107 lines
4.0 KiB
C
107 lines
4.0 KiB
C
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/*
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* Copyright (C) 2023 The Android Open Source Project
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*
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* Licensed under the Apache License, Version 2.0 (the "License");
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* you may not use this file except in compliance with the License.
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* You may obtain a copy of the License at
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS,
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* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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* See the License for the specific language governing permissions and
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* limitations under the License.
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*/
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#pragma once
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#include <jni.h>
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#include <thread>
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namespace android {
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namespace webcam {
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typedef struct {
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jmethodID setStreamConfig;
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jmethodID startStreaming;
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jmethodID stopStreaming;
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jmethodID returnImage;
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jmethodID stopService;
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} JavaMethods;
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/**
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* Container class for java interactions. All interaction to/from java must happen from this class.
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*/
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class DeviceAsWebcamNative {
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public:
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static const JNINativeMethod sMethods[];
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static int registerJNIMethods(JNIEnv* e, JavaVM* jvm);
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static JavaVM* kJVM;
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// Native implementations of Java Methods.
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static jint com_android_DeviceAsWebcam_encodeImage(JNIEnv* env, jobject thiz,
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jobject hardwareBuffer, jlong timestamp);
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static jint com_android_DeviceAsWebcam_setupServicesAndStartListening(JNIEnv* env,
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jobject thiz);
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static jboolean com_android_DeviceAsWebcam_shouldStartService(JNIEnv*, jclass);
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static void com_android_DeviceAsWebcam_onDestroy(JNIEnv*, jobject);
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// Methods that call back into java code. The method signatures match their java counterparts
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// All threads calling these functions must be bound to kJVM and pass their JNIEnv to
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// these functions
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static void setStreamConfig(jobject thiz, bool mjpeg, uint32_t width, uint32_t height,
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uint32_t fps);
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static void startStreaming(jobject thiz);
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static void stopStreaming(jobject thiz);
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static void returnImage(jobject thiz, long timestamp);
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static void stopService(jobject thiz);
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// Utility method to get JNIEnv associated with the current thread or abort the program. Care
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// must be taken to only call this from a thread that is attached to kJVM as it will
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// terminate the program otherwise.
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static JNIEnv* getJNIEnvOrAbort();
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/**
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* Returns a std::thread can call Java methods in the current JVM.
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* There is a non-trivial cost to attaching and detaching threads to the JVM, these
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* threads must not be spammed. Better to have a long running thread that is attached instead.
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*
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* Usage:
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* std::thread myThread = createJniAttachedThread([] () -> {
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* // Thread logic that might call into java
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* ...
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* });
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*/
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template <class F, typename... Args>
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static std::thread createJniAttachedThread(F f, Args&&... args) {
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return std::thread([f, args...]() mutable {
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// Attach Thread to JVM for java calls
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JNIEnv* env;
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ScopedAttach _jniScope(&env);
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// Call the passed function
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std::invoke(f, std::forward<Args...>(args...));
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// Thread detaches from the JVM automatically when _jniScope goes out of scope
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});
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}
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// Methods that call back into java code
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// must only be called via their corresponding public methods.
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static JavaMethods kJavaMethods;
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/**
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* Class to Provide a RAII style means for attaching the current thread to the JVM. The thread
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* is attached to the JVM when this object is created, and detached when the object goes out of
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* scope.
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*/
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class ScopedAttach {
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public:
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explicit ScopedAttach(JNIEnv** env) { kJVM->AttachCurrentThread(env, nullptr); }
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~ScopedAttach() { kJVM->DetachCurrentThread(); }
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};
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};
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} // namespace webcam
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} // namespace android
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