J2735-High-Performance-Toolkit

J2735 High-Performance Toolkit

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)

⚡ The Performance Invariant

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.

Metric	Standard ASN.1 Parsers	This Toolkit
Complexity	O(N) (Must parse everything)	O(1) (Jump to specific bits)
Memory	O(N) (Allocates mirror structs)	O(1) (Reads buffer in-place)
Startup	Slow (Allocation + Init)	Instant (Stateless macros)

🛠️ Integration

Header-only. No libraries to link.

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

Critical Requirement: Buffer Padding

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];

💻 Usage & Documentation

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.

Build & Test

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

Contributing

See CONTRIBUTING.md.

License

Apache 2.0 - Copyright 2026 Yogev Neumann