// by the standard library.
package ioutil

import (
	"errors"
	"io"
)

// ErrOverread is returned to the reader when the hard limit of HardLimitReader is exceeded.
var ErrOverread = errors.New("input provided more bytes than specified")

// HardLimitReader returns a Reader that reads from r
// but returns an error if the source provides more data than allowed.

// Calling Close on this will close upstream.
func NewChecker(rc io.ReadCloser, h hash.Hash, wantSum []byte, length int64) *Checker {
	return &Checker{c: rc, r: ioutil.HardLimitReader(rc, length), h: h, want: wantSum}
}

// Read satisfies io.Reader
func (c Checker) Read(p []byte) (n int, err error) {
	n, err = c.r.Read(p)
	if n > 0 {
		c.h.Write(p[:n])
	}
	if errors.Is(err, io.EOF) {