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refactor(cpu): extract magic numbers to decimal enums

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This commit is contained in:
Stevan Freeborn
2026-07-18 15:16:21 -05:00
parent 35572cb76a
commit 4f3ea9697e
1 changed files with 91 additions and 39 deletions
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main.c
+91 -39
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@@ -15,6 +15,59 @@
#define SCREEN_WIDTH 64 #define SCREEN_WIDTH 64
#define SCREEN_HEIGHT 32 #define SCREEN_HEIGHT 32
enum OpcodeGroups {
OPCODE_GROUP_SYS_OR_RET = 0,
OPCODE_GROUP_JUMP = 4096,
OPCODE_GROUP_CALL = 8192,
OPCODE_GROUP_SE_VX_BYTE = 12288,
OPCODE_GROUP_SNE_VX_BYTE = 16384,
OPCODE_GROUP_SE_VX_VY = 20480,
OPCODE_GROUP_LD_VX_BYTE = 24576,
OPCODE_GROUP_ADD_VX_BYTE = 28672,
OPCODE_GROUP_ARITHMETIC = 32768,
OPCODE_GROUP_SNE_VX_VY = 36864,
OPCODE_GROUP_LD_I_ADDR = 40960,
OPCODE_GROUP_JP_V0_ADDR = 45056,
OPCODE_GROUP_RND_VX_BYTE = 49152,
OPCODE_GROUP_DRW_VX_VY_N = 53248,
OPCODE_GROUP_KEY_SKIP = 57344,
OPCODE_GROUP_MISC = 61440
};
enum SysOpcodes {
OPCODE_CLS = 224,
OPCODE_RET = 238
};
enum ArithmeticSubOpcodes {
SUB_OP_LD = 0,
SUB_OP_OR = 1,
SUB_OP_AND = 2,
SUB_OP_XOR = 3,
SUB_OP_ADD = 4,
SUB_OP_SUB = 5,
SUB_OP_SHR = 6,
SUB_OP_SUBN = 7,
SUB_OP_SHL = 14
};
enum KeySkipOpcodes {
OPCODE_SKP = 158,
OPCODE_SKNP = 161
};
enum MiscSubOpcodes {
SUB_OP_LD_VX_DT = 7,
SUB_OP_LD_VX_K = 10,
SUB_OP_LD_DT_VX = 21,
SUB_OP_LD_ST_VX = 24,
SUB_OP_ADD_I_VX = 30,
SUB_OP_LD_F_VX = 41,
SUB_OP_LD_B_VX = 51,
SUB_OP_LD_I_REG = 85,
SUB_OP_LD_REG_I = 101
};
const uint8_t fontset[80] = { const uint8_t fontset[80] = {
0xF0, 0x90, 0x90, 0x90, 0xF0, // 0 0xF0, 0x90, 0x90, 0x90, 0xF0, // 0
0x20, 0x60, 0x20, 0x20, 0x70, // 1 0x20, 0x60, 0x20, 0x20, 0x70, // 1
@@ -305,125 +358,124 @@ int main(int argc, char *argv[]) {
uint16_t kk = opcode & 255; uint16_t kk = opcode & 255;
switch(opcode & 61440) { switch(opcode & 61440) {
case 0: case OPCODE_GROUP_SYS_OR_RET:
if (opcode == 224) { // 00E0 if (opcode == OPCODE_CLS) {
memset(chip->display, 0, sizeof(chip->display)); memset(chip->display, 0, sizeof(chip->display));
} else if (opcode == 238) { // 00EE } else if (opcode == OPCODE_RET) {
chip->sc -= 1; chip->sc -= 1;
chip->pc = chip->stack[chip->sc]; chip->pc = chip->stack[chip->sc];
} }
break; break;
case 4096: // 1nnn case OPCODE_GROUP_JUMP:
chip->pc = nnn; chip->pc = nnn;
break; break;
case 8192: // 2nnn case OPCODE_GROUP_CALL:
