mirror of https://github.com/k3s-io/k3s
68 lines
2.4 KiB
Go
68 lines
2.4 KiB
Go
// 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.
|
|
|
|
// 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
|
|
|
|
import "github.com/opencontainers/go-digest"
|
|
|
|
// 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)
|
|
|
|
if len(chainIDs) == 0 {
|
|
return ""
|
|
}
|
|
return chainIDs[len(chainIDs)-1]
|
|
}
|
|
|
|
// 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
|
|
}
|
|
|
|
parent := digest.FromBytes([]byte(dgsts[0] + " " + dgsts[1]))
|
|
next := dgsts[1:]
|
|
next[0] = parent
|
|
ChainIDs(next)
|
|
|
|
return dgsts
|
|
}
|