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void | (*FpiSsmCompletedCallback) () |
void | (*FpiSsmHandlerCallback) () |
#define | fpi_ssm_new() |
FpiSsm * | fpi_ssm_new_full () |
void | fpi_ssm_free () |
void | fpi_ssm_start () |
void | fpi_ssm_start_subsm () |
void | fpi_ssm_next_state () |
void | fpi_ssm_next_state_delayed () |
void | fpi_ssm_jump_to_state () |
void | fpi_ssm_jump_to_state_delayed () |
void | fpi_ssm_cancel_delayed_state_change () |
void | fpi_ssm_mark_completed () |
void | fpi_ssm_mark_failed () |
void | fpi_ssm_set_data () |
gpointer | fpi_ssm_get_data () |
GError * | fpi_ssm_get_error () |
GError * | fpi_ssm_dup_error () |
int | fpi_ssm_get_cur_state () |
void | fpi_ssm_usb_transfer_cb () |
Asynchronous driver design encourages some kind of state machine behind it. In most cases, the state machine is entirely linear - you only go to the next state, you never jump or go backwards. The FpiSsm functions help you implement such a machine.
e.g. S1
↦ S2
↦ S3
↦ S4
S1
is the start state
There is also an implicit error state and an implicit accepting state
(both with implicit edges from every state).
You can also jump to any arbitrary state (while marking completion of the current state) while the machine is running. In other words there are implicit edges linking one state to every other state.
To create an fpi_ssm, you pass a state handler function and the total number of
states (4 in the above example) to fpi_ssm_new()
. Note that the state numbers
start at zero, making them match the first value in a C enumeration.
To start a ssm, you pass in a completion callback function to fpi_ssm_start()
which gets called when the ssm completes (both on error and on failure).
Starting a ssm also takes ownership of it.
To iterate to the next state, call fpi_ssm_next_state()
. It is legal to
attempt to iterate beyond the final state - this is equivalent to marking
the ssm as successfully completed.
To mark successful completion of a SSM, either iterate beyond the final
state or call fpi_ssm_mark_completed()
from any state.
This will also invalidate the machine, freeing it.
To mark failed completion of a SSM, call fpi_ssm_mark_failed()
from any
state. You must pass a non-zero error code.
Your state handling function looks at the return value of
fpi_ssm_get_cur_state()
in order to determine the current state and hence
which operations to perform (a switch statement is appropriate).
Typically, the state handling function fires off an asynchronous communication with the device (such as a libsub transfer), and the callback function iterates the machine to the next state upon success (or fails).
Your completion callback should examine the return value of
fpi_ssm_get_error()
in ordater to determine whether the FpiSsm completed or
failed. An error code of zero indicates successful completion.
void (*FpiSsmCompletedCallback) (FpiSsm *ssm
,FpDevice *dev
,GError *error
);
The callback called when a state machine completes successfully,
as set when calling fpi_ssm_start()
.
ssm |
a FpiSsm state machine |
|
dev |
the fp_dev fingerprint device |
|
error |
The GError or |
[transfer full] |
void (*FpiSsmHandlerCallback) (FpiSsm *ssm
,FpDevice *dev
);
The callback called when a state machine transitions from one
state to the next, as set when calling fpi_ssm_new()
.
#define fpi_ssm_new(dev, handler, nr_states)
Allocate a new ssm, with nr_states
states. The handler
callback
will be called after each state transition.
This is a macro that calls fpi_ssm_new_full()
using the stringified
version of nr_states
, so will work better with named parameters.
FpiSsm * fpi_ssm_new_full (FpDevice *dev
,FpiSsmHandlerCallback handler
,int nr_states
,const char *machine_name
);
Allocate a new ssm, with nr_states
states. The handler
callback
will be called after each state transition.
void
fpi_ssm_free (FpiSsm *machine
);
Frees a state machine. This does not call any error or success callbacks, so you need to do this yourself.
void fpi_ssm_start (FpiSsm *ssm
,FpiSsmCompletedCallback callback
);
Starts a state machine. You can also use this function to restart
a completed or failed state machine. The callback
will be called
on completion.
Note that ssm
will be stolen when this function is called.
So that all associated data will be free'ed automatically, after the
callback
is ran.
ssm |
an FpiSsm state machine. |
[transfer full] |
callback |
the FpiSsmCompletedCallback callback to call on completion |
void fpi_ssm_start_subsm (FpiSsm *parent
,FpiSsm *child
);
Starts a state machine as a child of another. if the child completes successfully, the parent will be advanced to the next state. if the child fails, the parent will be marked as failed with the same error code.
The child will be automatically freed upon completion or failure.
void
fpi_ssm_next_state (FpiSsm *machine
);
Iterate to next state of a state machine. If the current state is the
last state, then the state machine will be marked as completed, as
if calling fpi_ssm_mark_completed()
.
void fpi_ssm_next_state_delayed (FpiSsm *machine
,int delay
,GCancellable *cancellable
);
Iterate to next state of a state machine with a delay of delay
ms. If the
current state is the last state, then the state machine will be marked as
completed, as if calling fpi_ssm_mark_completed()
.
Passing a valid GCancellable will cause the action to be cancelled when
cancellable
is.
void fpi_ssm_jump_to_state (FpiSsm *machine
,int state
);
Jump to the state
state, bypassing intermediary states.
If state
is the last state, the machine won't be completed unless
fpi_ssm_mark_completed()
isn't explicitly called.
void fpi_ssm_jump_to_state_delayed (FpiSsm *machine
,int state
,int delay
,GCancellable *cancellable
);
Jump to the state
state with a delay of delay
milliseconds, bypassing
intermediary states.
Passing a valid GCancellable will cause the action to be cancelled when
cancellable
is.
void
fpi_ssm_mark_completed (FpiSsm *machine
);
Mark a ssm as completed successfully. The callback set when creating
the state machine with fpi_ssm_new()
will be called synchronously.
void fpi_ssm_mark_failed (FpiSsm *machine
,GError *error
);
Mark a state machine as failed with error
as the error code, completing it.
void fpi_ssm_set_data (FpiSsm *machine
,gpointer ssm_data
,GDestroyNotify ssm_data_destroy
);
Sets machine
's data (freeing the existing data, if any).
gpointer
fpi_ssm_get_data (FpiSsm *machine
);
Retrieve the pointer to SSM data set with fpi_ssm_set_ssm_data()
GError *
fpi_ssm_get_error (FpiSsm *machine
);
Returns the error code set by fpi_ssm_mark_failed()
.
GError *
fpi_ssm_dup_error (FpiSsm *machine
);
Returns the error code set by fpi_ssm_mark_failed()
.
int
fpi_ssm_get_cur_state (FpiSsm *machine
);
Returns the value of the current state. Note that states are 0-indexed, so a value of 0 means “the first state”.
void fpi_ssm_usb_transfer_cb (FpiUsbTransfer *transfer
,FpDevice *device
,gpointer unused_data
,GError *error
);
Can be used in as a FpiUsbTransfer callback handler to automatically advance or fail a statemachine on transfer completion.
Make sure to set the FpiSsm on the transfer.