bilibili-socket.js

function encodeUtf8(str) {
    let bytes = [];
    let len, c;
    len = str.length;
    for (let i = 0; i < len; i++) {
        c = str.charCodeAt(i);
        if (c >= 0x010000 && c <= 0x10FFFF) {
            bytes.push(((c >> 18) & 0x07) | 0xF0);
            bytes.push(((c >> 12) & 0x3F) | 0x80);
            bytes.push(((c >> 6) & 0x3F) | 0x80);
            bytes.push((c & 0x3F) | 0x80);
        } else if (c >= 0x000800 && c <= 0x00FFFF) {
            bytes.push(((c >> 12) & 0x0F) | 0xE0);
            bytes.push(((c >> 6) & 0x3F) | 0x80);
            bytes.push((c & 0x3F) | 0x80);
        } else if (c >= 0x000080 && c <= 0x0007FF) {
            bytes.push(((c >> 6) & 0x1F) | 0xC0);
            bytes.push((c & 0x3F) | 0x80);
        } else {
            bytes.push(c & 0xFF);
        }
    }
    return bytes;
}

function byteToString(arr) {
    if (typeof arr === 'string') {
        return arr;
    }
    let str = '',
        _arr = arr;
    for (let i = 0; i < _arr.length; i++) {
        let one = _arr[i].toString(2),
            v = one.match(/^1+?(?=0)/);
        if (v && one.length == 8) {
            let bytesLength = v[0].length;
            let store = _arr[i].toString(2).slice(7 - bytesLength);
            for (let st = 1; st < bytesLength; st++) {
                store += _arr[st + i].toString(2).slice(2);
            }
            str += String.fromCharCode(parseInt(store, 2));
            i += bytesLength - 1;
        } else {
            str += String.fromCharCode(_arr[i]);
        }
    }
    return str;
}

class BilibiliSocket {
    /**
     * 
     * @param {number} roomId 
     */
    constructor(roomId) {
        /**
         * @type {WebSocket}
         */
        this.ws = null;
        /**
         * @type {boolean}
         */
        this.connecting = false;
        /**
         * @type {number}
         */
        this.roomId = roomId;
        /**
         * @type {(e: Event) => any}
         */
        this.onOpen = e => { };
        /**
         * @type {(value: number) => any}
         */
        this.onPopularityChange = value => { };
        /**
         * @type {(msg: string) => any}
         */
        this.onMessage = msg => { };
        /**
         * @type {(e: Event) => any}
         */
        this.onClose = e => { };
        /**
         * @type {(e: Event) => any}
         */
        this.onError = e => { };
    }
    connect() {
        this.ws = new WebSocket("wss://broadcastlv.chat.bilibili.com:2245/sub");

        this.ws.onopen = e => {
            this.connecting = true;

            let data = {
                "uid": 0,
                "roomid": this.roomId,
                "protover": 1,
                "platform": "web",
                "clientver": "1.4.0"
            };
            let body = encodeUtf8(JSON.stringify(data));
            let bodyLen = body.length;
            let headLen = 16;

            let header = [0, 0, 0, headLen + bodyLen, 0, headLen, 0, 1, 0, 0, 0, 7, 0, 0, 0, 1];

            let sendTxt = header.concat(body);

            this.ws.send(byteToString(sendTxt));

            let heart = [0, 0, 0, 18, 0, headLen, 0, 1, 0, 0, 0, 2, 0, 0, 0, 1, 123, 125];
            let startHeart = setInterval(() => {
                if (this.connecting) {
                    this.ws.send(byteToString(heart));
                } else {
                    clearInterval(startHeart);
                }
            }, 30000);

            this.onOpen(e);
        };
        this.ws.onclose = e => {
            this.connecting = false;
            this.onClose(e);
        };
        this.ws.onmessage = e => {
            let data = e.data;
            let cntt = 0;
            let offset = 0;
            while (offset < data.byteLength) {
                let total = 0;
                let totalLen = new Uint8Array(data.slice(offset, offset + 4));
                for (let [i, num] of totalLen.entries()) {
                    total += num * Math.pow(16, (3 - i) * 2);
                }

                let header = 0;
                let headerLen = new Uint8Array(data.slice(offset + 4, offset + 6));
                for (let [i, num] of headerLen.entries()) {
                    header += num * Math.pow(16, (1 - i) * 2);
                }

                let type = 0;
                let typeLen = new Uint8Array(data.slice(offset + 10, offset + 12));
                for (let [i, num] of typeLen.entries()) {
                    type += num * Math.pow(16, (1 - i) * 2);
                }

                let msg = null;
                switch (type) {
                    case 3: {
                        // 人气
                        let temp = 0;
                        let popuLen = new Uint8Array(data.slice(offset + 16, offset + total));
                        for (let [i, num] of popuLen.entries()) {
                            temp += num * Math.pow(16, (3 - i) * 2);
                        }
                        this.onPopularityChange(temp);
                        break;
                    }
                    case 5: {
                        // 弹幕
                        let msgLen = new Uint8Array(data.slice(offset + 16, offset + total));
                        let decode = false;
                        try {
                            msgLen = pako.inflate(msgLen);
                            decode = true;
                        } catch (e) {
                            decode = false;
                        }

                        if (decode) {
                            let i = 0;
                            let segLen = 0;
                            while (i < msgLen.length) {
                                segLen = msgLen[i + 2] * 256 + msgLen[i + 3];
                                let msg2 = byteToString(msgLen.slice(i + 16, i + segLen));

                                this.onMessage(msg2);
                                i = i + segLen;
                            }
                        } else {
                            this.onMessage(byteToString(msgLen));
                        }
                        break;
                    }
                }

                offset += total;
                ++cntt;
            }
        };
        this.ws.onerror = e => {
            this.onError(e);
            this.connect();
        };
        this.ws.binaryType = "arraybuffer";
    }
}