libacars

libacars is a library for decoding ACARS message contents.

Current stable version: 2.2.0 (released August 21, 2023)

Supported message types

• FANS-1/A ADS-C (Automatic Dependent Surveillance - Contract)
• FANS-1/A CPDLC (Controller-Pilot Data Link Communications)
• MIAM (Media Independent Aircraft Messaging)
• Media Advisory (Status of data links: VDL2, HF, Satcom, VHF ACARS)
• OHMA (diagnostic messages exchanged with Boeing 737MAX aircraft)

Installation

Binary packages

64-bit Windows binary packages of stable releases are provided in the Releases section.

Unzip the archive into any directory. You should be able to run example programs directly from bin subdirectory.

Building from source

Requirements:

• c11-capable C compiler
• cmake 3.1 or later
• zlib 1.2 (optional)
• libxml2 (optional)

The project should build and run correctly on the following platforms:

• Linux i686 and x86_64 (gcc)
• MacOS (clang)
• Windows (mingw or msvc)

Installing dependencies

• libacars needs zlib for MIAM and OHMA message decompression. If zlib is not present, decompression code will be disabled and compressed messages will be left undecoded. Therefore it is recommended to install zlib development package first. On Debian/Raspbian distros it is named zlib1g-dev:

apt install zlib1g-dev

• ACARS and MIAM CORE messages sometimes contain XML documents. libacars may optionally pretty-print these documents, ie. add proper formatting and indentation. To enable this feature, you need libxml2 library:

apt install libxml2-dev

• OHMA messages contain JSON-encoded data. libacars may optionally pretty-print these messages. This feature requires Jansson library:

apt install libjansson-dev

Compiling libacars (Linux)

• Option 1: To run stable and tested code, download the latest stable release tarball from Releases section and unpack it:

unzip libacars-x.y.z.zip
cd libacars-x.y.z

• Option 2: To run the latest development code which has not yet made it into a stable release, clone the source repository and checkout the unstable branch:

git clone https://github.com/szpajder/libacars
cd libacars
git checkout unstable

master branch is always in sync with the latest stable release. unstable branch is where the latest cutting-edge code goes first.

• Configure the build:

mkdir build
cd build
cmake ../

• Inspect the configuration summary in the cmake output and verify if all the dependencies have been detected properly:

-- libacars configuration summary:
-- - zlib:              requested: ON, enabled: TRUE
-- - libxml2:           requested: ON, enabled: TRUE
-- - jansson:           requested: ON, enabled: TRUE

• Compile and install:

make
sudo make install
sudo ldconfig

The library will be installed to /usr/local/lib (or /usr/local/lib64). Header files will land in /usr/local/include/libacars-2/libacars.

Compiling libacars (Mac)

Install dependencies and tools with brew:

brew install cmake zlib libxml2 jansson

Then follow the above instructions for Linux. Just skip the final sudo ldconfig step.

Advanced compilation options

The following options may be used when invoking cmake:

• -DCMAKE_BUILD_TYPE=Debug - enables debugging support.

• -DCMAKE_BUILD_TYPE=Release - disables debugging support (the default).

• -DEMIT_ASN_DEBUG=ON - enables debugging output of ASN.1 decoders (very verbose). This option requires -DCMAKE_BUILD_TYPE=Debug, otherwise it will do nothing.

• -DZLIB=FALSE - forcefully disables zlib support. It will not be used even if zlib is available.

• -DLIBXML2=FALSE - disables libxml2 support.

• -DJANSSON=FALSE - disables Jansson support.

Example applications

Example apps are provided in examples subdirectory:

• decode_acars_apps - reads messages from command line or from a file and decodes all ACARS applications supported by the library.

• adsc_get_position - illustrates how to extract position-related fields from decoded ADS-C message.

• cpdlc_get_position - illustrates how to extract position-related fields from CPDLC position reports.

Apps will be compiled together with the library. make install installs them to /usr/local/bin. Run each program with -h option for usage instructions.

API documentation

Refer to the following documents:

• doc/PROG_GUIDE.md - libacars Programmer's Guide
• doc/API_REFERENCE.md - libacars API Reference

Applications using libacars

• dumpvdl2, a VDL-2 decoder
• vdlm2dec, a VDL-2 decoder
• acarsdec, an ACARS decoder
• JAERO, a Satcom ACARS decoder

Credits and thanks

I hereby express my gratitude to everybody who helped with the development and testing of libacars. Special thanks go to:

• Fabrice Crohas
• Dick van Noort
• acarslogger
• Michał Miszewski

Licenses

libacars, Copyright (c) 2018-2023 Tomasz Lemiech szpajder@gmail.com

Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation files (the "Software"), to deal in the Software without restriction, including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so, subject to the following conditions:

The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software.

THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE X CONSORTIUM BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.

Contains code from the following software projects:

• Rocksoft^tm Model CRC Algorithm Table Generation Program V1.0 by Ross Williams

• asn1c, Copyright (c) 2003-2017 Lev Walkin vlm@lionet.info and contributors. All rights reserved.

Redistribution and use in source and binary forms, with or without modification, are permitted provided that the following conditions are met:

1. Redistributions of source code must retain the above copyright notice, this list of conditions and the following disclaimer.
2. Redistributions in binary form must reproduce the above copyright notice, this list of conditions and the following disclaimer in the documentation and/or other materials provided with the distribution.

THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.

Packaged releases for Windows include zlib library in binary DLL form. zlib data compression library, (C) 1995-2017 Jean-loup Gailly and Mark Adler.

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