string bench

string_bench_test.go

package main

import (
	"bytes"
	"fmt"
	"math"
	"strconv"
	"strings"
	"sync"
	"testing"
)

var bufPool = sync.Pool{
	New: func() interface{} { return new(bytes.Buffer) },
}

type benchFunc func(i int64) []byte
type benchFuncString func(i int64) string

func BenchmarkStringBuild(t *testing.B) {
	exp := "9223372036854775807-9223372036854775807-9223372036854775807"

	casesByte := map[string]benchFunc{
		"strconv.AppendInt": func(i int64) []byte {
			b := make([]byte, 0, 8*3+2)
			b = strconv.AppendInt(b, i, 10)
			b = append(b, '-')
			b = strconv.AppendInt(b, i, 10)
			b = append(b, '-')
			b = strconv.AppendInt(b, i, 10)
			return b
		},
		"bytes.Buffer": func(i int64) []byte {
			var b bytes.Buffer
			b.WriteString(strconv.FormatInt(i, 10))
			b.WriteByte('-')
			b.WriteString(strconv.FormatInt(i, 10))
			b.WriteByte('-')
			b.WriteString(strconv.FormatInt(i, 10))
			return b.Bytes()
		},
		"bytes.Buffer w pool": func(i int64) []byte {
			b := bufPool.Get().(*bytes.Buffer)
			b.Reset()
			b.WriteString(strconv.FormatInt(i, 10))
			b.WriteByte('-')
			b.WriteString(strconv.FormatInt(i, 10))
			b.WriteByte('-')
			b.WriteString(strconv.FormatInt(i, 10))
			out := make([]byte, b.Len())
			copy(out, b.Bytes())
			bufPool.Put(b)
			return out
		},
	}

	casesString := map[string]benchFuncString{
		"fmt": func(i int64) string {
			return fmt.Sprintf("%d-%d-%d", i, i, i)
		},
		"+ + +": func(i int64) string {
			return strconv.FormatInt(i, 10) + "-" + strconv.FormatInt(i, 10) + "-" + strconv.FormatInt(i, 10)

		},
		"strings.Join": func(i int64) string {
			return strings.Join([]string{strconv.FormatInt(i, 10), strconv.FormatInt(i, 10), strconv.FormatInt(i, 10)}, "-")
		},
	}

	for name, fn := range casesByte {
		out := fn(math.MaxInt64)
		if string(out) != exp {
			t.Fatal(name, string(out))
		}
		t.Run(name, func(tb *testing.B) {
			for i := int64(0); i < int64(tb.N); i++ {
				out = fn(i)
			}
		})
	}

	for name, fn := range casesString {
		out := fn(math.MaxInt64)
		if out != exp {
			t.Fatal(name, out)
		}
		t.Run(name, func(tb *testing.B) {
			for i := int64(0); i < int64(tb.N); i++ {
				out = fn(i)
			}
		})
	}
}

BenchmarkStringBuild/strconv.AppendInt-8            20000000            84.9 ns/op        32 B/op          1 allocs/op
BenchmarkStringBuild/bytes.Buffer-8                 10000000           199 ns/op         135 B/op          4 allocs/op
BenchmarkStringBuild/bytes.Buffer_w_pool-8          10000000           201 ns/op          55 B/op          4 allocs/op
BenchmarkStringBuild/fmt-8                           5000000           257 ns/op          56 B/op          4 allocs/op
BenchmarkStringBuild/+_+_+-8                        10000000           167 ns/op          55 B/op          4 allocs/op
BenchmarkStringBuild/strings.Join-8                 10000000           192 ns/op          87 B/op          5 allocs/op
PASS