crunchy/dist/subtitle/decode.js

Crunchy is a fork of Crunchyroll.js, capable of downloading anime episodes from the popular CrunchyRoll streaming service.

/* tslint:disable:no-bitwise false */
'use strict';
exports.__esModule = true;
var bigInt = require("big-integer");
var crypto = require("crypto");
var zlib = require("zlib");
/**
 * Decodes the data.
 */
function default_1(id, iv, data, done) {
    try {
        decompress(decrypt(id, iv, data), done);
    }
    catch (e) {
        done(e);
    }
}
exports["default"] = default_1;
/**
 * Decrypts the data.
 */
function decrypt(id, iv, data) {
    var ivBuffer = typeof iv === 'string' ? Buffer.from(iv, 'base64') : iv;
    var dataBuffer = typeof data === 'string' ? Buffer.from(data, 'base64') : data;
    var decipher = crypto.createDecipheriv('aes-256-cbc', key(id), ivBuffer);
    decipher.setAutoPadding(false);
    return Buffer.concat([decipher.update(dataBuffer), decipher.final()]);
}
/**
 * Decompresses the data.
 */
function decompress(data, done) {
    try {
        zlib.inflate(data, done);
    }
    catch (e) {
        done(null, data);
    }
}
/**
 * Generates a key.
 */
function key(subtitleId) {
    var hash = secret(20, 97, 1, 2) + magic(subtitleId);
    var result = Buffer.allocUnsafe(32);
    result.fill(0);
    crypto.createHash('sha1').update(hash).digest().copy(result);
    return result;
}
/**
 * Generates a magic number.
 */
function magic(subtitleId) {
    var base = Math.floor(Math.sqrt(6.9) * Math.pow(2, 25));
    var hash = bigInt(base).xor(subtitleId).toJSNumber();
    var multipliedHash = bigInt(hash).multiply(32).toJSNumber();
    return bigInt(hash).xor(hash >> 3).xor(multipliedHash).toJSNumber();
}
/**
 * Generates a secret string based on a Fibonacci sequence.
 */
function secret(size, modulo, firstSeed, secondSeed) {
    var currentValue = firstSeed + secondSeed;
    var previousValue = secondSeed;
    var result = '';
    for (var i = 0; i < size; i += 1) {
        var oldValue = currentValue;
        result += String.fromCharCode(currentValue % modulo + 33);
        currentValue += previousValue;
        previousValue = oldValue;
    }
    return result;
}
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