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minio/erasure-waitcloser.go

74 lines
2.1 KiB

/*
* Minio Cloud Storage, (C) 2016 Minio, Inc.
*
* 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 main
import (
"io"
"sync"
)
// waitCloser implements a Closer that blocks until released, this
// prevents the writer closing one end of a pipe while making sure
// that all data is written and committed to disk on the end.
// Additionally this also implements Write().
type waitCloser struct {
wg *sync.WaitGroup // Waitgroup for atomicity.
writer io.WriteCloser // Embedded writer.
}
// Write to the underlying writer.
func (b *waitCloser) Write(data []byte) (int, error) {
return b.writer.Write(data)
}
// Close blocks until another goroutine calls Release(error). Returns
// error code if either writer fails or Release is called with an error.
func (b *waitCloser) Close() error {
err := b.writer.Close()
b.wg.Wait()
return err
}
// CloseWithError closes the writer; subsequent read to the read
// half of the pipe will return the error err.
func (b *waitCloser) CloseWithError(err error) error {
w, ok := b.writer.(*io.PipeWriter)
if ok {
return w.CloseWithError(err)
}
return err
}
// release the Close, causing it to unblock. Only call this
// once. Calling it multiple times results in a panic.
func (b *waitCloser) release() {
b.wg.Done()
return
}
// newWaitCloser creates a new write closer that must be
// released by the read consumer.
func newWaitCloser(writer io.WriteCloser) *waitCloser {
// Wait group for the go-routine.
wg := &sync.WaitGroup{}
// Add to the wait group to wait for.
wg.Add(1)
return &waitCloser{
wg: wg,
writer: writer,
}
}