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README.md

This repo will contain Privategrity clients for all platforms.

Preparation to Build

To build this client, you will need to get the Android SDK and NDK, and get and initialize gomobile. I recommend getting the Android SDK and NDK using Android Studio. Download it from https://developer.android.com/studio/index.html and follow the instructions to install it. I recommend choosing the Standard setup option.

After running setup, at the Android Studio splash screen, click Configure->Settings towards the bottom. Navigate to Appearance & Behavior->System Settings->Android SDK, then SDK Tools, then check NDK. Click OK, follow the instructions, and before long you'll have an Android NDK installation.

Export ANDROID_HOME in your .profile or .bash_profile, pointing to the location of your Android SDK installation. Then, after confirming that the environment variable change has taken effect:

$ go get golang.org/x/mobile/cmd/gomobile

For Android support: $ gomobile init -ndk=/path/to/your/ndk/installation

On Linux, the NDK is in ~/Android/Sdk/ndk-bundle by default.

For iOS support: TODO.

In either case you will need to run $ gomobile init.

After these steps are complete, run $ glide up to get all the other Go dependencies.

Building

To build the .aar for the client, cd to privategrity/client/android/client and run this command:

$ gomobile bind -target=android gitlab.com/privategrity/client/api

Adding the .aar to the Android Studio project

In case you need to add another .aar to the Android Studio project, follow these steps:

  1. Go to File->New->New Module.
  2. Scroll to and click on Import .JAR/.AAR Package.
  3. Pick the .aar in the file chooser.
  4. Click through the rest of the wizard.

In any case, this isn't a recommended course of action because there might be some weirdness about gomobile generating more than one .aar, and the .aar that building generates has already been added to the project.

Project Structure

The top-level Go package is called "client". This package contains all of the APIs that the mobile apps will be able to access. If the mobile apps shouldn't be able to access some functions directly, put those functions in a different package!

The package crypto will contain client cryptops, and the package comms will contain client communications. When working tickets related to crypto or communications, ask yourself whether the code you're writing would belong better in the crypto or comms repositories instead.

Gomobile Usage and Caveats

Every exported symbol from the "client" package should be exported by the gomobile bindings. Only the following data types are allowed to be exported:

  • Signed integer and floating point types.

  • String and boolean types.

  • Byte slice types. Note that byte slices are passed by reference, and support mutation.

  • Any function type all of whose parameters and results have supported types. Functions must return either no results, one result, or two results where the type of the second is the built-in 'error' type.

  • Any interface type, all of whose exported methods have supported function types.

  • Any struct type, all of whose exported methods have supported function types and all of whose exported fields have supported types.

So, exporting a cyclic Int shouldn't work, and you should get an error if you try to. But it's totally OK to have a cyclic Int in the "client" package, as long as it's not exported, and it's totally OK to have a cyclic Int exported from a package that "client" depends on.

See https://godoc.org/golang.org/x/mobile/cmd/gobind for other important usage notes (avoiding reference cycles, calling Java or Objective-C from Go.)