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Fix typos & add more comments

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This commit is contained in:
bytedream 2022-04-16 00:17:36 +02:00
parent 2e9ce3cf52
commit 3617955bc5
16 changed files with 82 additions and 68 deletions
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30
downloader.go
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@ -20,7 +20,7 @@ import (
)
// NewDownloader creates a downloader with default settings which should
// fit the most needs
// fit the most needs.
func NewDownloader(context context.Context, writer io.Writer, goroutines int, onSegmentDownload func(segment *m3u8.MediaSegment, current, total int, file *os.File) error) Downloader {
tmp, _ := os.MkdirTemp("", "crunchy_")
@ -43,12 +43,12 @@ type Downloader struct {
// The files will be placed directly into the root of the directory.
// If empty a random temporary directory on the system's default tempdir
// will be created.
// If the directory does not exist, it will be created
// If the directory does not exist, it will be created.
TempDir string
// 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
// cancel Context.
DeleteTempAfter bool
// Context to control the download process with.
@ -56,7 +56,7 @@ type Downloader struct {
// process. So it is not recommend stopping the program immediately after calling
// the cancel function. It's better when canceling it and then exit the program
// when Format.Download throws an error. See the signal handling section in
// cmd/crunchyroll-go/cmd/download.go for an example
// cmd/crunchyroll-go/cmd/download.go for an example.
Context context.Context
// Goroutines is the number of goroutines to download segments with
@ -65,11 +65,11 @@ type Downloader struct {
// A method to call when a segment was downloaded.
// Note that the segments are downloaded asynchronously (depending on the count of
// Goroutines) and the function gets called asynchronously too, so for example it is
// first called on segment 1, then segment 254, then segment 3 and so on
// first called on segment 1, then segment 254, then segment 3 and so on.
OnSegmentDownload func(segment *m3u8.MediaSegment, current, total int, file *os.File) error
// If LockOnSegmentDownload is true, only one OnSegmentDownload function can be called at
// once. Normally (because of the use of goroutines while downloading) multiple could get
// called simultaneously
// called simultaneously.
LockOnSegmentDownload bool
// If FFmpegOpts is not nil, ffmpeg will be used to merge and convert files.
@ -82,7 +82,7 @@ type Downloader struct {
FFmpegOpts []string
}
// download's the given format
// download's the given format.
func (d Downloader) download(format *Format) error {
if err := format.InitVideo(); err != nil {
return err
@ -109,7 +109,7 @@ func (d Downloader) download(format *Format) error {
}
// mergeSegments reads every file in tempDir and writes their content to Downloader.Writer.
// The given output file gets created or overwritten if already existing
// The given output file gets created or overwritten if already existing.
func (d Downloader) mergeSegments(files []string) error {
for _, file := range files {
select {
@ -132,7 +132,7 @@ func (d Downloader) mergeSegments(files []string) error {
// mergeSegmentsFFmpeg reads every file in tempDir and merges their content to the outputFile
// with ffmpeg (https://ffmpeg.org/).
// The given output file gets created or overwritten if already existing
// The given output file gets created or overwritten if already existing.
func (d Downloader) mergeSegmentsFFmpeg(files []string) error {
list, err := os.Create(filepath.Join(d.TempDir, "list.txt"))
if err != nil {
@ -214,13 +214,13 @@ func (d Downloader) mergeSegmentsFFmpeg(files []string) error {
// After every segment download onSegmentDownload will be called with:
// the downloaded segment, the current position, the total size of segments to download,
// the file where the segment content was written to an error (if occurred).
// The filename is always <number of downloaded segment>.ts
// The filename is always <number of downloaded segment>.ts.
//
// Short explanation:
// 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
// See https://en.wikipedia.org/wiki/MPEG_transport_stream for more information.
func (d Downloader) downloadSegments(format *Format) ([]string, error) {
if err := format.InitVideo(); err != nil {
return nil, err
@ -318,7 +318,7 @@ func (d Downloader) downloadSegments(format *Format) ([]string, error) {
}
}
// getCrypt extracts the key and iv of a m3u8 segment and converts it into a cipher.Block and an iv byte sequence
// getCrypt extracts the key and iv of a m3u8 segment and converts it into a cipher.Block and an iv byte sequence.
func getCrypt(format *Format, segment *m3u8.MediaSegment) (block cipher.Block, iv []byte, err error) {
var resp *http.Response
@ -341,7 +341,7 @@ func getCrypt(format *Format, segment *m3u8.MediaSegment) (block cipher.Block, i
return block, iv, nil
}
// downloadSegment downloads a segment, decrypts it and names it after the given index
// downloadSegment downloads a segment, decrypts it and names it after the given index.
func (d Downloader) downloadSegment(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 := d.decryptSegment(format.crunchy.Client, segment, block, iv)
@ -361,7 +361,7 @@ func (d Downloader) downloadSegment(format *Format, segment *m3u8.MediaSegment,
return file, nil
}
// https://github.com/oopsguy/m3u8/blob/4150e93ec8f4f8718875a02973f5d792648ecb97/tool/crypt.go#L25
// https://github.com/oopsguy/m3u8/blob/4150e93ec8f4f8718875a02973f5d792648ecb97/tool/crypt.go#L25.
func (d Downloader) decryptSegment(client *http.Client, segment *m3u8.MediaSegment, block cipher.Block, iv []byte) ([]byte, error) {
req, err := http.NewRequestWithContext(d.Context, http.MethodGet, segment.URI, nil)
if err != nil {
@ -387,7 +387,7 @@ func (d Downloader) decryptSegment(client *http.Client, segment *m3u8.MediaSegme
return raw, nil
}
// https://github.com/oopsguy/m3u8/blob/4150e93ec8f4f8718875a02973f5d792648ecb97/tool/crypt.go#L47
// https://github.com/oopsguy/m3u8/blob/4150e93ec8f4f8718875a02973f5d792648ecb97/tool/crypt.go#L47.
func (d Downloader) pkcs5UnPadding(origData []byte) []byte {
length := len(origData)
unPadding := int(origData[length-1])