How to calculate 32 bit CRC in Ruby on rails

crc32.rb

[vitalyp]:~/dev/current/ultimate-proto on develop_prototype_listing*
$ irb
2.1.2 :001 > require 'zlib'
 => true 
2.1.2 :002 > crc32 = Zlib::crc32('input field value')
 => 1873826587 
2.1.2 :003 > crc32 = Zlib::crc32('input field ')
 => 1511246425 
2.1.2 :004 > crc32 = Zlib::crc32('a')
 => 3904355907 
2.1.2 :005 > crc32 = Zlib::crc32('a')
 => 3904355907 
2.1.2 :006 > crc32 = Zlib::crc32('ab')
 => 2659403885 
2.1.2 :007 > crc32 = Zlib::crc32('ba')
 => 749160980 
2.1.2 :008 > crc32 = Zlib::crc32('')
 => 0 
2.1.2 :009 > crc32 = Zlib::crc32('1')
 => 2212294583 
2.1.2 :010 > crc32 = Zlib::crc32('2')
 => 450215437 
2.1.2 :011 >