Jau Support Library (C++, Java, ...)

Original document location.

Git Repository

This project's canonical repositories is hosted on Gothel Software.


This project aims to provide general C++ and Java collections, algorithms and utilities - as well as basic concepts to support a Java JNI binding.

This project was extracted from Direct-BT to enable general use and enforce better encapsulation.


Build and clang-tidy clean on C++17 and C++20, passing all unit tests.

API Documentation

Up to date API documentation can be found:


See Direct-BT C++ API Doc.

Supported Platforms

Language requirements

See supported platforms for details.

Building Binaries

It is advised to include this library into your main project, e.g. as a git-submodule.

Then add jaulib/include/ to your C++ include-path and also add the C++ source files under jaulib/src/ into your build recipe.

The produced Java libraries are fully functional.

This library's build recipe are functional though, but currently only intended to support unit testing and to produce a Doxygen API doc.

Build Dependencies

  • CMake 3.13+ but >= 3.18 is recommended
  • C++ compiler
    • gcc >= 8.3.0 (C++17)
    • gcc >= 10.2.1 (C++17 and C++20)
    • clang >= 15 (C++17 and C++20)
  • Optional for lint validation
    • clang-tidy >= 15
  • Optional for vscodium integration
    • clangd >= 15
    • clang-tools >= 15
    • clang-format >= 15
  • Optional
    • libunwind8 >= 1.2.1
    • libcurl4 >= 7.74 (tested, lower may work)
  • Optional Java support
    • OpenJDK >= 11
    • junit4 >= 4.12

Install on FreeBSD

Installing build dependencies on FreeBSD >= 13:

pkg install git
pkg install sudo
pkg install cmake
pkg install libunwind
pkg install doxygen
pkg install squashfs-tools
pkg install bash
ln -s /usr/local/bin/bash /bin/bash

Install optional Java dependencies:

pkg install openjdk17
pkg install openjdk17-jre
pkg install junit

For Java ensure /etc/fstab includes:

fdesc   /dev/fd         fdescfs         rw      0       0
proc    /proc           procfs          rw      0       0

jau::fs::mount_image() and jau::fs::umount() are currenly not fully implemented under FreeBSD, hence testing using cmake option -DTEST_WITH_SUDO=ON is disabled.

To use URL streaming functionality via the curl library in jau_io_util.hpp and jau/io_util.cpp, the cmake option -DUSE_LIBCURL=ON must be set.
This also requires installation of the following packets:

pkg install curl
apt install mini-httpd

Note: mini-httpd is being used for unit testing URL streaming only.

Install on Debian or Ubuntu

Installing build dependencies on Debian >= 11 and Ubuntu >= 20.04:

apt install git
apt install build-essential g++ gcc libc-dev libpthread-stubs0-dev 
apt install clang-15 clang-tidy-15 clangd-15 clang-tools-15 clang-format-15
apt install libunwind8 libunwind-dev
apt install cmake cmake-extras extra-cmake-modules
apt install doxygen graphviz

If using the optional clang toolchain, perhaps change the clang version-suffix of above clang install line to the appropriate version.

After complete clang installation, you might want to setup the latest version as your default. For Debian you can use this clang alternatives setup script.

Install optional Java dependencies:

apt install openjdk-17-jdk openjdk-17-jre junit4

To test jau::fs::mount_image() and jau::fs::umount() under Linux with enabled cmake option -DTEST_WITH_SUDO=ON,
the following build dependencies are added

apt install libcap-dev libcap2-bin
apt install squashfs-tools

To use URL streaming functionality via the curl library in jau_io_util.hpp and jau/io_util.cpp, the cmake option -DUSE_LIBCURL=ON must be set.
This also requires installation of the following packets:

apt install libcurl4 libcurl4-gnutls-dev
apt install mini-httpd

Note: mini-httpd is being used for unit testing URL streaming only.

Build Procedure

For a generic build use:

git clone https://jausoft.com/cgit/jaulib.git
cd jaulib
mkdir build
cd build
make -j $CPU_COUNT install
make test
make doc

The install target of the last command will create the include/ and lib/ directories with a copy of the headers and library objects respectively in your build location. Note that doing an out-of-source build may cause issues when rebuilding later on.

You may also invoke scripts/build.sh, which resolves installed environment variables like JAVA_HOME and JUNIT_CP as well as building and distributing using os_arch type folders.

  • scripts/setup-machine-arch.sh .. generic setup for all scripts
  • scripts/build.sh .. initial build incl. install and unit testing
  • scripts/rebuild.sh .. rebuild
  • scripts/build-cross.sh .. cross-build
  • scripts/rebuild-cross.sh .. cross-build
  • scripts/test_java.sh .. invoke a java unit test
  • scripts/test_exe_template.sh .. invoke the symlink'ed files to invoke native unit tests

Our cmake configure has a number of options, cmake-gui or ccmake can show you all the options. The interesting ones are detailed below:

Changing install path from /usr/local to /usr


Building debug build:


Add unit tests to build (default: disabled)


Add unit tests requiring sudo to build (default: disabled).
This option requires -DBUILD_TESTING=ON to be effective.
Covered unit test requiring sudo are currently

  • Linux OS
    • jau::fs::mount_image()
    • jau::fs::umount()

Using clang instead of gcc:

-DCMAKE_C_COMPILER=/usr/bin/clang -DCMAKE_CXX_COMPILER=/usr/bin/clang++

Building with clang and clang-tidy lint validation


Disable stripping native lib even in non debug build:


Enable using libcurl (default: disabled)


Enable using libunwind (default: disabled)


Disable using C++ Runtime Type Information (RTTI) (default: enabled)


Override default javac debug arguments source,lines:



Building debug and instrumentation (sanitizer) build:


Cross-compiling on a different system:

-DCMAKE_CXX_FLAGS:STRING=-m32 -march=i586
-DCMAKE_C_FLAGS:STRING=-m32 -march=i586

To build Java bindings:


To build documentation run:

make doc

Cross Build

Also provided is a cross-build script using chroot into a target system using QEMU User space emulation and Linux kernel binfmt_misc to run on other architectures than the host.

See Build Procedure for general overview.

You may use our pi-gen branch to produce a Raspi-arm64, Raspi-armhf or PC-amd64 target image.

IDE Integration


IDE integration configuration files are provided for

  • Eclipse with extensions
    • CDT or CDT @ eclipse.org
    • Not used due to lack of subproject include file and symbol resolution:
      • CMake Support, install C/C++ CMake Build Support with ID org.eclipse.cdt.cmake.feature.group

From the project root directory, prepare the Debug folder using cmake


The existing project setup is just using external build via make.

You can import the project to your workspace via File . Import... and Existing Projects into Workspace menu item.

For Eclipse one might need to adjust some setting in the .project and .cproject (CDT) via Eclipse settings UI, but it should just work out of the box.

VSCodium or VS Code

IDE integration configuration files are provided for

For VSCodium one might copy the example root-workspace file to the parent folder of this project (note the filename change) and adjust the path to your filesystem.

cp .vscode/jaulib.code-workspace_example ../jaulib.code-workspace
vi ../jaulib.code-workspace

Then you can open it via File . Open Workspace from File... menu item.

  • All listed extensions are referenced in this workspace file to be installed via the IDE
  • The local settings.json has clang-tidy enabled
    • If using clang-tidy is too slow, just remove it from the settings file.
    • clangd will still contain a good portion of clang-tidy checks


See Changes.