Source file src/pkg/testing/iotest/writer.go

     1	// Copyright 2009 The Go Authors. All rights reserved.
     2	// Use of this source code is governed by a BSD-style
     3	// license that can be found in the LICENSE file.
     4	
     5	package iotest
     6	
     7	import "io"
     8	
     9	// TruncateWriter returns a Writer that writes to w
    10	// but stops silently after n bytes.
    11	func TruncateWriter(w io.Writer, n int64) io.Writer {
    12		return &truncateWriter{w, n}
    13	}
    14	
    15	type truncateWriter struct {
    16		w io.Writer
    17		n int64
    18	}
    19	
    20	func (t *truncateWriter) Write(p []byte) (n int, err error) {
    21		if t.n <= 0 {
    22			return len(p), nil
    23		}
    24		// real write
    25		n = len(p)
    26		if int64(n) > t.n {
    27			n = int(t.n)
    28		}
    29		n, err = t.w.Write(p[0:n])
    30		t.n -= int64(n)
    31		if err == nil {
    32			n = len(p)
    33		}
    34		return
    35	}