Kotlin C Interop

Kotlin is a great language! But what if you want to call an existing native library in Kotlin, or build your own native library for performance optimizations? This is also useful for making Kotlin a viable option for systems programming. Perhaps there’s an existing C or C++ library that would be great to have available in Kotlin, but it isn’t yet Kotlin-ready? We’ll take a look at how to access native libraries with Kotlin.

Transcript

1. Kotlin C Interop Matt Moore github: mattmoore twitter: mattmoore_io kotlinlang slack: mattmoore medium: mattmoore_io Rally Health https://www.builtinchicago.org/company/rally-health
2. C Interop on Two Platforms • Kotlin Native • Kotlin JVM
3. Let's Build A C Library Step 1: greeter.h Step 2: greeter.c Step 3: Compile libgreeter.dylib
4. C-Interop for Kotlin Native • When you want to use the Kotlin language without the JVM • Easier working with other native modules (system libraries in C/C++) • System programming - C/C++/Golang can be painful!
5. C-Interop for Kotlin Native cinterop Step 1: Create def file for library you want to use Step 2: Run cinterop to generate Kotlin library "libgreeter.klib" Step 3: Import "libgreeter.klib" into Kotlin program
6. Create C-Interop Kotlin Native Library Step 2: Compile Kotlin library "libgreeter.klib" Step 1: libgreeter.def
7. Using libgreeter.klib Step 2: Compile Step 1: Main.kt
8. Kotlin JVM: JNI (Java Native Interface) • Need another C library libgreeter_jni.dylib to translate between the JVM and libgreeter.dylib • Load libgreeter_jni.dylib in Kotlin JVM project
9. Kotlin JVM: JNI Conversion Library Step 1: greeter_jni.h
10. Kotlin JVM: JNI Conversion Library Step 2: greeter_jni.c
11. Kotlin JVM: JNI Conversion Library Step 3: Compile C code in "hello_jni.c" to shared library "libhello_jni.dylib"
12. Kotlin JVM: Using JNI Conversion Library Step 5: Call "hello()" native function
 in Main.kt Step 4: Create Kotlin C-Interop class "Greeter.kt" Step 6: Compile + Run Greeter.jar
13. program.kexe libgreeter.klib libgreeter.dylib java -jar -Djava.library.path=/usr/local/lib build/Greeter.jar libgreeter_jni.dylib libgreeter.dylib Kotlin Native ~ vs ~ Kotlin JVM libgreeter_jni.h libgreeter_jni.c libgreeter.def
14. Kotlin Native Kotlin JVM
15. How to Find Me Code/docs for this talk: https://github.com/mattmoore/kotlin-cinterop-talk Kotlin C-Interop: https://kotlinlang.org/docs/reference/native/c_interop.html Kotlin Native Overview: https://kotlinlang.org/docs/reference/native-overview.html Java Native Interface (JNI): https://medium.com/@mattmoore_io/kotlin-jni-for- native-code-835e93af7ddf Matt Moore Resources github: mattmoore twitter: mattmoore_io kotlinlang slack: mattmoore medium: mattmoore_io