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package limitwriter
import (
"errors"
"io"
)
var ErrWriteLimitExceeded = errors.New("write limit exceeded")
type limitWriter struct {
w io.Writer
limit int64
written int64
}
func New(w io.Writer, n int64) io.Writer {
return &limitWriter{w: w, limit: n}
}
func (w *limitWriter) Write(p []byte) (n int, err error) {
capacity := w.limit - w.written
if capacity <= 0 {
return 0, io.ErrShortWrite
}
if int64(len(p)) > capacity {
n, err = w.w.Write(p[:capacity])
if err == nil {
err = ErrWriteLimitExceeded
}
} else {
n, err = w.w.Write(p)
}
if n < 0 {
n = 0
}
w.written += int64(n)
return n, err
}
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