1 /* 2 Copyright 2016 The Kubernetes Authors. 3 4 Licensed under the Apache License, Version 2.0 (the "License"); 5 you may not use this file except in compliance with the License. 6 You may obtain a copy of the License at 7 8 http://www.apache.org/licenses/LICENSE-2.0 9 10 Unless required by applicable law or agreed to in writing, software 11 distributed under the License is distributed on an "AS IS" BASIS, 12 WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 13 See the License for the specific language governing permissions and 14 limitations under the License. 15 */ 16 17 package ioutils 18 19 import "io" 20 21 // LimitWriter is a copy of the standard library ioutils.LimitReader, 22 // applied to the writer interface. 23 // LimitWriter returns a Writer that writes to w 24 // but stops with EOF after n bytes. 25 // The underlying implementation is a *LimitedWriter. 26 func LimitWriter(w io.Writer, n int64) io.Writer { return &LimitedWriter{w, n} } 27 28 // A LimitedWriter writes to W but limits the amount of 29 // data returned to just N bytes. Each call to Write 30 // updates N to reflect the new amount remaining. 31 // Write returns EOF when N <= 0 or when the underlying W returns EOF. 32 type LimitedWriter struct { 33 W io.Writer // underlying writer 34 N int64 // max bytes remaining 35 } 36 37 func (l *LimitedWriter) Write(p []byte) (n int, err error) { 38 if l.N <= 0 { 39 return 0, io.ErrShortWrite 40 } 41 truncated := false 42 if int64(len(p)) > l.N { 43 p = p[0:l.N] 44 truncated = true 45 } 46 n, err = l.W.Write(p) 47 l.N -= int64(n) 48 if err == nil && truncated { 49 err = io.ErrShortWrite 50 } 51 return 52 } 53