add new youtubedl dependency
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285
downloader/vendor/github.com/kkdai/youtube/v2/decipher.go
generated
vendored
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285
downloader/vendor/github.com/kkdai/youtube/v2/decipher.go
generated
vendored
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@@ -0,0 +1,285 @@
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package youtube
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import (
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"bytes"
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"context"
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"errors"
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"fmt"
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"net/url"
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"regexp"
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"strconv"
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"github.com/dop251/goja"
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)
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func (c *Client) decipherURL(ctx context.Context, videoID string, cipher string) (string, error) {
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params, err := url.ParseQuery(cipher)
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if err != nil {
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return "", err
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}
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uri, err := url.Parse(params.Get("url"))
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if err != nil {
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return "", err
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}
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query := uri.Query()
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config, err := c.getPlayerConfig(ctx, videoID)
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if err != nil {
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return "", err
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}
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// decrypt s-parameter
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bs, err := config.decrypt([]byte(params.Get("s")))
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if err != nil {
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return "", err
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}
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query.Add(params.Get("sp"), string(bs))
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query, err = c.decryptNParam(config, query)
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if err != nil {
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return "", err
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}
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uri.RawQuery = query.Encode()
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return uri.String(), nil
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}
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// see https://github.com/kkdai/youtube/pull/244
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func (c *Client) unThrottle(ctx context.Context, videoID string, urlString string) (string, error) {
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config, err := c.getPlayerConfig(ctx, videoID)
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if err != nil {
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return "", err
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}
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uri, err := url.Parse(urlString)
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if err != nil {
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return "", err
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}
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// for debugging
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if artifactsFolder != "" {
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writeArtifact("video-"+videoID+".url", []byte(uri.String()))
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}
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query, err := c.decryptNParam(config, uri.Query())
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if err != nil {
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return "", err
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}
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uri.RawQuery = query.Encode()
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return uri.String(), nil
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}
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func (c *Client) decryptNParam(config playerConfig, query url.Values) (url.Values, error) {
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// decrypt n-parameter
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nSig := query.Get("v")
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log := Logger.With("n", nSig)
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if nSig != "" {
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nDecoded, err := config.decodeNsig(nSig)
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if err != nil {
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return nil, fmt.Errorf("unable to decode nSig: %w", err)
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}
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query.Set("v", nDecoded)
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log = log.With("decoded", nDecoded)
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}
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log.Debug("nParam")
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return query, nil
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}
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const (
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jsvarStr = "[a-zA-Z_\\$][a-zA-Z_0-9]*"
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reverseStr = ":function\\(a\\)\\{" +
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"(?:return )?a\\.reverse\\(\\)" +
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"\\}"
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spliceStr = ":function\\(a,b\\)\\{" +
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"a\\.splice\\(0,b\\)" +
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"\\}"
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swapStr = ":function\\(a,b\\)\\{" +
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"var c=a\\[0\\];a\\[0\\]=a\\[b(?:%a\\.length)?\\];a\\[b(?:%a\\.length)?\\]=c(?:;return a)?" +
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"\\}"
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)
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var (
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nFunctionNameRegexp = regexp.MustCompile("\\.get\\(\"n\"\\)\\)&&\\(b=([a-zA-Z0-9$]{0,3})\\[(\\d+)\\](.+)\\|\\|([a-zA-Z0-9]{0,3})")
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actionsObjRegexp = regexp.MustCompile(fmt.Sprintf(
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"var (%s)=\\{((?:(?:%s%s|%s%s|%s%s),?\\n?)+)\\};", jsvarStr, jsvarStr, swapStr, jsvarStr, spliceStr, jsvarStr, reverseStr))
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actionsFuncRegexp = regexp.MustCompile(fmt.Sprintf(
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"function(?: %s)?\\(a\\)\\{"+
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"a=a\\.split\\(\"\"\\);\\s*"+
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"((?:(?:a=)?%s\\.%s\\(a,\\d+\\);)+)"+
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"return a\\.join\\(\"\"\\)"+
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"\\}", jsvarStr, jsvarStr, jsvarStr))
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reverseRegexp = regexp.MustCompile(fmt.Sprintf("(?m)(?:^|,)(%s)%s", jsvarStr, reverseStr))
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spliceRegexp = regexp.MustCompile(fmt.Sprintf("(?m)(?:^|,)(%s)%s", jsvarStr, spliceStr))
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swapRegexp = regexp.MustCompile(fmt.Sprintf("(?m)(?:^|,)(%s)%s", jsvarStr, swapStr))
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)
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func (config playerConfig) decodeNsig(encoded string) (string, error) {
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fBody, err := config.getNFunction()
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if err != nil {
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return "", err
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}
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return evalJavascript(fBody, encoded)
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}
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func evalJavascript(jsFunction, arg string) (string, error) {
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const myName = "myFunction"
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vm := goja.New()
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_, err := vm.RunString(myName + "=" + jsFunction)
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if err != nil {
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return "", err
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}
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var output func(string) string
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err = vm.ExportTo(vm.Get(myName), &output)
