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// Copyright 2021 The gVisor Authors.
//
// 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 sync
// WaitGroupErr is similar to WaitGroup but allows goroutines to report error.
// Only the first error is retained and reported back.
//
// Example usage:
// wg := WaitGroupErr{}
// wg.Add(1)
// go func() {
// defer wg.Done()
// if err := ...; err != nil {
// wg.ReportError(err)
// return
// }
// }()
// return wg.Error()
//
type WaitGroupErr struct {
WaitGroup
// mu protects firstErr.
mu Mutex
// firstErr holds the first error reported. nil is no error occurred.
firstErr error
}
// ReportError reports an error. Note it does not call Done().
func (w *WaitGroupErr) ReportError(err error) {
w.mu.Lock()
defer w.mu.Unlock()
if w.firstErr == nil {
w.firstErr = err
}
}
// Error waits for the counter to reach 0 and returns the first reported error
// if any.
func (w *WaitGroupErr) Error() error {
w.Wait()
w.mu.Lock()
defer w.mu.Unlock()
return w.firstErr
}
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