Go 字符串拼接的 7 种姿势

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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)
    }
}