codec.js

class CoreEncode {
  buffer = [];
  view = new DataView(new ArrayBuffer(8));
  
  write(...bytes) {
    this.buffer.push(...bytes);
  }
  
  start_arr(len) {
    if (len > 15 && len < 65535) {
      this.write(0xdc, len >>> 8, len);
    } else if (len < 15)
      this.write(0x90 + len);
    else {
      this.write(0xdd, len >>> 24, len >>> 16, len >>> 8, len);
    }
    
    return this;
  }
  
  fixstr(str) {
    const strenc = str.split("").map(_ => _.charCodeAt(0));
    if (strenc.length <= 31) {
      return this.write(0xa0 + strenc.length, ...strenc);
    } else if (strenc.length < 255) {
      this.write(0xd9, strenc.length, ...strenc);
    } else if (strenc.length < 65535) {
      this.write(0xda, strenc.length >>> 8, strenc.length, ...strenc);
    } else if (strenc.length < 4294967295) {
      this.write(0xdb, strenc.length >>> 24, strenc.length >>> 16, strenc.length >>> 8, strenc.length, ...strenc);
    }
    
    return this;
  }
  
  map(length) {
    if (length > 15 && length < 65535) {
      this.write(0xde, length >>> 8, length);
    } else if (length < 15)
      this.write(0x80 + length);
    else {
      this.write(0xdf, length >>> 24, length >>> 16, length >>> 8, length);
    }
    
    return this;
  }
  
  add_num(num) {
    if (typeof num == "bigint") num = Number(num);
    if (!Number.isInteger(num)) {
      this.view.setFloat64(0, num);
        
      this.write(0xcb, ...new Uint8Array(this.view.buffer));
      
      return this;
    }

    if (num == 0) this.write(0);
    else if (num > 0) { 
      if (num < 127) {
        this.write(num);
      } else if (num < 256) {
        this.write(0xcc, num);
      } else if (num < 65535) {
        this.write(0xcd, num >>> 8, num);
        } else if (num < 4294967296) {
          this.write(0xce, num >>> 24, num >>> 16, num >>> 8, num);
        } else if (num <= 18446744073709552000) {
          let h = num / 4294967296, l = num % 4294967296;
          this.write(0xcf, h >>> 24, h >>> 16, h >>> 8, h, l >>> 24, l >>> 16, l >>> 8, l);
        } else this.write(0xcf, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff);
      } else {
      if (num > -128) {
        this.write(0xd0, num);
      } else if (num > -32768) {
        this.write(0xd1, num >>> 8, num);
      } else if (num > -4294967296) {
          this.write(0xd2, num >>> 24, num >>> 16, num >>> 8, num);
        } else if (num >= -18446744073709552000) {
          let h = num / 4294967296, l = num % 4294967296;
          this.write(0xd3, h >>> 24, h >>> 16, h >>> 8, h, l >>> 24, l >>> 16, l >>> 8, l);
        } else this.write(0xd3, 0x80, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00);
    }
    
    return this;
  }
  
  encode(data, noReset) {
    if (!noReset) this.buffer.length = 0;
    if (data?.constructor?.name == "Array") {
      this.start_arr(data.length);
      for (let i = 0; i < data.length; i++) this.encode(data[i], true);
    } else if (typeof data == "object" && !!data) {
      const keys = Object.keys(data);
      this.map(keys.length);
      
      for (let i = 0; i < keys.length; i++) {
        this.encode(keys[i], true);
        this.encode(data[keys[i]], true);
      }
    } else if (typeof data == "string") this.fixstr(data);
    else if (typeof data == "number" || typeof data == "bigint") this.add_num(data);
    else if (typeof data == "boolean") this.write(data ? 0xC3 : 0xC2);
    else if (typeof data == "undefined" || isNaN(data) || data == null) this.write(0xc0);
    
    return this.buffer;
  }
}

class CoreDecode {
  buffer = [];
  offset = 0;
  
  readByte() {
    return this.buffer[this.offset++];
  }
  
  readBytes(amount) {
    return this.buffer.slice(this.offset, this.offset += amount);
  }
  
