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package limio

import "io"

type limitedWriter struct {
	W io.Writer
	N int64
}

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

// LimitWriter works like io.LimitReader. It writes at most n bytes
// to the underlying Writer. It returns io.ErrShortWrite if more than n
// bytes are attempted to be written.
func LimitWriter(w io.Writer, n int64) io.Writer {
	return &limitedWriter{W: w, N: n}
}