size.rb

# -*- coding: utf-8 -*-

=begin

irb(main):001:0> Size.amount( '2GB' )
=> 2000000000.0
irb(main):002:0> Size.amount( '2GiB' )
=> 2147483648.0

LICENSE : two-clause BSD

=end

module Size
  def self.amount( str )
    val = 0

    if ( str.match( /\A([0-9.]+) *([A-Z])(i)?B\z/ ) and
         unit.include?( $2 ) )
      if ( $3 == 'i' )
        val = $1.to_f * ib_unit[$2]
      else
        val = $1.to_f * si_unit[$2]
      end
    end
    
    return val
  end
  
  def self.unit
    return %w( K M G T P )
  end
  
  def self.ib_unit
    u = {}
    
    i = 10
    unit.each { |e|
      u[e] = 2 ** i
      i   += 10
    }
    
    return u
  end
  
  def self.si_unit
    u = {}
    
    i = 3
    unit.each { |e|
      u[e] = 10 ** i
      i   += 3
    }
    
    return u
  end
end