哲学驱动式软件架构法——基于易经的软件架构系统观与实践（ 12.2）

12.2 一个缓冲式多进程请求反馈串口模块的通讯修复

（1） 模块架构简述 该模块采用分层设计，自上而下依次为：

• 插件接口层：通过 PLUG_DLL_EXPORT 导出标准函数（newSerial、releaseSerial、serialEat、serialSetOption），便于动态加载与集成。
• 状态机管理层：以有限状态机（FSM）管理串口的整个生命周期（就绪、打开、等待、超时、错误、关闭等）。
• 数据缓冲层：利用双向链表（list_t）缓存待发送的数据包，并提供流量控制能力。
• I/O处理层：支持 select 和 epoll 两种多路复用机制，负责实际的数据读写。
• 线程同步层：通过互斥锁与条件变量协调发送与接收线程，确保线程安全。

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应用层

插件接口

状态机管理

数据缓冲队列

发送线程

接收线程

select/epoll

物理串口

串口的工作流程天然具有状态性：打开 → 空闲 → 发送 → 等待响应 → 接收 → 完成/超时/错误 → 关闭。该模块将这一流程抽象为7个明确的状态：

每个状态都绑定了进入函数与离开函数。例如进入 OPENED 状态时会打印日志，离开时则根据触发数据决定下一状态。状态间的转换由条件函数控制，使得逻辑清晰且易于扩展。 初始化时，通过 fsmAddStat 注册各状态，并通过 fsmAddTrans 添加转换条件。这种设计将业务逻辑（如超时处理、错误恢复）封装在对应状态函数中，主流程因此变得异常简洁。

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