Rusty Greetings

A Rust shared library example for iOS and Android

Rust install steps (mandatory)

Install Rust via:

curl https://sh.rustup.rs -sSf | sh

Complete the installer using default install settings.

iOS install steps

Rust comes with preinstalled packet manager cargo. For iOS you have to additionally install cargo-lipo:

cargo install cargo-lipo

Note: cargo-lipo does currently not support Bitcode. You find a more in-depth explanation here. Disabling Bitcode in Xcode settings via ENABLE_BITCODE = NO is currently the only option.

Add iOS target architectures:

rustup target add aarch64-apple-ios armv7-apple-ios armv7s-apple-ios x86_64-apple-ios i386-apple-ios

Android install steps

Install the following Android tools by going to Android Studio > Preferences > ... > SDK Tools:

Android SDK Tools
NDK
CMake
LLDB

Add the following environment variables:

export ANDROID_HOME=/Users/$USER/Library/Android/sdk
export NDK_HOME=$ANDROID_HOME/ndk-bundle

Create standalone versions of the NDK to compile against. The make_standalone_toolchain.py script inside the Android NDK is used for this. Output is a folder called ndk inside the android folder of this project.

cd android
mkdir ndk
${NDK_HOME}/build/tools/make_standalone_toolchain.py --api 26 --arch arm64 --install-dir NDK/arm64
${NDK_HOME}/build/tools/make_standalone_toolchain.py --api 26 --arch arm --install-dir NDK/arm
${NDK_HOME}/build/tools/make_standalone_toolchain.py --api 26 --arch x86 --install-dir NDK/x86

Add a new template file called cargo-config.toml.templ that will contain information for cargo where to look for NDKs during cross compilation. Replace with the path to the project on the current maschine.

[target.aarch64-linux-android]
ar = "<project path>/rustygreetings_ios_android/android/ndk/arm64/bin/aarch64-linux-android-ar"
linker = "<project path>/rustygreetings_ios_android/android/ndk/arm64/bin/aarch64-linux-android-clang"

[target.armv7-linux-androideabi]
ar = "<project path>/rustygreetings_ios_android/android/ndk/arm/bin/arm-linux-androideabi-ar"
linker = "<project path>/rustygreetings_ios_android/android/ndk/arm/bin/arm-linux-androideabi-clang"

[target.i686-linux-android]
ar = "<project path>/rustygreetings_ios_android/android/ndk/x86/bin/i686-linux-android-ar"
linker = "<project path>/rustygreetings_ios_android/android/ndk/x86/bin/i686-linux-android-clang"

In order to make the SDKs visible for cargo the template file need to be copied to the .cargo directory in the user's home folder:

cp cargo-config.toml.templ ~/.cargo/config

Add the newly created Android architectures to rustup:

rustup target add aarch64-linux-android armv7-linux-androideabi i686-linux-android

There are no universal libraries for Android. Hence, separate libs for each target have to be created:

cd cargo
cargo build --target aarch64-linux-android --release
cargo build --target armv7-linux-androideabi --release
cargo build --target i686-linux-android --release

Create architecture folder and symlinks for Android Studio. Replace with the path to the project on the current maschine:

cd ../rustygreetings/app/src/main

mkdir jniLibs
mkdir jniLibs/arm64
mkdir jniLibs/armeabi
mkdir jniLibs/x86


ln -s <project_path>/rustygreetings_ios_android/android/cargo/target/aarch64-linux-android/release/libgreetings.so jniLibs/arm64/libgreetings.so
ln -s <project_path>/rustygreetings_ios_android/android/cargo/target/armv7-linux-androideabi/release/libgreetings.so jniLibs/armeabi/libgreetings.so
ln -s <project_path>/rustygreetings_ios_android/android/cargo/target/i686-linux-android/release/libgreetings.so jniLibs/x86/libgreetings.so