content: /*
   * HalfNES by Andrew Hoffman
   * Licensed under the GNU GPL Version 3. See LICENSE file
   */
  package com.grapeshot.halfnes.mappers;
  
  import com.grapeshot.halfnes.*;
  
  public class VRC2Mapper extends Mapper {
      //vrc2a mapper(INES #22); vrc2b is mapped to 23 along with the one form of vrc4
  
      int prgbank0, prgbank1 = 0;
      int[] chrbank = {0, 0, 0, 0, 0, 0, 0, 0};
  
      @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) {
              //map last banks in to start off
              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 > 0xffff) {
              super.cartWrite(addr, data);
              return;
          }
          boolean bit0 = ((addr & (utils.BIT1)) != 0);
          boolean bit1 = ((addr & (utils.BIT0)) != 0);
          switch (addr >> 12) {
              case 0x8:
                  prgbank0 = data & 0xf;
                  break;
              case 0x9:
                  //mirroring
                  switch (data & 1) {
                      case 0:
                          setmirroring(Mapper.MirrorType.V_MIRROR);
                          break;
                      case 1:
                          setmirroring(Mapper.MirrorType.H_MIRROR);
                          break; 
                  }
                  //4-4-2016: seems VRC2 only has 1 mirroring bit
                  break;
              case 0xa:
                  prgbank1 = data & 0xf;
                  break;
              case 0xb:
              case 0xc:
              case 0xd:
              case 0xe:
                  //chr bank select. black magic
                  data &= 0xf;
                  int whichreg = ((addr - 0xb000) >> 11) + ((bit1) ? 1 : 0);
                  int oldval = chrbank[whichreg];
                  if (!bit0) {
                      oldval &= 0xf0;
                      oldval |= data;
                  } else {
                      oldval &= 0xf;
                      oldval |= (data << 4);
                  }
                  chrbank[whichreg] = oldval;
                  break;
          }
  
          if (addr < 0xf000) {
              setbanks();
          }
      }
  
      private void setbanks() {
          //map prg banks
          //last 2 banks fixed to last two in rom
          for (int i = 1; i <= 16; ++i) {
              prg_map[32 - i] = prgsize - (1024 * i);
          }
          //first bank set to prg0 register
          for (int i = 0; i < 8; ++i) {
              prg_map[i] = (1024 * (i + 8 * prgbank0)) % prgsize;
          }
          //second bank set to prg1 register
          for (int i = 0; i < 8; ++i) {
              prg_map[i + 8] = (1024 * (i + 8 * prgbank1)) % prgsize;
          }
  
          //map chr banks
          for (int i = 0; i < 8; ++i) {
              setppubank(1, i, chrbank[i] >> 1);
          }
  
      }
  
      private void setppubank(int banksize, int bankpos, int banknum) {
  //        System.err.println(banksize + ", " + bankpos + ", "+ banknum);
          for (int i = 0; i < banksize; ++i) {
              chr_map[i + bankpos] = (1024 * ((banknum) + i)) % chrsize;
          }
  //        utils.printarray(chr_map);
      }
  }
  