b站直播间 ws协议爬取

let {brotliDecompressSync} = require("zlib");
var wsBinaryHeaderList = [{
    "name": "Header Length",
    "key": "headerLen",
    "bytes": 2,
    "offset": 4,
    "value": 16
}, {"name": "Protocol Version", "key": "ver", "bytes": 2, "offset": 6, "value": 1}, {
    "name": "Operation",
    "key": "op",
    "bytes": 4,
    "offset": 8,
    "value": 1
}, {"name": "Sequence Id", "key": "seq", "bytes": 4, "offset": 12, "value": 1}];

function mergeArrayBuffer(t, e) {
    var n = new Uint8Array(t)
        , o = new Uint8Array(e)
        , i = new Uint8Array(n.byteLength + o.byteLength);
    return i.set(n, 0),
        i.set(o, n.byteLength),
        i.buffer
}

function convertToArrayBuffer(t, e) {
    if (e != 2) {
        t = JSON.stringify(t);
    }
    this.encoder = new TextEncoder();
    var n = new ArrayBuffer(16)
        , i = new DataView(n, 0)
        , s = this.encoder.encode(t);
    return i.setInt32(0, 16 + s.byteLength),
        wsBinaryHeaderList[2].value = e,
        wsBinaryHeaderList.forEach(function (t) {
            4 === t.bytes ? i.setInt32(t.offset, t.value) : 2 === t.bytes && i.setInt16(t.offset, t.value)
        }),
        [...new Uint8Array(mergeArrayBuffer(n, s))];
}

function convertToObject(t) {
    t = new Uint8Array(t).buffer;
    var e = new DataView(t)
        , n = {
        body: []
    };
    if (n.packetLen = e.getInt32(0),
        wsBinaryHeaderList.forEach(function (t) {
            4 === t.bytes ? n[t.key] = e.getInt32(t.offset) : 2 === t.bytes && (n[t.key] = e.getInt16(t.offset))
        }),
    n.packetLen < t.byteLength && convertToObject(t.slice(0, n.packetLen)),
        this.decoder = new TextDecoder(),
    !n.op || 5 !== n.op && n.op !== 8)
        n.op && 3 === n.op && (n.body = {
            count: e.getInt32(16)
        });
    else
        for (var i = 0, s = n.packetLen, a = "", u = ""; i < t.byteLength; i += s) {
            s = e.getInt32(i),
                a = e.getInt16(i + 4);
            if (n.ver === 0) {
                var c = this.decoder.decode(t.slice(i + a, i + s));
                u = 0 !== c.length ? JSON.parse(c) : null
            } else if (n.ver === 3) {
                var l = t.slice(i + a, i + s)
                    , h = new Int8Array(brotliDecompressSync(l));
                u = convertToObject(h.buffer).body
            }
            u && n.body.push(u)
        }
    return n
}