зеркало из https://github.com/mozilla/gecko-dev.git
Bug 1187552 - Support direct ownership of C++ objects by Java objects; r=snorp
Add a direct ownership model where the Java object owns the corresponding C++ object directly, in addition to the WeakPtr model where the Java object owns a WeakPtr to the C++ object. The WeakPtr model is chosen when the implementing C++ class inherits from SupportsWeakPtr. Otherwise, the direct ownership model is chosen. Under the direct ownership model, a UniquePtr object must be used to attach the containing C++ object to a Java object, to ensure ownership is passed on to the Java object.
This commit is contained in:
Jim Chen
Родитель
d900eeb8ba
Коммит
81d1a5cdea
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@ -3,6 +3,9 @@
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#include <jni.h>
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#include "mozilla/Move.h"
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#include "mozilla/TypeTraits.h"
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#include "mozilla/UniquePtr.h"
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#include "mozilla/WeakPtr.h"
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#include "mozilla/jni/Accessors.h"
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#include "mozilla/jni/Refs.h"
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@ -12,53 +15,162 @@
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namespace mozilla {
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namespace jni {
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// Get the native pointer stored in a Java instance.
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/**
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* C++ classes implementing instance (non-static) native methods can choose
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* from one of two ownership models, when associating a C++ object with a Java
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* instance.
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*
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* * If the C++ class inherits from mozilla::SupportsWeakPtr, weak pointers
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* will be used. The Java instance will store and own the pointer to a
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* WeakPtr object. The C++ class itself is otherwise not owned or directly
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* referenced. To attach a Java instance to a C++ instance, pass in a pointer
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* to the C++ class (i.e. MyClass*).
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*
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* class MyClass : public SupportsWeakPtr<MyClass>
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* , public MyJavaClass::Natives<MyClass>
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* {
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* // ...
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*
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* public:
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* MOZ_DECLARE_WEAKREFERENCE_TYPENAME(MyClass)
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* using MyJavaClass::Natives<MyClass>::Dispose;
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*
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* void AttachTo(const MyJavaClass::LocalRef& instance)
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* {
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* MyJavaClass::Natives<MyClass>::AttachInstance(instance, this);
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*
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* // "instance" does NOT own "this", so the C++ object
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* // lifetime is separate from the Java object lifetime.
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* }
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* };
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*
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* * If the C++ class doesn't inherit from mozilla::SupportsWeakPtr, the Java
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* instance will store and own a pointer to the C++ object itself. This
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* pointer must not be stored or deleted elsewhere. To attach a Java instance
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* to a C++ instance, pass in a reference to a UniquePtr of the C++ class
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* (i.e. UniquePtr<MyClass>).
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*
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* class MyClass : public MyJavaClass::Natives<MyClass>
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* {
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* // ...
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*
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* public:
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* using MyJavaClass::Natives<MyClass>::Dispose;
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*
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* static void AttachTo(const MyJavaClass::LocalRef& instance)
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* {
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* MyJavaClass::Natives<MyClass>::AttachInstance(
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* instance, mozilla::MakeUnique<MyClass>());
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*
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* // "instance" owns the newly created C++ object, so the C++
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* // object is destroyed as soon as instance.dispose() is called.
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* }
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* };
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*/
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namespace {
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uintptr_t CheckNativeHandle(JNIEnv* env, uintptr_t handle)
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{
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if (!handle) {
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if (!env->ExceptionCheck()) {
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ThrowException(env, "java/lang/NullPointerException",
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"Null native pointer");
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}
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return 0;
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}
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return handle;
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}
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template<class Impl, bool UseWeakPtr = mozilla::IsBaseOf<
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SupportsWeakPtr<Impl>, Impl>::value /* = false */>
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struct NativePtr
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{
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static Impl* Get(JNIEnv* env, jobject instance)
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{
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return reinterpret_cast<Impl*>(CheckNativeHandle(
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env, GetNativeHandle(env, instance)));
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}
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template<class LocalRef>
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static Impl* Get(const LocalRef& instance)
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{
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return Get(instance.Env(), instance.Get());
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}
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template<class LocalRef>
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static void Set(const LocalRef& instance, UniquePtr<Impl>&& ptr)
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{
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Clear(instance);
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SetNativeHandle(instance.Env(), instance.Get(),
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reinterpret_cast<uintptr_t>(ptr.release()));
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HandleUncaughtException(instance.Env());
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}
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template<class LocalRef>
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static void Clear(const LocalRef& instance)
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{
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UniquePtr<Impl> ptr(reinterpret_cast<Impl*>(
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GetNativeHandle(instance.Env(), instance.Get())));
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HandleUncaughtException(instance.Env());
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if (ptr) {
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SetNativeHandle(instance.Env(), instance.Get(), 0);
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HandleUncaughtException(instance.Env());
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}
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}
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};
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template<class Impl>
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Impl* GetNativePtr(JNIEnv* env, jobject instance)
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struct NativePtr<Impl, /* UseWeakPtr = */ true>
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{
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const auto ptr = reinterpret_cast<const WeakPtr<Impl>*>(
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GetNativeHandle(env, instance));
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if (!ptr) {
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return nullptr;
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static Impl* Get(JNIEnv* env, jobject instance)
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{
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const auto ptr = reinterpret_cast<WeakPtr<Impl>*>(
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CheckNativeHandle(env, GetNativeHandle(env, instance)));
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if (!ptr) {
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return nullptr;
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}
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Impl* const impl = *ptr;
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if (!impl) {
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ThrowException(env, "java/lang/NullPointerException",
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"Native object already released");
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}
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return impl;
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}
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Impl* const impl = *ptr;
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if (!impl) {
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ThrowException(env, "java/lang/NullPointerException",
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"Native object already released");
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template<class LocalRef>
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static Impl* Get(const LocalRef& instance)
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{
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return Get(instance.Env(), instance.Get());
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}
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return impl;
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}
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template<class Impl, class LocalRef>
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Impl* GetNativePtr(const LocalRef& instance)
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{
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return GetNativePtr<Impl>(instance.Env(), instance.Get());
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}
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template<class Impl, class LocalRef>
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void ClearNativePtr(const LocalRef& instance)
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{
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JNIEnv* const env = instance.Env();
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const auto ptr = reinterpret_cast<WeakPtr<Impl>*>(
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GetNativeHandle(env, instance.Get()));
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if (ptr) {
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SetNativeHandle(env, instance.Get(), 0);
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delete ptr;
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} else {
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// GetNativeHandle throws an exception when returning null.
