From a7aabca6180b7d60bf49023dfb88526951bc2b39 Mon Sep 17 00:00:00 2001
From: Lior Halphon <LIJI32@gmail.com>
Date: Tue, 3 Jul 2018 21:43:46 +0300
Subject: [PATCH] Starting to add CGB-C support

---
 Core/gb.c     | 15 +++++++++++++++
 Core/gb.h     |  3 ++-
 Core/memory.c | 27 +++++++++++++++++++++------
 3 files changed, 38 insertions(+), 7 deletions(-)

diff --git a/Core/gb.c b/Core/gb.c
index 2c3dfbb7..c3fa4cc8 100644
--- a/Core/gb.c
+++ b/Core/gb.c
@@ -473,6 +473,21 @@ static void reset_ram(GB_gameboy_t *gb)
             }
             break;
 #endif
+        
+        case GB_MODEL_CGB_C:
+            for (unsigned i = 0; i < gb->ram_size; i++) {
+                if ((i & 0x808) == 0x800 || (i & 0x808) == 0x008) {
+                    gb->ram[i] = 0;
+                }
+                else {
+                    gb->ram[i] = (random() | random() | random() | random())  & 0xFF;
+                }
+            }
+            break;
+    }
+    
+    for (unsigned i = 0; i < sizeof(gb->extra_oam); i++) {
+        gb->extra_oam[i] = (random() & 0xFF);
     }
 }
 
diff --git a/Core/gb.h b/Core/gb.h
index 31840d94..32546247 100644
--- a/Core/gb.h
+++ b/Core/gb.h
@@ -43,7 +43,7 @@ typedef enum {
     // GB_MODEL_CGB_0 = 0x200,
     // GB_MODEL_CGB_A = 0x201,
     // GB_MODEL_CGB_B = 0x202,
-    // GB_MODEL_CGB_C = 0x203,
+    GB_MODEL_CGB_C = 0x203,
     // GB_MODEL_CGB_D = 0x204,
     GB_MODEL_CGB_E = 0x205,
     GB_MODEL_AGB = 0x206,
@@ -301,6 +301,7 @@ struct GB_gameboy_internal_s {
         /* Misc state */
         bool infrared_input;
         GB_printer_t printer;
+        uint8_t extra_oam[0xff00 - 0xfea0];
     );
 
     /* DMA and HDMA */
diff --git a/Core/memory.c b/Core/memory.c
index ee9ad188..5f6a89af 100644
--- a/Core/memory.c
+++ b/Core/memory.c
@@ -244,13 +244,21 @@ static uint8_t read_high_memory(GB_gameboy_t *gb, uint16_t addr)
             return gb->oam[addr & 0xFF];
         }
         
-        /* Unusable. CGB results are verified, but DMG results were tested on a SGB2 */
-        /* Also, writes to this area are not emulated */
-        if ((gb->io_registers[GB_IO_STAT] & 0x3) >= 2) { /* Seems to be disabled in Modes 2 and 3 */
+        if (gb->oam_read_blocked) {
             return 0xFF;
         }
-        if (GB_is_cgb(gb)) {
-            return (addr & 0xF0) | ((addr >> 4) & 0xF);
+        
+        switch (gb->model) {
+            case GB_MODEL_CGB_E:
+            case GB_MODEL_AGB:
+                return (addr & 0xF0) | ((addr >> 4) & 0xF);
+            
+            case GB_MODEL_CGB_C:
+                addr &= ~0x18;
+                return gb->extra_oam[addr - 0xfea0];
+                
+            default:
+                ;
         }
     }
 
@@ -535,10 +543,17 @@ static void write_high_memory(GB_gameboy_t *gb, uint16_t addr, uint8_t value)
             if (addr < 0xFEA0) {
                 gb->oam[addr & 0xFF] = value;
             }
+            switch (gb->model) {
+                case GB_MODEL_CGB_C:
+                    addr &= ~0x18;
+                    gb->extra_oam[addr - 0xfea0] = value;
+                    break;
+                default:
+                    break;
+            }
             return;
         }
         
-        /* Todo: This is writable, but glitchy, on CGB-B and CGB-D. */
         if (addr < 0xFEA0) {
             if (gb->accessed_oam_row == 0xa0) {
                 for (unsigned i = 0; i < 8; i++) {