-
Notifications
You must be signed in to change notification settings - Fork 0
/
chip8.c
322 lines (307 loc) · 10.4 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
#include "chip8.h"
#include <SDL2/SDL_events.h>
#include "log.h"
#include <stdlib.h>
#include <stdio.h>
#include <string.h>
#include <time.h>
void chip8_init(chip8 *chip)
{
srand(time(NULL));
memset(chip, 0, sizeof *chip);
memcpy(chip->memory, fonts, sizeof fonts);
chip->pc = 0x200;
chip->i = 0;
chip->clockspeed = DEFAULT_CLOCK;
chip->settings = chip8_default_settings;
}
void chip8_interpret(chip8 *chip)
{
for (int i = 0; i < chip->clockspeed / 60; ++i) {
uint16_t op = chip->memory[chip->pc] << 8 | chip->memory[chip->pc+1];
if (chip->key_waiting) return;
if (op == 0x0) return;
/* OP -> AxyB */
int x = (op & 0x0F00) >> 8;
int y = (op & 0x00F0) >> 4;
int n = op & 0x000F;
int nn = op & 0x00FF;
int nnn = op & 0x0FFF;
chip->pc += 2;
switch (op & 0xF000) {
case 0x0000:
switch (nn) {
case 0xE0:
/* CLR */
memset(chip->screen, 0, sizeof chip->screen);
break;
case 0xEE:
/* RET */
chip->pc = chip->stack[--chip->sp];
break;
case 0xFA:
/* COMPAT */
//chip->FX55_FX65_change_I ^= 1;
break;
/* 0NNN - sys is not implemented as is not needed anymore */
}
break;
case 0x1000:
/* JUMP TO nnn */
chip->pc = nnn;
break;
case 0x2000:
/* call subroutine at nnn */
chip->stack[chip->sp++] = chip->pc;
chip->pc = nnn;
break;
case 0x3000:
/* SE Vx, byte */
if (chip->v[x] == nn)
chip->pc += 2;
break;
case 0x4000:
/* SNE Vx, byte */
if (chip->v[x] != nn)
chip->pc += 2;
break;
case 0x5000:
/* SE Vx, Vy */
if (chip->v[x] == chip->v[y])
chip->pc += 2;
break;
case 0x6000:
chip->v[x] = nn;
break;
case 0x7000:
chip->v[x] += nn;
break;
case 0x8000:
switch (n) {
case 0x0:
chip->v[x] = chip->v[y];
break;
case 0x1:
chip->v[x] |= chip->v[y];
if (chip->settings.op_8xy1_2_3_reset_vf)
chip->v[0xF] = 0;
break;
case 0x2:
chip->v[x] &= chip->v[y];
if (chip->settings.op_8xy1_2_3_reset_vf)
chip->v[0xF] = 0;
break;
case 0x3:
chip->v[x] ^= chip->v[y];
if (chip->settings.op_8xy1_2_3_reset_vf)
chip->v[0xF] = 0;
break;
case 0x4: {
/* Vx = Vx + Vy, VF = carry */
int flag = ((int)chip->v[x] + (int)chip->v[y]) > 0xFF;
chip->v[x] += chip->v[y];
chip->v[0xF] = flag;
break;
}
case 0x5: {
/* Vx = Vx - Vy, VF = NOT borrow */
int flag = chip->v[x] > chip->v[y];
chip->v[x] = chip->v[x] - chip->v[y];
chip->v[0xF] = flag;
break;
}
case 0x6: {
/* Vx = Vx SHR 1 */
if (chip->settings.op_8xy6_8xye_do_vy)
chip->v[x] = chip->v[y];
int flag = chip->v[x] & 1;
chip->v[x] >>= 1;
chip->v[0xF] = flag;
break;
}
case 0x7: {
/* Vx = Vy - Vx, VF = NOT borrow */
int flag = chip->v[y] > chip->v[x];
chip->v[x] = chip->v[y] - chip->v[x];
chip->v[0xF] = flag;
break;
}
case 0xE: {
/* Vx = Vx SHL 1 */
if (chip->settings.op_8xy6_8xye_do_vy)
chip->v[x] = chip->v[y];
int flag = chip->v[x] >> 7;
chip->v[x] <<= 1;
chip->v[0xF] = flag;
break;
}
}
break;
case 0x9000:
if (chip->v[x] != chip->v[y])
chip->pc += 2;
break;
case 0xA000:
chip->i = nnn;
break;
case 0xB000:
chip->pc = chip->v[0] + nnn;
break;
case 0xC000:
chip->v[x] = (rand() % 256) & nn;
break;
case 0xD000:
chip->v[0xF] = 0;
for (int row = 0; row < n; row++) {
