Golang regexp vs strings.Map

bench

bash-3.2$ go test -bench=.
PASS
BenchmarkRegexReplace-4   500000              2470 ns/op          19.83 MB/s         113 B/op          1 allocs/op
BenchmarkMapReplace-4    2000000               813 ns/op          60.22 MB/s           0 B/op          0 allocs/op

main.go

package main

import (
	"regexp"
	"strings"
	"unicode"
)

var topicRegex, _ = regexp.Compile("[^A-Za-z0-9-_.~% ]+")

func regexReplace(str string) string {
	return topicRegex.ReplaceAllLiteralString(str, "")
}

func mapReplace(str string) string {
	return strings.Map(func(r rune) rune {
		if isValidTopicRune(r) {
			return r
		}
		return -1
	}, str)
}

func isValidTopicRune(r rune) bool {
	isDash := r == rune('-')
	isUnderscore := r == rune('_')
	isDot := r == rune('.')
	isTilde := r == rune('~')
	isPercent := r == rune('%')
	return unicode.IsLetter(r) || unicode.IsNumber(r) || unicode.IsSpace(r) || isDash || isUnderscore || isDot || isTilde || isPercent
}

main_test.go

package main

import (
	"math/rand"
	"testing"
	"time"
)

var testString = "Res Proposal In A....H.!@#$%[]^&*()_?><.02.87A\u0000SDA"
var expected = "Res Proposal In A....H.%_.02.87ASDA"

func Test_regexReplace(t *testing.T) {
	type args struct {
		str string
	}
	tests := []struct {
		name string
		args args
		want string
	}{
		{args: args{testString}, want: expected},
	}
	for _, tt := range tests {
		if got := regexReplace(tt.args.str); got != tt.want {
			t.Errorf("%q. regexReplace() = %v, want %v", tt.name, got, tt.want)
		}
	}
}

func Test_mapReplace(t *testing.T) {
	type args struct {
		str string
	}
	tests := []struct {
		name string
		args args
		want string
	}{
		{args: args{testString}, want: expected},
	}
	for _, tt := range tests {
		if got := mapReplace(tt.args.str); got != tt.want {
			t.Errorf("%q. mapReplace() = %v, want %v", tt.name, got, tt.want)
		}
	}
}

func BenchmarkRegexReplace(b *testing.B) {
	seed := time.Now().UnixNano()
	popr := rand.New(rand.NewSource(seed))
	total := 0
	pops := make([]string, 10000)
	for i := 0; i < 10000; i++ {
		pops[i] = randStringModel(popr)
	}

	b.ReportAllocs()
	b.ResetTimer()
	for i := 0; i < b.N; i++ {
		total += len(regexReplace(pops[i%10000]))
	}
	b.SetBytes(int64(total / b.N))
}

func BenchmarkMapReplace(b *testing.B) {
	popr := rand.New(rand.NewSource(0))
	total := 0
	pops := make([]string, 10000)
	for i := 0; i < 10000; i++ {
		pops[i] = randStringModel(popr)
	}

	b.ReportAllocs()
	b.ResetTimer()
	for i := 0; i < b.N; i++ {
		total += len(mapReplace(pops[i%10000]))
	}
	b.SetBytes(int64(total / b.N))
}

type randyModel interface {
	Float32() float32
	Float64() float64
	Int63() int64
	Int31() int32
	Uint32() uint32
	Intn(n int) int
}

func randStringModel(r randyModel) string {
	v32 := r.Intn(100)
	tmps := make([]rune, v32)
	for i := 0; i < v32; i++ {
		tmps[i] = randUTF8RuneModel(r)
	}
	return string(tmps)
}

func randUTF8RuneModel(r randyModel) rune {
	ru := r.Intn(62)
	if ru < 10 {
		return rune(ru + 48)
	} else if ru < 36 {
		return rune(ru + 55)
	}
	return rune(ru + 61)
}