Hi,

First of all, pardon my English. English isn’t my native language J.

I am reading the method switch_core_session_run(switch_core_session_t *session) and I would be really appreciated if someone could shed some light on how the method works. Below is the logic according to my understanding:

1. LINE 303:              while ((state = switch_channel_get_state(session->channel)) != CS_DESTROY)

ð if state is CS_DESTROY return and do nothing ?

2. Inside if (state != switch_channel_get_running_state(session->channel) || state >= CS_HANGUP)

{

…

}                                             

a. LINE 308:              state != switch_channel_get_running_state(session->channel) || state >= CS_HANGUP

ð to check if channel->state and channel->running_state not equal. This is to avoid running the STATE_MACRO multiple times. However I don’t understand why do we need (state >= CS_HANGUP) ?.

b. Inside STATE_MACRO code block

i. LINE 229:              midstate = state

ð  to save the current state.

ii. LINE 231:              if (!driver_state_handler->on_##__STATE || (driver_state_handler->on_##__STATE(session) == SWITCH_STATUS_SUCCESS)

ð to check either endpoint_interface->state_handler is NULL or return SWITCH_STATUS_SUCCESS so it will continue to execute handlers in session->channel, runtime.state_handlers and core standard state handlers. It means if the condition is not true, channel->state_handlers, runtime.state_handlers and core standard state handlers will NOT be executed at all ?

iii. LINE 246:              if (!proceed) global_proceed = 0;

ð If something wrong in the previous while loop, do not run core standard state handlers ?

iv. LINE 247:              proceed = 1;                                                                                                                                                                                      

LINE 248:              while (do_extra_handlers && proceed && (application_state_handler = switch_core_get_state_handler(index++)) != 0) { …}

ð Since we set proceed = 1, do we still need (&& proceed) inside the condition in while loop ?

v. LINE 260:              if (!proceed || midstate != switch_channel_get_state(session->channel)) global_proceed = 0;

ð If not proceed or the channel state has changed by some of the state handlers executed earlier, do not execute core standard state handler ?

vi. LINE 266:              while (silly)

ð silly is never changed, does it mean we could go into an endless while loop ?

Sorry for the long email and some questions are probably dumb but I am trying to understand about FreeSwitch, especially the core and the core state machine. If it is documented somewhere about the workflow happening inside FreeSwitch, please enlighten me as what I am doing now is to read the code line by line and figure out which may not be the most efficient .

Thank you for reading this

Regards

Alex To