Contents

module Bytepack
  class Basic < Struct
    
    class << self
      def preprocess(bytes, offset, format, length = 0)
        format += length.to_s if !(self <= FixedSize) && length > 1
        format = offset > 0 ? "@#{offset}#{format}" : format
        offset += length
        [offset, format]
      end
      
      def intToBytes(length, value)
        bitlength = length*8
        div = nil
        x = [[32, 'N'], [16, 'n'], [8, 'C']].find {|a| (div = bitlength.divmod(a[0])) && div[0] != 0 && div[1] == 0}
        b = (2**x[0])-1
        ([value & b] + (2..div[0]).map {|i| (value >> x[0]*(i-1)) & b}).reverse.pack(x[1]*div[0])
      end
    
      def bytesToInt(length, bytes, offset = 0) # bytes = array of 8-bit unsigned
        format = "C#{length}"
        format.prepend("@#{offset}") if offset > 0
        bytes = bytes.unpack(format)
        most_significant_bit = 1 << 7
        negative = (bytes[0] & most_significant_bit) != 0
        unscaled_value = -(bytes[0] & most_significant_bit) << length*8-8
        # Clear the highest bit
        # Unleash the powers of the butterfly
        bytes[0] &= ~most_significant_bit
        # Get the 2's complement
        (0..length-1).each {|i| unscaled_value += bytes[i] << ((length-1 - i) * 8)}
        unscaled_value * -1 if negative
        unscaled_value
      end
    end
    
  end
end

require 'bytepack/basic/fixed_size'
require 'bytepack/basic/varbinary'
require 'bytepack/basic/string'
require 'bytepack/basic/symbol'

Version data entries

1 entries across 1 versions & 1 rubygems

Version	Path
bytepack-0.0.1	lib/bytepack/basic.rb