https://github.com/peterc/bitarray
Pure Ruby bit array/bitfield implementation
https://github.com/peterc/bitarray
Last synced: 11 months ago
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Pure Ruby bit array/bitfield implementation
- Host: GitHub
- URL: https://github.com/peterc/bitarray
- Owner: peterc
- License: mit
- Created: 2012-01-18T04:37:31.000Z (over 14 years ago)
- Default Branch: main
- Last Pushed: 2024-02-11T13:44:54.000Z (over 2 years ago)
- Last Synced: 2025-06-08T00:16:43.340Z (about 1 year ago)
- Language: Ruby
- Homepage:
- Size: 37.1 KB
- Stars: 105
- Watchers: 3
- Forks: 14
- Open Issues: 1
-
Metadata Files:
- Readme: README.md
- License: LICENSE
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README
# BitArray: Pure Ruby bit-array/bitfield library
A simple, pure-Ruby 'bit field' object.
Originally built to help power a bloom filter, although there are other higher level libraries for that task now (https://github.com/igrigorik/bloomfilter-rb is a popular one.)
BitArray has changed little over the years, but has been maintained to work within a typical, modern Ruby environment and, as of February 2024, is confirmed to work with both Ruby 3.0.1 and Ruby 3.3.0.
## Installation
```ruby
bundle add bitarray
```
## Examples
To use:
```ruby
require 'bitarray'
```
Create a bit array 1000 bits wide:
```ruby
ba = BitArray.new(1000)
```
Setting and reading bits:
```ruby
ba[100] = 1
ba[100]
#=> 1
ba[100] = 0
ba[100]
#=> 0
```
More:
```ruby
ba = BitArray.new(20)
[1,3,5,9,11,13,15].each { |i| ba[i] = 1 }
ba.to_s
#=> "01010100010101010000"
ba.total_set
#=> 7
```
Initializing `BitArray` with a custom field value:
```ruby
ba = BitArray.new(16, ["0000111111110000"].pack('B*'))
ba.to_s # "1111000000001111"
```
`BitArray` by default stores the bits in reverse order for each byte. If for example, you are initializing `BitArray` with Redis raw value manipulated with `setbit` / `getbit` operations, you will need to tell `BitArray` to not reverse the bits in each byte using the `reverse_byte: false` option:
```ruby
ba = BitArray.new(16, ["0000111111110000"].pack('B*'), reverse_byte: false)
ba.to_s # "0000111111110000"
```
## History
- 1.3.1 in 2024 (no changes other than adding license to gemspec)
- 1.3 in 2022 (cleanups and a minor perf tweak)
- 1.2 in 2018 (Added option to skip reverse the bits for each byte by @dalibor)
- 1.1 in 2018 (fixed a significant bug)
- 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.
Further thanks to @tdeo, @JoshuaSP, @dalibor, @yegct and @m1lt0n for pull requests.
## License
MIT licensed. Copyright 2007-2024 Peter Cooper.