[WIP] ProcessorBase multi-threading

[WIP] Depends on !89 (merged) .

Add a ThreadedBaseClass that ProcessorBase inherit from.

It allows the computation of the ProcessorBase::process(...) to be performed in a separated thread. Threads aren't instantiated/killed but instead are put to sleep waiting for new CaptureBase.

ThreadedBaseClass API is rather simple :

• Constructor with argument max_frequency allowing the user to set guess what, a max frequency at which the processor operates.
• run() to start the thread and so the processor.
• stop() allows to stop the thread and so the processor.
• isRunning() let the user know if the processor is running or not.

Finally it has the pure virtual function :

• executeImpl() where the derived class do its job.

src/examples/test_processor_imu.cpp

@@ -13,6 +13,7 @@
 #include "state_block.h"
 #include "state_quaternion.h"
 #include "processor_imu.h"
+#include "timer.h"
 
 //std
 #include <iostream>
@@ -104,6 +105,7 @@ int main(int argc, char** argv)
     // main loop
     using namespace std;
     clock_t begin = clock();
+    wolf::timer_usecs timer;
     int n = 1;
     while(!data_file_acc.eof() && n < 1000){
         n++;
@@ -155,6 +157,7 @@ int main(int argc, char** argv)
 
     }
     clock_t end = clock();
+    double elapsed_usecs = timer.toc();
     double elapsed_secs = double(end - begin) / CLOCKS_PER_SEC;
 
     // Final state
@@ -187,6 +190,9 @@ int main(int argc, char** argv)
     std::cout << "duration  : " << tf-t0 << " s" << std::endl;
     std::cout << "N samples : " << N << std::endl;
     std::cout << "frequency : " << (N-1)/(tf-t0) << " Hz" << std::endl;
+    std::cout << "time      : " << elapsed_usecs/1e6        << " s"   << "\n";
+    std::cout << "s/integr  : " << elapsed_usecs/(N-1)      << " us"  << "\n";
+    std::cout << "integr/s  : " << (N-1)/elapsed_usecs*1e6  << " ips" << "\n";
     std::cout << "CPU time  : " << elapsed_secs << " s" << std::endl;
     std::cout << "s/integr  : " << elapsed_secs/(N-1)*1e6 << " us" << std::endl;
     std::cout << "integr/s  : " << (N-1)/elapsed_secs << " ips" << std::endl;