chip->stack[chip->sc] = chip->pc; chip->stack[chip->sc] = chip->pc;
chip->sc += 1; chip->sc += 1;
chip->pc = nnn; chip->pc = nnn;
break; break;
case 12288: // 3xkk case OPCODE_GROUP_SE_VX_BYTE:
if (chip->V[x] == kk) { if (chip->V[x] == kk) {
chip->pc += 2; chip->pc += 2;
} }
break; break;
case 16384: // 4xkk case OPCODE_GROUP_SNE_VX_BYTE:
if (chip->V[x] != kk) { if (chip->V[x] != kk) {
chip->pc += 2; chip->pc += 2;
} }
break; break;
case 20480: // 5xy0 case OPCODE_GROUP_SE_VX_VY:
if (chip->V[x] == chip->V[y]) { if (chip->V[x] == chip->V[y]) {
chip->pc += 2; chip->pc += 2;
} }
break; break;
case 24576: // 6xkk case OPCODE_GROUP_LD_VX_BYTE:
chip->V[x] = kk; chip->V[x] = kk;
break; break;
case 28672: // 7xkk case OPCODE_GROUP_ADD_VX_BYTE:
chip->V[x] += kk; chip->V[x] += kk;
break; break;
case 32768: // 8xy0 case OPCODE_GROUP_ARITHMETIC:
// TODO: Maybe switch? if (n == SUB_OP_LD) {
if (n == 0) {
chip->V[x] = chip->V[y]; chip->V[x] = chip->V[y];
} else if (n == 1) { } else if (n == SUB_OP_OR) {
chip->V[x] = chip->V[x] | chip->V[y]; chip->V[x] = chip->V[x] | chip->V[y];
} else if (n == 2) { } else if (n == SUB_OP_AND) {
chip->V[x] = chip->V[x] & chip->V[y]; chip->V[x] = chip->V[x] & chip->V[y];
} else if (n == 3) { } else if (n == SUB_OP_XOR) {
chip->V[x] = chip->V[x] ^ chip->V[y]; chip->V[x] = chip->V[x] ^ chip->V[y];
} else if (n == 4) { } else if (n == SUB_OP_ADD) {
uint16_t r = chip->V[x] + chip->V[y]; uint16_t r = chip->V[x] + chip->V[y];
chip->V[15] = (r > 255) ? 1 : 0; chip->V[15] = (r > 255) ? 1 : 0;
chip->V[x] = r & 255; chip->V[x] = r & 255;
} else if (n == 5) { } else if (n == SUB_OP_SUB) {
chip->V[15] = (chip->V[x] >= chip->V[y]) ? 1 : 0; chip->V[15] = (chip->V[x] >= chip->V[y]) ? 1 : 0;
chip->V[x] = chip->V[x] - chip->V[y]; chip->V[x] = chip->V[x] - chip->V[y];
} else if (n == 6) { } else if (n == SUB_OP_SHR) {
uint8_t flag = chip->V[x] & 1; uint8_t flag = chip->V[x] & 1;
chip->V[15] = flag; chip->V[15] = flag;
chip->V[x] /= 2; chip->V[x] /= 2;
} else if (n == 7) { } else if (n == SUB_OP_SUBN) {
chip->V[15] = (chip->V[y] >= chip->V[x]) ? 1 : 0; chip->V[15] = (chip->V[y] >= chip->V[x]) ? 1 : 0;
chip->V[x] = chip->V[y] - chip->V[x]; chip->V[x] = chip->V[y] - chip->V[x];
} else if (n == 14) { } else if (n == SUB_OP_SHL) {
uint8_t flag = (chip->V[x] & 128) >> 7; uint8_t flag = (chip->V[x] & 128) >> 7;
chip->V[15] = flag; chip->V[15] = flag;
chip->V[x] *= 2; chip->V[x] *= 2;
} }
break; break;
case 36864: // 9xy0 case OPCODE_GROUP_SNE_VX_VY:
if (chip->V[x] != chip->V[y]) { if (chip->V[x] != chip->V[y]) {
