How to retun a array of bytes from a thread

Anubisbot · February 18, 2009, 4:29am

Hi i get nuts, i try now since 2 days to get that to work.

i have setup a threat and send and recive data via serial port on this thread, but how do i retun the array???

  
class threadedObject : public ofxThread{  
  
	public:  
  
        ofSerial	serial;  
	    int count;  // threaded fucntions that share data need to use lock (mutex)  
	                // and unlock in order to write to that data  
	                // otherwise it's possible to get crashes.  
	                //  
	                // also no opengl specific stuff will work in a thread...  
	                // threads can't create textures, or draw stuff on the screen  
	                // since opengl is single thread safe  
        unsigned char* holdme[85];  
        unsigned char bytessend[22];  
		//--------------------------  
		threadedObject(){  
			count = 0;  
		}  
  
		void start(){  
  
        bytessend[0]=0x7E ;  
        bytessend[1]=0x00 ;  
        bytessend[2]=0x13 ;  
  
        bytessend[3]=0x10 ;  
        bytessend[4]=0x00 ;  
        bytessend[5]=0x00 ;  
        bytessend[6]=0x13 ;  
        bytessend[7]=0xA2 ;  
        bytessend[8]=0x00 ;  
        bytessend[9]=0x40 ;  
        bytessend[10]=0x30 ;  
        bytessend[11]=0x94 ;  
        bytessend[12]=0x67 ;  
        bytessend[13]=0xFF ;  
        bytessend[14]=0xFE ;  
        bytessend[15]=0x00 ;  
        bytessend[16]=0x00 ;  
        serial.setup("\\\\.\\COM21", 115200);  
          startThread(true, false);   // blocking, verbose  
        }  
  
        void stop(){  
            stopThread();  
        }  
  
		//--------------------------  
		void threadedFunction(){  
  
			while( isThreadRunning() != 0 ){  
				if( lock() ){  
  
                bytessend[17]=5 ;  
                bytessend[18]=(unsigned char)ofRandom(0,255) ;  
                bytessend[19]=(unsigned char)ofRandom(0,255) ;  
                bytessend[20]=(unsigned char)ofRandom(0,255) ;  
                bytessend[21]=(unsigned char)ofRandom(0,255) ;  
  
                unsigned char sum;  
                sum = 0xFF - (bytessend[3]+bytessend[4]+bytessend[5]+bytessend[6]+bytessend[7]+bytessend[8]+bytessend[9]+bytessend[10]+bytessend[11]+bytessend[12]+bytessend[13]+bytessend[14]+bytessend[15]+bytessend[16]+bytessend[17]+bytessend[18]+bytessend[19]+bytessend[20]+bytessend[21]) ;  
                bytessend[22]= sum;  
  
                serial.writeBytes(bytessend,23);  
                if(serial.readByte()==0x7E){  
                serial.readBytes(*holdme,85);  
                cout<< "wow";  
                }  
  
  
  
					unlock();  
				}  
			}  
		}  
  
		//--------------------------  
		unsigned char* get_array(){  
        if ( lock() ) {  
        return *holdme;  
        }  
		}

to here:

  
void testApp::update(){  
  
unsigned char* bytesread[85]= TO.get_array();  
  
  
  
  
int ttime = ofGetElapsedTimeMillis();  
dsp = ttime-timestamp;  
timestamp= ttime;  
  
unsigned char sum;  
for (int i=2;i<85;i++) {  
sum = sum+ bytesread[i];  
}

I think it wokrs some how with pointers, but i still dont understand them ??

Best regards

jroge · February 18, 2009, 10:38am

returning the pointer with a method like:

  
  
//--------------------------  
      unsigned char* get_array(){  
        if ( lock() ) {  
        return &holdme;  
        }  
      }

will only return the pointer so an array of unsigned char it will not copy any data or anything.

*holdme gets only the element that the pointer holdme points to.

it would be better to write a method like:

  
  
      unsigned char holdme[85]; // don't use the pointer sign here!   
//--------------------------  
      void copy_array(unsigned char *arr){  
        if ( lock() ) {  
        for(int i = 0; i < 85; i++)  
        {  
          arr[i] = holdme[i];  
        }  
         unlock(); // don't forget to unlock!  
        }  
      }

you’d have to read your bytes like this:

  
  
serial.readBytes(&holdme,85);

and copy the bytes in your update method like this:

  
  
unsigned char bytesread[85]; // again: no pointer sign  
 TO.get_array(&bytesread);

this will also use the lock correctly because in your code you were only locking the return of the pointer (maybe not even unlock the mutex again). so copying the bytes would interfere with your thread.

best
joerg

Anubisbot · February 18, 2009, 2:04pm

thanx, but now i get a error on compiling about the serial,
D:\ofx\apps\examples\serialExample\src\threadedObject.h|84|error: no matching function for call to `ofSerial::readBytes(unsigned char (*)[85], int)’|

Seems the & in :

  
  
serial.readBytes(&holdme,85);

makes trouble???

Best regards

jroge · February 18, 2009, 2:07pm

did you change the defintion of holdme to:
unsigned char holdme[85];

or just try to leave out the &

best
joerg

Anubisbot · February 18, 2009, 2:25pm

yes i changed it , and when i leave the & out of the serial comand
i get this error on compiling.

