examples/Tutorial/RandomSource.cc

0001
0002 // Copyright 2020, Jefferson Science Associates, LLC.
0003 // Subject to the terms in the LICENSE file found in the top-level directory.
0004
0005
0006 #include "RandomSource.h"
0007
0008 #include <JANA/JApplication.h>
0009 #include <JANA/JEvent.h>
0010
0011 /// Include headers to any JObjects you wish to associate with each event
0012 #include "Hit.h"
0013
0014 /// There are two different ways of instantiating JEventSources
0015 /// 1. Creating them manually and registering them with the JApplication
0016 /// 2. Creating a corresponding JEventSourceGenerator and registering that instead
0017 ///    If you have a list of files as command line args, JANA will use the JEventSourceGenerator
0018 ///    to find the most appropriate JEventSource corresponding to that filename, instantiate and register it.
0019 ///    For this to work, the JEventSource constructor has to have the following constructor arguments:
0020
0021 RandomSource::RandomSource() : JEventSource() {
0022     SetTypeName(NAME_OF_THIS); // Provide JANA with class name
0023     SetCallbackStyle(CallbackStyle::ExpertMode);
0024 }
0025
0026 void RandomSource::Open() {
0027
0028     /// Open is called exactly once when processing begins.
0029
0030     /// Get any configuration parameters from the JApplication
0031     JApplication* app = GetApplication();
0032     app->SetDefaultParameter("random_source:max_emit_freq_hz",
0033                              m_max_emit_freq_hz,
0034                              "Maximum event rate [Hz] for RandomSource");
0035
0036     /// For opening a file, get the filename via:
0037     // std::string resource_name = GetResourceName();
0038     /// Open the file here!
0039 }
0040
0041 void RandomSource::Close() {
0042     // Close the file pointer here!
0043 }
0044
0045 JEventSource::Result RandomSource::Emit(JEvent& event) {
0046
0047     /// Calls to GetEvent are synchronized with each other, which means they can
0048     /// read and write state on the JEventSource without causing race conditions.
0049
0050     /// Configure event and run numbers
0051     static size_t current_event_number = 1;
0052     event.SetEventNumber(current_event_number++);
0053     event.SetRunNumber(22);
0054
0055     /// Slow down event source
0056     auto delay_ms = std::chrono::milliseconds(1000/m_max_emit_freq_hz);
0057     std::this_thread::sleep_for(delay_ms);
0058
0059     /// Insert simulated data into event
0060     std::vector<Hit*> hits;
0061     hits.push_back(new Hit(0, 0, 1.0, 0));
0062     hits.push_back(new Hit(0, 1, 1.0, 0));
0063     hits.push_back(new Hit(1, 0, 1.0, 0));
0064     hits.push_back(new Hit(1, 1, 1.0, 0));
0065     event.Insert(hits);
0066
0067     /// If you are reading a file of events and have reached the end
0068     /// Note that you should close the file handle in Close(), not here.
0069     // return Result::FailureFinished;
0070
0071     /// If you are streaming events and there are no new events in the message queue,
0072     /// tell JANA that GetEvent() was temporarily unsuccessful like this:
0073     // return Result::FailureTryAgain;
0074
0075     return Result::Success;
0076 }
0077
0078 std::string RandomSource::GetDescription() {
0079
0080     /// GetDescription() helps JANA explain to the user what is going on
0081     return "";
0082 }
0083
0084
0085 template <>
0086 double JEventSourceGeneratorT<RandomSource>::CheckOpenable(std::string resource_name) {
0087
0088     /// CheckOpenable() decides how confident we are that this EventSource can handle this resource.
0089     ///    0.0        -> 'Cannot handle'
0090     ///    (0.0, 1.0] -> 'Can handle, with this confidence level'
0091
0092     /// To determine confidence level, feel free to open up the file and check for magic bytes or metadata.
0093     /// Returning a confidence <- {0.0, 1.0} is perfectly OK!
0094
0095     return (resource_name == "random") ? 1.0 : 0.0;
0096 }