我们需要在C秒内实现一个简单的状态机
switch(state)
{
case STATE_1:
state = DoState1(transition);
break;
case STATE_2:
state = DoState2(transition);
break;
}
...
DoState2(int transition)
{
// Do State Work
...
if(transition == FROM_STATE_2) {
// New state when doing STATE 2 -> STATE 2
}
if(transition == FROM_STATE_1) {
// New State when moving STATE 1 -> STATE 2
}
return new_state;
}
有更好的方法吗
编辑: 对于C++，我认为Boost Statechart库可能是可行的.但是，它对C有not个帮助.让我们集中在C用例上.
对于大多数状态机，我更喜欢使用表驱动的方法:
typedef enum { STATE_INITIAL, STATE_FOO, STATE_BAR, NUM_STATES } state_t;
typedef struct instance_data instance_data_t;
typedef state_t state_func_t( instance_data_t *data );
state_t do_state_initial( instance_data_t *data );
state_t do_state_foo( instance_data_t *data );
state_t do_state_bar( instance_data_t *data );
state_func_t* const state_table[ NUM_STATES ] = {
do_state_initial, do_state_foo, do_state_bar
};
state_t run_state( state_t cur_state, instance_data_t *data ) {
return state_table[ cur_state ]( data );
};
int main( void ) {
state_t cur_state = STATE_INITIAL;
instance_data_t data;
while ( 1 ) {
cur_state = run_state( cur_state, &data );
// do other program logic, run other state machines, etc
}
}
当然，这可以扩展到支持多状态机等.也可以适应转换操作:
typedef void transition_func_t( instance_data_t *data );
void do_initial_to_foo( instance_data_t *data );
void do_foo_to_bar( instance_data_t *data );
void do_bar_to_initial( instance_data_t *data );
void do_bar_to_foo( instance_data_t *data );
void do_bar_to_bar( instance_data_t *data );
transition_func_t * const transition_table[ NUM_STATES ][ NUM_STATES ] = {
{ NULL, do_initial_to_foo, NULL },
{ NULL, NULL, do_foo_to_bar },
{ do_bar_to_initial, do_bar_to_foo, do_bar_to_bar }
};
state_t run_state( state_t cur_state, instance_data_t *data ) {
state_t new_state = state_table[ cur_state ]( data );
transition_func_t *transition =
transition_table[ cur_state ][ new_state ];
if ( transition ) {
transition( data );
}
return new_state;
};
表驱动方法更易于维护和扩展，并且更易于映射到状态图.