Asio.IPFS

A C++ Boost.Asio wrapper library over go-ipfs.

Features

• Boost.Asio based event loop
• Supports callbacks, futures and coroutines
• Cmake automatically downloads golang and go-ipfs + its dependencies
• Self contained: no need to run a separate ipfs daemon

Caveats/TODOs

• Destroying asio_ipfs::node will cancel all peding IPFS async operations, but at the moment they can't be cancelled individually.
• The asio::io_service can run in only one thread.
• Only a basic subset of IPFS operations are currently supported, have a look at asio_ipfs/node.h for details.
• The node::cat operation returns the content as a whole (this is OK for small contents, but some kind of stream would be preferred for big ones)

Requirements

To be able to use the Asio.IPFS in platforms like Android, where running IPFS as an independent daemon is not a possibility, the wrapper needs to embed IPFS by linking directly with its Go code. Thus the source of go-ipfs is needed to build the main glue between C++ and IPFS. Building that source requires a recent version of Go. To avoid extra system dependencies, the build process automatically downloads the Go system and builds IPFS itself.

In summary, the minimum build dependencies are:

• cmake 3.5+
• g++ capable of C++14 (clang not tested, but there's no reason to thing it wouldn't work)
• The Boost library v1.62 or higher

For Debian, this translates to the following packages:

• build-essential
• cmake
• curl
• libboost-dev
• libboost-system-dev
• libboost-coroutine-dev (only when it's to be used with coroutines)
• libboost-program-options-dev (only for the examples)

The build process is able to compile the Asio.IPFS to different platforms with the help of a properly configured cross-compilation environment. If you actually intend to cross-compile you will need proper C/C++ cross-compiler packages, Boost libraries for the target system and a toolchain file for CMake to use them.

To the date, the build process has only been tested on 64-bit GNU/Linux platforms and ARM based Androids.

Building

$ cd <PROJECT ROOT>
$ mkdir build
$ cd build
$ cmake ..
$ make

On success, the build directory shall contain the libipfs-bindings.so library, libasio-ipfs.a archive and one example programs ipfs-example.

To cross-compile to another system, you may either create a different build directory, or reuse the same directory and just remove the CMakeCache.txt file (thus you can reuse some downloads and build tools). Just remember to point CMake to the proper toolchain file. For the previous Raspbian example:

cmake -DCMAKE_TOOLCHAIN_FILE=/path/to/toolchain-linux-armhf-gcc6.cmake ..
make

Linux cross-compilation example

For building binaries in a Debian Strech machine which are able to run on Raspbian Stretch on the Raspberry Pi:

• Install the gcc-6-arm-linux-gnueabihf and g++-6-arm-linux-gnueabihf packages.

• As indicated in https://wiki.debian.org/Multiarch/HOWTO, add the new architecture with dpkg --add-architecture armhf and update your package list.

• Install the Boost libraries matching the target distribution, with the proper architecture suffix:

  • libboost-system1.62-dev:armhf
  • libboost-coroutine1.62-dev:armhf
  • libboost-program-options1.62-dev:armhf

• Create a toolchain file (e.g. toolchain-linux-armhf-gcc6.cmake) containing:

  set(CMAKE_SYSTEM_NAME Linux)
  set(CMAKE_SYSTEM_PROCESSOR armv6l)
  
  set(CMAKE_C_COMPILER /usr/bin/arm-linux-gnueabihf-gcc-6)
  set(CMAKE_CXX_COMPILER /usr/bin/arm-linux-gnueabihf-g++-6)
  

Android cross-compilation example

For building binaries able to run in Android KitKat and above on ARM processors you will need a Clang/LLVM standalone toolchain created with the Android NDK. Assuming that the NDK is under ~/opt/android-ndk-r15c, you may run:

$ ~/opt/android-ndk-r15c/build/tools/make-standalone-toolchain.sh \
  --platform=android-19 --arch=arm --stl=libc++ \
  --install-dir=$HOME/opt/ndk-android19-arm-libcpp

You will also need to build the Boost libraries for this platform. You may use Boost for Android. Assuming that Boost source is in ~/src/boost/<BOOST_VERSION>, edit doIt.sh and:

• set BOOST_SRC_DIR to $HOME/src/boost
• set BOOST_VERSION to the <BOOST_VERSION> above
• set GOOGLE_DIR to $HOME/opt/android-ndk-r15c
• modify build-boost.sh arguments, set --version=$BOOST_VERSION, --stdlibs="llvm-3.5", --linkage="shared" and --abis to the desired architectures (armeabi-v7a in our example)

Create the llvm-3.5 link as indicated in Boost for Android's readme and run ./doIt.sh to build the Boost libraries. This will create the directory build/boost/<BOOST_VERSION>.

After the previous steps you can use a CMake toolchain file like the following one:

set(CMAKE_SYSTEM_NAME Android)
set(CMAKE_SYSTEM_VERSION 19)
set(CMAKE_ANDROID_ARCH_ABI armeabi-v7a)
set(CMAKE_ANDROID_STANDALONE_TOOLCHAIN $ENV{HOME}/opt/ndk-android19-arm-libcpp)

set(BOOST_INCLUDEDIR /path/to/Boost-for-Android/build/boost/<BOOST_VERSION>/include)
set(BOOST_LIBRARYDIR /path/to/Boost-for-Android/build/boost/<BOOST_VERSION>/libs/${CMAKE_ANDROID_ARCH_ABI}/llvm-3.5)