feat: communication api (#21)

This PR adds the communication API added with SU13.

---------

Co-authored-by: Saschl <[email protected]>

msfs/src/bindgen_support/wrapper.h

@@ -4,5 +4,6 @@
 #include <MSFS/MSFS.h>
 #include <MSFS/MSFS_Render.h>
 #include <MSFS/MSFS_Network.h>
+#include <MSFS/MSFS_CommBus.h>
 #include <MSFS/Render/nanovg.h>
 #include <SimConnect.h>

msfs/src/commbus.rs

@@ -0,0 +1,141 @@
+//! Bindings for the commbus API available in the MSFS SDK.
+use crate::sys;
+use std::{
+    cell::RefCell,
+    ffi::{self, CString},
+    rc::Rc,
+    slice,
+};
+
+// SAFETY: It should be safe to use `FnMut` as callback
+// as the execution is not happen in parallel (hopefully).
+type CommBusCallback<'a> = Box<dyn FnMut(&str) + 'a>;
+
+/// Used to specify the type of module/gauge to broadcast an event to.
+#[derive(Default)]
+pub enum CommBusBroadcastFlags {
+    JS,
+    WASM,
+    WASMSelfCall,
+    #[default]
+    Default,
+    AllWASM,
+    All,
+}
+
+impl From<CommBusBroadcastFlags> for sys::FsCommBusBroadcastFlags {
+    fn from(value: CommBusBroadcastFlags) -> Self {
+        match value {
+            CommBusBroadcastFlags::JS => sys::FsCommBusBroadcastFlags_FsCommBusBroadcast_JS,
+            CommBusBroadcastFlags::WASM => sys::FsCommBusBroadcastFlags_FsCommBusBroadcast_Wasm,
+            CommBusBroadcastFlags::WASMSelfCall => {
+                sys::FsCommBusBroadcastFlags_FsCommBusBroadcast_WasmSelfCall
+            }
+            CommBusBroadcastFlags::Default => {
+                sys::FsCommBusBroadcastFlags_FsCommBusBroadcast_Default
+            }
+            CommBusBroadcastFlags::AllWASM => {
+                sys::FsCommBusBroadcastFlags_FsCommBusBroadcast_AllWasm
+            }
+            CommBusBroadcastFlags::All => sys::FsCommBusBroadcastFlags_FsCommBusBroadcast_All,
+        }
+    }
+}
+
+#[derive(Default)]
+pub struct CommBus<'a> {
+    events: Vec<Rc<RefCell<Option<CommBusEvent<'a>>>>>,
+}
+impl<'a> CommBus<'a> {
+    /// Registers to a communication event.
+    /// Returns the event if the registration was successful.
+    /// By calling `take` on the returned value the event gets unregistered.
+    pub fn register(
+        &mut self,
+        event_name: &str,
+        callback: impl FnMut(&str) + 'a,
+    ) -> Option<Rc<RefCell<Option<CommBusEvent<'a>>>>> {
+        if let Some(event) = CommBusEvent::register(event_name, callback) {
+            let event = Rc::new(RefCell::new(Some(event)));
+            self.events.push(event.clone());
+            Some(event)
+        } else {
+            None
+        }
+    }
+
+    /// Calls a communication event.
+    /// Returns `true` if the call was successful.
+    pub fn call(event_name: &str, args: &str, called: CommBusBroadcastFlags) -> bool {
+        if let (Ok(event_name), Ok(args_cstr)) = (CString::new(event_name), CString::new(args)) {
+            unsafe {
+                sys::fsCommBusCall(
+                    event_name.as_ptr(),
+                    args_cstr.as_ptr(),
+                    (args.len() + 1) as ffi::c_uint,
+                    called.into(),
+                )
+            }
+        } else {
+            false
+        }
+    }
+
+    /// Deregisters all communication events registered with this `CommBus` instance.
+    /// The same functionality can be achieved by dropping the `CommBus` instance and creating a new instance.
+    pub fn unregister_all(&mut self) {
+        for event in &self.events {
+            event.take();
+        }
+        self.events.clear();
+    }
+}
+
+/// CommBus handle. When this handle goes out of scope the callback will be unregistered.
+pub struct CommBusEvent<'a> {
+    event_name: CString,
+    callback: Box<CommBusCallback<'a>>,
+}
+impl<'a> CommBusEvent<'a> {
+    /// Registers to a communication event.
+    pub fn register(event_name: &str, callback: impl FnMut(&str) + 'a) -> Option<Self> {
+        let this = Self {
+            event_name: CString::new(event_name).ok()?,
+            callback: Box::new(Box::new(callback)),
+        };
+        let res = unsafe {
+            sys::fsCommBusRegister(
+                this.event_name.as_ptr(),
+                Some(Self::c_callback),
+                this.callback.as_ref() as *const _ as *mut _,
+            )
+        };
+        if res {
+            Some(this)
+        } else {
+            None
+        }
+    }
+
+    extern "C" fn c_callback(args: *const ffi::c_char, size: ffi::c_uint, ctx: *mut ffi::c_void) {
+        if !ctx.is_null() {
+            let (mut callback, args) = unsafe {
+                (
+                    Box::from_raw(ctx as *mut CommBusCallback<'a>),
+                    // SAFETY: because i8/u8 is 1 byte we can use size directly as length of the slice
+                    slice::from_raw_parts(args as *const u8, size as usize),
+                )
+            };
+            callback(&String::from_utf8_lossy(args));
+            // Don't free callback as it's still registered
+            Box::leak(callback);
+        }
+    }
+}
+impl Drop for CommBusEvent<'_> {
+    fn drop(&mut self) {
+        unsafe {
+            sys::fsCommBusUnregister(self.event_name.as_ptr(), Some(Self::c_callback));
+        }
+    }
+}

msfs/src/lib.rs

@@ -6,6 +6,7 @@
 //! - SimConnect API
 //! - NanoVG API
 //! - Networking API
+//! - Communication Bus API
 //!
 //! ## Building
 //!
@@ -43,5 +44,8 @@ pub mod nvg;
 #[cfg(any(target_arch = "wasm32", doc))]
 pub mod network;
 
+#[cfg(any(target_arch = "wasm32", doc))]
+pub mod commbus;
+
 #[doc(hidden)]
 pub mod executor;