Bitwise

Fast, memory efficient bitwise operations on large binary strings.

Internally a bit array is represented as a ruby string with Encoding::BINARY encoding, which keeps billions of bits in a workable footprint.

• 1,000,000 bits = 125KB
• 10,000,000 bits = 1.25MB
• 100,000,000 bits = 12.5MB
• 1,000,000,000 bits = 125MB

If you need a bit storage for ActiveRecord instead, take a look at ActiveFlag.

Install

gem install bitwise

Usage

Set and unset bits:

b=Bitwise.new("\x00")b.bits=>"00000000"b.set_at(1)b.set_at(4)b.bits=>"01001000"b.unset_at(1)b.bits=>"00001000"b.set_at?(4)=>trueb.unset_at?(4)=>false

String-based accessor:

b=Bitwise.newb.raw="abc"b.size=>3b.bits=>"011000010110001001100011"b.raw.unpack('C*')=>[97,98,99]

Index-based accessor:

b=Bitwise.newb.indexes=[1,2,4,8,16]b.bits=>"011010001000000010000000"b.indexes=>[1,2,4,8,16]b.cardinality=>5b.set_at(10)b.bits=>"011010001010000010000000"b.indexes=>[1,2,4,8,10,16]b.cardinality=>6

Bit-based accessor is also provided for convenience, but be aware that it's not efficient. Use string-based accessor whenever possible.

b=Bitwise.newb.bits='0100100010'b.bits=>"0100100010000000"

NOT, OR, AND and XOR:

b1=Bitwise.newb2=Bitwise.newb1.indexes=[1,2,3,5,6]b2.indexes=[1,2,4,8,16](~b1).indexes=>[0,4,7](b1 | b2).indexes=>[1,2,3,4,5,6,8,16](b1 & b2).indexes=>[1,2](b1 ^ b2).indexes=>[3,4,5,6,8,16]

As a bonus, Bitwise.string_not, Bitwise.string_union, Bitwise.string_intersect, and Bitwise.string_xor can be used as a standalone utility to work with any binary string.

Bitwise.string_not"\xF0"=>"\x0F"Bitwise.string_union"\xF0","\xFF"=>"\xFF"Bitwise.string_intersect"\xF0","\xFF"=>"\xF0"Bitwise.string_xor"\xF0","\xFF"=>"\x0F"