网上有些字符串连接的性能测试，先看一个错误的
+连接
func BenchmarkAddStringWithOperator(b *testing.B) {
hello := "hello"
world := "world"
for i := 0; i < b.N; i++ {
_ = hello + "," + world
}
}
测试结果
50000000 30.1 ns/op
PASS
ok workspace/version 1.548sfmt连接
func BenchmarkAddStringWithSprintf(b *testing.B) {
hello := "hello"
world := "world"
for i := 0; i < b.N; i++ {
_ = fmt.Sprintf("%s,%s", hello, world)
}
}测试结果
10000000 222 ns/op
PASS
ok workspace/version 2.458s
join连接
func BenchmarkAddStringWithJoin(b *testing.B) {
hello := "hello"
world := "world"
for i := 0; i < b.N; i++ {
_ = strings.Join([]string{hello, world}, ",")
}
}
测试结果
20000000 62.0 ns/op
PASS
ok workspace/version 1.314sbytes连接
func BenchmarkAddStringWithBuffer(b *testing.B) {
hello := "hello"
world := "world"
for i := 0; i < b.N; i++ { var buffer bytes.Buffer
buffer.WriteString(hello)
buffer.WriteString(",")
buffer.WriteString(world)
_ = buffer.String()
}
}20000000 91.0 ns/op
PASS
ok workspace/version 1.925s
通过上面错误的测试其实很容易误导人，感觉是不是通过+连接就是最好的方式呢？其实上面的答案是错误的
错误的还不是一处两处。首先就是字符串+方式的拼接没有生成最终字符串，其次是buffer连接的时候每次生成
buffer对象等，都是降低性能的事情，下面看一个正确的测试的
package main
import (
"bytes"
"fmt"
"strings"
"time"
)
func benchmarkStringFunction(n int, index int) (d time.Duration) {
v := "ni shuo wo shi bu shi tai wu liao le a?"
var s string
var buf bytes.Buffer
t0 := time.Now()
for i := 0; i < n; i++ {
switch index {
case 0: // fmt.Sprintf
s = fmt.Sprintf("%s[%s]", s, v)
case 1: // string +
s = s + "[" + v + "]"
case 2: // strings.Join
s = strings.Join([]string{s, "[", v, "]"}, "")
case 3: // temporary bytes.Buffer
b := bytes.Buffer{}
b.WriteString("[")
b.WriteString(v)
b.WriteString("]")
s = b.String()
case 4: // stable bytes.Buffer
buf.WriteString("[")
buf.WriteString(v)
buf.WriteString("]")
}
if i == n-1 {
if index == 4 { // for stable bytes.Buffer
s = buf.String()
}
fmt.Println(len(s)) // consume s to avoid compiler optimization
}
}
t1 := time.Now()
d = t1.Sub(t0)
fmt.Printf("time of way(%d)=%v\n", index, d)
return d
}
func main() {
k := 5
d := [5]time.Duration{}
for i := 0; i < k; i++ {
d[i] = benchmarkStringFunction(100000, i)
}
for i := 0; i < k-1; i++ {
fmt.Printf("way %d is %6.1f times of way %d\n", i, float32(d[i])/float32(d[k-1]), k-1)
}
}
测试结果
410000
time of way(0)=354.647961ms
410000
time of way(1)=188.914254ms
410000
time of way(2)=532.93828ms
41
time of way(3)=1.386461ms
410000
time of way(4)=474.988µs
way 0 is 746.6 times of way 4
way 1 is 397.7 times of way 4
way 2 is 1122.0 times of way 4
way 3 is 2.9 times of way 4这个里面充分显示了buffer连接的优势