bool M6502High::execute()

in atari_py/ale_interface/src/emucore/m6502/src/M6502Hi.cxx [98:207]

• 81 lines of code
• 16 McCabe index (conditional complexity)

bool M6502High::execute(uInt32 number)
{
  // Clear all of the execution status bits except for the fatal error bit
  myExecutionStatus &= FatalErrorBit;

  // Loop until execution is stopped or a fatal error occurs
  for(;;)
  {
    for(; !myExecutionStatus && (number != 0); --number)
    {
      uInt16 operandAddress = 0;
      uInt8 operand = 0;

#ifdef DEBUGGER_SUPPORT
      if(myJustHitTrapFlag)
      {
        if(myDebugger->start(myHitTrapInfo.message, myHitTrapInfo.address))
        {
          myJustHitTrapFlag = false;
          return true;
        }
      }

      if(myBreakPoints != NULL)
      {
        if(myBreakPoints->isSet(PC))
        {
          if(myDebugger->start("Breakpoint hit: ", PC))
            return true;
        }
      }

      int cond = evalCondBreaks();
      if(cond > -1)
      {
        string buf = "CBP: " + myBreakCondNames[cond];
        if(myDebugger->start(buf))
          return true;
      }
#endif

#ifdef DEBUG
      debugStream << "PC=" << hex << setw(4) << PC << " ";
#endif

      // Fetch instruction at the program counter
      IR = peek(PC++);

#ifdef DEBUG
      debugStream << "IR=" << hex << setw(2) << (int)IR << " ";
      debugStream << "<" << ourAddressingModeTable[IR] << " ";
#endif

      // Call code to execute the instruction
      switch(IR)
      {
        // 6502 instruction emulation is generated by an M4 macro file
        #include "M6502Hi.ins"

        default:
          // Oops, illegal instruction executed so set fatal error flag
          myExecutionStatus |= FatalErrorBit;
      }

      myTotalInstructionCount++;

#ifdef DEBUG
      debugStream << hex << setw(4) << operandAddress << " ";
      debugStream << setw(4) << ourInstructionMnemonicTable[IR];
      debugStream << "> ";
      debugStream << "A=" << ::hex << setw(2) << (int)A << " ";
      debugStream << "X=" << ::hex << setw(2) << (int)X << " ";
      debugStream << "Y=" << ::hex << setw(2) << (int)Y << " ";
      debugStream << "PS=" << ::hex << setw(2) << (int)PS() << " ";
      debugStream << "SP=" << ::hex << setw(2) << (int)SP << " ";
      debugStream << "Cyc=" << dec << mySystem->cycles();
      debugStream << endl;
#endif
    }

    // See if we need to handle an interrupt
    if((myExecutionStatus & MaskableInterruptBit) || 
        (myExecutionStatus & NonmaskableInterruptBit))
    {
      // Yes, so handle the interrupt
      interruptHandler();
    }

    // See if execution has been stopped
    if(myExecutionStatus & StopExecutionBit)
    {
      // Yes, so answer that everything finished fine
      return true;
    }

    // See if a fatal error has occured
    if(myExecutionStatus & FatalErrorBit)
    {
      // Yes, so answer that something when wrong
      return false;
    }

    // See if we've executed the specified number of instructions
    if(number == 0)
    {
      // Yes, so answer that everything finished fine
      return true;
    }
  }
}