Cloudpods/backend/pkg/util/ioutils/ioutils.go

// Copyright 2019 Yunion
//
// 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.

/*
Copyright 2015 The Kubernetes 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 ioutils

import "io"

// LimitWriter is a copy of the standard library ioutils.LimitReader,
// applied to the writer interface.
// LimitWriter returns a Writer that writes to w
// but stops with EOF after n bytes.
// The underlying implementation is a *LimitedWriter.
func LimitWriter(w io.Writer, n int64) io.Writer { return &LimitedWriter{w, n} }

// A LimitedWriter writes to W but limits the amount of
// data returned to just N bytes. Each call to Write
// updates N to reflect the new amount remaining.
// Write returns EOF when N <= 0 or when the underlying W returns EOF.
type LimitedWriter struct {
	W io.Writer // underlying writer
	N int64     // max bytes remaining
}

func (l *LimitedWriter) Write(p []byte) (n int, err error) {
	if l.N <= 0 {
		return 0, io.ErrShortWrite
	}
	truncated := false
	if int64(len(p)) > l.N {
		p = p[0:l.N]
		truncated = true
	}
	n, err = l.W.Write(p)
	l.N -= int64(n)
	if err == nil && truncated {
		err = io.ErrShortWrite
	}
	return
}