Expose src_addr and des_addr in espnow recv cb

Currently the espnow bindings for `register_recv_cb` only give a handle
on the src_addr from the sending peer. This makes it impossible to
determine if the frame was sent on the BROADCAST address.

This change updates the first argument to the receive cb to accept a new
ReceiveInfo struct containing `src_addr` and `des_addr`. The terminology
was taken directly from the esp-idf docs.

src/espnow.rs

@@ -20,8 +20,14 @@ type Singleton<T> = Mutex<Option<Box<T>>>;
 
 pub const BROADCAST: [u8; 6] = [0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF];
 
+#[derive(Debug)]
+pub struct ReceiveInfo<'a> {
+    pub src_addr: &'a [u8; 6],
+    pub des_addr: &'a [u8; 6],
+}
+
 #[allow(clippy::type_complexity)]
-static RECV_CALLBACK: Singleton<dyn FnMut(&[u8], &[u8]) + Send + 'static> = Mutex::new(None);
+static RECV_CALLBACK: Singleton<dyn FnMut(&ReceiveInfo, &[u8]) + Send + 'static> = Mutex::new(None);
 #[allow(clippy::type_complexity)]
 static SEND_CALLBACK: Singleton<dyn FnMut(&[u8], SendStatus) + Send + 'static> = Mutex::new(None);
 
@@ -168,12 +174,12 @@ impl<'a> EspNow<'a> {
 
     pub fn register_recv_cb<F>(&self, callback: F) -> Result<(), EspError>
     where
-        F: FnMut(&[u8], &[u8]) + Send + 'a,
+        F: FnMut(&ReceiveInfo, &[u8]) + Send + 'a,
     {
         #[allow(clippy::type_complexity)]
-        let callback: Box<dyn FnMut(&[u8], &[u8]) + Send + 'a> = Box::new(callback);
+        let callback: Box<dyn FnMut(&ReceiveInfo, &[u8]) + Send + 'a> = Box::new(callback);
         #[allow(clippy::type_complexity)]
-        let callback: Box<dyn FnMut(&[u8], &[u8]) + Send + 'static> =
+        let callback: Box<dyn FnMut(&ReceiveInfo, &[u8]) + Send + 'static> =
             unsafe { core::mem::transmute(callback) };
 
         *RECV_CALLBACK.lock() = Some(Box::new(callback));
@@ -229,12 +235,20 @@ impl<'a> EspNow<'a> {
         data_len: core::ffi::c_int,
     ) {
         #[cfg(not(any(esp_idf_version_major = "4")))]
-        let mac_addr = unsafe { *esp_now_info }.src_addr.cast_const();
-        let c_mac = unsafe { core::slice::from_raw_parts(mac_addr, 6usize) };
+        let src_addr = unsafe { *esp_now_info }.src_addr.cast_const();
+        let des_addr = unsafe { *esp_now_info }.des_addr.cast_const();
+        let c_src_addr = unsafe { &*(src_addr as *const [u8; 6]) };
+        let c_des_addr = unsafe { &*(des_addr as *const [u8; 6]) };
         let c_data = unsafe { core::slice::from_raw_parts(data, data_len as usize) };
 
         if let Some(ref mut callback) = *RECV_CALLBACK.lock() {
-            callback(c_mac, c_data)
+            callback(
+                &ReceiveInfo {
+                    src_addr: c_src_addr,
+                    des_addr: c_des_addr,
+                },
+                c_data,
+            )
         } else {
             panic!("EspNow callback not available");
         }