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)
=> true
b.unset_at?(4)
=> falseString-based accessor:
b = Bitwise.new
b.raw = "abc"
b.size
=> 3
b.bits
=> "011000010110001001100011"
b.raw.unpack('C*')
=> [97, 98, 99]Index-based accessor:
b = Bitwise.new
b.indexes = [1, 2, 4, 8, 16]
b.bits
=> "011010001000000010000000"
b.indexes
=> [1, 2, 4, 8, 16]
b.cardinality
=> 5
b.set_at(10)
b.bits
=> "011010001010000010000000"
b.indexes
=> [1, 2, 4, 8, 10, 16]
b.cardinality
=> 6Bit-based accessor is also provided for convenience, but be aware that it's not efficient. Use string-based accessor whenever possible.
b = Bitwise.new
b.bits = '0100100010'
b.bits
=> "0100100010000000"NOT, OR, AND and XOR:
b1 = Bitwise.new
b2 = Bitwise.new
b1.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"