sys/src/games/md/md.c

   1 #include <u.h>
   2 #include <libc.h>
   3 #include <thread.h>
   4 #include <draw.h>
   5 #include <keyboard.h>
   6 #include "../eui.h"
   7 #include "dat.h"
   8 #include "fns.h"
   9
  10 u16int *prg;
  11 int nprg;
  12 u8int *sram;
  13 u32int sramctl, nsram, sram0, sram1;
  14 int savefd = -1;
  15
  16 int dmaclock, vdpclock, z80clock, audioclock, ymclock, saveclock;
  17
  18 void
  19 flushram(void)
  20 {
  21         if(savefd >= 0)
  22                 pwrite(savefd, sram, nsram, 0);
  23         saveclock = 0;
  24 }
  25
  26 static void
  27 loadbat(char *file)
  28 {
  29         static char buf[512];
  30
  31         strncpy(buf, file, sizeof buf - 5);
  32         strcat(buf, ".sav");
  33         savefd = create(buf, ORDWR | OEXCL, 0666);
  34         if(savefd < 0)
  35                 savefd = open(buf, ORDWR);
  36         if(savefd < 0)
  37                 print("open: %r\n");
  38         else
  39                 readn(savefd, sram, nsram);
  40 }
  41
  42 static void
  43 loadrom(char *file)
  44 {
  45         static uchar hdr[512], buf[4096];
  46         u32int v;
  47         u16int *p;
  48         int fd, rc, i;
  49
  50         fd = open(file, OREAD);
  51         if(fd < 0)
  52                 sysfatal("open: %r");
  53         if(readn(fd, hdr, 512) < 512)
  54                 sysfatal("read: %r");
  55         if(memcmp(hdr + 0x100, "SEGA MEGA DRIVE ", 16) != 0 && memcmp(hdr + 0x100, "SEGA GENESIS    ", 16) != 0)
  56                 sysfatal("invalid rom");
  57         v = hdr[0x1a0] << 24 | hdr[0x1a1] << 16 | hdr[0x1a2] << 8 | hdr[0x1a3];
  58         if(v != 0)
  59                 sysfatal("rom starts at nonzero address");
  60         v = hdr[0x1a4] << 24 | hdr[0x1a5] << 16 | hdr[0x1a6] << 8 | hdr[0x1a7];
  61         nprg = v = v+2 & ~1;
  62         if(nprg == 0)
  63                 sysfatal("invalid rom");
  64         p = prg = malloc(v);
  65         if(prg == nil)
  66                 sysfatal("malloc: %r");
  67         seek(fd, 0, 0);
  68         while(v != 0){
  69                 rc = readn(fd, buf, sizeof buf);
  70                 if(rc == 0)
  71                         break;
  72                 if(rc < 0)
  73                         sysfatal("read: %r");
  74                 if(rc > v)
  75                         rc = v;
  76                 for(i = 0; i < rc; i += 2)
  77                         *p++ = buf[i] << 8 | buf[i+1];
  78                 v -= rc;
  79         }
  80         close(fd);
  81         if(hdr[0x1b0] == 0x52 && hdr[0x1b1] == 0x41){
  82                 sramctl = SRAM | hdr[0x1b2] >> 1 & ADDRMASK;
  83                 if((hdr[0x1b2] & 0x40) != 0)
  84                         sramctl |= BATTERY;
  85                 sram0 = hdr[0x1b4] << 24 | hdr[0x1b5] << 16 | hdr[0x1b6] << 8 | hdr[0x1b7] & 0xfe;
  86                 sram1 = hdr[0x1b8] << 24 | hdr[0x1b9] << 16 | hdr[0x1ba] << 8 | hdr[0x1bb] | 1;
  87                 if(sram1 <= sram0){
  88                         print("SRAM of size <= 0?\n");
  89                         sramctl = 0;
  90                 }else{
  91                         nsram = sram1 - sram0;
  92                         if((sramctl & ADDRMASK) != ADDRBOTH)
  93                                 nsram >>= 1;
  94                         sram = malloc(nsram);
  95                         if(sram == nil)
  96                                 sysfatal("malloc: %r");
  97                         if((sramctl & BATTERY) != 0){
  98                                 loadbat(file);
  99                                 atexit(flushram);
 100                         }
 101                 }
 102         }
 103 }
 104
 105 void
 106 usage(void)
 107 {
 108         fprint(2, "usage: %s [-a] [-x scale] rom\n", argv0);
 109         exits("usage");
 110 }
 111
 112 void
 113 threadmain(int argc, char **argv)
 114 {
 115         int t;
 116
 117         ARGBEGIN{
 118         case 'a':
 119                 initaudio();
 120                 break;
 121         case 'x':
 122                 fixscale = strtol(EARGF(usage()), nil, 0);
 123                 break;
 124         default:
 125                 usage();
 126         } ARGEND;
 127         if(argc < 1)
 128                 usage();
 129         loadrom(*argv);
 130         initemu(320, 224, 4, XRGB32, 1, nil);
 131         regkey("a", 'c', 1<<5);
 132         regkey("b", 'x', 1<<4);
 133         regkey("y", 'z', 1<<12);
 134         regkey("start", '\n', 1<<13);
 135         regkey("up", Kup, 0x101);
 136         regkey("down", Kdown, 0x202);
 137         regkey("left", Kleft, 1<<2);
 138         regkey("right", Kright, 1<<3);
 139         cpureset();
 140         vdpmode();
 141         ymreset();
 142         for(;;){
 143                 if(paused != 0){
 144                         qlock(&pauselock);
 145                         qunlock(&pauselock);
 146                 }
 147                 if(dma != 1){
 148                         t = step() * CPUDIV;
 149                         if(dma != 0)
 150                                 dmastep();
 151                 }else{
 152                         t = CPUDIV;
 153                         dmastep();
 154                 }
 155                 z80clock -= t;
 156                 vdpclock -= t;
 157                 audioclock += t;
 158                 ymclock += t;
 159
 160                 while(vdpclock < 0){
 161                         vdpstep();
 162                         vdpclock += 8;
 163                 }
 164                 while(z80clock < 0)
 165                         z80clock += z80step() * Z80DIV;
 166                 while(audioclock >= SAMPDIV){
 167                         audiosample();
 168                         audioclock -= SAMPDIV;
 169                 }
 170                 while(ymclock >= YMDIV){
 171                         ymstep();
 172                         ymclock -= YMDIV;
 173                 }
 174                 if(saveclock > 0){
 175                         saveclock -= t;
 176                         if(saveclock <= 0){
 177                                 saveclock = 0;
 178                                 flushram();
 179                         }
 180                 }
 181         }
 182 }
 183
 184 void
 185 flush(void)
 186 {
 187         flushmouse(1);
 188         flushscreen();
 189         flushaudio(audioout);
 190 }