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if err != nil {
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return "", err
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}
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return output(arg), nil
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}
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func (config playerConfig) getNFunction() (string, error) {
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nameResult := nFunctionNameRegexp.FindSubmatch(config)
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if len(nameResult) == 0 {
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return "", errors.New("unable to extract n-function name")
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}
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var name string
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if idx, _ := strconv.Atoi(string(nameResult[2])); idx == 0 {
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name = string(nameResult[4])
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} else {
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name = string(nameResult[1])
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}
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return config.extraFunction(name)
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}
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func (config playerConfig) extraFunction(name string) (string, error) {
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// find the beginning of the function
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def := []byte(name + "=function(")
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start := bytes.Index(config, def)
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if start < 1 {
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return "", fmt.Errorf("unable to extract n-function body: looking for '%s'", def)
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}
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// start after the first curly bracket
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pos := start + bytes.IndexByte(config[start:], '{') + 1
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var strChar byte
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// find the bracket closing the function
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for brackets := 1; brackets > 0; pos++ {
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b := config[pos]
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switch b {
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case '{':
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if strChar == 0 {
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brackets++
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}
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case '}':
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if strChar == 0 {
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brackets--
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}
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case '`', '"', '\'':
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if config[pos-1] == '\\' && config[pos-2] != '\\' {
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continue
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}
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if strChar == 0 {
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strChar = b
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} else if strChar == b {
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strChar = 0
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}
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}
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}
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return string(config[start:pos]), nil
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}
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func (config playerConfig) decrypt(cyphertext []byte) ([]byte, error) {
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operations, err := config.parseDecipherOps()
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if err != nil {
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return nil, err
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}
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// apply operations
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bs := []byte(cyphertext)
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for _, op := range operations {
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bs = op(bs)
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}
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return bs, nil
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}
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/*
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parses decipher operations from https://youtube.com/s/player/4fbb4d5b/player_ias.vflset/en_US/base.js
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var Mt={
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splice:function(a,b){a.splice(0,b)},
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reverse:function(a){a.reverse()},
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EQ:function(a,b){var c=a[0];a[0]=a[b%a.length];a[b%a.length]=c}};
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a=a.split("");
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Mt.splice(a,3);
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Mt.EQ(a,39);
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Mt.splice(a,2);
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Mt.EQ(a,1);
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Mt.splice(a,1);
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Mt.EQ(a,35);
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Mt.EQ(a,51);
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Mt.splice(a,2);
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Mt.reverse(a,52);
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return a.join("")
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*/
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func (config playerConfig) parseDecipherOps() (operations []DecipherOperation, err error) {
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objResult := actionsObjRegexp.FindSubmatch(config)
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funcResult := actionsFuncRegexp.FindSubmatch(config)
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if len(objResult) < 3 || len(funcResult) < 2 {
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return nil, fmt.Errorf("error parsing signature tokens (#obj=%d, #func=%d)", len(objResult), len(funcResult))
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}
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obj := objResult[1]
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objBody := objResult[2]
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funcBody := funcResult[1]
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var reverseKey, spliceKey, swapKey string
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if result := reverseRegexp.FindSubmatch(objBody); len(result) > 1 {
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reverseKey = string(result[1])
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}
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if result := spliceRegexp.FindSubmatch(objBody); len(result) > 1 {
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spliceKey = string(result[1])
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}
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if result := swapRegexp.FindSubmatch(objBody); len(result) > 1 {
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swapKey = string(result[1])
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}
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regex, err := regexp.Compile(fmt.Sprintf("(?:a=)?%s\\.(%s|%s|%s)\\(a,(\\d+)\\)", regexp.QuoteMeta(string(obj)), regexp.QuoteMeta(reverseKey), regexp.QuoteMeta(spliceKey), regexp.QuoteMeta(swapKey)))
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if err != nil {
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return nil, err
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}
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var ops []DecipherOperation
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for _, s := range regex.FindAllSubmatch(funcBody, -1) {
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switch string(s[1]) {
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case reverseKey:
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ops = append(ops, reverseFunc)
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case swapKey:
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arg, _ := strconv.Atoi(string(s[2]))
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ops = append(ops, newSwapFunc(arg))
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case spliceKey:
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arg, _ := strconv.Atoi(string(s[2]))
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ops = append(ops, newSpliceFunc(arg))
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}
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}
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return ops, nil
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}
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