-
Notifications
You must be signed in to change notification settings - Fork 8
/
chip8.c
446 lines (372 loc) · 15.9 KB
/
chip8.c
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <SDL/SDL.h>
#undef main
#define memsize 4096
#define SCREEN_W 640
#define SCREEN_H 320
#define SCREEN_BPP 32
#define W 64
#define H 32
unsigned char chip8_fontset[80] =
{
0xF0, 0x90, 0x90, 0x90, 0xF0, // 0
0x20, 0x60, 0x20, 0x20, 0x70, // 1
0xF0, 0x10, 0xF0, 0x80, 0xF0, // 2
0xF0, 0x10, 0xF0, 0x10, 0xF0, // 3
0x90, 0x90, 0xF0, 0x10, 0x10, // 4
0xF0, 0x80, 0xF0, 0x10, 0xF0, // 5
0xF0, 0x80, 0xF0, 0x90, 0xF0, // 6
0xF0, 0x10, 0x20, 0x40, 0x40, // 7
0xF0, 0x90, 0xF0, 0x90, 0xF0, // 8
0xF0, 0x90, 0xF0, 0x10, 0xF0, // 9
0xF0, 0x90, 0xF0, 0x90, 0x90, // A
0xE0, 0x90, 0xE0, 0x90, 0xE0, // B
0xF0, 0x80, 0x80, 0x80, 0xF0, // C
0xE0, 0x90, 0x90, 0x90, 0xE0, // D
0xF0, 0x80, 0xF0, 0x80, 0xF0, // E
0xF0, 0x80, 0xF0, 0x80, 0x80 // F
};
static int keymap[0x10] = {
SDLK_0,
SDLK_1,
SDLK_2,
SDLK_3,
SDLK_4,
SDLK_5,
SDLK_6,
SDLK_7,
SDLK_8,
SDLK_9,
SDLK_a,
SDLK_b,
SDLK_c,
SDLK_d,
SDLK_e,
SDLK_f
};
typedef struct chip8{
FILE * game;
unsigned short opcode;
unsigned char memory[memsize];
unsigned char V[0x10];
unsigned short I;
unsigned short pc;
unsigned char graphics[64 * 32];
unsigned char delay_timer;
unsigned char sound_timer;
unsigned short stack[0x10];
unsigned short sp;
unsigned char key[0x10];
} C8;
//0x000-0x1FF - Chip 8 interpreter (contains font set in emu)
//0x050-0x0A0 - Used for the built in 4x5 pixel font set (0-F)
//0x200-0xFFF - Program ROM and work RAM
void chip8_initialize(C8 *, char *);
void chip8_execute(C8 *);
void chip8_draw(C8 *);
void chip8_prec(char *, SDL_Event *);
void chip8_prepare(char *);
void chip8_start();
void chip8_start(){
char name[100];
printf("Enter the name of the game: ");
scanf("%s", name);
chip8_prepare(name);
}
void chip8_prepare(char * name){
C8 CH8;
chip8_initialize(&CH8, name);
Uint8 * keys;
SDL_Event event;
SDL_Init(SDL_INIT_EVERYTHING);
SDL_SetVideoMode(SCREEN_W, SCREEN_H, SCREEN_BPP, SDL_HWSURFACE | SDL_DOUBLEBUF);
for(;;){
if(SDL_PollEvent (&event))
continue;
chip8_execute(&CH8);
chip8_draw(&CH8);
chip8_prec(name, &event);
}
}
void chip8_initialize(C8 * CH8, char * name){
int i;
CH8->game = fopen(name, "rb");
if (!CH8->game) {
printf("Wrong game name!");
fflush(stdin);
getchar();
exit(1);
}
fread(CH8->memory+0x200, 1, memsize-0x200, CH8->game); // load game into memory
for(i = 0; i < 80; ++i)
CH8->memory[i] = chip8_fontset[i]; // load fontset into memory
memset(CH8->graphics, 0, sizeof(CH8->graphics)); // clear graphics
memset(CH8->stack, 0, sizeof(CH8->stack)); // clear stack
memset(CH8->V, 0, sizeof(CH8->V)); // clear chip8 registers
CH8->pc = 0x200;
CH8->sp &= 0;
CH8->opcode = 0x200;
}
void chip8_draw(C8 * CH8){
int i, j;
