add gb.h

1 files changed, 123 insertions, 0 deletions

diff --git a/gb.h b/gb.h
new file mode 100644
index 0000000..6be3a94
--- /dev/null
+++ b/gb.h
@@ -0,0 +1,123 @@
+#ifndef GB_H
+#define GB_H
+
+#ifdef __cplusplus
+extern "C" {
+#endif /* __cplusplus */
+
+#include <stdint.h>
+
+typedef enum {
+  STATE_RUN,
+  STATE_STOP,
+  STATE_HALT,
+  STATE_INVALID,
+  STATE_NOT_IMPLEMENTED,
+  STATE_LAST,
+} gb_cpu_state_t;
+
+#define GB_BTN_UP     1
+#define GB_BTN_DOWN   (1 << 1)
+#define GB_BTN_LEFT   (1 << 2)
+#define GB_BTN_RIGHT  (1 << 3)
+#define GB_BTN_A      (1 << 4)
+#define GB_BTN_B      (1 << 5)
+#define GB_BTN_SELECT (1 << 6)
+#define GB_BTN_START  (1 << 7)
+
+typedef struct {
+  struct {
+    _Bool in_bios;
+
+    // FIXME: combine these?
+    uint8_t bios[0x100]; // bios (256 bytes)
+    uint8_t ram[0x2000]; // working ram (8k)
+    uint8_t eram[65536]; // external ram (banked, up to 64k)
+    uint8_t vram[0x2000]; // vram (8k)
+    uint8_t oam[0xA0]; // oam (160 bytes)
+    uint8_t zram[0x7F]; // zram (128 bytes)
+
+    // rom (at least 32k)
+    const uint8_t *rom;
+    uint32_t rom_size;
+
+    union {
+      struct {
+        // current rom bank (5 bits); see note about
+        // rom_ram_mode below
+        uint8_t rom_bank;
+
+        // is external ram enabled?
+        _Bool ram_enable;
+
+        // ram bank
+        // rom_ram_mode == 0: high two bits of rom bank
+        // rom_ram_mode == 1: ram bank
+        uint8_t ram_bank;
+
+        // set interpretation of ram_bank
+        _Bool rom_ram_mode;
+      } mbc1;
+
+      struct {
+        // current rom bank (4 bits)
+        uint8_t rom_bank;
+
+        // is eram enabled?
+        _Bool ram_enable;
+      } mbc2;
+    };
+
+    // interrupts
+    // ie: interrupt enable (addr: 0xFFFF)
+    // iv: interrupt vector (addr: 0xFF0F)
+    // (gb-manual, p26)
+    uint8_t ie;
+    uint8_t iv;
+
+    // buttons (addr: 0xFF00)
+    // gb-manual, p23
+    uint8_t p1_mode;
+    uint8_t btns;
+  } mmu;
+
+  struct {
+    uint16_t clock;
+    uint8_t mode,
+            lcdc,
+            stat,
+            scy,
+            scx,
+            wy,
+            wx,
+            bgp,
+            obp0,
+            obp1,
+            line,
+            lyc;
+    uint8_t rgb[3 * 160 * 144];
+    uint32_t frame;
+  } gpu;
+
+  struct {
+    uint16_t div;
+    uint32_t tima; // NOTE: cannot be uint16_t because of 10-bit shift
+    uint8_t tma,
+            tac;
+  } timer;
+
+  struct {
+    uint16_t rs[6 /* RW_LAST */];
+    uint32_t clock; /* FIXME: uint16_t? */
+    gb_cpu_state_t state;
+
+    // interrupt master enable
+    _Bool ime;
+  } cpu;
+} gb_t;
+
+#ifdef __cplusplus
+};
+#endif /* __cplusplus */
+
+#endif /* GB_H */