Flutter类型化消息处理插件typed_messages的使用

Flutter类型化消息处理插件typed_messages的使用

消息（Messages）

消息是一段可以在节点之间共享的信息。

让我们定义一个消息：

class ClientInfoMessage extends Message {
  const ClientInfoMessage(this.name, this.avatar, this.clientId)
      : assert(
          name.length <= 20,
          'client info name can not exceed 20 bytes : ${name.length}',
        );

  final int clientId; // 20 bytes Uint
  final String name; // 字符长度在[0, 20]范围内
  final int avatar; // 2 bytes Uint
}

原型（Prototypes）

原型用于在发送前对消息进行编码，并验证和解码传入的消息。

const int kClientInfoMessageId = 0;

// 定义或分配原型到__MessagesPrototypes__单例
IMessagePrototype.definePrototype(const ClientInfoMessagePrototype());

class ClientInfoMessagePrototype implements IMessagePrototype<ClientInfoMessage> {
  const ClientInfoMessagePrototype();

  [@override](/user/override)
  Uint8List encode(ClientInfoMessage message) {
    final writer = BytesWriter(22 + message.name.length);
    writer.writeSingleByte(kClientInfoMessageId); // 写入消息ID
    writer.writeSingleByte(message.name.length); // 写入名称长度
    writer.writeText(message.name); // 写入名称
    writer.writeUint(message.avatar, 2); // 写入头像
    writer.writeUint(message.clientId, 20); // 写入客户端ID
    return writer.toBuffer(); // 返回字节列表
  }

  [@override](/user/override)
  ClientInfoMessage decode(Uint8List bytes) {
    final reader = BytesReader(bytes);
    final int nameLength = reader.readSingleByte(1); // 读取名称长度
    final String name = reader.readText(2, nameLength); // 读取名称
    final int avatar = reader.readUint(2 + nameLength, 2); // 读取头像
    final int id = reader.readUint(4 + nameLength, 20); // 读取客户端ID
    return ClientInfoMessage(name, avatar, id); // 返回解码后的消息
  }

  [@override](/user/override)
  bool validate(Uint8List bytes) {
    final reader = BytesReader(bytes);

    if (reader.length < 22 || reader.length > 42) return false; // 验证字节长度

    final int id = reader.readSingleByte(0); // 读取消息ID
    final int nameLength = reader.readSingleByte(1); // 读取名称长度

    return id == kClientInfoMessageId && nameLength >= 0 && nameLength <= 20; // 验证消息ID和名称长度
  }
}

使用（Usage）

现在我们已经创建了ClientInfoMessage类并定义了其原型ClientInfoMessagePrototype，使用IMessagePrototype.definePrototype方法。

我们有两种方式来编码和解码数据：

方法1：使用Message抽象类

final message = ClientInfoMessage("My Client", 0, 568978596);

final Uint8List bytes = Message.encode(message); // 编码消息

final ClientInfoMessage? decodedMessage = Message.decode(bytes); // 解码消息

方法2：使用MessagesPrototypes单例和原型直接

final instance = MessagesPrototypes.instance;
final message = ClientInfoMessage("My Client", 0, 568978596);

// 编码
final Uint8List? bytes = instance.encodeMessage(message);

// 解码
final ClientInfoMessage? decodedMessage = instance.decodeBytes(bytes!);

// 使用定义的原型
final IMessagePrototype<ClientInfoMessage>? prototype = instance.findPrototypeByMessageType<ClientInfoMessage>();

prototype.encode(message); // 编码消息
prototype.decode(bytes!); // 解码消息
prototype.validate(bytes!); // 验证消息

示例代码

import 'dart:typed_data';

import 'package:typed_messages/typed_messages.dart';

const int kClientInfoMessageId = 0;

class ClientInfoMessage extends Message {
  const ClientInfoMessage(this.name, this.avatar, this.clientId)
      : assert(
          name.length >= 0 && name.length <= 20,
          'name length must be in range [0, 20] characters',
        );

  final String name;
  final int avatar;
  final int clientId;
}

class ClientInfoMessagePrototype
    implements IMessagePrototype<ClientInfoMessage> {
  const ClientInfoMessagePrototype();

  [@override](/user/override)
  Uint8List encode(ClientInfoMessage message) {
    final writer = BytesWriter(22 + message.name.length);
    writer.writeSingleByte(kClientInfoMessageId);
    writer.writeSingleByte(message.name.length);
    writer.writeText(message.name);
    writer.writeUint(message.avatar, 2);
    writer.writeUint(message.clientId, 20);
    return writer.toBuffer();
  }

  [@override](/user/override)
  ClientInfoMessage decode(Uint8List bytes) {
    final reader = BytesReader(bytes);
    final int nameLength = reader.readSingleByte(1);
    final String name = reader.readText(2, nameLength);
    final int avatar = reader.readUint(2 + nameLength, 2);
    final int clientId = reader.readUint(4 + nameLength, 20);
    return ClientInfoMessage(name, avatar, clientId);
  }

  [@override](/user/override)
  bool validate(Uint8List bytes) {
    final reader = BytesReader(bytes);
    if (reader.length < 22 || reader.length > 42) return false;
    final int id = reader.readSingleByte(0);
    final int nameLength = reader.readSingleByte(1);
    return id == kClientInfoMessageId && nameLength >= 0 && nameLength <= 20;
  }
}

void main() {
  IMessagePrototype.definePrototype(const ClientInfoMessagePrototype());

  final message = ClientInfoMessage("My Client", 0, 568978596);
  Uint8List bytes;
  ClientInfoMessage? decodedMessage;

  // 编码
  bytes = Message.encode(message);

  // 解码
  decodedMessage = Message.decode<ClientInfoMessage>(bytes);

  // 使用MessagesPrototypes实例
  final instance = MessagesPrototypes.instance;
  final IMessagePrototype<ClientInfoMessage>? prototype =
      instance.findPrototypeByMessageType<ClientInfoMessage>();

  bytes = prototype!.encode(message);
  final bool isValidBytes = prototype.validate(bytes);
  decodedMessage = prototype.decode(bytes);
}