golang 带进度条的文件下载

普通文件下载

package main
import (
"io"
"net/http"
"os"
)
func main() {
    // 下载地址:
    fileUrl := "http://xxxxxx.com/files/"
    if err := DownloadFile("保存文件名.png", fileUrl); err != nil {
    panic(err)
    }
    }
    // download file会将url下载到本地文件，它会在下载时写入，而不是将整个文件加载到内存中。
    func DownloadFile(filepath string, url string) error {
    // Get the data
    resp, err := http.Get(url)
    if err != nil {
    return err
    }
    defer resp.Body.Close()
    // Create the file
    out, err := os.Create(filepath)
    if err != nil {
    return err
    }
    defer out.Close()
    // Write the body to file
    _, err = io.Copy(out, resp.Body)
    return err
}

带进度条的大文件下载

package main
import (
    "fmt"
    "io"
    "net/http"
    "os"
    "strings"
    "github.com/dustin/go-humanize"
)
type WriteCounter struct {
    Total uint64
}
func (wc *WriteCounter) Write(p []byte) (int, error) {
    n := len(p)
    wc.Total += uint64(n)
    wc.PrintProgress()
    return n, nil
}
func (wc WriteCounter) PrintProgress() {
    fmt.Printf("\r%s", strings.Repeat(" ", 35))
    fmt.Printf("\rDownloading... %s complete", humanize.Bytes(wc.Total))
}
func main() {
    fmt.Println("Download Started")
    // 下载地址:
    fileUrl := "http://xxxxxx.com/files/文件名称""
    err := DownloadFile("保存文件名.png", fileUrl)
    if err != nil {
        panic(err)
    }
    fmt.Println("Download Finished")
}

func DownloadFile(filepath string, url string) error {
    out, err := os.Create(filepath + ".tmp")
    if err != nil {
        return err
    }
    resp, err := http.Get(url)
    if err != nil {
        out.Close()
        return err
    }
    defer resp.Body.Close()
    counter := &WriteCounter{}
    /*
    io.TeeReader则可以传递计数器来跟踪进度
    io.TeeReader返回一个将其从r读取的数据写入w的Reader接口。所有通过该接口对r的读取都会执行对应的对w的写入。没有内部的缓冲;
    写入必须在读取完成前完成。写入时遇到的任何错误都会作为读取错误返回。
    */
    if _, err = io.Copy(out, io.TeeReader(resp.Body, counter)); err != nil {
        out.Close()
        return err
    }
    fmt.Print("\n")
    out.Close()
    if err = os.Rename(filepath+".tmp", filepath); err != nil {
        return err
    }
    return nil
}