2.34. Calculating a 32-Bit CRC

The Cyclic Redundancy Checksum (CRC) is a well-known way of obtaining a “signature” for a file or other collection of bytes. The CRC has the property that the chance of data being changed and keeping the same CRC is 1 in 2**N, where N is the number of bits in the result (most often 32 bits).

The zlib library, created by Ueno Katsuhiro, enables you to do this.

The method crc32 computes a CRC given a string as a parameter:

require 'zlib'
include Zlib
crc = crc32("Hello")             # 4157704578
crc = crc32(" world!",crc)       # 461707669
crc = crc32("Hello world!")      # 461707669 (same as above)

A previous CRC can be specified as an optional second parameter; the result will be as if the strings were concatenated and a single CRC was ...

Get The Ruby Way: Solutions and Techniques in Ruby Programming, Second Edition now with the O’Reilly learning platform.

O’Reilly members experience books, live events, courses curated by job role, and more from O’Reilly and nearly 200 top publishers.