crcglot 0.2.0

Verified CRC source-code for C, Rust, VHDL, Python — catalogue-driven, self-test embedded.

crcglot

Verified CRC source code for C, Rust, VHDL, and Python. Catalogue-driven, self-test embedded, multi-language by design.

LLMs will gladly write you CRC code. It might even be right. crcglot guarantees the generated code matches the canonical reveng catalogue test vector (crc("123456789") == <check value>) and ships a self-test you can run on your toolchain to prove it.

Quick start

pip install crcglot

crcglot c crc32 --slice8 file=mycrc       # → mycrc.h + mycrc.c
crcglot rust crc64-xz --slice8 > mycrc.rs
crcglot vhdl crc32 > mycrc.vhd
crcglot python crc16-modbus > mycrc.py

crcglot list                              # browse the catalogue
crcglot info crc32                        # show parameters

What you get per language

Function	Purpose
<fname>_init / _update / _finalize	Streaming triple — feed data chunk by chunk
<fname>	One-shot wrapper that calls the streaming triple
<fname>_self_test	Verify against the reveng check value on your toolchain

C / Rust / VHDL ship _self_test() returning 0/1 (or boolean for VHDL). Python verifies via the docstring's check: line — the same interpreter generated it.

CLI reference

crcglot <command> [options...]

crcglot list [GLOB]

Browse the catalogue. Optional GLOB filters by shell-style pattern (e.g. crc16-*). Exit code 1 if nothing matches.

crcglot list                # all 71 algorithms
crcglot list 'crc32-*'      # just the CRC-32 family

crcglot info <name>

Print parameters (width, poly, init, refin, refout, xorout, check, desc) for one algorithm. Exit 1 on unknown name.

crcglot info crc64-xz

crcglot {c | python | rust | vhdl} <algorithm> [options...] [tokens...]

Generate source code for the chosen target language.

Option / token	Effect
(default) bit-by-bit	Smallest code, zero RAM table, slowest. All widths.
--table	256-entry lookup table, 4-8× faster. All widths.
--slice8	8 lookup tables, 5-10× faster than --table. CRC-32 / CRC-64 only.
--custom	Use raw Rocksoft/Williams params instead of a catalogue lookup (see below).
file=STEM	Write to disk. C → STEM.h + STEM.c; python/rust/vhdl → STEM.py/.rs/.vhd. Omit for stdout.
symbol=NAME	Override the emitted function name. Default: derived from algorithm, or from file=STEM if given.

Rules:

• --table and --slice8 are mutually exclusive (exit 2 if both given).
• --slice8 python silently falls back to --table (CPython's per-int overhead eats the slice-by-8 speedup; stderr warns).
• Without file=, output goes to stdout. For C, header is emitted first, then source.
• C / Rust / VHDL files embed <symbol>_self_test() returning 0 on success. In constrained embedded targets, standard toolchain flags (-Wl,--gc-sections for C, LTO for Rust) strip whatever you don't call.

--custom (raw Rocksoft/Williams parameters)

For algorithms not in the catalogue:

crcglot c --custom width=16 poly=0x1234 init=0xFFFF \
         refin=true refout=true xorout=0x0000 file=mycustom

Param	Required	Notes
width=N	yes	8, 16, 32, or 64 only
poly=X	yes	Hex (0x...) or decimal
init=X	no	Default 0. Hex or decimal.
refin=B	no	Default false. Accepts true/false/1/0/yes/no/on/off.
refout=B	no	Default false. Same boolean syntax.
xorout=X	no	Default 0.
name=NAME	no	Default crc_custom. Used in generated comments.
desc=TEXT	no	Free-form description in comments.

The check value for the custom parameters is computed automatically (_generic_crc(b"123456789", ...)) and embedded into the generated _self_test().

Catalogue

64+ algorithms covering everything from CRC-8 (ATM, AUTOSAR, Bluetooth, Maxim 1-Wire) through CRC-16 (Modbus, XMODEM, CCITT, IBM SDLC) through CRC-32 (Ethernet, bzip2, iSCSI, AUTOSAR) to CRC-64 (XZ, ECMA-182, NVMe, Redis). Browse with crcglot list.

Example output

See EXAMPLES.md for the actual generated source for crc32 across all 9 language × implementation combinations (C / Rust / Python / VHDL crossed with bit-by-bit, table-driven, and slice-by-8 where supported). Every block is reproducible with one CLI command.

Acknowledgments

CRC catalogue data is derived from Greg Cook's reveng project — the canonical source for CRC algorithm parameters since 1999.

License

MIT