SDL_Surface * surface = SDL_GetVideoSurface();
SDL_LockSurface(surface);
Uint32 * screen = (Uint32 *)surface->pixels;
memset (screen,0,surface->w*surface->h*sizeof(Uint32));
for (i = 0; i < SCREEN_H; i++)
for (j = 0; j < SCREEN_W; j++){
screen[j+i*surface->w] = CH8->graphics[(j/10)+(i/10)*64] ? 0xFFFFFFFF : 0;
}
SDL_UnlockSurface(surface);
SDL_Flip(surface);
SDL_Delay(15);
}
void chip8_timers(C8 * CH8){
if(CH8->delay_timer > 0)
CH8->delay_timer--;
if(CH8->sound_timer > 0)
CH8->sound_timer--;
if(CH8->sound_timer != 0)
printf("%c", 7);
}
void chip8_prec(char * name, SDL_Event * event){
Uint8 * keys = SDL_GetKeyState(NULL);
if(keys[SDLK_ESCAPE])
exit(1);
if(keys[SDLK_r])
chip8_prepare(name);
if(keys[SDLK_c])
chip8_start();
if(keys[SDLK_p]){
while(1){
if(SDL_PollEvent(event)){
keys = SDL_GetKeyState(NULL);
if(keys[SDLK_ESCAPE])
exit(1);
if(keys[SDLK_u])
break;
}
}
}
}
void chip8_execute(C8 * CH8){
Uint8 * keys;
int y, x, vx, vy, times, i;
unsigned height, pixel;
for(times = 0; times < 10; times++){
CH8->opcode = CH8->memory[CH8->pc] << 8 | CH8->memory[CH8->pc + 1];
printf ("Executing %04X at %04X , I:%02X SP:%02X\n", CH8->opcode, CH8->pc, CH8->I, CH8->sp);
switch(CH8->opcode & 0xF000){
case 0x0000:
switch(CH8->opcode & 0x000F){
case 0x0000: // 00E0: Clears the screen
memset(CH8->graphics, 0, sizeof(CH8->graphics));
CH8->pc += 2;
break;
case 0x000E: // 00EE: Returns from subroutine
CH8->pc = CH8->stack[(--CH8->sp)&0xF] + 2;
break;
default: printf("Wrong opcode: %X\n", CH8->opcode); getchar();
}
break;
case 0x1000: // 1NNN: Jumps to address NNN
CH8->pc = CH8->opcode & 0x0FFF;
break;
case 0x2000: // 2NNN: Calls subroutine at NNN
CH8->stack[(CH8->sp++)&0xF] = CH8->pc;
CH8->pc = CH8->opcode & 0x0FFF;
break;
case 0x3000: // 3XNN: Skips the next instruction if VX equals NN
if(CH8->V[(CH8->opcode & 0x0F00) >> 8] == (CH8->opcode & 0x00FF))
CH8->pc += 4;
else
CH8->pc += 2;
break;
case 0x4000: // 4XNN: Skips the next instruction if VX doesn't equal NN
if(CH8->V[(CH8->opcode & 0x0F00) >> 8] != (CH8->opcode & 0x00FF))
CH8->pc += 4;
else
CH8->pc += 2;
break;
case 0x5000: // 5XY0: Skips the next instruction if VX equals VY
if(CH8->V[(CH8->opcode & 0x0F00) >> 8] == CH8->V[(CH8->opcode & 0x00F0) >> 4])
CH8->pc += 4;
else
CH8->pc += 2;
break;
case 0x6000: // 6XNN: Sets VX to NN
CH8->V[(CH8->opcode & 0x0F00) >> 8] = (CH8->opcode & 0x00FF);
CH8->pc += 2;
break;
case 0x7000: // 7XNN: Adds NN to VX
CH8->V[(CH8->opcode & 0x0F00) >> 8] += (CH8->opcode & 0x00FF);
CH8->pc += 2;
break;
case 0x8000:
switch(CH8->opcode & 0x000F){
case 0x0000: // 8XY0: Sets VX to the value of VY
CH8->V[(CH8->opcode & 0x0F00) >> 8] = CH8->V[(CH8->opcode & 0x00F0) >> 4];
CH8->pc += 2;
break;
case 0x0001: // 8XY1: Sets VX to VX or VY
CH8->V[(CH8->opcode & 0x0F00) >> 8] = CH8->V[(CH8->opcode & 0x0F00) >> 8] | CH8->V[(CH8->opcode & 0x00F0) >> 4];
