この記事では、Go 言語でファイルをコピーする最も一般的に使用される 3 つの方法を紹介します。これら 3 つの方法にはそれぞれ長所と短所があります。必要なのは、最も適切なものを選択することだけです。アプリケーションの性能を盲目的に追求する必要はありません。 方法 1
最初の方法では、標準 Go ライブラリの <span style="box-sizing: border-box;background-image: initial;background-position: initial;background-size: initial;background-repeat: initial;background-attachment: initial;background-origin: initial;background-clip: initial;display: inline-block;padding-right: 2px;padding-left: 2px;font-size: 14px;">io</span><span style="box-sizing: border-box;background-image: initial;background-position: initial;background-size: initial;background-repeat: initial;background-attachment: initial;background-origin: initial;background-clip: initial;display: inline-block;padding-right: 2px;padding-left: 2px;font-size: 14px;">.</span><span style="box-sizing: border-box;background-image: initial;background-position: initial;background-size: initial;background-repeat: initial;background-attachment: initial;background-origin: initial;background-clip: initial;display: inline-block;padding-right: 2px;padding-left: 2px;font-size: 14px;"> コピーを使用します。 ＃＃＃＃＃＃（）＃＃＃＃＃＃ 関数。以下は、io.Copy() を使用して実装されたファイルをコピーするためのコード スニペットです: </span><div class="code" style="position:relative; padding:0px; margin:0px;"><pre class="brush:php;toolbar:false;">func copy(src, dst string) (int64, error) {
sourceFileStat, err := os.Stat(src)
if err != nil {
return 0, err
}
if !sourceFileStat.Mode().IsRegular() {
return 0, fmt.Errorf("%s is not a regular file", src)
}
source, err := os.Open(src)
if err != nil {
return 0, err
}
defer source.Close()
destination, err := os.Create(dst)
if err != nil {
return 0, err
}
defer destination.Close()
nBytes, err := io.Copy(destination, source)
return nBytes, err
}</pre><div class="contentsignin">ログイン後にコピー</div></div><h3 style="box-sizing: border-box;margin-top: 1.5rem;margin-bottom: 1rem;color: rgb(21, 153, 87);line-height: 1.35;font-size: 20px;white-space: normal;">方法 2</h3><p style="box-sizing: border-box;margin-top: 15px;margin-bottom: 15px;font-size: 16px;white-space: pre-line;line-height: 30px;color: rgb(74, 74, 74);font-family: Avenir, -apple-system-font, 微软雅黑, sans-serif;">2 番目の方法は、<code style="box-sizing: border-box;background: rgb(243, 241, 241);color: rgb(88, 88, 88);line-height: 18px;"><span style="box-sizing: border-box;background-image: initial;background-position: initial;background-size: initial;background-repeat: initial;background-attachment: initial;background-origin: initial;background-clip: initial;display: inline-block;padding-right: 2px;padding-left: 2px;font-size: 14px;">ioutil</span><span style="box-sizing: border-box;background-image: initial;background-position: initial;background-size: initial;background-repeat: initial;background-attachment: initial;background-origin: initial;background-clip: initial;display: inline-block;padding-right: 2px;padding-left: 2px;font-size: 14px;">.</span><span style="box-sizing: border-box;background-image: initial;background-position: initial;background-size: initial;background-repeat: initial;background-attachment: initial;background-origin: initial;background-clip: initial;display: inline-block;padding-right: 2px;padding-left: 2px;font-size: 14px;">WriteFile</span><span style="box-sizing: border-box;background-image: initial;background-position: initial;background-size: initial;background-repeat: initial;background-attachment: initial;background-origin: initial;background-clip: initial;display: inline-block;padding-right: 2px;padding-left: 2px;font-size: 14px;">( )</span> を使用することです。 および <span style="box-sizing: border-box;background-image: initial;background-position: initial;background-size: initial;background-repeat: initial;background-attachment: initial;background-origin: initial;background-clip: initial;display: inline-block;padding-right: 2px;padding-left: 2px;font-size: 14px;">ioutil</span><span style="box-sizing: border-box;background-image: initial;background-position: initial;background-size: initial;background-repeat: initial;background-attachment: initial;background-origin: initial;background-clip: initial;display: inline-block;padding-right: 2px;padding-left: 2px;font-size: 14px;">.</span><span style="box-sizing: border-box;background-image: initial;background-position: initial;background-size: initial;background-repeat: initial;background-attachment: initial;background-origin: initial;background-clip: initial;display: inline-block;padding-right: 2px;padding-left: 2px;font-size: 14px;">ReadFile</span><span style="box-sizing: border-box;background-image: initial;background-position: initial;background-size: initial;background-repeat: initial;background-attachment: initial;background-origin: initial;background-clip: initial;display: inline-block;padding-right: 2px;padding-left: 2px;font-size: 14px;">()</span> ただし、ワンタイム読み取りの使用が原因です。ファイルをフェッチして一度にファイルに書き込むため、この方法は大きなファイルには適しておらず、メモリ オーバーフローが発生する傾向があります。
input, err := ioutil.ReadFile(sourceFile)
if err != nil {
fmt.Println(err)
return
}
err = ioutil.WriteFile(destinationFile, input, 0644)
if err != nil {
fmt.Println("Error creating", destinationFile)
fmt.Println(err)
return
}ログイン後にコピー
方法三
