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-rw-r--r--sources/main.c350
1 files changed, 350 insertions, 0 deletions
diff --git a/sources/main.c b/sources/main.c
new file mode 100644
index 0000000..56630df
--- /dev/null
+++ b/sources/main.c
@@ -0,0 +1,350 @@
+#define _DEFAULT_SOURCE
+#include <stdlib.h>
+#include <stdio.h>
+#include <string.h>
+#include <assert.h>
+#include <time.h>
+
+#include <endian.h>
+
+#include "bits.c"
+#include "fnt.c"
+
+
+#define C8_RESET_VECTOR 0x200
+#define C8_CYCLES_PER_FRAME 1000
+
+
+typedef struct
+{
+ u16 pc;
+ u8 sp;
+
+ u16 i;
+ u16 keys;
+
+ u64 cycles;
+
+ /* timers: */
+ u8 dt; /* - delay */
+ u8 st; /* - sound */
+
+ bool running;
+
+ union
+ {
+ struct
+ {
+ u8 v[16];
+ u64 disp[32];
+ u8 font[sizeof(fnt)];
+ u16 stack[16];
+
+ } sys;
+ u8 ram[4*KB];
+ } mem;
+
+} chip8;
+
+#include "instr.c"
+
+#define V mem.sys.v
+#define STACK mem.sys.stack
+#define DISPLAY mem.sys.disp
+#define FONT mem.sys.font
+#define RAM mem.ram
+
+
+void c8_reset(chip8* c8)
+{
+ assert(c8);
+ assert(sizeof(c8->mem) > sizeof(fnt));
+ assert(sizeof(c8->mem) >= 4*KB);
+
+ memcpy(c8->FONT, fnt, sizeof(fnt));
+
+ c8->pc = C8_RESET_VECTOR;
+}
+
+void c8_dump_state(chip8* c8, bool stack)
+{
+ int i = 0;
+
+ for(i = 0; i < (int)sizeof(c8->V); i += 4)
+ {
+ printf(" V%x: %02X (%-3d) ", i+0, c8->V[i+0], c8->V[i+0]);
+ printf("V%x: %02X (%-3d) ", i+1, c8->V[i+1], c8->V[i+1]);
+ printf("V%x: %02X (%-3d) ", i+2, c8->V[i+2], c8->V[i+2]);
+ printf("V%x: %02X (%-3d)\n", i+3, c8->V[i+3], c8->V[i+3]);
+ }
+
+ printf(" I:%04X SP: %02X DT: %02X ST: %02X\n", c8->i, c8->sp, c8->dt, c8->st);
+
+ if(stack)
+ {
+ printf("stack:\n");
+ for(i = 0; i < (int)sizeof(c8->STACK); i += 2)
+ {
+ printf(" %-2d: %04X ", i+0, c8->STACK[i+0]);
+ printf("%-2d: %04X\n", i+1, c8->STACK[i+1]);
+ }
+ }
+}
+
+void _c8_loop(chip8* c8, bool disasm, u16 from, u16 len)
+{
+ u16 to = 0;
+ u16 pc = 0;
+
+ assert(c8);
+
+ if(disasm)
+ {
+ pc = c8->pc;
+ c8->pc = from;
+ to = from + len*2;
+ }
+
+ c8->running = true;
+ while(c8->running)
+ {
+ int tmp;
+ u16 word, instr, nnn;
+ u8 o, x, y, n, kk;
+
+ if(c8->pc >= sizeof(c8->mem))
+ {
+ printf("PC Overflow!\n");
+ c8->running = false;
+ break;
+ }
+
+ if(c8->pc & 0x0001)
+ {
+ printf("PC is not aligned!\n");
+ c8->running = false;
+ break;
+ }
+
+ word = *(u16*)(c8->RAM + c8->pc);
+ instr = be16toh(word);
+ o = (instr & 0xF000) >> 12;
+ nnn = (instr & 0x0FFF);
+ x = (instr & 0x0F00) >> 8;
+ y = (instr & 0x00F0) >> 4;
+ n = (instr & 0x000F);
+ kk = (instr & 0x00FF);
+
+ printf("%04X: ", c8->pc);
+ switch(o)
+ {
+ case 1:
+ printf(" %04X JP 0x%03X\n", instr, nnn);
+ if(disasm) break;
+ c8->pc = nnn - 2;
+ break;
+
+ case 2:
+ printf(" %04X CALL 0x%03X\n", instr, nnn);
+ if(disasm) break;
+ c8->STACK[c8->sp++] = c8->pc; /* docs says ++sp then stack[sp] = pc ??? */
+ c8->pc = nnn - 2;
+ break;
+
+ case 3:
+ printf(" %04X SE V%x, 0x%02X\n", instr, x, kk);
+ if(disasm) break;
+ if(c8->V[x] == kk) c8->pc += 2;
+ break;
+
+ case 5:
+ printf(" %04X SE V%x, V%x\n", instr, x, y);
+ if(disasm) break;
+ if(c8->V[x] == c8->V[y]) c8->pc += 2;
+ break;
+
+ case 6:
+ printf(" %04X LD V%x, 0x%02X\n", instr, x, kk);
+ if(disasm) break;
+ c8->V[x] = kk;
+ break;
+
