Class: ErlangBitstream

Inherits:
Object
  • Object
show all
Defined in:
lib/inspec/utils/erlang_parser.rb

Constant Summary collapse

TYPES = 
{
  "integer" => 8,
  "float" => 8 * 8,
  "utf8" => 8,
  "utf16" => 8 * 2,
  "utf32" => 8 * 4,
}.freeze

Instance Method Summary collapse

Constructor Details

#initialize ⇒ ErlangBitstream

Returns a new instance of ErlangBitstream.



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# File 'lib/inspec/utils/erlang_parser.rb', line 81

def initialize
  @data = []     # a stream of 8-bit numbers
  @cur_bits = "" # a string of binary bits 10010010...
end

Instance Method Details

#add(i) ⇒ Object 



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# File 'lib/inspec/utils/erlang_parser.rb', line 101

def add(i)
  if i[:integer].nil? && i[:string].nil?
    raise "No data provided, internal error for binary-stream processing!"
  end

  s = bit_size(i[:size], i[:type])
  unless i[:string].nil?
    str2int(i[:string].to_s, i[:type]).map { |e| add_bits(int2bits(e, 8)) }
  else
    add_int(i[:integer], s)
  end
rescue RuntimeError => e
  raise "Error processing Erlang bit string "\
        "'#{i[:string] || i[:integer]}:#{i[:size]}/#{i[:type]}'. #{e.message}"
end

#add_bits(s) ⇒ Object 



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# File 'lib/inspec/utils/erlang_parser.rb', line 136

def add_bits(s)
  b = (@cur_bits + s).scan(/.{1,8}/)
  @data += b[0..-2].map { |x| x.to_i(2) }
  @cur_bits = b.last
end

#add_int(v, size) ⇒ Object 



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# File 'lib/inspec/utils/erlang_parser.rb', line 131

def add_int(v, size)
  x = v.to_i & (2**size - 1) # only get the bits specified in size
  add_bits(int2bits(x, size))
end

#bit_size(size, type) ⇒ Object 



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# File 'lib/inspec/utils/erlang_parser.rb', line 94

def bit_size(size, type)
  raise "Cannot specify size and type at the same time." if !type.nil? && !size.nil?
  return (size || 8).to_i if type.nil?

  TYPES[type] || raise("Cannot handle binary-stream type #{type}")
end

#int2bits(i, len) ⇒ Object 



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# File 'lib/inspec/utils/erlang_parser.rb', line 127

def int2bits(i, len)
  format("%0#{len}b", i)
end

#str2int(s, type) ⇒ Object 



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# File 'lib/inspec/utils/erlang_parser.rb', line 117

def str2int(s, type)
  case type
  when "utf8" then s.encode("utf-8").unpack("C*")
  when "utf16" then s.encode("utf-16").unpack("C*").drop(2)
  when "utf32" then s.encode("utf-32").unpack("C*").drop(4)
  when "integer", "float" then raise "Cannot handle bit string as type #{type}"
  else s.split("").map { |x| x.ord & 0xff }
  end
end

#value(encoding = "utf-8") ⇒ Object 



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# File 'lib/inspec/utils/erlang_parser.rb', line 142

def value(encoding = "utf-8")
  # fill in the rest
  rest = "0" * (8 - @cur_bits.length) + @cur_bits
  arr = @data + [rest.to_i(2)]
  s = arr.pack("C*")
  s.force_encoding(encoding) unless encoding.nil?
  s
end