上一节课我们已经找到了生成signature这个字段的代码位置，就是这个B函数，嗯......听起来好像有点奇怪，但是它确实叫B啊，笑死。不管了，看一下里面的逻辑是啥。
注意e参数的内容是：
{"app_name": "douyin_web","version_code": "180800","webcast_sdk_version": "1.0.14-beta.0","update_version_code": "1.0.14-beta.0","compress": "gzip","device_platform": "web","cookie_enabled": true,"screen_width": 1512,"screen_height": 982,"browser_language": "zh-CN","browser_platform": "MacIntel","browser_name": "Mozilla","browser_version": "5.0 (Macintosh; Intel Mac OS X 10_15_7) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/126.0.0.0 Safari/537.36","browser_online": true,"tz_name": "Asia/Shanghai","cursor": "t-1718942296076_r-1_d-1_u-1_h-7382800685396382772","internal_ext": "internal_src:dim|wss_push_room_id:7382777844734167858|wss_push_did:7347516590731134502|first_req_ms:1718942295989|fetch_time:1718942296076|seq:1|wss_info:0-1718942296076-0-0|wrds_v:7382800932146251064","host": "https://live.douyin.com","aid": "6383","live_id": 1,"did_rule": 3,"endpoint": "live_pc","support_wrds": 1,"user_unique_id": "7347516590731134502","im_path": "/webcast/im/fetch/","identity": "audience","need_persist_msg_count": "15","insert_task_id": "","live_reason": "","room_id": "7382777844734167858","heartbeatDuration": "0"
}注意t是很多参数的e里面的websocket_key数组，它里面是：
[{param_name: 'live_id',param_type: 'string',},{param_name: 'aid',param_type: 'string',},{param_name: 'version_code',param_type: 'string',},{param_name: 'webcast_sdk_version',param_type: 'string',},{param_name: 'room_id',param_type: 'string',},{param_name: 'sub_room_id',param_type: 'string',},{param_name: 'sub_channel_id',param_type: 'string',},{param_name: 'did_rule',param_type: 'string',},{param_name: 'user_unique_id',param_type: 'string',},{param_name: 'device_platform',param_type: 'string',},{param_name: 'device_type',param_type: 'string',},{param_name: 'ac',param_type: 'string',},{param_name: 'identity',param_type: 'string',},]
有了这两个参数传递过来，那我们就可以安心研究B里面的逻辑了。
看一下这个for循环吧，它的逻辑就是取出e里面的参数（将t里面的参数名称），然后拼接到o这个字符串上，然后再把o传递给V()这个函数：
V()这个函数里面又做了什么事情呢？V()其实会返回一个函数，这个函数可以传递两个参数，
接下来继续看返回的这个函数里面代码逻辑：
其实这里继续深入研究，会发现是把e参数转为Bytes数组了：
这个转换函数也可以自己写一个：
const o =',live_id=1,aid=6383,version_code=180800,webcast_sdk_version=1.0.14-beta.0,room_id=7382777844734167858,sub_room_id=,sub_channel_id=,did_rule=3,user_unique_id=7347516590731134502,device_platform=web,device_type=,ac=,identity=audience'const substr = o.substring(1)console.log('subStr----', substr)// 将字符串转Bytes数组const stringToBytes = (str) => {var array = new Uint8Array(str.length)for (var i = 0, l = str.length; i < l; i++) {array[i] = str.charCodeAt(i)}return array}console.log('字符串转为Bytes数组', stringToBytes(substr))转换完之后，又使用wordsToBytes函数将结果转成了另外一个形式：
然后再调用bytesToHex函数：
const bytesToHex = function (e) {for (var t = [], r = 0; r < e.length; r++)t.push((e[r] >>> 4).toString(16)), t.push((15 & e[r]).toString(16))return t.join('')
}
转换之后的结果格式为：a5faced0e2965a966b9fde2044e3ff1e
然后再调用frontierSign函数将上面这串字符串转为signature的值：
但是这个frontierSign是啥呢？这是一个webmssdk.es5.js包里面的函数，所以需要将这个webmssdk.es5.js包下载到本地，然后集成到window对象上，就可以调用这个函数了，我这里写了一个demo：可以看到已经生成了值
demo代码如下：
<!DOCTYPE html>