  skip(amount) {
    this.offset += amount;
  }
  
  decode(buff) {
    if (buff) {
      this.buffer = buff;
      this.view = new DataView(new Uint8Array(this.buffer).buffer);
      this.offset = 0;
    }
    
    const byte = this.readByte();
    if (byte >= 0xa0 && byte <= 0xbf) {
      const length = byte - 0xa0;
      return String.fromCharCode(...this.readBytes(length));
    } else if (byte == 0xd9) {
      return String.fromCharCode(...this.readBytes(this.readByte()));
    } else if (byte == 0xda) {
      return String.fromCharCode(...this.readBytes(this.readByte() << 8 | this.readByte()));
    } else if (byte == 0xdb) {
      return String.fromCharCode(...this.readBytes(this.readByte() >>> 24 | this.readByte() >>> 16 | this.readByte() >>> 8 | this.readByte()));
    } else if ((byte >= 0x90 && byte <= 0x9f) || byte == 0xdc || byte == 0xdd) {
      const length = byte == 0xdc ? (this.readByte() << 8 | this.readByte()) : byte == 0xdd ? (this.readByte() >>> 24 | this.readByte() >>> 16 | this.readByte() >>> 8 | this.readByte()) : byte - 0x90;
      const array = [];
      for (let i = 0; i < length; i++) {
        array.push(this.decode());
      }
      return array;
    } else if ((byte >= 0x80 && byte <= 0x8f) || byte == 0xde || byte == 0xdf) {
      const length = byte == 0xde ? (this.readByte() << 8 | this.readByte()) : byte == 0xdf ? (this.readByte() >>> 24 | this.readByte() >>> 16 | this.readByte() >>> 8 | this.readByte()) : byte - 0x80;
      const map = {};
      for (let i = 0; i < length; i++) {
        const key = this.decode();
        const value = this.decode();
        if (key != "__proto__") map[key] = value;
      }
      return map;
    } else if (byte > 0 && byte < 0x7f) {
      return byte;
    } else if (byte == 0xcc) {
      return this.readByte();
    } else if (byte == 0xcd) {
      return this.readByte() << 8 | this.readByte();
    } else if (byte == 0xce) {
      return this.readByte() << 24 | this.readByte() << 16 | this.readByte() << 8 | this.readByte();
    } else if (byte == 0xcf) {
      return BigInt(this.readByte()) << 8n | BigInt(this.readByte()) << 16n | BigInt(this.readByte()) << 24n | BigInt(this.readByte()) << 32n | BigInt(this.readByte()) << 40n | BigInt(this.readByte()) << 48n | BigInt(this.readByte()) << 56n | BigInt(this.readByte()) << 64n;
    } else if (byte >= 0xe0 && byte <= 0xff) {
      return 0xff - byte - 1;
    } else if (byte == 0xd0) {
      return this.readByte() - 256;
    } else if (byte == 0xd1) {
      return -(this.readByte() << 8 | this.readByte());
    } else if (byte == 0xd2) {
      return -(this.readByte() << 24 | this.readByte() << 16 | this.readByte() << 8 | this.readByte());
    } else if (byte == 0xd3) {
      return (0n | BigInt(this.readByte()) << 8n | BigInt(this.readByte()) << 16n | BigInt(this.readByte()) << 24n | BigInt(this.readByte()) << 32n | BigInt(this.readByte()) << 40n | BigInt(this.readByte()) << 48n | BigInt(this.readByte()) << 56n | BigInt(this.readByte()) << 64n) * (-1n);
    } else if (byte == 0xcb) {
      const res = this.view.getFloat64(this.offset);
      this.skip(8);
      return res;
    } else if (byte == 0xc3) return true;
    else if (byte == 0xc2) return false;
    else if (byte == 0xc0) return null;
    else return byte;
  }
}

const encoder = new CoreEncode();
const decoder = new CoreDecode();

const msgpack = {
  pack(data) {
    return new Promise((accept, reject) => {
      try {
        accept(this._encode(data));
      } catch(e) {
        reject(e);
      }
    })
  },
  unpack(buffer) {
    return new Promise((accept, reject) => {
      try {
        accept(this._decode(buffer));
      } catch(e) {
        reject(e);
      }
    });
  },
  _encode: encoder.encode.bind(encoder),
  _decode: decoder.decode.bind(decoder)
};