BitArray: A simple bit-array/bitfield library in pure Ruby

Basic, pure Ruby bit field. Works well for Bloom filters (the use case for which I originally wrote it).

Originally written in 2007 and left without significant update until 2017, it has now been updated to work within a typical, modern Ruby environment while maintaining the same API.

Installation

gem install bitarray

Examples

To use:

require 'bitarray'

Create a bit array 1000 bits wide:

ba = BitArray.new(1000)

Setting and reading bits:

ba[100] = 1
ba[100]
#=> 1

ba[100] = 0
ba[100]
#=> 0

More:

ba = BitArray.new(20)
[1,3,5,9,11,13,15].each { |i| ba[i] = 1 }
ba.to_s
#=> "01010100010101010000"
ba.total_set
#=> 7

History

• 1.0 in 2017 (updated for modern Ruby, more efficient storage, and 10th birthday)
• 0.0.1 in 2012 (original v5 released on GitHub)
• v5 (added support for flags being on by default, instead of off)
• v4 (fixed bug where setting 0 bits to 0 caused a set to 1)
• v3 (supports dynamic bitwidths for array elements.. now doing 32 bit widths default)
• v2 (now uses 1 << y, rather than 2 ** y .. it's 21.8 times faster!)
• v1 (first release)

Thanks

Thanks to Michael Slade for encouraging me to update this library on its 10th birthday and for suggesting finally using String's getbyte and setbyte methods now that we're all on 1.9+ compatible implementations.

License

MIT licensed. Copyright 2007-2017 Peter Cooper.