mirror of
https://github.com/ko-build/ko.git
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76 lines
1.9 KiB
Go
76 lines
1.9 KiB
Go
// Copyright 2018 Google LLC All Rights Reserved.
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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 publish
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import (
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"sync"
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"github.com/google/go-containerregistry/pkg/name"
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)
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func newFuture(work func() (name.Reference, error)) *future {
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// Create a channel on which to send the result.
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ch := make(chan *result)
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// Initiate the actual work, sending its result
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// along the above channel.
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go func() {
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ref, err := work()
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ch <- &result{ref: ref, err: err}
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}()
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// Return a future for the above work. Callers should
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// call .Get() on this result (as many times as needed).
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// One of these calls will receive the result, store it,
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// and close the channel so that the rest of the callers
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// can consume it.
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return &future{
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promise: ch,
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}
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}
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type result struct {
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ref name.Reference
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err error
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}
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type future struct {
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m sync.RWMutex
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result *result
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promise chan *result
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}
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// Get blocks on the result of the future.
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func (f *future) Get() (name.Reference, error) {
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// Block on the promise of a result until we get one.
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result, ok := <-f.promise
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if ok {
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func() {
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f.m.Lock()
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defer f.m.Unlock()
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// If we got the result, then store it so that
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// others may access it.
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f.result = result
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// Close the promise channel so that others
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// are signaled that the result is available.
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close(f.promise)
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}()
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}
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f.m.RLock()
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defer f.m.RUnlock()
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return f.result.ref, f.result.err
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}
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