content: package com.grapeshot.halfnes.mappers;
  
  import com.grapeshot.halfnes.*;
  
  public class IremH3001Mapper extends Mapper {
  
      private int[] chrbank = {0, 0, 0, 0, 0, 0, 0, 0};
      private int irqctr, irqreload = 0;
      private boolean irqenable, interrupted = false;
  
      @Override
      public void loadrom() throws BadMapperException {
          // needs to be in every mapper. Fill with initial cfg
          super.loadrom();
          for (int i = 1; i <= 32; ++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(int addr, int data) {
          if (addr < 0x8000 || addr > 0xCFFF) {
              super.cartWrite(addr, data);
              return;
          }
  
          if (addr >= 0x8000 && addr <= 0x8FFF) { //PRG Reg 0
              for (int i = 0; i < 8; ++i) {
                  prg_map[i] = (1024 * (i + (data * 8))) & (prgsize - 1);
              }
          } else if (addr == 0x9001) {    //Mirroring
              setmirroring(((data & (utils.BIT7)) != 0) ? MirrorType.H_MIRROR : MirrorType.V_MIRROR);
          } else if (addr == 0x9003) {    //IRQ Enable
              irqenable = ((data & (utils.BIT7)) != 0);
              if (interrupted) {
                  --cpu.interrupt;
                  interrupted = false;
              }
          } else if (addr == 0x9004) {    //IRQ Reload
              irqctr = irqreload;
              if (interrupted) {
                  --cpu.interrupt;
                  interrupted = false;
              }
          } else if (addr == 0x9005) {    //High 8 bits of IRQ Reload
              irqreload = (irqreload & 0x00FF) | (data << 8);
          } else if (addr == 0x9006) {    //Low 8 bits of IRQ Reload
              irqreload = (irqreload & 0xFF00) | data;
          } else if (addr >= 0xA000 && addr <= 0xAFFF) {  //PRG Reg 1
              for (int i = 0; i < 8; ++i) {
                  prg_map[i + 8] = (1024 * (i + data * 8)) & (prgsize - 1);
              }
          } else if (addr >= 0xB000 && addr <= 0xBFFF) {  //CHR Regs
              chrbank[addr & 7] = data;
              setppubank(1, (addr & 7), chrbank[addr & 7]);
          } else if (addr >= 0xC000 && addr <= 0xCFFF) {  //PRG Reg 2
              for (int i = 0; i < 8; ++i) {
                  prg_map[i + 16] = (1024 * (i + data * 8)) & (prgsize - 1);
              }
          }
      }
  
      @Override
      public void cpucycle(final int cycles) {
          if (irqenable) {
              if (irqctr <= 0) {
                  if (!interrupted) {
                      ++cpu.interrupt;
                      interrupted = true;
                  }
                  irqenable = false;
              } else {
                  irqctr -= cycles;
              }
          }
      }
  
      private void setppubank(int banksize, int bankpos, int banknum) {
          for (int i = 0; i < banksize; ++i) {
              chr_map[i + bankpos] = (1024 * (banknum + i)) & (chrsize - 1);
          }
      }
  }
  