+ case 7:
+ printf(" %04X ADD V%x, 0x%02X\n", instr, x, kk);
+ if(disasm) break;
+ tmp = (int)c8->V[x] + (int)kk;
+ c8->V[0xf] = (tmp > 255);
+ /* c8->V[x] = (u8)tmp; /* spec says Vf not set */
+ break;
+
+ case 8:
+ {
+ switch(n)
+ {
+ case 4:
+ printf(" %04X ADD V%x, V%x\n", instr, x, y);
+ if(disasm) break;
+ tmp = (int)c8->V[x] + (int)c8->V[y];
+ c8->V[0xf] = (tmp > 255);
+ c8->V[x] = (u8)tmp;
+ break;
+
+ default:
+ printf(" %04X Unknown instruction\n", instr);
+ if(disasm) break;
+ c8->running = false;
+ break;
+ }
+ }
+ break;
+
+ case 0xA:
+ printf(" %04X LD I, 0x%03X\n", instr, nnn);
+ if(disasm) break;
+ c8->i = nnn;
+ break;
+
+ case 0xC:
+ printf(" %04X RND V%x, 0x%02X\n", instr, x, kk);
+ if(disasm) break;
+ c8->V[x] = (rand() % 256) & kk;
+ break;
+
+ case 0xD:
+ printf(" %04X DRW V%x, V%x, %d\n", instr, x, y, n);
+ if(disasm) break;
+ /* TODO: implement */
+ break;
+
+ case 0xE:
+ if(kk == 0x9E)
+ {
+ printf(" %04X SKP V%x\n", instr, x);
+ if(disasm) break;
+ if(c8->keys & bit(x)) c8->pc += 2;
+ }
+ else if(kk == 0xA1)
+ {
+ printf(" %04X SKNP V%x\n", instr, x);
+ if(disasm) break;
+ if(!(c8->keys & bit(x))) c8->pc += 2;
+ }
+ else
+ {
+ printf(" %04X Unknown instruction\n", instr);
+ if(disasm) break;
+ c8->running = false;
+ }
+ break;
+
+ case 0xF:
+ if(kk == 0x07)
+ {
+ printf(" %04X LD V%x, DT\n", instr, x);
+ if(disasm) break;
+ c8->V[x] = c8->dt;
+ }
+ else if(kk == 0x15)
+ {
+ printf(" %04X LD DT, V%x\n", instr, x);
+ if(disasm) break;
+ c8->dt= c8->V[x];
+ }
+ else
+ {
+ printf(" %04X Unknown instruction\n", instr);
+ if(disasm) break;
+ c8->running = false;
+ }
+ break;
+
+ default:
+ printf(" %04X Unknown instruction\n", instr);
+ if(disasm) break;
+ c8->running = false;
+ break;
+ }
+
+ if(!disasm) c8_dump_state(c8, false);
+
+ c8->pc += 2;
+ c8->cycles++;
+ if((c8->cycles % C8_CYCLES_PER_FRAME) == 0)
+ {
+ if(c8->dt) c8->dt--;
+ if(c8->st) c8->st--;
+ }
+
+ if(disasm && (c8->pc >= to)) c8->running = false;
+ }
+
+ if(disasm) c8->pc = pc;
+}
+
+
+int main(int argc, char** argv)
+{
+ u64 sz = 0;
+ FILE* f = NULL;
+ chip8 c8 = {0};
+
+ srand(time(NULL));
+
+ c8_reset(&c8);
+
+ if(argc > 1)
+ {
+ u64 got = 0;
+
+ f = fopen(argv[1], "r");
+ if(!f) return 1;
+
+ fseek(f, 0, SEEK_END);
+ sz = (u64)ftell(f);
+ rewind(f);
+
+ if(sz >= (sizeof(c8.RAM) - 512)) return 2;
+
+ got = fread(c8.RAM + C8_RESET_VECTOR, 1, sz, f);
+ if(got != sz) return 3;
+
+ fclose(f);
+ }
+ else
+ {
+ c8.RAM[C8_RESET_VECTOR + iota] = 0x60;
+ c8.RAM[C8_RESET_VECTOR + iota] = 0x04;
+
+ c8.RAM[C8_RESET_VECTOR + iota] = 0x61;
+ c8.RAM[C8_RESET_VECTOR + iota] = 0x03;
+
+ c8.RAM[C8_RESET_VECTOR + iota] = 0x72;
+ c8.RAM[C8_RESET_VECTOR + iota] = 0x01;
+
+ c8.RAM[C8_RESET_VECTOR + iota] = 0x80;
+ c8.RAM[C8_RESET_VECTOR + iota] = 0x14;
+
+ c8.RAM[C8_RESET_VECTOR + iota] = 0x30;
+ c8.RAM[C8_RESET_VECTOR + iota] = 0x10;
+
+ c8.RAM[C8_RESET_VECTOR + iota] = 0x12;
+ c8.RAM[C8_RESET_VECTOR + iota] = 0x04;
+
+ sz = iota;
+ }
+
+ printf("Disasm:\n");
+ {
+ u64 i;
+ char buf[512] = {0};
+
+ for(i = 0; i < sz; i += 2)
+ {
+ u16 pc = C8_RESET_VECTOR + i;
+ c8_disasm(c8.RAM, pc, buf);
+ printf("%04X: %s\n", pc, buf);
+ }
+ }
+
+ return 0;
+}
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