Class: JsonBloomfilter::BitArray

Inherits:
Object
  • Object
show all
Includes:
Enumerable
Defined in:
lib/json-bloomfilter/bitarray.rb

Constant Summary collapse

ELEMENT_WIDTH = 
32

Instance Attribute Summary collapse

Instance Method Summary collapse

Constructor Details

#initialize(size, field = nil) ⇒ BitArray

Returns a new instance of BitArray.



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# File 'lib/json-bloomfilter/bitarray.rb', line 9

def initialize(size, field = nil)
  @size = size
  @field = field || Array.new(((size - 1) / ELEMENT_WIDTH) + 1, 0)
end

Instance Attribute Details

#field ⇒ Object (readonly)

Returns the value of attribute field.



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# File 'lib/json-bloomfilter/bitarray.rb', line 4

def field
  @field
end

#size ⇒ Object (readonly)

Returns the value of attribute size.



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# File 'lib/json-bloomfilter/bitarray.rb', line 3

def size
  @size
end

Instance Method Details

#[]=(position, value) ⇒ Object

Set a bit (1/0)

Raises:

  • (ArgumentError) 


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# File 'lib/json-bloomfilter/bitarray.rb', line 23

def []=(position, value)
  raise ArgumentError.new("Position out of bound (#{position} for max #{@size})") if position >= @size
  if value == 1
    @field[position / ELEMENT_WIDTH] |= 1 << (position % ELEMENT_WIDTH)
  elsif (@field[position / ELEMENT_WIDTH]) & (1 << (position % ELEMENT_WIDTH)) != 0
    @field[position / ELEMENT_WIDTH] ^= 1 << (position % ELEMENT_WIDTH)
  end
end

#add(position) ⇒ Object 



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# File 'lib/json-bloomfilter/bitarray.rb', line 14

def add position
  self[position] = 1
end

#each(&block) ⇒ Object

Iterate over each bit



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# File 'lib/json-bloomfilter/bitarray.rb', line 39

def each(&block)
  @size.times { |position| yield self.get(position) }
end

#get(position) ⇒ Object

Read a bit (1/0)

Raises:

  • (ArgumentError) 


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# File 'lib/json-bloomfilter/bitarray.rb', line 33

def get position
  raise ArgumentError.new("Position out of bound (#{position} for max #{@size})") if position >= @size
  @field[position / ELEMENT_WIDTH] & 1 << (position % ELEMENT_WIDTH) > 0 ? 1 : 0
end

#remove(position) ⇒ Object 



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# File 'lib/json-bloomfilter/bitarray.rb', line 18

def remove position
  self[position] = 0
end

#to_s ⇒ Object

Returns the field as a string like “0101010100111100,” etc.



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# File 'lib/json-bloomfilter/bitarray.rb', line 44

def to_s
  inject("") { |a, b| a + b.to_s }
end