Zero-copy, O(1) parser for SAE J2735 V2X structures.

Designed for embedded RSU/OBU firmware where CPU cycles and memory bandwidth are critical.

⚠️ Early Development: The API is currently unstable. Refer to the tests/ directory for the most up-to-date usage examples.

Specification: SAE J2735_202409 (September 2024 revision)

Standard ASN.1 parsers (like asn1c) deserialize the entire message into a struct before you can read a single field. This toolkit does not deserialize. It calculates bit-offsets on the fly.

Why can't you just cast a C struct over the buffer? Because J2735 UPER is bit-aligned, not byte-aligned:

Byte:     [  0   ] [  1   ] [  2   ]
Bits:     76543210 76543210 76543210
Fields:   [ A   ][ B          ]
          7 bits  12 bits      <-- Spans across byte boundaries

Traditional parsers copy everything to a struct. We jump directly to the bits you need.

Header-only. No libraries to link.

1. Copy the src/ folder to your project.
2. Include J2735_api.h or specific internal headers.

You must allocate 7 extra bytes at the end of your input buffer.

• Why? The parser performs safe 64-bit unaligned loads. Without padding, reading the last byte of a message could trigger a memory access violation.
• Invariant: uint8_t buf[MSG_SIZE + 7];

Because this library is in active alpha, the code itself is the source of truth.

1. For API Examples: See tests/.
   • The test files (e.g., tests/J2735_internal_DF_BSMcoreData_test.c) contain compiled, verified examples of how to access fields.
2. For Available Types: See src/.
   • Header files define the exact macros available for each J2735 Data Frame.

make check     # Static analysis (cppcheck)
make clean     # Clean build artifacts
make format    # Code formatting (clang-format)
make pre-push  # Run ALL checks (recommended before pushing)
make sanitize  # ASan + UBSan
make test      # Build and run tests
make tidy      # Static analysis (clang-tidy)
make valgrind  # Memory leak check

Supports GCC, Clang, and MSVC. To use a specific compiler:

CC=clang make test

See CONTRIBUTING.md.

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