<html lang="en"><head><meta charset="UTF-8" /><meta name="viewport" content="width=device-width, initial-scale=1.0" /><title>Document</title><script src="./vFun.js"></script><script src="./webmssdk.es5.js"></script></head><body><div>测试代码</div></body><script>const config = [{param_name: 'live_id',param_type: 'string',},{param_name: 'aid',param_type: 'string',},{param_name: 'version_code',param_type: 'string',},{param_name: 'webcast_sdk_version',param_type: 'string',},{param_name: 'room_id',param_type: 'string',},{param_name: 'sub_room_id',param_type: 'string',},{param_name: 'sub_channel_id',param_type: 'string',},{param_name: 'did_rule',param_type: 'string',},{param_name: 'user_unique_id',param_type: 'string',},{param_name: 'device_platform',param_type: 'string',},{param_name: 'device_type',param_type: 'string',},{param_name: 'ac',param_type: 'string',},{param_name: 'identity',param_type: 'string',},]// 使用for便利试试for (let { param_name: i } of config) {console.log('i----', i)}const o =',live_id=1,aid=6383,version_code=180800,webcast_sdk_version=1.0.14-beta.0,room_id=7382772251994655488,sub_room_id=,sub_channel_id=,did_rule=3,user_unique_id=7347516590731134502,device_platform=web,device_type=,ac=,identity=audience'const substr = o.substring(1)console.log('subStr----', substr)// s函数就是stringToBytesconst sResult = sFunc(substr)// V()函数就是console.log('s函数stringToBytes结果', sResult)// 有了s的返回结果，再调用i.wordsToBytes// var r = i.wordsToBytes(s(e, t));const r = wordsToBytes(sResult)console.log('r----', r)// 最后调用bytesToHex;// return t && t.asBytes ? r : t && t.asString ? a.bytesToString(r) : i.bytesToHex(r)const bytesRes = bytesToHex(r)console.log('bytesRes----', bytesRes)const frontierSignRes = window.byted_acrawler.frontierSign({'X-MS-STUB': bytesRes,})console.log('frontierSignRes----', frontierSignRes)</script>
</html>
vFun.js的代码如下：
var sFunc = function (e, t) {// 判断e是不是string类型，是的话，把t赋值给e，然后e.constructor == String? stringToBytes(e): oFunc(e)? (e = Array.prototype.slice.call(e, 0)): Array.isArray(e) || e.constructor === Uint8Array || (e = e.toString())for (var r = bytesToWords(e),l = 8 * e.length,c = 1732584193,u = -271733879,p = -1732584194,d = 271733878,h = 0;h < r.length;h++)r[h] =(((r[h] << 8) | (r[h] >>> 24)) & 16711935) |(((r[h] << 24) | (r[h] >>> 8)) & 4278255360);(r[l >>> 5] |= 128 << l % 32), (r[(((l + 64) >>> 9) << 4) + 14] = l)for (var m = sff, f = sgg, g = shh, _ = sii, h = 0; h < r.length; h += 16) {var v = c,C = u,y = p,T = d;(c = m(c, u, p, d, r[h + 0], 7, -680876936)),(d = m(d, c, u, p, r[h + 1], 12, -389564586)),(p = m(p, d, c, u, r[h + 2], 17, 606105819)),(u = m(u, p, d, c, r[h + 3], 22, -1044525330)),(c = m(c, u, p, d, r[h + 4], 7, -176418897)),(d = m(d, c, u, p, r[h + 5], 12, 1200080426)),(p = m(p, d, c, u, r[h + 6], 17, -1473231341)),(u = m(u, p, d, c, r[h + 7], 22, -45705983)),(c = m(c, u, p, d, r[h + 8], 7, 1770035416)),(d = m(d, c, u, p, r[h + 9], 12, -1958414417)),(p = m(p, d, c, u, r[h + 10], 17, -42063)),(u = m(u, p, d, c, r[h + 11], 22, -1990404162)),(c = m(c, u, p, d, r[h + 12], 7, 1804603682)),(d = m(d, c, u, p, r[h + 13], 12, -40341101)),(p = m(p, d, c, u, r[h + 14], 17, -1502002290)),(u = m(u, p, d, c, r[h + 15], 22, 1236535329)),(c = f(c, u, p, d, r[h + 1], 5, -165796510)),(d = f(d, c, u, p, r[h + 6], 9, -1069501632)),(p = f(p, d, c, u, r[h + 11], 14, 643717713)),(u = f(u, p, d, c, r[h + 0], 20, -373897302)),(c = f(c, u, p, d, r[h + 5], 5, -701558691)),(d = f(d, c, u, p, r[h + 10], 9, 38016083)),(p = f(p, d, c, u, r[h + 15], 14, -660478335)),(u = f(u, p, d, c, r[h + 4], 20, -405537848)),(c = f(c, u, p, d, r[h + 9], 5, 568446438)),(d = f(d, c, u, p, r[h + 14], 9, -1019803690)),(p = f(p, d, c, u, r[h + 3], 14, -187363961)),(u = f(u, p, d, c, r[h + 8], 20, 1163531501)),(c = f(c, u, p, d, r[h + 13], 5, -1444681467)),(d = f(d, c, u, p, r[h + 2], 9, -51403784)),(p = f(p, d, c, u, r[h + 7], 14, 1735328473)),(u = f(u, p, d, c, r[h + 12], 20, -1926607734)),(c = g(c, u, p, d, r[h + 5], 4, -378558)),(d = g(d, c, u, p, r[h + 8], 11, -2022574463)),(p = g(p, d, c, u, r[h + 11], 16, 1839030562)),(u = g(u, p, d, c, r[h + 14], 23, -35309556)),(c = g(c, u, p, d, r[h + 1], 4, -1530992060)),(d = g(d, c, u, p, r[h + 4], 11, 1272893353)),(p = g(p, d, c, u, r[h + 7], 16, -155497632)),(u = g(u, p, d, c, r[h + 10], 23, -1094730640)),(c = g(c, u, p, d, r[h + 13], 4, 681279174)),(d = g(d, c, u, p, r[h + 0], 11, -358537222)),(p = g(p, d, c, u, r[h + 3], 16, -722521979)),(u = g(u, p, d, c, r[h + 6], 23, 76029189)),(c = g(c, u, p, d, r[h + 9], 4, -640364487)),(d = g(d, c, u, p, r[h + 12], 11, -421815835)),(p = g(p, d, c, u, r[h + 15], 16, 530742520)),(u = g(u, p, d, c, r[h + 2], 23, -995338651)),(c = _(c, u, p, d, r[h + 0], 6, -198630844)),(d = _(d, c, u, p, r[h + 7], 10, 1126891415)),(p = _(p, d, c, u, r[h + 14], 15, -1416354905)),(u = _(u, p, d, c, r[h + 5], 21, -57434055)),(c = _(c, u, p, d, r[h + 12], 6, 1700485571)),(d = _(d, c, u, p, r[h + 3], 10, -1894986606)),(p = _(p, d, c, u, r[h + 10], 15, -1051523)),(u = _(u, p, d, c, r[h + 1], 21, -2054922799)),(c = _(c, u, p, d, r[h + 8], 6, 1873313359)),(d = _(d, c, u, p, r[h + 15], 10, -30611744)),(p = _(p, d, c, u, r[h + 6], 15, -1560198380)),(u = _(u, p, d, c, r[h + 13], 21, 1309151649)),(c = _(c, u, p, d, r[h + 4], 6, -145523070)),(d = _(d, c, u, p, r[h + 11], 10, -1120210379)),(p = _(p, d, c, u, r[h + 2], 15, 718787259)),(u = _(u, p, d, c, r[h + 9], 21, -343485551)),(c = (c + v) >>> 0),(u = (u + C) >>> 0),(p = (p + y) >>> 0),(d = (d + T) >>> 0)}return endian([c, u, p, d])
}// (s._blocksize = 16)
// (s._digestsize = 16)const sff = function (e, t, r, i, n, o, a) {var s = e + ((t & r) | (~t & i)) + (n >>> 0) + areturn ((s << o) | (s >>> (32 - o))) + t
}const sgg = function (e, t, r, i, n, o, a) {var s = e + ((t & i) | (r & ~i)) + (n >>> 0) + areturn ((s << o) | (s >>> (32 - o))) + t
}const shh = function (e, t, r, i, n, o, a) {var s = e + (t ^ r ^ i) + (n >>> 0) + areturn ((s << o) | (s >>> (32 - o))) + t
}const sii = function (e, t, r, i, n, o, a) {var s = e + (r ^ (t | ~i)) + (n >>> 0) + areturn ((s << o) | (s >>> (32 - o))) + t
}const stringToBytes = function (str) {var array = new Uint8Array(str.length)for (var i = 0, l = str.length; i < l; i++) {array[i] = str.charCodeAt(i)}return array
}const oFunc = function (e) {return (null != e &&(t(e) ||('function' == typeof e.readFloatLE &&'function' == typeof e.slice &&t(e.slice(0, 0))) ||!!e._isBuffer))
}const bytesToWords = function (e) {for (var t = [], r = 0, i = 0; r < e.length; r++, i += 8)t[i >>> 5] |= e[r] << (24 - (i % 32))return t
}const wordsToBytes = function (e) {for (var t = [], r = 0; r < 32 * e.length; r += 8)t.push((e[r >>> 5] >>> (24 - (r % 32))) & 255)return t
}const endian = function (e) {if (e.constructor == Number)return (16711935 & rotl(e, 8)) | (4278255360 & rotl(e, 24))for (var t = 0; t < e.length; t++) e[t] = endian(e[t])return e
}const rotl = function (e, t) {return (e << t) | (e >>> (32 - t))
}const bytesToHex = function (e) {for (var t = [], r = 0; r < e.length; r++)t.push((e[r] >>> 4).toString(16)), t.push((15 & e[r]).toString(16))return t.join('')
}