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// Copyright 2012-2019 the u-root Authors. All rights reserved
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.
// Discard implementation copied from the Go project:
// https://golang.org/src/io/ioutil/ioutil.go.
// Copyright 2009 The Go Authors. All rights reserved.
package uio
import (
"io"
"sync"
)
// devNull implements an io.Writer and io.ReaderFrom that discards any writes.
type devNull struct{}
// devNull implements ReaderFrom as an optimization so io.Copy to
// ioutil.Discard can avoid doing unnecessary work.
var _ io.ReaderFrom = devNull{}
// Write is an io.Writer.Write that discards data.
func (devNull) Write(p []byte) (int, error) {
return len(p), nil
}
// Name is like os.File.Name() and returns "null".
func (devNull) Name() string {
return "null"
}
// WriteString implements io.StringWriter and discards given data.
func (devNull) WriteString(s string) (int, error) {
return len(s), nil
}
var blackHolePool = sync.Pool{
New: func() interface{} {
b := make([]byte, 8192)
return &b
},
}
// ReadFrom implements io.ReaderFrom and discards data being read.
func (devNull) ReadFrom(r io.Reader) (n int64, err error) {
bufp := blackHolePool.Get().(*[]byte)
var readSize int
for {
readSize, err = r.Read(*bufp)
n += int64(readSize)
if err != nil {
blackHolePool.Put(bufp)
if err == io.EOF {
return n, nil
}
return
}
}
}
// Close does nothing.
func (devNull) Close() error {
return nil
}
// WriteNameCloser is the interface that groups Write, Close, and Name methods.
type WriteNameCloser interface {
io.Writer
io.Closer
Name() string
}
// Discard is a WriteNameCloser on which all Write and Close calls succeed
// without doing anything, and the Name call returns "null".
var Discard WriteNameCloser = devNull{}
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