func HardLimitReader(r io.Reader, n int64) io.Reader { return &HardLimitedReader{r, n} }

// A HardLimitedReader reads from R but limits the amount of
// data returned to just N bytes. Each call to Read
// updates N to reflect the new amount remaining.
// Read returns EOF when N <= 0 or when the underlying R returns EOF.
type HardLimitedReader struct {
	R io.Reader // underlying reader