids = ChainIDs(ids) | ||
t.Log("after", ids) | ||
if !reflect.DeepEqual(ids, testcase.Expected) { | ||
t.Errorf("unexpected chain: %v != %v", ids, testcase.Expected) | ||
} | ||
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if len(testcase.Digests) == 0 { | ||
return | ||
} | ||
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// Make sure parent stays stable | ||
if ids[0] != testcase.Digests[0] { | ||
t.Errorf("parent changed: %v != %v", ids[0], testcase.Digests[0]) | ||
} | ||
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// make sure that the ChainID function takes the last element | ||
id := ChainID(testcase.Digests) | ||
if id != ids[len(ids)-1] { | ||
t.Errorf("incorrect chain id returned from ChainID: %v != %v", id, ids[len(ids)-1]) | ||
} | ||
}) | ||
} | ||
} |
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// Copyright 2016 The Linux Foundation | ||
// | ||
// 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. | ||
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package identity | ||
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import ( | ||
_ "crypto/sha256" // side-effect to install impls, sha256 | ||
_ "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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// FromReader consumes the content of rd until io.EOF, returning canonical | ||
// digest. | ||
func FromReader(rd io.Reader) (digest.Digest, error) { | ||
return digest.Canonical.FromReader(rd) | ||
} | ||
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// FromBytes digests the input and returns a Digest. | ||
func FromBytes(p []byte) digest.Digest { | ||
return digest.Canonical.FromBytes(p) | ||
} | ||
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// FromString digests the input and returns a Digest. | ||
func FromString(s string) digest.Digest { | ||
return digest.Canonical.FromString(s) | ||
} |
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