golang字符串拼接性能测试

Golang 字符串拼接方式有：

1. 加号连接
2. fmt.Sprintf 格式化连接
3. strings.Builder 类型
4. bytes.Buffer 字节缓存拼接
5. byte 数组 append 拼接
6. slice to string
7. array to string

结论：+号 > array to string > bytes.Buffer > strings.Builder > fmt.Sprintf > slice to string > byte 数组拼接

测试结果如下：

BenchmarkString-16                        661976              1709 ns/op
BenchmarkFmtSprintfString-16              619222              1994 ns/op
BenchmarkBuilderString-16                 670098              1821 ns/op
BenchmarkByteBufferString-16              677284              1806 ns/op
BenchmarkByteConcatString-16                 320           3555811 ns/op
BenchmarkSliceToString-16                 600052              2016 ns/op
BenchmarkArrToString-16                   694024              1763 ns/op

测试代码如下：

package main

import (
        "bytes"
        "fmt"
        "strconv"
        "strings"
        "testing"
        "time"
)

var tm string

// 1. 直接拼接
func BenchmarkString(b *testing.B) {
        for i := 0; i < b.N; i++ {
                tm = "STD.V3." +
                        time.Now().Format("20060102") +
                        "." +
                        "app_id" +
                        "." +
                        "slot_id" +
                        "." +
                        "agent_id" +
                        "." +
                        "code_id"
        }
}

// 2. fmt.Sprintf("%s",xxxxx)
func BenchmarkFmtSprintfString(b *testing.B) {
        for i := 0; i < b.N; i++ {
                tm = fmt.Sprintf("STD.V3.%s.%s.%s.%s.%s",
                        time.Now().Format("20060102"),
                        "app_id",
                        "slot_id",
                        "agent_id",
                        "code_id",
                )
        }
}

// 3. string.Builder
func BenchmarkBuilderString(b *testing.B) {
        for i := 0; i < b.N; i++ {
                var builder strings.Builder
                builder.WriteString("STD.V3.")
                builder.WriteString(time.Now().Format("20060102"))
                builder.WriteString(".")
                builder.WriteString("app_id")
                builder.WriteString(".")
                builder.WriteString("slot_id")
                builder.WriteString(".")
                builder.WriteString("agent_id")
                builder.WriteString(".")
                builder.WriteString("code_id")

                tm = builder.String()
        }
}

// 4. bytes.Builder
func BenchmarkByteBufferString(b *testing.B) {
        for i := 0; i < b.N; i++ {
                buffer := new(bytes.Buffer)
                buffer.WriteString("STD.V3.")
                buffer.WriteString(time.Now().Format("20060102"))
                buffer.WriteString(".")
                buffer.WriteString("app_id")
                buffer.WriteString(".")
                buffer.WriteString("slot_id")
                buffer.WriteString(".")
                buffer.WriteString("agent_id")
                buffer.WriteString(".")
                buffer.WriteString("code_id")
                tm = buffer.String()
        }
}

// 5. byte 拼接
func BenchmarkByteConcatString(b *testing.B) {
        elems := make([]string, 100000, 100000)
        for i := 0; i < len(elems); i++ {
                elems[i] = strconv.Itoa(i)
        }
        length := len(elems)
        buf := make([]byte, 0, len(elems))
        b.ResetTimer()
        for i := 0; i < b.N; i++ {
                for j := 0; j < length; j++ {
                        buf = append(buf, elems[j]...)
                }
        }
        b.StopTimer()
}

// 6. slice to string
func BenchmarkSliceToString(b *testing.B) {
        for i := 0; i < b.N; i++ {
                ks := []string{"STD", "V3"}

                ks = append(ks, time.Now().Format("20060102"))
                ks = append(ks, "app_id")
                ks = append(ks, "slot_id")
                ks = append(ks, "agent_id")
                ks = append(ks, "code_id")

                tm = strings.Join(ks, ".")
        }
}

// 7. array to string
func BenchmarkArrToString(b *testing.B) {
        for i := 0; i < b.N; i++ {
                ks := [...]string{
                        "STD",
                        "V3",
                        time.Now().Format("20060102"),
                        "app_id",
                        "slot_id",
                        "agent_id",
                        "code_id",
                }

                tm = strings.Join(ks[:], ".")
        }
}