最后是使用os包中的 <span style="box-sizing: border-box;background-image: initial;background-position: initial;background-size: initial;background-repeat: initial;background-attachment: initial;background-origin: initial;background-clip: initial;display: inline-block;padding-right: 2px;padding-left: 2px;font-size: 14px;">os</span><span style="box-sizing: border-box;background-image: initial;background-position: initial;background-size: initial;background-repeat: initial;background-attachment: initial;background-origin: initial;background-clip: initial;display: inline-block;padding-right: 2px;padding-left: 2px;font-size: 14px;">.</span><span style="box-sizing: border-box;background-image: initial;background-position: initial;background-size: initial;background-repeat: initial;background-attachment: initial;background-origin: initial;background-clip: initial;display: inline-block;padding-right: 2px;padding-left: 2px;font-size: 14px;">Read</span><span style="box-sizing: border-box;background-image: initial;background-position: initial;background-size: initial;background-repeat: initial;background-attachment: initial;background-origin: initial;background-clip: initial;display: inline-block;padding-right: 2px;padding-left: 2px;font-size: 14px;">()</span> 和 <span style="box-sizing: border-box;background-image: initial;background-position: initial;background-size: initial;background-repeat: initial;background-attachment: initial;background-origin: initial;background-clip: initial;display: inline-block;padding-right: 2px;padding-left: 2px;font-size: 14px;">os</span><span style="box-sizing: border-box;background-image: initial;background-position: initial;background-size: initial;background-repeat: initial;background-attachment: initial;background-origin: initial;background-clip: initial;display: inline-block;padding-right: 2px;padding-left: 2px;font-size: 14px;">.</span><span style="box-sizing: border-box;background-image: initial;background-position: initial;background-size: initial;background-repeat: initial;background-attachment: initial;background-origin: initial;background-clip: initial;display: inline-block;padding-right: 2px;padding-left: 2px;font-size: 14px;">Write</span><span style="box-sizing: border-box;background-image: initial;background-position: initial;background-size: initial;background-repeat: initial;background-attachment: initial;background-origin: initial;background-clip: initial;display: inline-block;padding-right: 2px;padding-left: 2px;font-size: 14px;">()</span>，此方法是按块读取文件，块的大小也会影响到程序的性能。
buf := make([]byte, BUFFERSIZE)
for {
n, err := source.Read(buf)
if err != nil && err != io.EOF {
return err
}
if n == 0 {
break
}
if _, err := destination.Write(buf[:n]); err != nil {
return err
}
}ログイン後にコピー
性能
这三种方式都能很方便的实现拷贝文件功能，那他们的性能如何呢，下面我们来尝试对比一下。三种方式都来拷贝同一个500M的文件，
以下是拷贝文件的时间明细（ <span style="box-sizing: border-box;background-image: initial;background-position: initial;background-size: initial;background-repeat: initial;background-attachment: initial;background-origin: initial;background-clip: initial;display: inline-block;padding-right: 2px;padding-left: 2px;font-size: 14px;">cp1</span><span style="box-sizing: border-box;background-image: initial;background-position: initial;background-size: initial;background-repeat: initial;background-attachment: initial;background-origin: initial;background-clip: initial;display: inline-block;padding-right: 2px;padding-left: 2px;font-size: 14px;">.</span><span style="box-sizing: border-box;background-image: initial;background-position: initial;background-size: initial;background-repeat: initial;background-attachment: initial;background-origin: initial;background-clip: initial;display: inline-block;padding-right: 2px;padding-left: 2px;font-size: 14px;">go</span>是第一种方式， <span style="box-sizing: border-box;background-image: initial;background-position: initial;background-size: initial;background-repeat: initial;background-attachment: initial;background-origin: initial;background-clip: initial;display: inline-block;padding-right: 2px;padding-left: 2px;font-size: 14px;">cp2</span><span style="box-sizing: border-box;background-image: initial;background-position: initial;background-size: initial;background-repeat: initial;background-attachment: initial;background-origin: initial;background-clip: initial;display: inline-block;padding-right: 2px;padding-left: 2px;font-size: 14px;">.</span><span style="box-sizing: border-box;background-image: initial;background-position: initial;background-size: initial;background-repeat: initial;background-attachment: initial;background-origin: initial;background-clip: initial;display: inline-block;padding-right: 2px;padding-left: 2px;font-size: 14px;">go</span>是第二种方式， <span style="box-sizing: border-box;background-image: initial;background-position: initial;background-size: initial;background-repeat: initial;background-attachment: initial;background-origin: initial;background-clip: initial;display: inline-block;padding-right: 2px;padding-left: 2px;font-size: 14px;">cp3</span><span style="box-sizing: border-box;background-image: initial;background-position: initial;background-size: initial;background-repeat: initial;background-attachment: initial;background-origin: initial;background-clip: initial;display: inline-block;padding-right: 2px;padding-left: 2px;font-size: 14px;">.</span><span style="box-sizing: border-box;background-image: initial;background-position: initial;background-size: initial;background-repeat: initial;background-attachment: initial;background-origin: initial;background-clip: initial;display: inline-block;padding-right: 2px;padding-left: 2px;font-size: 14px;">go</span>是第三种方式）
$ ls -l INPUT
-rw-r--r-- 1 mtsouk staff 512000000 Jun 5 09:39 INPUT
$ time go run cp1.go INPUT /tmp/cp1
Copied 512000000 bytes!
real 0m0.980s
user 0m0.219s
sys 0m0.719s
$ time go run cp2.go INPUT /tmp/cp2
real 0m1.139s
user 0m0.196s
sys 0m0.654s
$ time go run cp3.go INPUT /tmp/cp3 1000000
Copying INPUT to /tmp/cp3
real 0m1.025s
user 0m0.195s
sys 0m0.486s
ログイン後にコピー
从以上数据来看3种方式的性能非常接近，但依然可以看出Go的io标准包的性能更优。
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