1 // Copyright 2022, The Android Open Source Project 2 // 3 // Licensed under the Apache License, Version 2.0 (the "License"); 4 // you may not use this file except in compliance with the License. 5 // You may obtain a copy of the License at 6 // 7 // http://www.apache.org/licenses/LICENSE-2.0 8 // 9 // Unless required by applicable law or agreed to in writing, software 10 // distributed under the License is distributed on an "AS IS" BASIS, 11 // WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 12 // See the License for the specific language governing permissions and 13 // limitations under the License. 14 15 //! Takes a JavaVM to a static reference. 16 //! 17 //! JavaVM is shared as multiple JavaVM within a single process is not allowed 18 //! per [JNI spec](https://docs.oracle.com/javase/8/docs/technotes/guides/jni/spec/invocation.html) 19 //! The unique JavaVM need to be shared over (potentially) different threads. 20 21 use std::sync::{Arc, Once}; 22 23 use jni::JavaVM; 24 use uwb_core::error::Result; 25 26 static mut JVM: Option<Arc<JavaVM>> = None; 27 static INIT: Once = Once::new(); 28 /// Sets the unique JavaVM that can be then accessed using [`get_static_ref`]. 29 /// 30 /// The function shall only be called once. set_once(jvm: JavaVM) -> Result<()>31pub(crate) fn set_once(jvm: JavaVM) -> Result<()> { 32 // Safety: follows [this pattern](https://doc.rust-lang.org/std/sync/struct.Once.html). 33 // Modification to static mut is nested inside call_once. 34 unsafe { 35 INIT.call_once(|| { 36 JVM = Some(Arc::new(jvm)); 37 }); 38 } 39 Ok(()) 40 } 41 /// Gets a `'static` reference to the unique JavaVM. Returns `None` if [`set_once`] was never called. get_static_ref() -> Option<&'static Arc<JavaVM>>42pub(crate) fn get_static_ref() -> Option<&'static Arc<JavaVM>> { 43 // Safety: follows [this pattern](https://doc.rust-lang.org/std/sync/struct.Once.html). 44 // Modification to static mut is nested inside call_once. 45 unsafe { JVM.as_ref() } 46 } 47