4Developers2016: Michał Kowalczyk- Djinni - bridge pomiędzy Java, Objective-C, Swift i C++
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The document discusses the use of C++ in developing multiplatform applications, highlighting the benefits of a consistent architecture and performance potential across various platforms. It introduces Djinni, an open-source tool for bridging C++ with Java and Objective-C, facilitating easier app development and maintenance. The pros and cons of using such a bridging approach are also outlined, emphasizing reduced code complexity and faster development against limitations like interface inheritance and increased app size.
4Developers2016: Michał Kowalczyk- Djinni - bridge pomiędzy Java, Objective-C, Swift i C++
- 1. Djinni Java/Objective-C and C++ bridging
- 2. Agenda 1. Multiplatform app 2. App architecture 3. C++11 4. Djinni 5. Demo 6. Pros & cons
- 3. Me • over 10 years in IT • over 4 years as C++ software engineer • some Java experience • no Objective-C experience • last half of year of free time (boring guy) spent on Android/iOS mobile app development, Swift learning, etc. • want to share idea of broad usage of C++ in mobile app development world
- 4. Multiplatform app • multiplatform app is… mobile / web / “traditional”, Android / iOS / MacOS / Linux / Windows, etc. • native look & feel • performance
- 5. Potential issues • Each of app platform version in native language (Java, Objective-C, C# etc.) • Duplicated code • More code - harder maintenance • Slow development
- 6. App architecture platform-specific (Java, Objective-C/Swift; UI)platform-specific (Java, Objective-C/Swift; UI) platform-agnostic (C/C++/C++11; business logic) platform-specific (Java, Objective-C/Swift; UI) ————————————————————————— cross-language bridge ————————————————————————— platform-agnostic (C/C++/C++11; business logic)
- 7. C++11 (modern C++) “C++ feels like a new language. That is, I can express my ideas more clearly, more simply, and more directly in C++11 than I could in C++98. Furthermore, the resulting programs are better checked by the compiler and run faster.” Bjarne Stroustrup, The C++ programming language
- 8. C++11 (modern C++) • auto • foreach • lambdas • smart pointers • move semantics • constexpr • many libraries • a lot more…
- 9. Cross-language bridge • Java Native Interface (JNI): C++ <-> Java • Objective-C++: C++ <-> Objective-C • Consistent interface across languages • Data types that are the same in all languages • Object’s lifetime • Error handling
- 10. JNI code example JNIEnv* env; if (m_javaVM->AttachCurrentThread(&env, nullptr) < 0) { return; } jclass applicationClass = env->GetObjectClass(cameraSupportClassPointer); if (applicationClass) { jmethodID getFrameID = env->GetMethodID(applicationClass, "getFrame", "()[B"); jobject frameObject = env->CallObjectMethod(cameraSupportClassPointer, getFrameID); if (frameObject) { jbyteArray *frameByteArray = reinterpret_cast<jbyteArray*>(&frameObject); jsize frameByteArrayLength = env->GetArrayLength(*frameByteArray); env->GetByteArrayRegion(*frameByteArray, 0, frameByteArrayLength, reinterpret_cast<jbyte*>(yuv)); jbyte *frameBytePointer = env->GetByteArrayElements(*frameByteArray, nullptr); env->ReleaseByteArrayElements(*frameByteArray, frameBytePointer, 0); } } m_javaVM->DetachCurrentThread(); JNIEnv* env; if (m_javaVM->AttachCurrentThread(&env, nullptr) < 0) { return; } jclass applicationClass = env->GetObjectClass(cameraSupportClassPointer); if (applicationClass) { jmethodID getFrameID = env->GetMethodID(applicationClass, "getFrame", "()[B"); jobject frameObject = env->CallObjectMethod(cameraSupportClassPointer, getFrameID); if (frameObject) { jbyteArray *frameByteArray = reinterpret_cast<jbyteArray*>(&frameObject); jsize frameByteArrayLength = env->GetArrayLength(*frameByteArray); env->GetByteArrayRegion(*frameByteArray, 0, frameByteArrayLength, reinterpret_cast<jbyte*>(yuv)); jbyte *frameBytePointer = env->GetByteArrayElements(*frameByteArray, nullptr); env->ReleaseByteArrayElements(*frameByteArray, frameBytePointer, 0); } } m_javaVM->DetachCurrentThread();
- 11. Djinni • Dropbox’s Carousel and Mailbox • Bridge between C++ and Java/Objective-C • Bridge between C++ and Python (experimental) • Open source • Facebook’s Moments
- 12. Djinni’s Interface Definition Language (IDL) • Enums • Records • Interfaces • Implementation languages
- 13. C++11: auto std::vector<std::string> vec; std::vector<std::string>::iterator iter = vec.begin(); vintage C++
- 14. C++11: auto std::vector<std::string> vec; std::vector<std::string>::iterator iter = vec.begin(); std::vector<std::string> vec; auto iter = vec.begin(); modern C++ vintage C++
- 15. C++11: smart pointers auto d = new Dynamic; do_sth(d); // may throw vintage C++
- 16. C++11: smart pointers auto d = new Dynamic; do_sth(d); // may throw delete d; vintage C++
- 17. C++11: smart pointers auto d = new Dynamic; try { do_sth(d); // may throw } catch (...) { delete d; throw; // rethrow } delete d; vintage C++
- 18. C++11: smart pointers auto d = new Dynamic; try { do_sth(d); // may throw } catch (...) { delete d; throw; // rethrow } delete d; auto d = std::make_shared<Dynamic>(); do_sth(d); // may throw modern C++ vintage C++
- 19. C++11: std::move Huge h; do_sth(h); Huge h; do_sth(std::move(h)); modern C++ vintage C++
- 20. Demo
- 21. Pros • Less code • Easier maintenance • More consistency between app platform versions • Faster development • Better performance • Easy switch from single- to multi-platform
- 22. Cons • Reasonable use of bridges • Djinni’s limitations (lack of interface inheritance) • Compilers issues (AndroidNDK vs CrystaxNDK) • Size of Android app increases (architectures) • No single IDE
- 23. Links • github.com/dropbox/djinni • github.com/michal-kowalczyk/ trambambule-helper • mobilecpptutorials.com • code.facebook.com/posts/498597036962415/ under-the-hood-building-moments