字符串拼接性能
最后更新于：2022-04-02 02:36:11
[TOC]
> [参考](https://geektutu.com/post/hpg-string-concat.html)
## 对比
使用 +
```
func plusConcat(n int, str string) string {
s := ""
for i := 0; i < n; i++ {
s += str
}
return s
}
```
使用 fmt.Sprintf
```
func sprintfConcat(n int, str string) string {
s := ""
for i := 0; i < n; i++ {
s = fmt.Sprintf("%s%s", s, str)
}
return s
}
```
使用 strings.Builder
```
func builderConcat(n int, str string) string {
var builder strings.Builder
for i := 0; i < n; i++ {
builder.WriteString(str)
}
return builder.String()
}
```
使用 bytes.Buffer
```
func bufferConcat(n int, s string) string {
buf := new(bytes.Buffer)
for i := 0; i < n; i++ {
buf.WriteString(s)
}
return buf.String()
}
```
使用 []byte
```
func byteConcat(n int, str string) string {
buf := make([]byte, 0)
for i := 0; i < n; i++ {
buf = append(buf, str...)
}
return string(buf)
}
```
定长
```
func preByteConcat(n int, str string) string {
buf := make([]byte, 0, n*len(str))
for i := 0; i < n; i++ {
buf = append(buf, str...)
}
return string(buf)
}
```
string.Builder 也提供了预分配内存的方式 Grow
```
func builderConcat(n int, str string) string {
var builder strings.Builder
builder.Grow(n * len(str))
for i := 0; i < n; i++ {
builder.WriteString(str)
}
return builder.String()
}
```
## 性能对比
```
BenchmarkPlusConcat-8 19 56 ms/op 530 MB/op 10026 allocs/op
BenchmarkSprintfConcat-8 10 112 ms/op 835 MB/op 37435 allocs/op
BenchmarkBuilderConcat-8 8901 0.13 ms/op 0.5 MB/op 23 allocs/op
BenchmarkBufferConcat-8 8130 0.14 ms/op 0.4 MB/op 13 allocs/op
BenchmarkByteConcat-8 8984 0.12 ms/op 0.6 MB/op 24 allocs/op
BenchmarkPreByteConcat-8 17379 0.07 ms/op 0.2 MB/op 2 allocs/op
BenchmarkBuilderConcat-8 16855 0.07 ns/op 0.1 MB/op 1 allocs/op
```
> 一般推荐使用`strings.Builder`来拼接字符串
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