Fix crash of concurrent Win TTS synthesis

CHANGELOG.md

@@ -10,7 +10,10 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 - Added `ActivateGroup` API which allows to activate groups with late activation.
 - Added `DestroyGroup` API which removes the entire group from the game world.
 - `DestroyUnit` API
+
+### Fixed
 - Fixed `MarkAddEvent`, `MarkChangeEvent` and `MarkRemoveEvent` position
+- Fixed crash of concurrent Windows TTS synthesis ([#223](https://github.com/DCS-gRPC/rust-server/issues/223))
 
 ## [0.7.1] - 2023-01-08
 

Cargo.toml

@@ -21,7 +21,7 @@ log = "0.4"
 serde = { version = "1.0", features = ["derive"] }
 serde_json = "1.0"
 thiserror = "1.0"
-tokio = { version = "1.24", features = ["rt-multi-thread", "io-util", "net", "sync", "time"] }
+tokio = { version = "1.24", features = ["rt-multi-thread", "io-util", "net", "sync", "time", "parking_lot"] }
 tokio-stream = { version = "0.1", features = ["sync"] }
 tonic = "0.8"
 

tts/src/win.rs

@@ -1,5 +1,6 @@
 use std::borrow::Cow;
 
+use tokio::sync::Mutex;
 use windows::core::HSTRING;
 use windows::Media::SpeechSynthesis::SpeechSynthesizer;
 use windows::Storage::Streams::DataReader;
@@ -9,10 +10,15 @@ pub struct WinConfig {
     pub voice: Option<String>,
 }
 
+static MUTEX: Mutex<()> = Mutex::const_new(());
+
 pub async fn synthesize(text: &str, config: &WinConfig) -> Result<Vec<Vec<u8>>, WinError> {
     // Note, there does not seem to be a way to explicitly set 16000kHz, 16 audio bits per
     // sample and mono channel.
 
+    // Prevent concurrent Windows TTS synthesis, as this might cause a crash.
+    let lock = MUTEX.lock().await;
+
     let mut voice_info = None;
     if let Some(voice) = &config.voice {
         let all_voices = SpeechSynthesizer::AllVoices()?;
@@ -91,6 +97,8 @@ pub async fn synthesize(text: &str, config: &WinConfig) -> Result<Vec<Vec<u8>>,
     let mut wav = vec![0u8; size as usize];
     rd.ReadBytes(wav.as_mut_slice())?;
 
+    drop(lock);
+
     Ok(crate::wav_to_opus(wav.into()).await?)
 }