uint8_t sprite = chip->memory[chip->i + row];
for (int col = 0; col < 8; col++) {
int bit = sprite >> (7 - col) & 1;
uint8_t dx = chip->v[x] + col;
uint8_t dy = chip->v[y] + row;
if (chip->settings.screen_wrap_around) {
dx %= WIDTH;
dy %= HEIGHT;
} else if (dx >= WIDTH || dy >= HEIGHT) {
continue;
}
if (bit && chip->screen[dy][dx])
chip->v[0xF] = 1;
chip->screen[dy][dx] ^= bit;
}
}
break;
case 0xE000:
switch (nn) {
case 0x9E:
/* SKP Vx */
if (chip->keys & (1 << chip->v[x]))
chip->pc += 2;
break;
case 0xA1:
/* SKNP Vx */
if (!(chip->keys & (1 << chip->v[x])))
chip->pc += 2;
break;
}
break;
case 0xF000:
switch (nn) {
case 0x07:
chip->v[x] = chip->delaytimer;
break;
case 0x0A:
chip8_wait_for_key(chip, x);
break;
case 0x15:
chip->delaytimer = chip->v[x];
break;
case 0x18:
chip->soundtimer = chip->v[x];
break;
case 0x1E:
chip->i += chip->v[x];
chip->v[0xF] = chip->i > 0x0FFF;
break;
case 0x29:
chip->i = chip->v[x] * 5;
break;
case 0x33:
chip->memory[chip->i] = chip->v[x] / 100;
chip->memory[chip->i+1] = (chip->v[x] % 100) / 10;
chip->memory[chip->i+2] = chip->v[x] % 10;
break;
case 0x55:
for (int i = 0; i <= x; i++)
chip->memory[chip->i+i] = chip->v[i];
if (chip->settings.op_fx55_fx65_increment)
chip->i += x + 1;
break;
case 0x65:
for (int i = 0; i <= x; i++)
chip->v[i] = chip->memory[chip->i+i];
if (chip->settings.op_fx55_fx65_increment)
chip->i += x + 1;
break;
}
break;
default:
printf("Invalid OPCODE %4x\n", op);
break;
}
}
}
void chip8_load_rom(chip8 *chip, uint8_t *buf, size_t size)
{
chip->pc = 0x200;
chip->i = 0;
memset(chip->screen, 0, sizeof chip->screen);
memcpy(chip->memory + 0x200, buf, size);
}
int chip8_load_rom_from_file(chip8 *chip, const char *path)
{
chip->pc = 0x200;
memset(chip->screen, 0, sizeof chip->screen);
chip->i = 0;
FILE *rom = fopen(path, "rb");
if (rom == NULL) {
warn("Failed opening rom file");
return -1;
}
fseek(rom, 0, SEEK_END);
size_t rom_size = ftell(rom);
rewind(rom);
if ((MEMORY_SIZE - 0x200) < rom_size) {
warn("Rom too big!");
return -1;
}
size_t result = fread(chip->memory+0x200, 1, rom_size, rom);
if (result != rom_size) {
warn("Error reading rom to memory");
return -1;
}
fclose(rom);
return 0;
}
void chip8_update_timer(chip8 *chip)
{
if (chip->delaytimer > 0)
chip->delaytimer--;
if (chip->soundtimer > 0)
chip->soundtimer--;
}
void chip8_wait_for_key(chip8 *chip, int reg) {
if (chip->key_waiting) return;
chip->key_waiting = true;
chip->register_waiting = reg;
}
void chip8_save_to_file(chip8 *chip, const char *path) {
FILE *fp = fopen(path, "w");
if (fp == NULL) {
warn("Failed to open file for saving");
return;
}
fwrite(chip, sizeof *chip, 1, fp);
fclose(fp);
}
void chip8_restore_from_file(chip8 *chip, const char *path) {
FILE *fp = fopen(path, "rb");
if (fp == NULL) {
warn("Failed to open file for restoring");
return;
}
fread(chip, sizeof *chip, 1, fp);
fclose(fp);
}
bool chip8_keyisdown(chip8 *chip, int key) {
return chip->keys & (1 << key);
}
void chip8_keydown(chip8 *chip, int key) {
chip->keys |= 1 << key;
}
void chip8_keyup(chip8 *chip, int key) {
if (chip->key_waiting) {
chip->key_waiting = false;
chip->v[chip->register_waiting] = key;
}
chip->keys &= ~(1 << key);
}