Function DownloadFile

src/lib/download/download.go:23–117

(ctx context.Context, url, dest string, progressBarWidth int)

)

func DownloadFile(ctx context.Context, url, dest string, progressBarWidth int) (string, error) {
	if ctx == nil {
		ctx = context.Background()
	}

	resumeOffset := int64(0)
	info, err := downloadStatFile(dest)
	if err == nil {
		resumeOffset = info.Size()
	} else if !errors.Is(err, os.ErrNotExist) {
		return "", err
	}

	req, err := http.NewRequestWithContext(ctx, "GET", url, nil)
	if err != nil {
		return "", err
	}
	if resumeOffset > 0 {
		req.Header.Set("Range", fmt.Sprintf("bytes=%d-", resumeOffset))
	}
	resp, err := http.DefaultClient.Do(req)
	if err != nil {
		return "", err
	}
	defer resp.Body.Close()

	if resp.StatusCode == http.StatusRequestedRangeNotSatisfiable && resumeOffset > 0 {
		return downloadCalcSHA256(dest)
	}
	if resp.StatusCode < http.StatusOK || resp.StatusCode >= http.StatusMultipleChoices {
		return "", fmt.Errorf("unexpected status code: %d", resp.StatusCode)
	}

	appendMode := resumeOffset > 0 && resp.StatusCode == http.StatusPartialContent
	if !appendMode {
		resumeOffset = 0
	}

	openFlags := os.O_CREATE | os.O_WRONLY | os.O_TRUNC
	if appendMode {
		openFlags = os.O_CREATE | os.O_WRONLY | os.O_APPEND
	}

	f, err := os.OpenFile(dest, openFlags, 0644)
	if err != nil {
		return "", err
	}
	defer f.Close()

	size := resp.ContentLength
	if appendMode && size > 0 {
		size += resumeOffset
	}

	if size == 0 {
		if progressBarWidth > 0 {
			errutil.ErrorRedPrintln("Failed to get total file size")
		}