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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
}