47 lines
1.9 KiB
Markdown
47 lines
1.9 KiB
Markdown
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Title: Generate code from ASN.1
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# How to generate code from ASN.1 definitions
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Generating new ASN.1 structs based on ASN.1 definitions can be a daunting task requiring the appropriate ASN.1 compiler.
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In particular, we use the **asn1c** fork maintained by [mouse07410](https://github.com/mouse07410/asn1c).
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Though the Vanetza repository comes with various pre-generated ASN.1 messages, you may want to add further or revised versions of these messages.
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In this case, the following steps guide you how to generate code from ASN.1 definitions on your own.
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## Prerequisites
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We have streamlined the process of installing and using **asn1c** by relying on a Docker container.
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1. Install Docker on your system
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2. Build the Docker container from the `vanetza/asn1/Dockerfile` as `vanetza-asn1c:latest`
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```bash
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docker build --tag vanetza-asn1c:latest vanetza/asn1
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```
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## Generate ASN.1 code
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Our CMake build environment comes with a `generate_asn1c` code generation target.
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This target is available if the the `VANETZA_ASN1_WITH_ASN1C` CMake option is enabled.
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When you invoke this target, CMake will run the Docker container for you with suitable arguments.
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You can specify a custom image by modifying the `VANETZA_ASN1C_CONTAINER` CMake cache variable.
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By default, CMake will use the `vanetza-asn1c:latest` image.
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1. Update your copy of Vanetza with the new or updated ASN.1 definitions
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2. Update the **CMakeLists.txt** file at **vanetza/asn1** accordingly
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3. Create a fresh build directory and configure CMake with enabled ASN.1 targets
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4. Invoke **asn1c** and compile Vanetza with newly generated code
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```bash
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# Create a new build directory at the project's root
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mkdir build.asn1 && cd build.asn1
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# Configure the build with enabled ASN.1 targets and retrieval of ISO ASN.1 files
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cmake -DVANETZA_ASN1_WITH_ASN1C=ON -DVANETZA_ASN1_WITH_ISO=ON ..
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# Invoke the target calling asn1c
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make generate_asn1c
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# Compile Vanetza with newly generated ASN.1 code
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cmake --build .
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```
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