content: package com.grapeshot.halfnes.mappers;
  
  import com.grapeshot.halfnes.*;
  
  public class Sunsoft03Mapper extends Mapper {
  
      int[] chrbank = {0, 0, 0, 0};
      private int irqctr = 0;
      private boolean irqenable = false;
      private boolean interrupted = false;
      private boolean irqtoggle = false;
  
      @Override
      public void loadrom() throws BadMapperException {
          //needs to be in every mapper. Fill with initial cfg
          super.loadrom();
          //swappable bank
          for (int i = 0; i < 16; ++i) {
              prg_map[i] = (1024 * i) & (prgsize - 1);
          }
          //fixed bank
          for (int i = 1; i <= 16; ++i) {
              prg_map[32 - i] = prgsize - (1024 * i);
          }
          for (int i = 0; i < 8; ++i) {
              chr_map[i] = (1024 * i) & (chrsize - 1);
          }
      }
  
      @Override
      public final void cartWrite(final int addr, final int data) {
          if (addr >= 0x8800 && addr <= 0x8FFF) {
              chrbank[0] = data;
              setupchr();
          } else if (addr >= 0x9800 && addr <= 0x9FFF) {
              chrbank[1] = data;
              setupchr();
          } else if (addr >= 0xA800 && addr <= 0xAFFF) {
              chrbank[2] = data;
              setupchr();
          } else if (addr >= 0xB800 && addr <= 0xBFFF) {
              chrbank[3] = data;
              setupchr();
          } else if (addr >= 0xC800 && addr <= 0xCFFF) {
              if (!irqtoggle) {
                  //first write
                  irqctr = (irqctr & 0xFF) | (data << 8);
                  irqtoggle = true;
              } else {
                  //second write
                  irqctr = (irqctr & 0xFF00) | (data & 0xFF);
                  irqtoggle = false;
              }
          } else if (addr >= 0xD800 && addr <= 0xDFFF) {
              if (interrupted) {
                  --cpu.interrupt;
                  interrupted = false;
              }
              irqenable = ((data & (utils.BIT4)) != 0);
              irqtoggle = false;
          } else if (addr >= 0xE800 && addr <= 0xEFFF) {
              switch (data & 3) {
                  case 0:
                      setmirroring(MirrorType.V_MIRROR);
                      break;
                  case 1:
                      setmirroring(MirrorType.H_MIRROR);
                      break;
                  case 2:
                      setmirroring(MirrorType.SS_MIRROR0);
                      break;
                  case 3:
                      setmirroring(MirrorType.SS_MIRROR1);
                      break;
              }
          } else if (addr >= 0xF800 && addr <= 0xFFFF) {
              for (int i = 0; i < 16; ++i) {
                  prg_map[i] = (1024 * (i + 16 * data)) & (prgsize - 1);
              }
          }
      }
  
      @Override
      public void cpucycle(final int cycles) {
          if (irqenable) {
              if (irqctr <= 0) {
                  irqctr = 0xFFFF;
                  if (!interrupted) {
                      ++cpu.interrupt;
                      interrupted = true;
                  }
                  irqenable = false;
              } else {
                  irqctr -= cycles;
              }
          }
      }
  
      private void setupchr() {
          setppubank(2, 0, chrbank[0]);
          setppubank(2, 2, chrbank[1]);
          setppubank(2, 4, chrbank[2]);
          setppubank(2, 6, chrbank[3]);
      }
  
      private void setppubank(int banksize, int bankpos, int banknum) {
          for (int i = 0; i < banksize; ++i) {
              chr_map[i + bankpos] = (1024 * (i + 2 * banknum)) % chrsize;
          }
      }
  }
  