Fix: corebluetooth write without response

Cargo.toml

@@ -59,6 +59,7 @@ objc2-foundation = { version = "0.2.2", default-features = false, features = [
     "NSString",
     "NSUUID",
     "NSValue",
+    "NSProcessInfo",
 ] }
 objc2-core-bluetooth = { version = "0.2.2", default-features = false, features = [
     "std",

src/corebluetooth/internal.rs

@@ -31,13 +31,14 @@ use objc2_core_bluetooth::{
     CBCharacteristicProperties, CBCharacteristicWriteType, CBDescriptor, CBManager,
     CBManagerAuthorization, CBManagerState, CBPeripheral, CBPeripheralState, CBService, CBUUID,
 };
-use objc2_foundation::{NSArray, NSData, NSMutableDictionary, NSNumber};
+use objc2_foundation::{NSArray, NSData, NSMutableDictionary, NSNumber, NSProcessInfo};
 use std::{
     collections::{BTreeSet, HashMap, VecDeque},
     ffi::CString,
     fmt::{self, Debug, Formatter},
     ops::Deref,
     thread,
+    time::Duration,
 };
 use tokio::runtime;
 use uuid::Uuid;
@@ -361,6 +362,12 @@ impl PeripheralInternal {
     }
 }
 
+/// Optional CoreBluetooth API capabilities that are available depending on the macOS version.
+struct CoreBluetoothFeatures {
+    /// `peripheral.canSendWriteWithoutResponse` property is available (since macOS 11.2.0)
+    can_send_write_without_response: bool,
+}
+
 // All of CoreBluetooth is basically async. It's all just waiting on delegate
 // events/callbacks. Therefore, we should be able to round up all of our wacky
 // ass mut *Object values, keep them in a single struct, in a single thread, and
@@ -375,6 +382,7 @@ struct CoreBluetoothInternal {
     // task::block this when sending even though it'll never actually block.
     event_sender: Sender<CoreBluetoothEvent>,
     message_receiver: Fuse<Receiver<CoreBluetoothMessage>>,
+    features: CoreBluetoothFeatures,
 }
 
 impl Debug for CoreBluetoothInternal {
@@ -473,6 +481,16 @@ pub enum CoreBluetoothEvent {
     },
 }
 
+fn get_features() -> CoreBluetoothFeatures {
+    let process_info = NSProcessInfo::processInfo();
+    let version = process_info.operatingSystemVersion();
+    let current = (version.majorVersion, version.minorVersion);
+
+    CoreBluetoothFeatures {
+        can_send_write_without_response: current >= (11, 2),
+    }
+}
+
 impl CoreBluetoothInternal {
     pub fn new(
         message_receiver: Receiver<CoreBluetoothMessage>,
@@ -498,6 +516,7 @@ impl CoreBluetoothInternal {
             event_sender,
             message_receiver: message_receiver.fuse(),
             delegate,
+            features: get_features(),
         }
     }
 
@@ -887,6 +906,21 @@ impl CoreBluetoothInternal {
                 {
                     trace!("Writing value! With kind {:?}", kind);
                     unsafe {
+                        if kind == WriteType::WithoutResponse
+                            && self.features.can_send_write_without_response
+                        {
+                            // probably better idea would be to wait for the result of peripheral.peripheralIsReadyToSendWriteWithoutResponse
+                            let mut attempts = 0;
+                            while !peripheral.peripheral.canSendWriteWithoutResponse()
+                                && attempts < 100
+                            {
+                                attempts += 1;
+                                // min. connection interval time is 15ms. see the document:
+                                // https://developer.apple.com/library/archive/qa/qa1931/_index.html
+                                thread::sleep(Duration::from_millis(15));
+                            }
+                        }
+
                         peripheral.peripheral.writeValue_forCharacteristic_type(
                             &NSData::from_vec(data),
                             &characteristic.characteristic,