From cd69c2a54201b4e0c4ba86d4248937120e1957e7 Mon Sep 17 00:00:00 2001 From: Lukas Larsson Date: Wed, 8 Jan 2014 18:54:15 +0100 Subject: ose: Create OSE application Create an specific OSE application that mainly contains documentation around the OSE specific part of Erlang/OTP. --- lib/ose/doc/src/ose_signals_chapter.xml | 197 ++++++++++++++++++++++++++++++++ 1 file changed, 197 insertions(+) create mode 100644 lib/ose/doc/src/ose_signals_chapter.xml (limited to 'lib/ose/doc/src/ose_signals_chapter.xml') diff --git a/lib/ose/doc/src/ose_signals_chapter.xml b/lib/ose/doc/src/ose_signals_chapter.xml new file mode 100644 index 0000000000..2a6ddb5765 --- /dev/null +++ b/lib/ose/doc/src/ose_signals_chapter.xml @@ -0,0 +1,197 @@ + + + + +
+ + 20132014 + Ericsson AB. All Rights Reserved. + + + The contents of this file are subject to the Erlang Public License, + Version 1.1, (the "License"); you may not use this file except in + compliance with the License. You should have received a copy of the + Erlang Public License along with this software. If not, it can be + retrieved online at http://www.erlang.org/. + + Software distributed under the License is distributed on an "AS IS" + basis, WITHOUT WARRANTY OF ANY KIND, either express or implied. See + the License for the specific language governing rights and limitations + under the License. + + + + Interacting with Enea OSE + Lukas Larsson + + 2014-01-08 + A + ose_signals_chapter.xml +
+ + +
+ Introduction +

The main way which programs on Enea OSE interact is through the + usage of message passing, much the same way as Erlang processes + communicate. There are two ways in which an Erlang programmer can + interact with the signals sent from other Enea OSE processes; either + through the provided ose module, or by writing a custom linked-in + driver. This User's Guide describes and provides examples for both + approaches. +

+
+ + +
+ Signals in Erlang +
+ + +
+ Signals in a Linked-in driver +

+ Writing Linked-in drivers for OSE is very similar to how it is done + for Unix/Windows. It is only the way in which the driver subscribes + and consumed external events that is different. In Unix (and Windows) + file descriptiors (and Event Objects) are used to select on. On OSE + we use signals to deliver the same functionality. There are two large + differences between a signal and an fd. +

+

+ In OSE it is not possible for a signal number to be a unique identifier + for a resource in the same way as an fd is. For example; let's say we + implement a driver that does an asynchronous hunt that uses signal + number 1234 as the hunt_sig. If we want to be able to have multiple + hunt ports running at the same time we have to have someway of routing + the signal to the correct port. This is achieved by supplying a secondary + id that can be retrieved through the meta-data or payload of the signal, + e.g: + ErlDrvEvent event = erl_drv_ose_event_alloc(1234,port,resolver); + The event you get back from + + erl_drv_ose_event_alloc can then be used by + driver_select + to subscribe to signals. The first argument is just the signal number + that we are interested in. The second is the id that we choose to use, + in this case the port id that we got in the + start callback is + used. The third argument is a function pointer to a function that can + be used to figure out the id from a given signal. There is a complete + example of what this could look like in + the next section. + It is very important to issue the driver_select call before + any of the signals you are interested in are sent. If driver_select + is called after the signal is sent, there is a high probability that it + will be lost. +

+

+ The other difference from unix is that in OSE the payload of the event + (i.e. the signal data) is already received when the ready_output/input + callbacks are called. This means that you access the data of a signal + by calling + erl_drv_ose_get_signal. Additionally multiple signals might be + associated with the event, so you should call + + erl_drv_ose_get_signal until NULL is returned. +

+
+ + +
+ Example Linked-in driver +#include "erl_driver.h" +#include "ose.h" + +struct huntsig { + SIGSELECT signo; + ErlDrvPort port; +}; + +union SIGNAL { + SIGSELECT signo; + struct huntsig; +} + +/* Here we have to get the id from the signal. In this case we use the + port id since we have control over the data structure of the signal. + It is however possible to use anything in here. The only restriction + is that the same id has to be used for all signals of the same number.*/ +ErlDrvOseEventId resolver(union SIGNAL *sig) { + return (ErlDrvOseEventId)sig->huntsig.port; +} + +static int drv_init(void) { return 0; }; + +static ErlDrvData drv_start(ErlDrvPort port, char *command) { + return (ErlDrvData)port; +} + +static ErlDrvSSizeT control(ErlDrvData driver_data, unsigned int cmd, + char *buf, ErlDrvSizeT len, + char **rbuf, ErlDrvSizeT rlen) { + ErlDrvPort port = (ErlDrvPort)driver_data; + + /* Create a new event to select on */ + ErlDrvOseEvent evt = erl_drv_ose_event_alloc(1234,port,resolver); + + /* Make sure to do the select call _BEFORE_ the signal arrives. + The signal might get lost if the hunt call is done before the + select. */ + driver_select(port,evt,ERL_DRV_READ|ERL_DRV_USE,1); + + union SIGNAL *sig = alloc(sizeof(union SIGNAL),1234); + sig->huntsig.port = port; + hunt("testprocess",0,NULL,&sig); + return 0; +} + +static void ready_input(ErlDrvData driver_data, ErlDrvEvent evt) { + /* Get the first signal payload from the event */ + union SIGNAL *sig = erl_drv_ose_get_signal(evt); + ErlDrvPort port = (ErlDrvPort)driver_data; + while (sig != NULL) { + if (sig->signo == 1234) { + /* If it is our signal we send a message with the sender of the signal + to the controlling erlang process */ + ErlDrvTermData reply[] = { ERL_DRV_UINT, (ErlDrvUInt)sender(&sig) }; + erl_drv_send_term(port,reply,sizeof(reply) / sizeof(reply[0])); + } + + /* Cleanup the signal and deselect on the event. + Note that the event itself has to be free'd in the stop_select + callback. */ + free_buf(&sig); + driver_select(port,evt,ERL_DRV_READ|ERL_DRV_USE,0); + + /* There could be more than one signal waiting in this event, so + we have to loop until sig == NULL */ + sig = erl_drv_ose_get_signal(evt); + } +} + +static void stop_select(ErlDrvEvent event, void *reserved) +{ + erl_drv_ose_event_free(event); +} + +/** + * Setup the driver entry for the Erlang runtime + **/ +ErlDrvEntry ose_signal_driver_entry = { + .init = drv_init, + .start = drv_start, + .stop = drv_stop, + .ready_input = ready_input, + .driver_name = DRIVER_NAME, + .control = control, + .extended_marker = ERL_DRV_EXTENDED_MARKER, + .major_version = ERL_DRV_EXTENDED_MAJOR_VERSION, + .minor_version = ERL_DRV_EXTENDED_MINOR_VERSION, + .driver_flags = ERL_DRV_FLAG_USE_PORT_LOCKING, + .stop_select = stop_select +}; + +
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