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copied!<p>I prefer to use a table driven approach for most state machines:</p> <pre><code>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 } } </code></pre> <p>This can of course be extended to support multiple state machines, etc. Transition actions can be accommodated as well:</p> <pre><code>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; }; </code></pre> <p>The table driven approach is easier to maintain and extend and simpler to map to state diagrams.</p>

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