Multiplayer SGB APIs/SGB detection

Core/gb.c

@@ -640,6 +640,8 @@ void GB_reset(GB_gameboy_t *gb)
     
     gb->accessed_oam_row = -1;
     
+    gb->sgb_player_count = 1;
+    
     /* Todo: Ugly, fixme, see comment in the timer state machine */
     gb->div_state = 3;
 

Core/gb.h

@@ -474,6 +474,8 @@ struct GB_gameboy_internal_s {
         bool sgb_ready_for_pulse;
         bool sgb_ready_for_write;
         bool sgb_disable_commands;
+        /* Multiplayer Input */
+        uint8_t sgb_player_count, sgb_current_player;
     );
 
     /* Unsaved data. This includes all pointers, as well as everything that shouldn't be on a save state */
@@ -500,7 +502,7 @@ struct GB_gameboy_internal_s {
         uint32_t background_palettes_rgb[0x20];
         uint32_t sprite_palettes_rgb[0x20];
         GB_color_correction_mode_t color_correction_mode;
-        bool keys[GB_KEY_MAX];
+        bool keys[4][GB_KEY_MAX];
                
         /* Timing */
         uint64_t last_sync;

Core/joypad.c

@@ -13,14 +13,19 @@ void GB_update_joyp(GB_gameboy_t *gb)
     gb->io_registers[GB_IO_JOYP] &= 0xF0;
     switch (key_selection) {
         case 3:
+            if (gb->sgb_player_count > 1) {
+                gb->io_registers[GB_IO_JOYP] |= 0xF - gb->sgb_current_player;
+            }
+            else {
                 /* Nothing is wired, all up */
                 gb->io_registers[GB_IO_JOYP] |= 0x0F;
+            }
             break;
 
         case 2:
             /* Direction keys */
             for (uint8_t i = 0; i < 4; i++) {
-                gb->io_registers[GB_IO_JOYP] |= (!gb->keys[i]) << i;
+                gb->io_registers[GB_IO_JOYP] |= (!gb->keys[gb->sgb_current_player][i]) << i;
             }
             /* Forbid pressing two opposing keys, this breaks a lot of games; even if it's somewhat possible. */
             if (!(gb->io_registers[GB_IO_JOYP] & 1)) {
@@ -34,13 +39,13 @@ void GB_update_joyp(GB_gameboy_t *gb)
         case 1:
             /* Other keys */
             for (uint8_t i = 0; i < 4; i++) {
-                gb->io_registers[GB_IO_JOYP] |= (!gb->keys[i + 4]) << i;
+                gb->io_registers[GB_IO_JOYP] |= (!gb->keys[gb->sgb_current_player][i + 4]) << i;
             }
             break;
 
         case 0:
             for (uint8_t i = 0; i < 4; i++) {
-                gb->io_registers[GB_IO_JOYP] |= (!(gb->keys[i] || gb->keys[i + 4])) << i;
+                gb->io_registers[GB_IO_JOYP] |= (!(gb->keys[gb->sgb_current_player][i] || gb->keys[gb->sgb_current_player][i + 4])) << i;
             }
             break;
 
@@ -60,5 +65,12 @@ void GB_update_joyp(GB_gameboy_t *gb)
 void GB_set_key_state(GB_gameboy_t *gb, GB_key_t index, bool pressed)
 {
     assert(index >= 0 && index < GB_KEY_MAX);
-    gb->keys[index] = pressed;
+    gb->keys[0][index] = pressed;
+}
+
+void GB_set_key_state_for_player(GB_gameboy_t *gb, GB_key_t index, unsigned player, bool pressed)
+{
+    assert(index >= 0 && index < GB_KEY_MAX);
+    assert(player < 4);
+    gb->keys[player][index] = pressed;
 }

Core/joypad.h

@@ -16,6 +16,7 @@ typedef enum {
 } GB_key_t;
 
 void GB_set_key_state(GB_gameboy_t *gb, GB_key_t index, bool pressed);
+void GB_set_key_state_for_player(GB_gameboy_t *gb, GB_key_t index, unsigned player, bool pressed);
 
 #ifdef GB_INTERNAL
 void GB_update_joyp(GB_gameboy_t *gb);

Core/memory.c

@@ -730,10 +730,10 @@ static void write_high_memory(GB_gameboy_t *gb, uint16_t addr, uint8_t value)
                 return;
 
             case GB_IO_JOYP:
+                GB_sgb_write(gb, value);
                 gb->io_registers[GB_IO_JOYP] &= 0x0F;
                 gb->io_registers[GB_IO_JOYP] |= value & 0xF0;
                 GB_update_joyp(gb);
-                GB_sgb_write(gb, value);
                 return;
 
             case GB_IO_BIOS:

Core/sgb.c

@@ -1,5 +1,9 @@
 #include "sgb.h"
 
+enum {
+    MLT_REQ = 0x11,
+};
+
 static void command_ready(GB_gameboy_t *gb)
 {
     /* SGB header commands are used to send the contents of the header to the SNES CPU.
@@ -31,12 +35,20 @@ static void command_ready(GB_gameboy_t *gb)
             gb->sgb_disable_commands = true;
         }
     }
+    
+    switch (gb->sgb_command[0] >> 3) {
+        case MLT_REQ:
+            gb->sgb_player_count = (uint8_t[]){1, 2, 1, 4}[gb->sgb_command[1] & 3];
+            gb->sgb_current_player = gb->sgb_player_count - 1;
+            break;
+    }
 }
 
 void GB_sgb_write(GB_gameboy_t *gb, uint8_t value)
 {
     if (!GB_is_sgb(gb)) return;
     if (gb->sgb_disable_commands) return;
+    
     switch ((value >> 4) & 3) {
         case 3:
             gb->sgb_ready_for_pulse = true;
@@ -73,6 +85,10 @@ void GB_sgb_write(GB_gameboy_t *gb, uint8_t value)
             gb->sgb_ready_for_write = true;
             gb->sgb_command_write_index = 0;
             memset(gb->sgb_command, 0, sizeof(gb->sgb_command));
+            if (gb->sgb_player_count > 1 && (value & 0x30) != (gb->io_registers[GB_IO_JOYP] & 0x30)) {
+                gb->sgb_current_player++;
+                gb->sgb_current_player &= gb->sgb_player_count - 1;
+            }
             break;
             
         default: