You are an expert in writing code in many different languages. Your goal is to perform code completion for the following code, keeping in mind the rest of the code and the file meta data.
    Metadata details:
    filename: replace.go
    path of file: ./repos/goreporter/linters/spellcheck/misspell/stringreplacer
    
    the code of the file until where you have to start completion: // Copyright 2011 The Go Authors. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.

package stringreplacer

import (
	"io"
	"log"
	"strings"
)

// Replacer replaces a list of strings with replacements.
// It is safe for concurrent use by multiple goroutines.
type Replacer struct {
	r replacer
}

// replacer is the interface that a replacement algorithm needs to implement.
type replacer interface {
	Replace(s string) string
	WriteString(w io.Writer, s string) (n int, err error)
}

// NewReplacer returns a new Replacer from a list of old, 
    
func (r *genericReplacer) WriteString(w io.Writer, s string) (n int, err error) {
	sw := getStringWriter(w)
	var last, wn int
	var prevMatchEmpty bool
	for i := 0; i <= len(s); {
		// Fast path: s[i] is not a prefix of any pattern.
		if i != len(s) && r.root.priority == 0 {
			index := int(r.mapping[s[i]])
			if index == r.tableSize || r.root.table[index] == nil {
				i++
				continue
			}
		}

		// Ignore the empty match iff the previous loop found the empty match.
		val, keylen, match := r.lookup(s[i:], prevMatchEmpty)
		prevMatchEmpty = match && keylen == 0
		if match {
			wn, err = sw.WriteString(s[last:i])
			n += wn
			if err != nil {
				return
			}
			wn, err = sw.WriteString(val)
			n += wn
			if err != nil {
				return
			}
			i += keylen
			last = i
			continue
		}
		i++
	}
	if last != len(s) {
		wn, err = sw.WriteString(s[last:])
		n += wn
	}
	return
}