class Packetman::Filter

Attributes

input[RW]

Public Class Methods

bit_density(radix=config.radix) click to toggle source
# File lib/packetman/filter.rb, line 21
def self.bit_density(radix=config.radix)
  (radix.nil?) ? 8 : Math.log2(radix).ceil
end
bit_length(num) click to toggle source
# File lib/packetman/filter.rb, line 12
def self.bit_length(num)
  case num
  when /^0x/
    $'.length * bit_density(16)
  else
    nil
  end
end
new(input) { |config| ... } click to toggle source
# File lib/packetman/filter.rb, line 7
def initialize(input)
  self.input = input
  yield config if block_given?
end

Public Instance Methods

bin_chr(chr) click to toggle source

Converts the `chr` from `config.radix` to binary, substituting wildcards as necessary

@param chr [String] character to convert to binary @return [String] binary string

# File lib/packetman/filter.rb, line 58
def bin_chr(chr)
  chr = '0' if chr == config.wildcard

  if config.radix
    raise "invalid character '#{chr}' for radix=#{config.radix}" if chr.downcase != chr.to_i(config.radix).to_s(config.radix).downcase
    chr.to_i(config.radix)
  else
    chr.ord
  end.to_s(2).rjust(self.class.bit_density, '0')
end
clauses() click to toggle source
# File lib/packetman/filter.rb, line 86
def clauses
  start_bit = 0
  [].tap do |filter|
    search_hex.zip(mask_hex).each do |search, mask|
      filter << Packetman::Clause.new(search, mask, start_bit)
      start_bit += self.class.bit_length(search)
    end
  end
end
hex_encode(bin_str) click to toggle source

Transform bin_str to array of 32, 16, and 8 bit hex encoded strings

# File lib/packetman/filter.rb, line 78
def hex_encode(bin_str)
  bin_str.reverse.scan(/.{1,4}/).map{ |chunk|
    chunk.reverse.to_i(2).to_s(16)
  }.reverse.join.scan(/.{8}|.{4}|.{2}/).map{ |hex|
    hex.prepend('0x')
  }
end
map_chr() { |chr| ... } click to toggle source
# File lib/packetman/filter.rb, line 25
def map_chr
  shift_and_pad(input.scan(/./).map{ |chr| yield chr }.join)
end
mask_chr(chr) click to toggle source

Mask string for chr substituting wildcards as necessary

# File lib/packetman/filter.rb, line 46
def mask_chr(chr)
  if chr == config.wildcard
    0
  else
    radix_mask
  end.to_s(2).rjust(self.class.bit_density, '0')
end
mask_hex() click to toggle source
# File lib/packetman/filter.rb, line 69
def mask_hex
  hex_encode(map_chr{ |c| mask_chr(c) })
end
radix_mask() click to toggle source

Mask for 1 character of current radix

# File lib/packetman/filter.rb, line 41
def radix_mask
  ("1"*self.class.bit_density).to_i(2)
end
search_hex() click to toggle source
# File lib/packetman/filter.rb, line 73
def search_hex
  hex_encode(map_chr{ |c| bin_chr(c) })
end
shift_and_pad(bin_str) click to toggle source
# File lib/packetman/filter.rb, line 29
def shift_and_pad(bin_str)
  #shift
  bin_str.ljust(target_bit_length, '0').
  #pad
    rjust(target_bit_length + config.offset_bits % 8, '0')
end
target_bit_length() click to toggle source
# File lib/packetman/filter.rb, line 36
def target_bit_length
  ((input.length*self.class.bit_density + config.offset_bits)/8.to_f).ceil*8 - config.offset_bits
end
to_s() click to toggle source
# File lib/packetman/filter.rb, line 96
def to_s
  clauses.map{ |clause| clause.to_s }.join(' && ')
end