This module is built upon Glish. Glish is a language (and supporting infrastructure) for constructing loosely coupled distributed systems. The values which Glish and this module deal with can either be arrays or records. Arrays correspond to the arrays found in C and other languages, and records correspond to the heterogeneous structures found in most languages, e.g. the C struct.
The major external classes in this module are:
For information about the Glish system in general, a general introduction (75K) to Glish is available as well as a complete users manual (1Meg). These documents as well as the Glish source are available from the Lawrence Berkeley Laboratory.
Procedural Example
The following example implements a simple statistics server for arrays which
have been sent from some other process (for example, a user interactively
manipulating a user interface). In this example, the Glish events are
handled serially with the process blocked waiting for the next event. This
is a procedural style where as the next example
is an event driven style.
#include <tasking/Glish.h> // 1
#include <casa/Arrays/ArrayMath.h> // 2
#include <casa/Arrays/IPosition.h> // 3
// 4
int main(int argc, char **argv) // 5
{ // 6
GlishSysEventSource eventStream(argc, argv); // 7
GlishSysEvent event; // 8
while (eventStream.connected()) { // 9
event = eventStream.nextGlishEvent(); // 10
if (event.type() == "statistics") { // 11
GlishArray ga = event.val(); // 12
Array<Double> ad(ga.shape()); // 13
ga.get(ad); // 14
GlishRecord response; // 15
response.add("mean", mean(ad)); // 16
response.add("median", median(ad)); // 17
eventStream.postEvent("statistics_result", response); // 18
} else if (event.type() != "shutdown") { // 19
eventStream.unrecognized(); // 20
} // 21
} // 22
return 0; // 23
} // 24
Event Driven Example
The previous example could also be written in an event driven style. This
is the style of programming familiar to developers of graphical user
interfaces. Here callbacks are set up for the Glish events and then
control is given up until the callbacks are called. This implements the
same functionality as the previous example.
See the event driven example
in the XSysEvent header file for an example of how X Windows
events can be combined with Glish events.
#include <tasking/Glish.h> // 1
#include <casa/Arrays/ArrayMath.h> // 2
#include <casa/Arrays/IPosition.h> // 3
// 4
Bool statCallbk(GlishSysEvent &e, void *) { // 5
GlishSysEventSource *es = e.glishSource(); // 6
GlishArray ga = e.val(); // 7
Array<Double> ad(ga.shape()); // 8
ga.get(ad); // 9
GlishRecord response; // 10
response.add("mean", mean(ad)); // 11
response.add("median", median(ad)); // 12
es->postEvent("statistics_result", response); // 13
return True; // 14
} // 15
// 16
int main(int argc, char **argv) // 17
{ // 18
GlishSysEventSource eventStream(argc, argv); // 19
eventStream.addTarget(statCallbk,"^statistics$"); // 20
eventStream.loop(); // 21
} // 22