Created
June 6, 2020 06:36
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A Simple CHIP-8 Disassembler
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| #include <stdio.h> | |
| #include <stdint.h> | |
| #include <stdlib.h> | |
| #include <string.h> | |
| char *get_instruction_string(uint16_t opcode) { | |
| char *result = malloc(sizeof(char) * 32); | |
| uint8_t add_newline = 0; | |
| uint8_t arg1 = (opcode & 0x0f00) >> 8; | |
| uint8_t arg2 = (opcode & 0x00f0) >> 4; | |
| uint8_t byte = opcode & 0xff; | |
| switch (opcode & 0xf000) { | |
| case 0x0000: { | |
| if (opcode & 0x000E) { | |
| strcpy(result, "ret"); | |
| add_newline = 1; | |
| } else { | |
| strcpy(result, "cls"); | |
| } | |
| break; | |
| } | |
| case 0x1000: { | |
| snprintf(result, 32, "jp $%x", opcode & 0x0fff); | |
| add_newline = 1; | |
| break; | |
| } | |
| case 0x2000: { | |
| snprintf(result, 32, "call $%x", opcode & 0x0fff); | |
| break; | |
| } | |
| case 0x3000: { | |
| snprintf(result, 32, "se V%x, $%x", arg1, byte); | |
| break; | |
| } | |
| case 0x4000: { | |
| snprintf(result, 32, "sne V%x, $%x", arg1, byte); | |
| break; | |
| } | |
| case 0x5000: { | |
| snprintf(result, 32, "se V%x, V%x", arg1, arg2); | |
| break; | |
| } | |
| case 0x6000: { | |
| snprintf(result, 32, "ld V%x, $%x", arg1, byte); | |
| break; | |
| } | |
| case 0x7000: { | |
| snprintf(result, 32, "add V%x, $%x", arg1, byte); | |
| break; | |
| } | |
| case 0x8000: { | |
| switch (opcode & 0x000f) { | |
| case 0x0: { | |
| snprintf(result, 32, "ld V%x, V%x", arg1, arg2); | |
| break; | |
| } | |
| case 0x1: { | |
| snprintf(result, 32, "or V%x, V%x", arg1, arg2); | |
| break; | |
| } | |
| case 0x2: { | |
| snprintf(result, 32, "and V%x, V%x", arg1, arg2); | |
| break; | |
| } | |
| case 0x3: { | |
| snprintf(result, 32, "xor V%x, V%x", arg1, arg2); | |
| break; | |
| } | |
| case 0x4: { | |
| snprintf(result, 32, "add V%x, V%x", arg1, arg2); | |
| break; | |
| } | |
| case 0x5: { | |
| snprintf(result, 32, "sub V%x, V%x", arg1, arg2); | |
| break; | |
| } | |
| case 0x6: { | |
| snprintf(result, 32, "shr V%x {, V%x}", arg1, arg2); | |
| break; | |
| } | |
| case 0x7: { | |
| snprintf(result, 32, "subn V%x, V%x", arg1, arg2); | |
| break; | |
| } | |
| case 0xE: { | |
| snprintf(result, 32, "shl V%x {, V%x}", arg1, arg2); | |
| break; | |
| } | |
| } | |
| break; | |
| } | |
| case 0x9000: { | |
| snprintf(result, 32, "sne V%x, V%x", arg1, arg2); | |
| break; | |
| } | |
| case 0xA000: { | |
| snprintf(result, 32, "ld I, $%x", opcode & 0x0fff); | |
| break; | |
| } | |
| case 0xB000: { | |
| snprintf(result, 32, "jp V0, $%x", opcode & 0x0fff); | |
| break; | |
| } | |
| case 0xC000: { | |
| snprintf(result, 32, "rnd V%x, $%x", opcode & 0x0fff); | |
| break; | |
| } | |
| case 0xD000: { | |
| snprintf(result, 32, "drw V%x, V%x, $%x", arg1, arg2, opcode & 0x000f); | |
| break; | |
| } | |
| case 0xE000: { | |
| if ((opcode & 0x000f) == 0xE) { | |
| snprintf(result, 32, "skp V%x", arg1); | |
| } else { | |
| snprintf(result, 32, "sknp V%x", arg1); | |
| } | |
| break; | |
| } | |
| case 0xF000: { | |
| switch (opcode & 0x00ff) { | |
| case 0x07: { | |
| snprintf(result, 32, "ld V%x, dt", arg1); | |
| break; | |
| } | |
| case 0x0A: { | |
| snprintf(result, 32, "ld V%x, {keypress}", arg1); | |
| break; | |
| } | |
| case 0x15: { | |
| snprintf(result, 32, "ld dt, V%x", arg1); | |
| break; | |
| } | |
| case 0x18: { | |
| snprintf(result, 32, "ld st, V%x", arg1); | |
| break; | |
| } | |
| case 0x1E: { | |
| snprintf(result, 32, "add I, V%x", arg1); | |
| break; | |
| } | |
| case 0x29: { | |
| snprintf(result, 32, "ld F, V%x", arg1); | |
| break; | |
| } | |
| case 0x33: { | |
| snprintf(result, 32, "ld B, V%x", arg1); | |
| break; | |
| } | |
| case 0x55: { | |
| snprintf(result, 32, "ld [I], V%x", arg1); | |
| break; | |
| } | |
| case 0x65: { | |
| snprintf(result, 32, "ld V%x, [I]", arg1); | |
| break; | |
| } | |
| } | |
| break; | |
| } | |
| default: | |
| strcpy(result, ""); | |
| } | |
| if (add_newline) { | |
| uint8_t offset = strlen(result); | |
| result[offset] = '\n'; | |
| result[offset + 1] = 0; | |
| } | |
| return result; | |
| } | |
| int main(int argc, char **argv) { | |
| if (argc < 2) { | |
| printf("Enter a file to disassemble\n"); | |
| return -1; | |
| } | |
| FILE *file = fopen(argv[1], "rb"); | |
| if (!file) { | |
| printf("could not open file"); | |
| return -1; | |
| } | |
| uint16_t rom_addr = 0x200; | |
| uint16_t num = 0; | |
| printf("rom_start:\n"); | |
| while (fread(&num, sizeof(uint16_t), 1, file) != 0) { | |
| uint16_t opcode = ((num & 0xff00) >> 8) | ((num & 0xff) << 8); | |
| char *instruction_string = get_instruction_string(opcode); | |
| printf("0x%04x: %s\n", rom_addr, instruction_string); | |
| free(instruction_string); | |
| rom_addr += 2; | |
| } | |
| return 0; | |
| } |
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