// Because the data returned from ReadSlice will be overwritten
// by the next I/O operation, most clients should use
// [Reader.ReadBytes] or ReadString instead.
// ReadSlice returns err != nil if and only if line does not end in delim.
func (b *Reader) ReadSlice(delim byte) (line []byte, err error) {
	s := 0 // search start index
	for {
		// Search buffer.