regex-vs-contains_test.go

package main

import (
	"bytes"
	"fmt"
	"regexp"
	"strings"
	"testing"
)

const (
	str1 = "aaaa"
	str2 = "bbbb"
)

var inputs = buildInputs("aaax", []string{str1, str2}, 128, 256, 512, 8192, 32768)

var matched bool

func BenchmarkRegex(b *testing.B) {
	re := regexp.MustCompile("(" + str1 + "|" + str2 + ")")

	b.ResetTimer()

	for name, input := range inputs {
		b.Run(name, func(b *testing.B) {
			for i := 0; i < b.N; i++ {
				if re.Match(input) {
					matched = true
				}
			}
		})
	}
}

func BenchmarkByteContains(b *testing.B) {
	for name, input := range inputs {
		b.Run(name, func(b *testing.B) {
			for i := 0; i < b.N; i++ {
				if bytes.Contains(input, []byte(str1)) || bytes.Contains(input, []byte(str2)) {
					matched = true
				}
			}
		})
	}
}

func gen(str string, n int) string {
	var b strings.Builder

	for i := 0; i < n; i++ {
		b.WriteString(str)
	}

	return b.String()
}

func buildInputs(junk string, needles []string, prefixLens ...int) map[string][]byte {
	inputs := make(map[string][]byte)

	for _, pl := range prefixLens {
		for _, str := range needles {
			prefix := gen(junk, pl/len(junk))
			name := fmt.Sprintf("prefix %d + %s", len(prefix), str)
			inputs[name] = []byte(prefix + str)
		}
	}

	return inputs
}