D:\ofx\apps\examples\serialExample\src\testApp.h|104|error: multiple types in one declaration|
||=== Build finished: 1 errors, 0 warnings ===|

  
        int dsp;  
        int timestamp;  
        int error_counter;  
        int transmission_counter;  
        int transmission_counter2;  
        int Delay_Frame_eeror;  
  
        threadedObject TO;  
};  
  
#endif

104 is where }; is mhhh threads are mean

arturo · February 18, 2009, 3:00pm

D:\ofx\apps\examples\serialExample\src\testApp.h|104|error: multiple types in one declaration|

is usually you are missing some ; at the end of a class declaration in a .h

Anubisbot · February 18, 2009, 3:12pm

Ok thats fixed but i still get one new error.

D:\ofx\apps\examples\serialExample\src\testApp.cpp||In member function virtual void testApp::update()':| D:\ofx\apps\examples\serialExample\src\testApp.cpp|63|error: no matching function for call tothreadedObject::get_array(unsigned char (*)[85])’|
D:\ofx\apps\examples\serialExample\src\threadedObject.h|95|note: candidates are: void threadedObject::get_array(unsigned char*)|
D:\ofx\apps\examples\serialExample\src\testApp.cpp||In member function void testApp::AFH(int, int)':| D:\ofx\apps\examples\serialExample\src\testApp.cpp|241|warning: converting toint’ from float'| D:\ofx\apps\examples\serialExample\src\testApp.cpp|258|warning: converting toint’ from `float’|
||=== Build finished: 1 errors, 2 warnings ===|

ok here i the code like it looks like now:

  
		//--------------------------  
#ifndef _THREADED_OBJECT  
#define _THREADED_OBJECT  
  
#include "ofMain.h"  
#define OF_ADDON_USING_OFXTHREAD  
  
#include "ofAddons.h"  
  
// this is not a very exciting example yet  
// but ofThread provides the basis for ofNetwork and other  
// operations that require threading.  
//  
// please be careful - threading problems are notoriously hard  
// to debug and working with threads can be quite difficult  
  
  
class threadedObject : public ofxThread{  
  
	public:  
  
        ofSerial	serial;  
	    int count;  // threaded fucntions that share data need to use lock (mutex)  
	                // and unlock in order to write to that data  
	                // otherwise it's possible to get crashes.  
	                //  
	                // also no opengl specific stuff will work in a thread...  
	                // threads can't create textures, or draw stuff on the screen  
	                // since opengl is single thread safe  
        unsigned char holdme[85];  
        unsigned char bytessend[22];  
		//--------------------------  
		threadedObject(){  
			count = 0;  
		}  
  
		void start(){  
  
        bytessend[0]=0x7E ;  
        bytessend[1]=0x00 ;  
        bytessend[2]=0x13 ;  
  
        bytessend[3]=0x10 ;  
        bytessend[4]=0x00 ;  
        bytessend[5]=0x00 ;  
        bytessend[6]=0x13 ;  
        bytessend[7]=0xA2 ;  
        bytessend[8]=0x00 ;  
        bytessend[9]=0x40 ;  
        bytessend[10]=0x30 ;  
        bytessend[11]=0x94 ;  
        bytessend[12]=0x67 ;  
        bytessend[13]=0xFF ;  
        bytessend[14]=0xFE ;  
        bytessend[15]=0x00 ;  
        bytessend[16]=0x00 ;  
        serial.setup("\\\\.\\COM21", 115200);  
          startThread(true, false);   // blocking, verbose  
        }  
  
        void stop(){  
            stopThread();  
        }  
  
		//--------------------------  
		void threadedFunction(){  
  
			while( isThreadRunning() != 0 ){  
				if( lock() ){  
  
                bytessend[17]=5 ;  
                bytessend[18]=(unsigned char)ofRandom(0,255) ;  
                bytessend[19]=(unsigned char)ofRandom(0,255) ;  
                bytessend[20]=(unsigned char)ofRandom(0,255) ;  
                bytessend[21]=(unsigned char)ofRandom(0,255) ;  
  
                unsigned char sum;  
                sum = 0xFF - (bytessend[3]+bytessend[4]+bytessend[5]+bytessend[6]+bytessend[7]+bytessend[8]+bytessend[9]+bytessend[10]+bytessend[11]+bytessend[12]+bytessend[13]+bytessend[14]+bytessend[15]+bytessend[16]+bytessend[17]+bytessend[18]+bytessend[19]+bytessend[20]+bytessend[21]) ;  
                bytessend[22]= sum;  
  
                serial.writeBytes(bytessend,23);  
                ofSleepMillis(5);  
                if(serial.readByte()==0x7E){  
                ofSleepMillis(30);  
                serial.readBytes(holdme,85);  
                }  
  
  
  
					unlock();  
				}  
			}  
		}  
  
		//--------------------------  
		void get_array(unsigned char * arr){  
        if ( lock() ) {  
        for(int i = 0; i < 85; i++)  
        {  
          arr[i] = holdme[i];  
        }  
         unlock(); // don't forget to unlock!  
        }  
		}  
  
  
  
};  
  
#endif

  
  
  
  
void testApp::update(){  
  
  
unsigned char bytesread[85];  
TO.get_array(&bytesread);