chip->pc += 2; chip->pc += 2;
} }
break; break;
case 40960: // ANNN case OPCODE_GROUP_LD_I_ADDR:
chip->I = nnn; chip->I = nnn;
break; break;
case 45056: // Bnnn case OPCODE_GROUP_JP_V0_ADDR:
chip->pc = nnn + chip->V[0]; chip->pc = nnn + chip->V[0];
break; break;
case 49152: // Cxkk case OPCODE_GROUP_RND_VX_BYTE:
uint8_t num = rand() % 256; uint8_t num = rand() % 256;
chip->V[x] = kk & num; chip->V[x] = kk & num;
break; break;
case 53248: // Dxyn case OPCODE_GROUP_DRW_VX_VY_N:
draw_sprite(chip, n, x, y); draw_sprite(chip, n, x, y);
break; break;
case 57344: // E000 case OPCODE_GROUP_KEY_SKIP:
if (nn == 158) { if (nn == OPCODE_SKP) {
if (chip->keys[chip->V[x] & 0x0F] == 1) { if (chip->keys[chip->V[x] & 0x0F] == 1) {
chip->pc += 2; chip->pc += 2;
} }
} else if (nn == 161) { } else if (nn == OPCODE_SKNP) {
if (chip->keys[chip->V[x] & 0x0F] != 1) { if (chip->keys[chip->V[x] & 0x0F] != 1) {
chip->pc += 2; chip->pc += 2;
} }
} }
break; break;
case 61440: // F000 case OPCODE_GROUP_MISC:
if (nn == 7) { if (nn == SUB_OP_LD_VX_DT) {
chip->V[x] = chip->dt; chip->V[x] = chip->dt;
} else if (nn == 10) { } else if (nn == SUB_OP_LD_VX_K) {
chip->waiting_for_key = true; chip->waiting_for_key = true;
chip->key_register = x; chip->key_register = x;
} else if (nn == 21) { } else if (nn == SUB_OP_LD_DT_VX) {
chip->dt = chip->V[x]; chip->dt = chip->V[x];
} else if (nn == 24) { } else if (nn == SUB_OP_LD_ST_VX) {
chip->st = chip->V[x]; chip->st = chip->V[x];
} else if (nn == 30) { } else if (nn == SUB_OP_ADD_I_VX) {
chip->I += chip->V[x]; chip->I += chip->V[x];
} else if (nn == 41) { } else if (nn == SUB_OP_LD_F_VX) {
chip->I = FONT_START + ((chip->V[x] & 0x0F) * 5); chip->I = FONT_START + ((chip->V[x] & 0x0F) * 5);
} else if (nn == 51) { } else if (nn == SUB_OP_LD_B_VX) {
chip->memory[chip->I] = chip->V[x] / 100; chip->memory[chip->I] = chip->V[x] / 100;
chip->memory[chip->I + 1] = (chip->V[x] / 10) % 10; chip->memory[chip->I + 1] = (chip->V[x] / 10) % 10;
chip->memory[chip->I + 2] = chip->V[x] % 10; chip->memory[chip->I + 2] = chip->V[x] % 10;
} else if (nn == 85) { } else if (nn == SUB_OP_LD_I_REG) {
for (int i = 0; i <= x; i++) { for (int i = 0; i <= x; i++) {
chip->memory[chip->I + i] = chip->V[i]; chip->memory[chip->I + i] = chip->V[i];
} }
} else if (nn == 101) { } else if (nn == SUB_OP_LD_REG_I) {
for (int i = 0; i <= x; i++) { for (int i = 0; i <= x; i++) {
chip->V[i] = chip->memory[chip->I + i]; chip->V[i] = chip->memory[chip->I + i];
} }