Buffer is NULL When Using Ring Mode Acquisition In C

Question

I put the data acquisition in a loop,and there is a error check part to determine whether the buffer is empty or not.
Error always occurs that buffer is always empty,what's worng with my code?
Here's part of my code:
void AcquireThread::Acquire(void)
sprintf_s(intfName, "img0");//img0 Basler///img3 Atmel
imgInterfaceOpen(intfName, &Iid);
imgSessionOpen(Iid, &Sid);
AcqWinWidth = globalOptions->IMAGEWIDTH;
AcqWinHeight = globalOptions->IMAGEHEIGHT;
imgSetAttribute2(Sid, IMG_ATTR_ROI_WIDTH, AcqWinWidth);
imgSetAttribute2(Sid, IMG_ATTR_ROI_HEIGHT, AcqWinHeight);
imgSetCameraAttributeNumeric(Sid, "Exposure Time", 12);
for (int i = 0; i<NUM_RING_BUFFERS; i++)
ImaqBuffers[i] = NULL;
// Setup and launch the ring acquisition
imgRingSetup(Sid, NUM_RING_BUFFERS, (void**)ImaqBuffers, 0, TRUE);
uInt32 currBufNum;
//Infinite Loop
//Temporarily we have incorporated an infinite loop. Stop the program execution by closing the program.
//Threads can also be suspended and resumed via the start/stop buttons
while (true)
DataFramePos = RawData; //Reset the DataFramePos pointer to the beginning, pointed to by RawData
if (globalOptions->volumeReady < 1)
for (int framenum = 0; framenum < globalOptions->NumFramesPerVol; framenum++)
if (breakLoop)
break;
imgSessionExamineBuffer2(Sid, IMG_CURRENT_BUFFER, &currBufNum, (void**)&ImaqBuffer);
if (!ImaqBuffer) { //Check if Camera is on and properly connected   
printf("ERROR: Camera is either off, or miscommunication with framegrabber.\n Exiting Program...\n");
Sleep(2000);
exit(1);
memcpy(DataFramePos, ImaqBuffer, AcqWinHeight*AcqWinWidth*sizeof(unsigned short));
DataFramePos = &DataFramePos[AcqWinHeight*AcqWinWidth];
imgSessionReleaseBuffer(Sid);
if (breakLoop) {
breakLoop = false; //Reset the breakLoop flag after each time
else {
globalOptions->volumeReady++;
else
if (globalOptions->saveVolumeflag == true)
fwrite(DataFramePos, 2, AcqWinWidth*AcqWinHeight*globalOptions->NumFramesPerVol, globalOptions->fid);
globalOptions->saveVolumeflag = false;
fclose(globalOptions->fid);
printf("VolumeData Has Been Saved...\n");
globalOptions->volumeReady = 0;
  P.S:I can connect my camera using NIMAX and Labview.

Answer 1

"string" is std::string type
and TrmUiProcessObj is initiated.
In my main of the java test code (you can see bellow)
I first create the TrmUiProcess using call to cCreate which is a JNI
the pointer to the object created is keept in pTrmUiProcess
and then I call handleXmlRequest which call cHandleXmlRequest which is a JNI written in my first question.
The catch (string &s) is catching it. ( I print inside the catch)
The same happened if I am throwing int and trying to catch it
string TrmUiProcess::handleRequest(char * buffer){
try{
int i=10;
throw i
catch (int & s){
cout << "catched int" <<endl;
catch (...){
cout <<"catch ..." <<endl;
in case the
catch (int & s){
cout << "catched int" <<endl;
exist in the code the java test is thrown on an unexpected exception
my java code is:
package javaProcess;
import java.util.*;
public class javaProcess{
private native long cCreate(String sessionId);
private native void cDestroy();
private native String cHandleXmlRequest(String xmlBuffer);
protected long pTrmUiProcess; //pointer to TrmUiProcess instance
static {
System.loadLibrary("trmUiNativeLib");
public static void main(String[] args) {
javaProcess processObj1=new javaProcess("111111");
     System.out.println("processObj1 created");
     String retBuf1=processObj1.handleXmlRequest("<screen> <screenName>msuDefinition</screenName> <screenFamily>trm</screenFamily> <data></data> <method>getScreen</method> </screen>");
     System.out.println("processObj1 ["+retBuf1+"]");
     processObj1.finalize();
     System.out.println("processObj1 destroyed");
public javaProcess(String sessionId) {
System.out.println("jProcess sessionId=[" sessionId"]");
pTrmUiProcess = cCreate(sessionId);
public String handleXmlRequest(String xmlBuffer) {
return cHandleXmlRequest(xmlBuffer);
public void finalize() {
close();
private boolean isClosed() {
return pTrmUiProcess == 0;
private void close() {
if (!isClosed()) {
cDestroy();
pTrmUiProcess = 0;