CH8->pc += 2;
break;
case 0x0002: // 8XY2: Sets VX to VX and VY
CH8->V[(CH8->opcode & 0x0F00) >> 8] = CH8->V[(CH8->opcode & 0x0F00) >> 8] & CH8->V[(CH8->opcode & 0x00F0) >> 4];
CH8->pc += 2;
break;
case 0x0003: // 8XY3: Sets VX to VX xor VY
CH8->V[(CH8->opcode & 0x0F00) >> 8] = CH8->V[(CH8->opcode & 0x0F00) >> 8] ^ CH8->V[(CH8->opcode & 0x00F0) >> 4];
CH8->pc += 2;
break;
case 0x0004: // 8XY4: Adds VY to VX. VF is set to 1 when there's a carry, and to 0 when there isn't
if(((int)CH8->V[(CH8->opcode & 0x0F00) >> 8 ] + (int)CH8->V[(CH8->opcode & 0x00F0) >> 4]) < 256)
CH8->V[0xF] &= 0;
else
CH8->V[0xF] = 1;
CH8->V[(CH8->opcode & 0x0F00) >> 8] += CH8->V[(CH8->opcode & 0x00F0) >> 4];
CH8->pc += 2;
break;
case 0x0005: // 8XY5: VY is subtracted from VX. VF is set to 0 when there's a borrow, and 1 when there isn't
if(((int)CH8->V[(CH8->opcode & 0x0F00) >> 8 ] - (int)CH8->V[(CH8->opcode & 0x00F0) >> 4]) >= 0)
CH8->V[0xF] = 1;
else
CH8->V[0xF] &= 0;
CH8->V[(CH8->opcode & 0x0F00) >> 8] -= CH8->V[(CH8->opcode & 0x00F0) >> 4];
CH8->pc += 2;
break;
case 0x0006: // 8XY6: Shifts VX right by one. VF is set to the value of the least significant bit of VX before the shift
CH8->V[0xF] = CH8->V[(CH8->opcode & 0x0F00) >> 8] & 7;
CH8->V[(CH8->opcode & 0x0F00) >> 8] = CH8->V[(CH8->opcode & 0x0F00) >> 8] >> 1;
CH8->pc += 2;
break;
case 0x0007: // 8XY7: Sets VX to VY minus VX. VF is set to 0 when there's a borrow, and 1 when there isn't
if(((int)CH8->V[(CH8->opcode & 0x0F00) >> 8] - (int)CH8->V[(CH8->opcode & 0x00F0) >> 4]) > 0)
CH8->V[0xF] = 1;
else
CH8->V[0xF] &= 0;
CH8->V[(CH8->opcode & 0x0F00) >> 8] = CH8->V[(CH8->opcode & 0x00F0) >> 4] - CH8->V[(CH8->opcode & 0x0F00) >> 8];
CH8->pc += 2;
break;
case 0x000E: // 8XYE: Shifts VX left by one. VF is set to the value of the most significant bit of VX before the shift
CH8->V[0xF] = CH8->V[(CH8->opcode & 0x0F00) >> 8] >> 7;
CH8->V[(CH8->opcode & 0x0F00) >> 8] = CH8->V[(CH8->opcode & 0x0F00) >> 8] << 1;
CH8->pc += 2;
break;
default: printf("Wrong opcode: %X\n", CH8->opcode); getchar();
}
break;
case 0x9000: // 9XY0: Skips the next instruction if VX doesn't equal VY
if(CH8->V[(CH8->opcode & 0x0F00) >> 8] != CH8->V[(CH8->opcode & 0x00F0) >> 4])
CH8->pc += 4;
else
CH8->pc += 2;
break;
case 0xA000: // ANNN: Sets I to the address NNN
CH8->I = CH8->opcode & 0x0FFF;
CH8->pc += 2;
break;
case 0xB000: // BNNN: Jumps to the address NNN plus V0
CH8->pc = (CH8->opcode & 0x0FFF) + CH8->V[0];
break;
case 0xC000: // CXNN: Sets VX to a random number and NN
CH8->V[(CH8->opcode & 0x0F00) >> 8] = rand() & (CH8->opcode & 0x00FF);
CH8->pc += 2;
break;
case 0xD000: // DXYN: Draws a sprite at coordinate (VX, VY) that has a width of 8 pixels and a height of N pixels
vx = CH8->V[(CH8->opcode & 0x0F00) >> 8];
