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// Copyright 2009 The Go Authors. All rights reserved.

// Use of this source code is governed by a BSD-style

// license that can be found in the LICENSE file.

package iotest

import "io"

// TruncateWriter returns a Writer that writes to w

// but stops silently after n bytes.

func TruncateWriter(w io.Writer, n int64) io.Writer {

        return &truncateWriter{w, n}

}

type truncateWriter struct {

        w io.Writer

        n int64

}

func (t *truncateWriter) Write(p []byte) (n int, err error) {

        if t.n <= 0 {

                return len(p), nil

        }

        // real write

        n = len(p)

        if int64(n) > t.n {

                n = int(t.n)

        }

        n, err = t.w.Write(p[0:n])

        t.n -= int64(n)

        if err == nil {

                n = len(p)

        }

        return

}