commit cd767c663149e68b4db03753e354d767dd97411e
Author: Toni <antpiasecki@gmail.com>
Date:   Fri Jul 11 14:02:04 2025 +0200

    disassembler

diff --git a/chip8.c b/chip8.c
new file mode 100644
index 0000000..8895457
--- /dev/null
+++ b/chip8.c
@@ -0,0 +1,207 @@
+// http://devernay.free.fr/hacks/chip8/C8TECH10.HTM
+#include <stdbool.h>
+#include <stdint.h>
+#include <stdio.h>
+#include <stdlib.h>
+
+typedef struct CHIP8 {
+  uint8_t *memory;
+  uint16_t pc;
+  uint16_t stack[16];
+  uint8_t sp;
+  uint8_t reg[16];
+  uint16_t I;
+  uint8_t delay_timer;
+  uint8_t sound_timer;
+} CHIP8;
+
+CHIP8 chip8_create() {
+  static const uint8_t fonts[] = {
+      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
+  };
+  CHIP8 c = {0};
+  c.memory = calloc(1, 4096);
+  for (size_t i = 0; i < 80; i++)
+    c.memory[i] = fonts[i];
+  c.pc = 0x200;
+  return c;
+}
+
+void chip8_disassemble(CHIP8 *c, size_t size) {
+  for (size_t i = 0; i < size; i++) {
+    uint8_t low = c->memory[c->pc++];
+    uint8_t high = c->memory[c->pc++];
+    uint16_t ins = (low << 8) | high;
+
+    uint16_t nnn = ins & 0x0FFF;
+    uint8_t n = ins & 0x000F;
+    uint8_t x = (ins >> 8) & 0x0F;
+    uint8_t y = (ins >> 4) & 0x0F;
+    uint8_t kk = ins & 0x00FF;
+
+    switch ((ins >> 12) & 0xF) {
+    case 0x0: {
+      switch (nnn) {
+      case 0x0E0:
+        puts("CLS");
+        break;
+      case 0x0EE:
+        puts("RET");
+        break;
+      default:
+        printf("SYS %hd\n", nnn);
+      }
+    } break;
+    case 0x1: {
+      printf("JP %hd\n", nnn);
+    } break;
+    case 0x2: {
+      printf("CALL %hd\n", nnn);
+    } break;
+    case 0x3: {
+      printf("SE V%x, %hhd\n", x, kk);
+    } break;
+    case 0x4: {
+      printf("SNE V%x, %hhd\n", x, kk);
+    } break;
+    case 0x5: {
+      printf("SE V%x, V%x\n", x, y);
+    } break;
+    case 0x6: {
+      printf("LD V%x, %hhd\n", x, kk);
+    } break;
+    case 0x7: {
+      printf("ADD V%x, %hhd\n", x, kk);
+    } break;
+    case 0x8: {
+      switch (n) {
+      case 0x0:
+        printf("LD V%x, V%x\n", x, y);
+        break;
+      case 0x1:
+        printf("OR V%x, V%x\n", x, y);
+        break;
+      case 0x2:
+        printf("AND V%x, V%x\n", x, y);
+        break;
+      case 0x3:
+        printf("XOR V%x, V%x\n", x, y);
+        break;
+      case 0x4:
+        printf("ADD V%x, V%x\n", x, y);
+        break;
+      case 0x5:
+        printf("SUB V%x, V%x\n", x, y);
+        break;
+      case 0x6:
+        printf("SHR V%x\n", x);
+        break;
+      case 0x7:
+        printf("SUBN V%x, V%x\n", x, y);
+        break;
+      case 0xE:
+        printf("SHL V%x\n", x);
+        break;
+      default:
+        fprintf(stderr, "unrecognized instruction\n");
+        exit(1);
+      }
+    } break;
+    case 0x9: {
+      printf("SNE V%x, V%x\n", x, y);
+    } break;
+    case 0xA: {
+      printf("LD I, %hd\n", nnn);
+    } break;
+    case 0xB: {
+      printf("JP V0, %hd\n", nnn);
+    } break;
+    case 0xC: {
+      printf("RND V%x, %hd\n", x, kk);
+    } break;
+    case 0xD: {
+      printf("DRW V%x, V%x, %hhd\n", x, y, n);
+    } break;
+    case 0xE: {
+      switch (kk) {
+      case 0x9E:
+        printf("SKP V%x\n", x);
+        break;
+      case 0xA1:
+        printf("SKNP V%x\n", x);
+        break;
+      default:
+        fprintf(stderr, "unrecognized instruction\n");
+        exit(1);
+      }
+    } break;
+    case 0xF: {
+      switch (kk) {
+      case 0x07:
+        printf("LD V%x, DT\n", x);
+        break;
+      case 0x0A:
+        printf("LD V%x, K\n", x);
+        break;
+      case 0x15:
+        printf("LD DT, V%x\n", x);
+        break;
+      case 0x18:
+        printf("LD ST, V%x\n", x);
+        break;
+      case 0x1E:
+        printf("ADD I, V%x\n", x);
+        break;
+      case 0x29:
+        printf("LD F, V%x\n", x);
+        break;
+      case 0x33:
+        printf("LD B, V%x\n", x);
+        break;
+      case 0x55:
+        printf("LD [I], V%x\n", x);
+        break;
+      case 0x65:
+        printf("LD V%x, [I]\n", x);
+        break;
+      default:
+        fprintf(stderr, "unrecognized instruction\n");
+        exit(1);
+      }
+    } break;
+    default:
+      fprintf(stderr, "unrecognized instruction\n");
+      exit(1);
+    }
+  }
+}
+
+int main(int argc, char *argv[]) {
+  CHIP8 c = chip8_create();
+
+  uint8_t buffer[100000];
+  FILE *f = fopen(argv[1], "rb");
+  size_t n = fread(buffer, 1, 100000, f);
+  fclose(f);
+
+  for (size_t i = 0; i < n; i++) {
+    c.memory[0x200 + i] = buffer[i];
+  }
+
+  chip8_disassemble(&c, n);
+}
\ No newline at end of file