golang 文件下载实现

示例如下：

下载文件过程中生成XXX.download中间文件，下载完成后再重命名为待下载文件XXX

package mainimport ("crypto/md5""errors""fmt""io""io/ioutil""net/http""os""strconv""time"
) 
func IsFileExist(filename string, filesize int64) bool {info, err := os.Stat(filename)if os.IsNotExist(err) {fmt.Println(info)return false}if filesize == info.Size() {fmt.Println("安装包已存在！", info.Name(), info.Size(), info.ModTime())return true}del := os.Remove(filename)if del != nil {fmt.Println(del)}return false
}
func downloadFile(url string, localPath string, fb func(length, downLen int64)) error {var (fsize   int64buf     = make([]byte, 32*1024)written int64)tmpFilePath := localPath + ".download"fmt.Println(tmpFilePath)//创建一个http clientclient := new(http.Client)//client.Timeout = time.Second * 60 //设置超时时间//get方法获取资源resp, err := client.Get(url)if err != nil {return err}//读取服务器返回的文件大小fsize, err = strconv.ParseInt(resp.Header.Get("Content-Length"), 10, 32)if err != nil {fmt.Println(err)}if IsFileExist(localPath, fsize) {return err}fmt.Println("fsize", fsize)//创建文件file, err := os.Create(tmpFilePath)if err != nil {return err}defer file.Close()if resp.Body == nil {return errors.New("body is null")}defer resp.Body.Close()//下面是 io.copyBuffer() 的简化版本for {//读取bytesnr, er := resp.Body.Read(buf)if nr > 0 {//写入bytesnw, ew := file.Write(buf[0:nr])//数据长度大于0if nw > 0 {written += int64(nw)}//写入出错if ew != nil {err = ewbreak}//读取是数据长度不等于写入的数据长度if nr != nw {err = io.ErrShortWritebreak}}if er != nil {if er != io.EOF {err = er}break}//没有错误了快使用 callbackfb(fsize, written)}fmt.Println(err)if err == nil {file.Close()err = os.Rename(tmpFilePath, localPath)fmt.Println(err)}return err
}

golang 文件 下载 实现