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MOZ_ASSERT(env->ExceptionCheck());
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env->ExceptionClear();
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template<class LocalRef>
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static void Set(const LocalRef& instance, SupportsWeakPtr<Impl>* ptr)
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{
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Clear(instance);
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SetNativeHandle(instance.Env(), instance.Get(),
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reinterpret_cast<uintptr_t>(new WeakPtr<Impl>(ptr)));
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HandleUncaughtException(instance.Env());
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}
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}
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template<class Impl, class LocalRef>
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void SetNativePtr(const LocalRef& instance, Impl* ptr)
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{
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ClearNativePtr<Impl>(instance);
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SetNativeHandle(instance.Env(), instance.Get(),
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reinterpret_cast<uintptr_t>(new WeakPtr<Impl>(ptr)));
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}
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template<class LocalRef>
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static void Clear(const LocalRef& instance)
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{
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const auto ptr = reinterpret_cast<WeakPtr<Impl>*>(
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GetNativeHandle(instance.Env(), instance.Get()));
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HandleUncaughtException(instance.Env());
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if (ptr) {
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SetNativeHandle(instance.Env(), instance.Get(), 0);
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HandleUncaughtException(instance.Env());
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delete ptr;
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}
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}
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};
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} // namespace
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namespace detail {
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@ -88,7 +200,7 @@ public:
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static ReturnJNIType Wrap(JNIEnv* env, jobject instance,
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typename TypeAdapter<Args>::JNIType... args)
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{
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Impl* const impl = GetNativePtr<Impl>(env, instance);
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Impl* const impl = NativePtr<Impl>::Get(env, instance);
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if (!impl) {
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return ReturnJNIType();
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}
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@ -101,7 +213,7 @@ public:
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static ReturnJNIType Wrap(JNIEnv* env, jobject instance,
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typename TypeAdapter<Args>::JNIType... args)
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{
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Impl* const impl = GetNativePtr<Impl>(env, instance);
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Impl* const impl = NativePtr<Impl>::Get(env, instance);
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if (!impl) {
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return ReturnJNIType();
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}
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@ -125,7 +237,7 @@ public:
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static void Wrap(JNIEnv* env, jobject instance,
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typename TypeAdapter<Args>::JNIType... args)
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{
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Impl* const impl = GetNativePtr<Impl>(env, instance);
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Impl* const impl = NativePtr<Impl>::Get(env, instance);
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if (!impl) {
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return;
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}
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@ -137,7 +249,7 @@ public:
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static void Wrap(JNIEnv* env, jobject instance,
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typename TypeAdapter<Args>::JNIType... args)
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{
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Impl* const impl = GetNativePtr<Impl>(env, instance);
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Impl* const impl = NativePtr<Impl>::Get(env, instance);
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if (!impl) {
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return;
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}
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@ -245,8 +357,28 @@ public:
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}
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protected:
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// Associate a C++ instance with a Java instance.
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static void AttachNative(const typename Cls::LocalRef& instance,
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SupportsWeakPtr<Impl>* ptr)
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{
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static_assert(mozilla::IsBaseOf<SupportsWeakPtr<Impl>, Impl>::value,
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"Attach with UniquePtr&& when not using WeakPtr");
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return NativePtr<Impl>::Set(instance, ptr);
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}
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static void AttachNative(const typename Cls::LocalRef& instance,
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UniquePtr<Impl>&& ptr)
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{
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static_assert(!mozilla::IsBaseOf<SupportsWeakPtr<Impl>, Impl>::value,
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"Attach with SupportsWeakPtr* when using WeakPtr");
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return NativePtr<Impl>::Set(instance, mozilla::Move(ptr));
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}
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// Get the C++ instance associated with a Java instance.
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// There is always a pending exception if the return value is nullptr.
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static Impl* GetNative(const typename Cls::LocalRef& instance) {
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return GetNativePtr<Impl>(instance);
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return NativePtr<Impl>::Get(instance);
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}
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NativeImpl() {
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@ -254,12 +386,8 @@ protected:
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Init();
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}
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void AttachNative(const typename Cls::LocalRef& instance) {
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SetNativePtr<>(instance, static_cast<Impl*>(this));
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}
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void DisposeNative(const typename Cls::LocalRef& instance) {
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ClearNativePtr<Impl>(instance);
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NativePtr<Impl>::Clear(instance);
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}
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};
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@ -111,14 +111,8 @@ uintptr_t GetNativeHandle(JNIEnv* env, jobject instance)
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return 0;
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}
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auto handle = static_cast<uintptr_t>(
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return static_cast<uintptr_t>(
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env->GetLongField(instance, sJNIObjectHandleField));
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if (!handle && !env->ExceptionCheck()) {
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ThrowException(env, "java/lang/NullPointerException",
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"Null native pointer");
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}
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return handle;
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}
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void SetNativeHandle(JNIEnv* env, jobject instance, uintptr_t handle)
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