Thoughts on the current state of ASN.1 and XML technologies.

ASN1C kits available for older Linux 64-bit systems using older glibc and ld libraries

A new ASN1C Linux 64-bit evaluation kit is now available for ASN1C version 7.3.3 to address problems reported by users with the current package. One problem reported was when executing the ASN1C binary, an error similar to this may be displayed: “version ‘GLIBC_2.12’ not found”. A second problem was in linking with libraries in the package in which an error to the effect of “unrecognized relocation” or “bad value” would be reported. This is because our binaries are now built with a newer version of glibc and ld (such as, currently, glibc 2.23 and ld/binutils 2.26). Older systems that have glibc versions such as 2.12 will fail to build with these libraries.

This new package contains executable files and libraries built with an older version of glibc.

The description of the existing package on our download page has been changed to:

  • Linux Ubuntu 16.04 (x64) 64-bit, glibc 2.23

The new package is

  • Linux Centos 6.5 (x64) 64-bit, glibc 2.12, no GUI

Note that in both of these cases, even though we have listed the specific Linux distribution used, the packages should work on any reasonably up-to-date Linux distributions such as SUSE, Fedora, Debian, etc. The only factor in determining which one to use would be the version of glibc.

Also note that the package that uses the older glibc does not contain the ASN1C GUI as it required the newer glibc version be available.

To check which version of glibc your system is currently using, enter the command “ldd –version”. This will print the version of ldd and glibc, with output similar to the following:

  • ldd (GNU libc) 2.12

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V2X API Library Update

With the recent release of ASN1C 7.3.3, we’ve also updated our V2X API library.  We’ve added support for ETSI TS 103 301 SPATEM, MAPEM, IVIM, SREM, and SSEM messages.

Our V2X API library provides support for encoding V2X (Vehicle-to-everything) messages.  The library is available for C++ (as a shared library) Java (JAR), and C# (DLL).   A simple Python wrapper for the C++ shared library is also provided.

Users of previous versions of the Java or C# library should be aware that a slight change was made: classes in the v2x package/namespace have been split into one of two sub-package/namespaces: v2x.j2735 or v2x.etsi.

Users of previous versions of the C++ or Python library should be aware that the shared library has been split into two files (*_j2735 and *_etsi).  Python users must have both libraries present as the Python wrapper library requires both of them.  C++ users can use whichever one is appropriate.

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Extending JSON Encoding Rules (JER)

ITU-T standardized the JSON encoding of ASN.1 data in X.697 (JER), but we believe customers want to support use cases the standard doesn’t address.  This post briefly describes two extensions to JER that we’re planning to implement in our ASN.1 compiler, ASN1C.  We plan to implement the first extension (for contents constraints) as an undocumented feature in a 7.3.x patch release in the September-October time frame.

Extension for Contents Constraints

The first extension relates to encoding of BIT STRING or OCTET STRING with a contents constraint.  For example:

OCTET STRING (CONTAINING SomeType)

In short, the purpose of this first extension is to allow the contained type to be encoded in JSON just as it would be encoded if it weren’t a contained type, instead of encoding it as a string of hexadecimal characters.  This extension is all about making the JSON more human-readable.  Here’s an example:

Say your ASN.1 has something like this:

   my-bit-string BIT STRING ( CONTAINING TwoStrings )
…

TwoStrings ::= SEQUENCE {
   one UTF8String,
   two UTF8String
}

The standard JER encoding would look something like:

"my-bit-string" : { "value" : "7B20226F6E6522203A20226D6F6E6579222C202274776F22203A202273686F7722207D", "length" : 280 }

Our extension would instead produce something like:

"my-bit-string" : { "value+" : { "one" : "money", "two" : "show" } }

Extension for Values of Unknown Types

The second extension relates to encoding values of unknown types, which may appear as SEQUENCE/SET/CHOICE extension elements or in open types.  It isn’t possible to convert values of unknown types from BER or PER to standard JER.  Since its type isn’t known, the value is stuck in BER or PER, so to speak.  So, in short, the purpose of our second extension is to enable converting the rest of your data to JSON while preserving what can’t be properly converted (in case you need it) and making a round trip back to the original encoding possible.  This is done by embedding the original encoding in the JSON in hexadecimal form, along with some supplemental information where necessary.

Below are some examples of the JSON that would be produced using our extension.

Handling an unknown open type value:

"some-open-type-element" : { 
   "encoding-rules+" : "BER",
   "encoded-data+" : "03020101"
}

Handling unknown SEQUENCE or SET extension elements:

"extensions+" : {
   "encoding-rules+" : "BER",
   "encoded-data+": [ "hex for extension X", "hex for extension Y" ]
}

Handling an unknown CHOICE extension element:

some-choice-field : {
   "extension+" : {
      "encoding-rules+" : "PER",
      "encoded-data+" : "04020301",
      "encoded-per-index+" : 5
   }
}

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The updated ASN1C Eclipse Plug-in

An updated version of our ASN1C Eclipse Plug-in is now available for Eclipse versions 4.6 (Neon) and higher.

A previous version of this plug-in had been available for Eclipse 3.x.  However, once Eclipse modified the way in which it installs and supports plug-ins, this version ceased to function and there was a significant delay in getting it up-to-date with newer Eclipse versions.  This upgrade is now complete.

Capabilities of this plug-in include:

  • ASN.1 editing and syntax checking
  • Code generation of C/C++, Java, and C# languages from ASN.1

Click on the “Eclipse Plugin” tab near the bottom of our ASN1C product page for more information and installation instructions.

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The ASN1C Visual Studio Wizard

You may or not be aware that ASN1C includes a Visual Studio Wizard that you can use from Visual Studio to build a library from one or more ASN.1 files. If you have at least ASN1C v732, the wizard is present and usable.

The files for the wizard are in the vswizard folder of your ASN1C installation. There are three files here that are the components of the wizard: ASN1CWizard.ico, ASN1CWizard.vsdir, and ASN1CWizard.vsz. There is also a README.txt file here that provides instructions for configuring and installing the wizard. One of the steps is to modify the .vsz file, and note in particular the instructions to remove the comment-like lines that are at the top. In ASN1C v7.4, which will likely be released in January, this .vsz file will be generated during the installation, and there will no longer be a need to edit it.

Once the files for the wizard are correct and in place, you can use Visual Studio to create a new project just like you normally would, but now you can choose ASN1C as the project type. The wizard will invoke the ASN1C GUI, with some of the irrelevant options disabled. You can use the GUI to choose the ASN.1 files and define how you want the code to be generated for your library. Then you click on the Compile button to generate the code and a Visual Studio project file. Once you exit the GUI, the project file will be loaded into Visual Studio.

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