download

README

download

Package download provides download functions.

Docs

• https://pkg.go.dev/github.com/northbright/download

License

• MIT License

Documentation

Index

• func Download(ctx context.Context, c *http.Client, req *http.Request, dst string) (n int64, err error)
• func DownloadBuffer(ctx context.Context, c *http.Client, req *http.Request, dst string, buf []byte) (n int64, err error)
• func DownloadBufferWithProgress(ctx context.Context, c *http.Client, req *http.Request, dst string, buf []byte, ...) (n int64, err error)
• func DownloadWithProgress(ctx context.Context, c *http.Client, req *http.Request, dst string, ...) (n int64, err error)

Examples

• DownloadBufferWithProgress

Functions

func Download

func Download(ctx context.Context, c *http.Client, req *http.Request, dst string) (n int64, err error)

Download does an HTTP request to download the content to a local file and returns the number of bytes downloaded. It accepts context.Context to make download cancalable.

func DownloadBuffer

func DownloadBuffer(ctx context.Context, c *http.Client, req *http.Request, dst string, buf []byte) (n int64, err error)

DownloadBuffer is the buffered version of Download.

func DownloadBufferWithProgress

func DownloadBufferWithProgress(
	ctx context.Context,
	c *http.Client,
	req *http.Request,
	dst string,
	buf []byte,
	downloaded int64,
	fn func(total, prev, current int64, percent float32)) (n int64, err error)

DownloadBufferWithProgress does an HTTP request to download the content to a local file and returns the number of bytes downloaded. It accepts context.Context to make download cancalable. It also accepts callback function on bytes written to report progress. downloaded: number of bytes downloaded previously. It can be used to resume the download. 1. Set downloaded to 0 when call DownloadBufferWithProgress for the first time. 2. User stops the download and DownloadBufferWithProgress returns the number of bytes downloaded and error. 3. Check if err == context.Canceled || err == context.DeadlineExceeded. 4. Set downloaded to the "n" return value of previous DownloadBufferWithProgress when make next call to resume the download. fn: callback on bytes written.

Example

package main

import (
	"context"
	"fmt"
	"log"
	"net/http"
	"os"
	"path/filepath"
	"time"

	"github.com/northbright/download"
	"github.com/northbright/pathelper"
)

func main() {
	url := "https://golang.google.cn/dl/go1.23.1.darwin-amd64.pkg"

	c := &http.Client{}
	req, _ := http.NewRequest("GET", url, nil)

	// Set User-Agent.
	req.Header.Set("User-Agent", "Mozilla/5.0 (Macintosh; Intel Mac OS X 10_15_7) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/118.0.0.0 Safari/537.36 Edg/118.0.2088.76")

	dst := filepath.Join(os.TempDir(), "go", "go1.23.1.darwin-amd64.pkg")

	// Create parent dir of dst if it does not exist.
	dir := filepath.Dir(dst)
	if err := pathelper.CreateDirIfNotExists(dir, 0755); err != nil {
		log.Printf("create dir(%s) error: %v", dir, err)
		return
	}
	log.Printf("create dir(%s) OK", dir)

	ctx, cancel := context.WithTimeout(context.Background(), time.Millisecond*800)
	defer cancel()

	log.Printf("download.DownloadBufferWithProgress() starts...\nurl: %v\ndst: %v", url, dst)

	buf := make([]byte, 1024*640)

	n, err := download.DownloadBufferWithProgress(
		ctx,
		c,
		req,
		dst,
		buf,
		// Number of bytes downloaded previously.
		0,
		// Callback to report progress.
		func(total, prev, current int64, percent float32) {
			log.Printf("%v / %v(%.2f%%) downloaded", prev+current, total, percent)
		},
	)

	if err != nil {
		if err != context.Canceled && err != context.DeadlineExceeded {
			log.Printf("download.DownloadBufferWithProgress() error: %v", err)
			return
		}
		log.Printf("download.DownloadBufferWithProgress() stopped, cause: %v. %v bytes downloaded", err, n)
	} else {
		log.Printf("download.DownloadBufferWithProgress() OK, %v bytes downloaded", n)
		fmt.Printf("download successfully, total %v bytes downloaded", n)
		return
	}

	log.Printf("download.DownloadBufferWithProgress() starts again to resume downloading...\nurl: %v\ndst: %v\ndownloaded: %v", url, dst, n)

	// Resume the download by setting downloaded to n.
	n2, err := download.DownloadBufferWithProgress(
		context.Background(),
		c,
		req,
		dst,
		buf,
		// Number of bytes downloaded.
		n,
		// Callback to report progress.
		func(total, prev, current int64, percent float32) {
			log.Printf("%v / %v(%.2f%%) downloaded", prev+current, total, percent)
		},
	)

	if err != nil {
		if err != context.Canceled && err != context.DeadlineExceeded {
			log.Printf("download.DownloadBufferWithProgress() error: %v", err)
			return
		}
		log.Printf("download.DownloadBufferWithProgress() stopped, cause: %v. %v bytes downloaded", err, n2)
	} else {
		log.Printf("download.DownloadBufferWithProgress() OK, %v bytes downloaded", n2)
	}

	log.Printf("total %v bytes downloaded", n+n2)
	fmt.Printf("download successfully, total %v bytes downloaded", n+n2)

	// Remove the files after test's done.
	os.Remove(dst)

}

Output:
download successfully, total 75917313 bytes downloaded

func DownloadWithProgress

func DownloadWithProgress(
	ctx context.Context,
	c *http.Client,
	req *http.Request,
	dst string,
	downloaded int64,
	fn func(total, prev, current int64, percent float32)) (n int64, err error)

DownloadWithProgress is the non-buffered version of DownloadBufferWithProgress.