Actually implement multiplayer

src/emulator.rs

@@ -114,6 +114,8 @@ impl Emulator {
             return Ok(());
         };
         self.load_rom(SimId::Player2, bytes)?;
+        let (first, second) = self.sims.split_at_mut(1);
+        first[0].link(&mut second[0]);
         Ok(())
     }
 

src/emulator/shrooms_vb_core.rs

@@ -62,6 +62,8 @@ extern "C" {
     fn vb_emulate_ex(sims: *mut *mut VB, count: c_uint, cycles: *mut u32) -> c_int;
     #[link_name = "vbGetCartROM"]
     fn vb_get_cart_rom(sim: *mut VB, size: *mut u32) -> *mut c_void;
+    #[link_name = "vbGetPeer"]
+    fn vb_get_peer(sim: *mut VB) -> *mut VB;
     #[link_name = "vbGetPixels"]
     fn vb_get_pixels(
         sim: *mut VB,
@@ -93,6 +95,8 @@ extern "C" {
     fn vb_set_keys(sim: *mut VB, keys: u16) -> u16;
     #[link_name = "vbSetOption"]
     fn vb_set_option(sim: *mut VB, key: VBOption, value: c_int);
+    #[link_name = "vbSetPeer"]
+    fn vb_set_peer(sim: *mut VB, peer: *mut VB);
     #[link_name = "vbSetSamples"]
     fn vb_set_samples(
         sim: *mut VB,
@@ -194,6 +198,10 @@ impl Sim {
         Some(vec)
     }
 
+    pub fn link(&mut self, peer: &mut Sim) {
+        unsafe { vb_set_peer(self.sim, peer.sim) };
+    }
+
     pub fn emulate_many(sims: &mut [Sim]) {
         let mut cycles = 20_000_000;
         let count = sims.len() as c_uint;
@@ -269,6 +277,12 @@ impl Drop for Sim {
         // SAFETY: we made this pointer ourselves, we can for sure free it
         unsafe { drop(Box::from_raw(ptr)) };
 
+        // If we're linked to another sim, unlink them from ourselves.
+        let peer = unsafe { vb_get_peer(self.sim) };
+        if !peer.is_null() {
+            unsafe { vb_set_peer(peer, ptr::null_mut()) };
+        }
+
         let len = unsafe { vb_size_of() }.div_ceil(4);
         // SAFETY: the sim's memory originally came from a Vec<u64>
         let bytes: Vec<u64> = unsafe { Vec::from_raw_parts(self.sim.cast(), len, len) };