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minio/pkg/ioutil/ioutil.go

61 lines
1.7 KiB

/*
* Minio Cloud Storage, (C) 2017 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 ioutil implements some I/O utility functions which are not covered
// by the standard library.
package ioutil
import (
"io"
)
// WriteOnCloser implements io.WriteCloser and always
// exectues at least one write operation if it is closed.
//
// This can be useful within the context of HTTP. At least
// one write operation must happen to send the HTTP headers
// to the peer.
type WriteOnCloser struct {
io.Writer
hasWritten bool
}
func (w *WriteOnCloser) Write(p []byte) (int, error) {
w.hasWritten = true
return w.Writer.Write(p)
}
// Close closes the WriteOnCloser. It behaves like io.Closer.
func (w *WriteOnCloser) Close() error {
if !w.hasWritten {
_, err := w.Write(nil)
if err != nil {
return err
}
}
if closer, ok := w.Writer.(io.Closer); ok {
return closer.Close()
}
return nil
}
// HasWritten returns true if at least one write operation was performed.
func (w *WriteOnCloser) HasWritten() bool { return w.hasWritten }
// WriteOnClose takes an io.Writer and returns an ioutil.WriteOnCloser.
func WriteOnClose(w io.Writer) *WriteOnCloser {
return &WriteOnCloser{w, false}
}