Added context to downloader and moved method from utils to downloader

downloader.go

@@ -1,6 +1,7 @@
 package crunchyroll
 
 import (
+	"context"
 	"crypto/aes"
 	"crypto/cipher"
 	"fmt"
@@ -23,9 +24,14 @@ type Downloader struct {
 	// If IgnoreExisting is true, existing Filename's and TempDir's may be
 	// overwritten or deleted
 	IgnoreExisting bool
-	// If DeleteTempAfter is true, the temp directory gets deleted afterwards
+	// If DeleteTempAfter is true, the temp directory gets deleted afterwards.
+	// Note that in case of a hard signal exit (os.Interrupt, ...) the directory
+	// will NOT be deleted. In such situations try to catch the signal and
+	// cancel Context
 	DeleteTempAfter bool
 
+	Context context.Context
+
 	// Goroutines is the number of goroutines to download segments with
 	Goroutines int
 
@@ -43,6 +49,7 @@ func NewDownloader(filename string, goroutines int, onSegmentDownload func(segme
 		Filename:          filename,
 		TempDir:           tmp,
 		DeleteTempAfter:   true,
+		Context:           context.Background(),
 		Goroutines:        goroutines,
 		OnSegmentDownload: onSegmentDownload,
 	}
@@ -57,7 +64,7 @@ func NewDownloader(filename string, goroutines int, onSegmentDownload func(segme
 // 		The actual crunchyroll video is split up in multiple segments (or video files) which have to be downloaded and merged after to generate a single video file.
 //		And this function just downloads each of this segment into the given directory.
 // 		See https://en.wikipedia.org/wiki/MPEG_transport_stream for more information
-func download(format *Format, tempDir string, goroutines int, onSegmentDownload func(segment *m3u8.MediaSegment, current, total int, file *os.File) error) error {
+func download(context context.Context, format *Format, tempDir string, goroutines int, onSegmentDownload func(segment *m3u8.MediaSegment, current, total int, file *os.File) error) error {
 	resp, err := format.crunchy.Client.Get(format.Video.URI)
 	if err != nil {
 		return err
@@ -100,15 +107,19 @@ func download(format *Format, tempDir string, goroutines int, onSegmentDownload
 		i := i
 
 		go func() {
+			defer wg.Done()
+
 			for j, segment := range segments[i:end] {
 				select {
+				case <-context.Done():
+					return
 				case <-quit:
-					break
+					return
 				default:
 					var file *os.File
 					k := 1
 					for ; k < 4; k++ {
-						file, err = downloadSegment(format, segment, filepath.Join(tempDir, fmt.Sprintf("%d.ts", i+j)), block, iv)
+						file, err = downloadSegment(context, format, segment, filepath.Join(tempDir, fmt.Sprintf("%d.ts", i+j)), block, iv)
 						if err == nil {
 							break
 						}
@@ -129,12 +140,13 @@ func download(format *Format, tempDir string, goroutines int, onSegmentDownload
 					file.Close()
 				}
 			}
-			wg.Done()
 		}()
 	}
 	wg.Wait()
 
 	select {
+	case <-context.Done():
+		return context.Err()
 	case <-quit:
 		return err
 	default:
@@ -166,9 +178,9 @@ func getCrypt(format *Format, segment *m3u8.MediaSegment) (block cipher.Block, i
 }
 
 // downloadSegment downloads a segment, decrypts it and names it after the given index
-func downloadSegment(format *Format, segment *m3u8.MediaSegment, filename string, block cipher.Block, iv []byte) (*os.File, error) {
+func downloadSegment(context context.Context, format *Format, segment *m3u8.MediaSegment, filename string, block cipher.Block, iv []byte) (*os.File, error) {
 	// every segment is aes-128 encrypted and has to be decrypted when downloaded
-	content, err := decryptSegment(format.crunchy.Client, segment, block, iv)
+	content, err := decryptSegment(context, format.crunchy.Client, segment, block, iv)
 	if err != nil {
 		return nil, err
 	}
@@ -184,3 +196,37 @@ func downloadSegment(format *Format, segment *m3u8.MediaSegment, filename string
 
 	return file, nil
 }
+
+// https://github.com/oopsguy/m3u8/blob/4150e93ec8f4f8718875a02973f5d792648ecb97/tool/crypt.go#L25
+func decryptSegment(context context.Context, client *http.Client, segment *m3u8.MediaSegment, block cipher.Block, iv []byte) ([]byte, error) {
+	req, err := http.NewRequest(http.MethodGet, segment.URI, nil)
+	if err != nil {
+		return nil, err
+	}
+	req.WithContext(context)
+
+	resp, err := client.Do(req)
+	if err != nil {
+		return nil, err
+	}
+	defer resp.Body.Close()
+
+	raw, err := ioutil.ReadAll(resp.Body)
+	if err != nil {
+		return nil, err
+	}
+
+	blockMode := cipher.NewCBCDecrypter(block, iv[:block.BlockSize()])
+	decrypted := make([]byte, len(raw))
+	blockMode.CryptBlocks(decrypted, raw)
+	raw = pkcs5UnPadding(decrypted)
+
+	return raw, nil
+}
+
+// https://github.com/oopsguy/m3u8/blob/4150e93ec8f4f8718875a02973f5d792648ecb97/tool/crypt.go#L47
+func pkcs5UnPadding(origData []byte) []byte {
+	length := len(origData)
+	unPadding := int(origData[length-1])
+	return origData[:(length - unPadding)]
+}