C/C++用狀態跳躍表聯合函數指標數組實現狀態機器FSM

標籤：狀態機器   函數指標   c++   c   枚舉   

狀態機器在工程中使用非常的頻繁，有如下常見的三種實現方法：
1. switch-case 實現，適合簡單的狀態機器；
2. 二維狀態表state-event實現，邏輯清晰，但是矩陣通常比較稀疏，而且維護麻煩；
3. 用狀態跳躍表stateTransfer Table實現，數組大小等於狀體轉移邊個數，易擴充；
下面用一個例子來進行詳細說明，描述的如下情境：

描述對象：門
狀態：開著、關著、鎖著 (這裡的關著指關了但未鎖的狀態)
事件：開門、關門、上鎖、解鎖

代碼實現用枚舉來定義狀態和事件，操作資料節點轉移到目的狀態用函數實現。枚舉本身預設是從0開始的int類型，利用這個特點將狀態轉移函數放到函數指標數組中與狀態對應起來，方便操作。
核心資料結構如下：

狀態：枚舉類型
事件：枚舉類型
狀態轉移結構體：{目前狀態、事件、下個狀態}，定義一個全域數組來使用
狀態變更函數：到下個狀態(放到數組中與狀態枚舉對應起來)

此種實現方法容易擴充，增加狀態和事件都比較容易。如果存在一個狀態通過對應事件可以轉移到多個狀態的情形，則可以擴充狀態轉移函數，或者在狀態轉移結構中增加一個判斷函數欄位。
代碼實現如下：

#include <iostream>using namespace std;typedef enum{    OPENED,    CLOSED,    LOCKED,}  State;typedef enum{    OPEN,    CLOSE,    LOCK,    UNLOCK} Event;typedef struct{    State currentState;    Event event;    State NextState;} StateTransfer;typedef struct{    State state;    int transferTimes;}Door;StateTransfer g_stateTransferTable[]{    {OPENED, CLOSE,  CLOSED},    {CLOSED, OPEN,   OPENED},    {CLOSED, LOCK,   LOCKED},    {LOCKED, UNLOCK, CLOSED},};void toOpen(Door& door);void toClose(Door& door);void toLock(Door& door);typedef void (*pfToState)(Door& door);pfToState g_pFun[] = {toOpen, toClose, toLock}; //狀態枚舉值對應下標void toOpen(Door& door){    door.state = OPENED;    cout << "open the door!\n";}void toClose(Door& door){    door.state = CLOSED;    cout << "close the door!\n";}void toLock(Door& door){    door.state = LOCKED;    cout << "lock the door!\n";}void transfer(Door& door,const Event event){    for (int i = 0; i < sizeof(g_stateTransferTable)/sizeof(StateTransfer); ++i) {        if(door.state == g_stateTransferTable[i].currentState &&           event == g_stateTransferTable[i].event){            g_pFun[g_stateTransferTable[i].NextState](door);            door.transferTimes++;            cout << "transfer ok!\n";            return;        }    }    cout << "This event cannot transfer current state!!\n";    return;}void printDoor(const Door& door){    string stateNote[] = {"opened","closed","locked"}; // 下標正好對應狀態枚舉值    cout << "the door‘s state is: " << stateNote[door.state] << endl;    cout << "the door transfer times is: " << door.transferTimes << endl;}int main(){    Door door = {CLOSED, 0};    printDoor(door);    transfer(door, OPEN);    printDoor(door);    transfer(door, LOCK);    printDoor(door);    transfer(door, CLOSE);    printDoor(door);    return 0;}

運行結果如下：

the door’s state is: closed
the door transfer times is: 0
open the door!
transfer ok!
the door’s state is: opened
the door transfer times is: 1
This event cannot transfer current state!!
the door’s state is: opened
the door transfer times is: 1
close the door!
transfer ok!
the door’s state is: closed
the door transfer times is: 2

著作權聲明：本文為博主原創文章，未經博主允許不得轉載。[http://blog.csdn.net/thisinnocence]

C/C++用狀態跳躍表聯合函數指標數組實現狀態機器FSM