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-rw-r--r--sources/chip8.c212
1 files changed, 212 insertions, 0 deletions
diff --git a/sources/chip8.c b/sources/chip8.c
new file mode 100644
index 0000000..f5a28a8
--- /dev/null
+++ b/sources/chip8.c
@@ -0,0 +1,212 @@
+#define C8_RESET_VECTOR 0x200
+#define C8_CYCLES_PER_FRAME 1000
+
+static const u8 fnt[] =
+{
+ 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 */
+};
+
+
+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;
+
+#define V mem.sys.v
+#define STACK mem.sys.stack
+#define DISPLAY mem.sys.disp
+#define FONT mem.sys.font
+#define RAM mem.ram
+
+typedef enum
+{
+ C8_ILL,
+/* Onnn = 0,1,2,A,B */
+/* 00E0 - CLS */ C8_CLS,
+/* 00EE - RET */ C8_RET,
+/* 0nnn - SYS addr */ C8_SYS,
+/* 1nnn - JP addr */ C8_JP,
+/* 2nnn - CALL addr */ C8_CALL,
+/* Annn - LD I, addr */ C8_LDI,
+/* Bnnn - JP V0, addr */ C8_JPV,
+/* Oxkk = 3,4,6,7,C,E,F */
+/* 3xkk - SE Vx, byte */ C8_SEB,
+/* 4xkk - SNE Vx, byte */ C8_SNEB,
+/* 6xkk - LD Vx, byte */ C8_LD,
+/* 7xkk - ADD Vx, byte */ C8_ADDB,
+/* Cxkk - RND Vx, byte */ C8_RND,
+/* Ex9E - SKP Vx */ C8_SKP,
+/* ExA1 - SKNP Vx */ C8_SKNP,
+/* Fx07 - LD Vx, DT */ C8_MVDT,
+/* Fx0A - LD Vx, K */ C8_LDK,
+/* Fx15 - LD DT, Vx */ C8_LDDT,
+/* Fx18 - LD ST, Vx */ C8_LDST,
+/* Fx1E - ADD I, Vx */ C8_ADDI,
+/* Fx29 - LD F, Vx */ C8_HEX,
+/* Fx33 - LD B, Vx */ C8_BCD,
+/* Fx55 - LD [I], Vx */ C8_SAVE,
+/* Fx65 - LD Vx, [I] */ C8_RESTORE,
+/* Oxyn = 5,8,9,D */
+/* 5xy0 - SE Vx, Vy */ C8_SE,
+/* 8xy0 - LD Vx, Vy */ C8_MOVE,
+/* 8xy1 - OR Vx, Vy */ C8_OR,
+/* 8xy2 - AND Vx, Vy */ C8_AND,
+/* 8xy3 - XOR Vx, Vy */ C8_XOR,
+/* 8xy4 - ADD Vx, Vy */ C8_ADD,
+/* 8xy5 - SUB Vx, Vy */ C8_SUB,
+/* 8xy6 - SHR Vx {, Vy} */ C8_SHR,
+/* 8xy7 - SUBN Vx, Vy */ C8_SUBN,
+/* 8xyE - SHL Vx {, Vy} */ C8_SHL,
+/* 9xy0 - SNE Vx, Vy */ C8_SNE,
+/* Dxyn - DRW Vx, Vy, nibble */ C8_DRW,
+ C8_OP_CNT
+
+} chip8_op;
+
+
+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;
+ c8->running = true;
+}
+
+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 CYCLES: %llu\n",
+ c8->i, c8->sp, c8->dt, c8->st, c8->cycles);
+
+ 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]);
+ }
+ }
+}
+
+
+
+#define c8_decode_generate(name) \
+void c8_##name(u8* code, u16 offset, void* usrdat) \
+{ \
+ u16 word, instr, nnn; \
+ u8 o, x, y, n, kk; \
+ \
+ (void)usrdat; \
+ \
+ word = *(u16*)(code + offset); \
+ instr = be16toh(word); \
+ o = (instr & 0xF000) >> 12; \
+ nnn = (instr & 0x0FFF); \
+ x = (instr & 0x0F00) >> 8; \
+ y = (instr & 0x00F0) >> 4; \
+ n = (instr & 0x000F); \
+ kk = (instr & 0x00FF); \
+ \
+ (void)o; \
+ (void)nnn; \
+ (void)x; \
+ (void)y; \
+ (void)n; \
+ (void)kk; \
+ \
+ X_C8_PRELUDE; \
+ \
+ if(o == 0 && nnn == 0x0E0) X_C8_CLS; \
+ else if(o == 0 && nnn == 0x0EE) X_C8_RET; \
+ else if(o == 0) X_C8_SYS; \
+ else if(o == 1) X_C8_JP; \
+ else if(o == 2) X_C8_CALL; \
+ else if(o == 0xA) X_C8_LDI; \
+ else if(o == 0xB) X_C8_JPV; \
+ else if(o == 3) X_C8_SEB; \
+ else if(o == 4) X_C8_SNEB; \
+ else if(o == 6) X_C8_LD; \
+ else if(o == 7) X_C8_ADDB; \
+ else if(o == 0xC) X_C8_RND; \
+ else if(o == 0xE && kk == 0x9E) X_C8_SKP; \
+ else if(o == 0xE && kk == 0xA1) X_C8_SKNP; \
+ else if(o == 0xF && kk == 0x07) X_C8_MVDT; \
+ else if(o == 0xF && kk == 0x0A) X_C8_LDK; \
+ else if(o == 0xF && kk == 0x15) X_C8_LDDT; \
+ else if(o == 0xF && kk == 0x18) X_C8_LDST; \
+ else if(o == 0xF && kk == 0x1E) X_C8_ADDI; \
+ else if(o == 0xF && kk == 0x29) X_C8_HEX; \
+ else if(o == 0xF && kk == 0x33) X_C8_BCD; \
+ else if(o == 0xF && kk == 0x55) X_C8_SAVE; \
+ else if(o == 0xF && kk == 0x65) X_C8_RESTORE; \
+ else if(o == 5 && n == 0) X_C8_SE; \
+ else if(o == 8 && n == 0) X_C8_MOVE; \
+ else if(o == 8 && n == 1) X_C8_OR; \
+ else if(o == 8 && n == 2) X_C8_AND; \
+ else if(o == 8 && n == 3) X_C8_XOR; \
+ else if(o == 8 && n == 4) X_C8_ADD; \
+ else if(o == 8 && n == 5) X_C8_SUB; \
+ else if(o == 8 && n == 6) X_C8_SHR; \
+ else if(o == 8 && n == 7) X_C8_SUBN; \
+ else if(o == 8 && n == 0xE) X_C8_SHL; \
+ else if(o == 9 && n == 0) X_C8_SNE; \
+ else if(o == 0xD) X_C8_DRW; \
+ else X_C8_ILL; \
+ \
+ X_C8_EPILOGUE; \
+}
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