vy = CH8->V[(CH8->opcode & 0x00F0) >> 4];
height = CH8->opcode & 0x000F;
CH8->V[0xF] &= 0;
for(y = 0; y < height; y++){
pixel = CH8->memory[CH8->I + y];
for(x = 0; x < 8; x++){
if(pixel & (0x80 >> x)){
if(CH8->graphics[x+vx+(y+vy)*64])
CH8->V[0xF] = 1;
CH8->graphics[x+vx+(y+vy)*64] ^= 1;
}
}
}
CH8->pc += 2;
break;
case 0xE000:
switch(CH8->opcode & 0x000F){
case 0x000E: // EX9E: Skips the next instruction if the key stored in VX is pressed
keys = SDL_GetKeyState(NULL);
if(keys[keymap[CH8->V[(CH8->opcode & 0x0F00) >> 8]]])
CH8->pc += 4;
else
CH8->pc += 2;
break;
case 0x0001: // EXA1: Skips the next instruction if the key stored in VX isn't pressed
keys = SDL_GetKeyState(NULL);
if(!keys[keymap[CH8->V[(CH8->opcode & 0x0F00) >> 8]]])
CH8->pc += 4;
else
CH8->pc += 2;
break;
default: printf("Wrong opcode: %X\n", CH8->opcode); getchar();
}
break;
case 0xF000:
switch(CH8->opcode & 0x00FF){
case 0x0007: // FX07: Sets VX to the value of the delay timer
CH8->V[(CH8->opcode & 0x0F00) >> 8] = CH8->delay_timer;
CH8->pc += 2;
break;
case 0x000A: // FX0A: A key press is awaited, and then stored in VX
keys = SDL_GetKeyState(NULL);
for(i = 0; i < 0x10; i++)
if(keys[keymap[i]]){
CH8->V[(CH8->opcode & 0x0F00) >> 8] = i;
CH8->pc += 2;
}
break;
case 0x0015: // FX15: Sets the delay timer to VX
CH8->delay_timer = CH8->V[(CH8->opcode & 0x0F00) >> 8];
CH8->pc += 2;
break;
case 0x0018: // FX18: Sets the sound timer to VX
CH8->sound_timer = CH8->V[(CH8->opcode & 0x0F00) >> 8];
CH8->pc += 2;
break;
case 0x001E: // FX1E: Adds VX to I
CH8->I += CH8->V[(CH8->opcode & 0x0F00) >> 8];
CH8->pc += 2;
break;
case 0x0029: // FX29: Sets I to the location of the sprite for the character in VX. Characters 0-F (in hexadecimal) are represented by a 4x5 font
CH8->I = CH8->V[(CH8->opcode & 0x0F00) >> 8] * 5;
CH8->pc += 2;
break;
case 0x0033: // FX33: Stores the Binary-coded decimal representation of VX, with the most significant of three digits at the address in I, the middle digit at I plus 1, and the least significant digit at I plus 2
CH8->memory[CH8->I] = CH8->V[(CH8->opcode & 0x0F00) >> 8] / 100;
CH8->memory[CH8->I+1] = (CH8->V[(CH8->opcode & 0x0F00) >> 8] / 10) % 10;
CH8->memory[CH8->I+2] = CH8->V[(CH8->opcode & 0x0F00) >> 8] % 10;
CH8->pc += 2;
break;
case 0x0055: // FX55: Stores V0 to VX in memory starting at address I
for(i = 0; i <= ((CH8->opcode & 0x0F00) >> 8); i++)
CH8->memory[CH8->I+i] = CH8->V[i];
CH8->pc += 2;
break;
case 0x0065: //FX65: Fills V0 to VX with values from memory starting at address I
for(i = 0; i <= ((CH8->opcode & 0x0F00) >> 8); i++)
CH8->V[i] = CH8->memory[CH8->I + i];
CH8->pc += 2;
break;
default: printf("Wrong opcode: %X\n", CH8->opcode); getchar();
}
break;
default: printf("Wrong opcode: %X\n", CH8->opcode); getchar();
}
chip8_timers(CH8);
}
}
int main(){
chip8_start();
return 0;
}