ldk-swift

Automatic Swift bindings generation for rust-lightning.

Installation

In order to use the automatically generated bindings, simply drag *.xcframework file into an Xcode project.

The *.xcframework files are either available on the Releases page, or can be compiled from scratch.

Compilation

Prerequisites

A Mac with Xcode
Python3
Rust

For Rust specifically, there are a couple additional requirements that can be installed once the Rust toolchain is set up:

rustup target add aarch64-apple-darwin aarch64-apple-ios x86_64-apple-ios
cargo install cargo-lipo
cargo install cbindgen

Cloning Dependencies

In order to generate these bindings from scratch, you will need to clone two dependency repositories:

rust-lightning, (a specific branch built for bindings compatibility)

git clone --branch 2021-03-java-bindings-base git@github.com:TheBlueMatt/rust-lightning.git

ldk-c-bindings

git clone git@github.com:lightningdevkit/ldk-c-bindings.git

Generating Rust-to-C-bindings

Now, navigate to the ldk-c-bindings directory and run the genbindings.sh script:

cd /path/to/ldk-c-bindings
./genbindings.sh /path/to/rust-lightning true

Generating C-to-Swift-bindings

If using Docker

If you're using Docker to generate the Swift bindings, navigate (if you're not already there from the previous step) to the ldk-c-bindings directory and open the file located here:

/path/to/ldk-c-bindings/lightning-c-bindings/Cargo.toml

In that file, you will see four lines specifying the lightning, lightning-persister, lightning-invoice, and lightning-background-processor dependencies. They will most likely show local paths to the rust-lightning folder due to the previous genbindings.sh step. As Docker won't have access to local paths, replace those lines with the following:

lightning = { git = "https://github.com/thebluematt/rust-lightning", rev = "xxx", features = ["std"] }
lightning-persister = { git = "https://github.com/thebluematt/rust-lightning", rev = "xxx" }
lightning-invoice = { git = "https://github.com/thebluematt/rust-lightning", rev = "xxx" }
lightning-background-processor = { git = "https://github.com/thebluematt/rust-lightning", rev = "xxx" }

You will note that the revision is unspecified and is currently just placeholder xxxs. To obtain the revision, just navigate to the just clone custom rust-lightning directory and run:

cd /path/to/rust-lightning
git rev-parse HEAD

Take that commit hash and replace the xxx instances with it.

Generating the Swift files

To generate the Swift files, navigate to the ldk-swift repository and run the following:

EXPORT LDK_SWIFT_GENERATOR_INPUT_HEADER_PATH="/path/to/ldk-c-bindings/lightning-c-bindings/include/lightning.h"
python3 ./

Now, the contents of the bindings/LDK folder will have been completely regenerated.

Generating the *.xcframework files

With the Swift files completely regenerated, you will need to make sure the Xcode projects that serve as bases for the *.xcframeworks reference them correctly. So navigate here:

path/to/ldk-swift/xcode

and open the respective *.xcodeproj files located in the LDKFramework and LDKFramework_Mac directories. Do the following steps for both projects:

Remove the LDK references in the Xcode file tree
Drag the path/to/ldk-swift/bindings/LDK folder to that same location in the file tree
Check Copy items if needed and pick Create groups in the dialog box

Next, navigate back to the xcode directory, and run the following scripts:

./compile_dependency_binaries.sh /path/to/ldk-c-bindings
./build_framework.sh

Finally, navigate to path/to/ldk-swift/bindings/bin, and you should find multiple *.xcframework files waiting for you there.

jkczyz/ldk-swift