Documentation
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Overview ¶
Package crc computes and identifies cyclic redundancy checks against the standard CRC catalogue (the parameters Greg Cook's reveng catalogue publishes). It is a protocol reverse-engineering aid: when a captured RF or wired frame ends in a checksum of an unknown algorithm — the constant case when bringing up a new decoder — this computes the CRC under each catalogue model, and the identify mode reports which model(s) reproduce an observed CRC over the data.
Wrap-vs-native judgement ¶
Native. A CRC is a parameterised bit-walk — (width, polynomial, init, reflect-in, reflect-out, xor-out) — about thirty lines of shift/xor. There is nothing to wrap, and the project already computes specific CRCs inline across its decoders (canfd, adsb, pocsag); this generalises that into a reusable catalogue.
Verifiable / no confidently-wrong output ¶
Every model in the catalogue carries its published "check" value — the CRC of the ASCII string "123456789", the universal CRC self-test vector. The unit tests assert that this package computes exactly that check value for every model, so a model only ships if its parameters reproduce the authoritative reference. The identify mode makes no guesses: it reports the models whose output equals the supplied CRC, and an empty result is an honest "no catalogue model matches".
Covered / deferred ¶
Covered: the common CRC-8 / CRC-16 / CRC-32 models seen in embedded, RF, and fieldbus protocols, plus CRC-24 (OpenPGP, Bluetooth LE PDU, FlexRay) — each with a published check value. Rarer widths (CRC-5/USB, CRC-64) and the full reveng search (brute-forcing unknown polynomials) are deliberately out of scope here.
Index ¶
Constants ¶
This section is empty.
Variables ¶
var Catalogue = []Model{ {"CRC-8/SMBUS", 8, 0x07, 0x00, false, false, 0x00, 0xF4}, {"CRC-8/MAXIM-DOW", 8, 0x31, 0x00, true, true, 0x00, 0xA1}, {"CRC-16/ARC", 16, 0x8005, 0x0000, true, true, 0x0000, 0xBB3D}, {"CRC-16/CCITT-FALSE", 16, 0x1021, 0xFFFF, false, false, 0x0000, 0x29B1}, {"CRC-16/XMODEM", 16, 0x1021, 0x0000, false, false, 0x0000, 0x31C3}, {"CRC-16/MODBUS", 16, 0x8005, 0xFFFF, true, true, 0x0000, 0x4B37}, {"CRC-16/KERMIT", 16, 0x1021, 0x0000, true, true, 0x0000, 0x2189}, {"CRC-24/OPENPGP", 24, 0x864CFB, 0xB704CE, false, false, 0x000000, 0x21CF02}, {"CRC-24/BLE", 24, 0x00065B, 0x555555, true, true, 0x000000, 0xC25A56}, {"CRC-24/FLEXRAY-A", 24, 0x5D6DCB, 0xFEDCBA, false, false, 0x000000, 0x7979BD}, {"CRC-32/ISO-HDLC", 32, 0x04C11DB7, 0xFFFFFFFF, true, true, 0xFFFFFFFF, 0xCBF43926}, {"CRC-32/BZIP2", 32, 0x04C11DB7, 0xFFFFFFFF, false, false, 0xFFFFFFFF, 0xFC891918}, {"CRC-32/MPEG-2", 32, 0x04C11DB7, 0xFFFFFFFF, false, false, 0x00000000, 0x0376E6E7}, }
Catalogue is the set of supported CRC models. Each Check value is from the reveng catalogue and is asserted by the unit tests.
Functions ¶
This section is empty.
Types ¶
type Model ¶
type Model struct {
Name string `json:"name"`
Width int `json:"width"`
Poly uint32 `json:"poly"`
Init uint32 `json:"init"`
RefIn bool `json:"ref_in"`
RefOut bool `json:"ref_out"`
XorOut uint32 `json:"xor_out"`
Check uint32 `json:"check"` // CRC of "123456789"
}
Model is one parameterised CRC algorithm.
Source Files