cl-crc64

cl-crc64 implements 64 bit cyclic redundancy checks in Common Lisp.

A cyclic redundancy check (CRC) is a type of hash function that produces a checksum (a small, fixed number of bits) against a block of data, such as a packet of network traffic or a block of a computer file. The checksum is used to detect errors after transmission or storage.

CRCs can also act as a kind of electronic fingerprint for identifying blocks of data. SWISS-PROT + TREMBL use a 64-bit Cyclic Redundancy Check for the amino acid sequences. My interest was in using CRC64 to index data in a semantic web triple store.

This implementation is influenced heavily by Python code by Gian Paolo Ciceri and crc.lisp by R. Matthew Emerson. My thanks to both these authors.

For a more thorough discussion of CRC see W. H. Press, S. A.Teukolsky, W. T. Vetterling, and B. P. Flannery, "Numerical recipes in C", 2nd ed., Cambridge University Press. Pages 896ff.

The code comes with BSD-style license so you can basically do whatever you want with it.

Example

cl-crc64 is ASDF installable, but assuming that you have QuickLisp installed:

 Rob-Blackwells-MacBook:cl-crc64 reb$ sbcl
 This is SBCL 1.0.29, an implementation of ANSI Common Lisp.
 More information about SBCL is available at <http://www.sbcl.org/>.
 
 SBCL is free software, provided as is, with absolutely no warranty.
 It is mostly in the public domain; some portions are provided under
 BSD-style licenses.  See the CREDITS and COPYING files in the
 distribution for more information.
 * (ql:quickload "cl-crc64")
 To load "cl-crc64":
   Load 1 ASDF system:
       cl-crc64
       ; Loading "cl-crc64"
       [package cl-crc64].
       ("cl-crc64")
   * (use-package :cl-crc64)

   T
   * (initialise-crc64 +polynomial+)
   
   NIL
   * (format nil "~X" (crc64-sequence "IHATEMATH"))

   "E3DCADD69B01ADD1"
   * 

WARNING: This is old code that I've pulled out, repackaged and open sourced. It was used as part of a demo some years back, but you probably want to test it thoroughly for new projects.

Rob Blackwell

October 2010