Go 字符串拼接的 7 种姿势

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str += "test-string"

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str = fmt.Sprintf("%s%s", str, "test-string")

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str = strings.Join([]string{str, "test-string"}, "")

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buf := new(bytes.Buffer)
buf.WriteString("test-string")
str := buf.String()

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var b []byte
s := "test-string"
b = append(b, s...)
str := string(b)

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ts := "test-string"
n := 5
tsl := len(ts) * n
bs := make([]byte, tsl)
bl := 0

for bl < tsl {
    bl += copy(bs[bl:], ts)
}

str := string(bs)

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var builder strings.Builder
builder.WriteString("test-string")
str := builder.String()

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package main

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

const (
    sss = "hello world!"
    cnt = 10000
)

var expected = strings.Repeat(sss, cnt)

func BenchmarkStringConcat(b *testing.B) {
    var result string
    for n := 0; n < b.N; n++ {
        var str string
        for i := 0; i < cnt; i++ {
            str += sss
        }
        result = str
    }
    b.StopTimer()
    if result != expected {
        b.Errorf("unexpected result; got=%s, want=%s", string(result), expected)
    }
}

func BenchmarkStringSprintf(b *testing.B) {
    var result string
    for n := 0; n < b.N; n++ {
        var str string
        for i := 0; i < cnt; i++ {
            str = fmt.Sprintf("%s%s", str, sss)
        }
        result = str
    }
    b.StopTimer()
    if result != expected {
        b.Errorf("unexpected result; got=%s, want=%s", string(result), expected)
    }
}

func BenchmarkStringJoin(b *testing.B) {
    var result string
    for n := 0; n < b.N; n++ {
        var str string
        for i := 0; i < cnt; i++ {
            str = strings.Join([]string{str, sss}, "")
        }
        result = str
    }
    b.StopTimer()
    if result != expected {
        b.Errorf("unexpected result; got=%s, want=%s", string(result), expected)
    }
}

func BenchmarkBufferWrite(b *testing.B) {
    var result string
    for n := 0; n < b.N; n++ {
        buf := new(bytes.Buffer)
        for i := 0; i < cnt; i++ {
            buf.WriteString(sss)
        }
        result = buf.String()
    }
    b.StopTimer()
    if result != expected {
        b.Errorf("unexpected result; got=%s, want=%s", string(result), expected)
    }
}

func BenchmarkBytesAppend(b *testing.B) {
    var result string
    for n := 0; n < b.N; n++ {
        var bbb []byte

        for i := 0; i < cnt; i++ {
            bbb = append(bbb, sss...)
        }
        result = string(bbb)
    }
    b.StopTimer()
    if result != expected {
        b.Errorf("unexpected result; got=%s, want=%s", string(result), expected)
    }
}

func BenchmarkStringCopy(b *testing.B) {
    var result string
    for n := 0; n < b.N; n++ {
        tsl := len(sss) * cnt
        bs := make([]byte, tsl)
        bl := 0

        for bl < tsl {
            bl += copy(bs[bl:], sss)
        }

        result = string(bs)
    }
    b.StopTimer()
    if result != expected {
        b.Errorf("unexpected result; got=%s, want=%s", string(result), expected)
    }
}

func BenchmarkStringBuilder(b *testing.B) {
    var result string
    for n := 0; n < b.N; n++ {
        var builder strings.Builder

        for i := 0; i < cnt; i++ {
            builder.WriteString(sss)
        }

        result = builder.String()
    }
    b.StopTimer()
    if result != expected {
        b.Errorf("unexpected result; got=%s, want=%s", string(result), expected)
    }
}

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BenchmarkStringConcat-4               19          61431933 ns/op        632845167 B/op     10005 allocs/op
BenchmarkStringSprintf-4              10         109283838 ns/op        1075688336 B/op    29688 allocs/op
BenchmarkStringJoin-4                 15          75854431 ns/op        632844905 B/op     10003 allocs/op
BenchmarkBufferWrite-4             10743            113597 ns/op          441616 B/op         13 allocs/op
BenchmarkBytesAppend-4             15578             73796 ns/op          645104 B/op         24 allocs/op
BenchmarkStringCopy-4              21416             55761 ns/op          245760 B/op          2 allocs/op
BenchmarkStringBuilder-4           15961             74010 ns/op          522224 B/op         23 allocs/op