bios.c

void bios_objaffineset(u32 b_src, u32 b_dest, u32 b_num, u32 b_offset)

    {
  save_reg();
  u32 b_i;
  for(b_i = 0; b_i < b_num; b_i++) {
    s16 b_rx = read_memory16(b_src);
    b_src+=2;
    s16 b_ry = read_memory16(b_src);
    b_src+=2;
    u16 b_theta = read_memory16(b_src)>>8;
    b_src+=4; // keep structure alignment

    s32 b_a = (s32)b_sinetable[(b_theta+0x40)&255];
    s32 b_b = (s32)b_sinetable[b_theta];

    s16 b_dx =  ((s32)b_rx * b_a)>>14;
    s16 b_dmx = ((s32)b_rx * b_b)>>14;
    s16 b_dy =  ((s32)b_ry * b_b)>>14;
    s16 b_dmy = ((s32)b_ry * b_a)>>14;

    write_memory16(b_dest, b_dx);
    b_dest += b_offset;
    write_memory16(b_dest, -b_dmx);
    b_dest += b_offset;
    write_memory16(b_dest, b_dy);
    b_dest += b_offset;
    write_memory16(b_dest, b_dmy);
    b_dest += b_offset;
  }
  load_reg();
}