func (r *ffReader) Reset(d []byte) {
	r.s = d
	r.i = 0
	r.l = len(d)
}
Reset the reader, and add new input.
package v1
import (
	"fmt"
	"io"
	"unicode"
	"unicode/utf16"
)
const sliceStringMask = cIJC | cNFP
type ffReader struct {
	s []byte
	i int
	l int
}
func newffReader(d []byte) *ffReader {
	return &ffReader{
		s: d,
		i: 0,
		l: len(d),
	}
}
func (r *ffReader) Slice(start, stop int) []byte {
	return r.s[start:stop]
}
func (r *ffReader) Pos() int {
	return r.i
}