Class: Erlectricity::Decoder

Inherits:
Object
  • Object
show all
Includes:
External::Types
Defined in:
lib/erlectricity/decoder.rb,
ext/decoder.c

Constant Summary

Constants included from External::Types

External::Types::ATOM, External::Types::BIN, External::Types::FLOAT, External::Types::FUN, External::Types::INT, External::Types::LARGE_BIGNUM, External::Types::LARGE_TUPLE, External::Types::LIST, External::Types::NEW_FUN, External::Types::NEW_REF, External::Types::NIL, External::Types::PID, External::Types::PORT, External::Types::REF, External::Types::SMALL_BIGNUM, External::Types::SMALL_INT, External::Types::SMALL_TUPLE, External::Types::STRING

Instance Attribute Summary collapse

Class Method Summary collapse

Instance Method Summary collapse

Constructor Details

#initialize(ins) ⇒ Decoder

Returns a new instance of Decoder.



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# File 'lib/erlectricity/decoder.rb', line 10

def initialize(ins)
  @in = ins
  @peeked = ""
end

Instance Attribute Details

#in ⇒ Object

Returns the value of attribute in.



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# File 'lib/erlectricity/decoder.rb', line 3

def in
  @in
end

Class Method Details

.decode(rString) ⇒ Object 



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# File 'ext/decoder.c', line 381

def self.decode(string)
  new(StringIO.new(string)).read_any
end

Instance Method Details

#fail(str) ⇒ Object

Raises:



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# File 'lib/erlectricity/decoder.rb', line 208

def fail(str)
  raise DecodeError, str
end

#peek(length) ⇒ Object 



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# File 'lib/erlectricity/decoder.rb', line 58

def peek(length)
  if length <= @peeked.length
    @peeked[0...length]
  else
    read_bytes = @in.read(length - @peeked.length)
    @peeked << read_bytes if read_bytes
    @peeked
  end
end

#peek_1 ⇒ Object 



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# File 'lib/erlectricity/decoder.rb', line 68

def peek_1
  peek(1).unpack("C").first
end

#peek_2 ⇒ Object 



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# File 'lib/erlectricity/decoder.rb', line 72

def peek_2
  peek(2).unpack("n").first
end

#read(length) ⇒ Object 



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# File 'lib/erlectricity/decoder.rb', line 41

def read(length)
  if length < @peeked.length
    result = @peeked[0...length]
    @peeked = @peeked[length..-1]
    length = 0
  else
    result = @peeked
    @peeked = ''
    length -= result.length
  end

  if length > 0
    result << @in.read(length)
  end
  result
end

#read_1 ⇒ Object 



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# File 'lib/erlectricity/decoder.rb', line 76

def read_1
  read(1).unpack("C").first
end

#read_2 ⇒ Object 



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# File 'lib/erlectricity/decoder.rb', line 80

def read_2
  read(2).unpack("n").first
end

#read_4 ⇒ Object 



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# File 'lib/erlectricity/decoder.rb', line 84

def read_4
  read(4).unpack("N").first
end

#read_any ⇒ Object 



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# File 'lib/erlectricity/decoder.rb', line 15

def read_any
  fail("Bad Magic") unless read_1 == Erlectricity::External::VERSION
  read_any_raw
end

#read_any_raw ⇒ Object 



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# File 'lib/erlectricity/decoder.rb', line 20

def read_any_raw
  case peek_1
    when ATOM then read_atom
    when SMALL_INT then read_small_int
    when INT then read_int
    when SMALL_BIGNUM then read_small_bignum
    when LARGE_BIGNUM then read_large_bignum
    when FLOAT then read_float
    when NEW_REF then read_new_reference
    when PID then read_pid
    when SMALL_TUPLE then read_small_tuple
    when LARGE_TUPLE then read_large_tuple
    when NIL then read_nil
    when STRING then read_erl_string
    when LIST then read_list
    when BIN then read_bin
    else
      fail("Unknown term tag: #{peek_1}")
  end
end

#read_atom ⇒ Object 



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# File 'lib/erlectricity/decoder.rb', line 92

def read_atom
  fail("Invalid Type, not an atom") unless read_1 == ATOM
  length = read_2
  a = read_string(length)
  case a
    when "true"
      true
    when "false"
      false
    when ""
      Marshal.load("\004\b:\005") # Workaround for inability to do ''.to_sym
    else
      a.to_sym
  end
end

#read_bin ⇒ Object 



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# File 'lib/erlectricity/decoder.rb', line 202

def read_bin
  fail("Invalid Type, not an erlang binary") unless read_1 == BIN
  length = read_4
  read_string(length)
end

#read_erl_string ⇒ Object 



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# File 'lib/erlectricity/decoder.rb', line 188

def read_erl_string
  fail("Invalid Type, not an erlang string") unless read_1 == STRING
  length = read_2
  Erlectricity::List.new(read_string(length).unpack('C' * length))
end

#read_float ⇒ Object 



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# File 'lib/erlectricity/decoder.rb', line 147

def read_float
  fail("Invalid Type, not a float") unless read_1 == FLOAT
  string_value = read_string(31)
  result = string_value.to_f
end

#read_int ⇒ Object 



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# File 'lib/erlectricity/decoder.rb', line 113

def read_int
  fail("Invalid Type, not an int") unless read_1 == INT
  value = read_4
  negative = (value >> 31)[0] == 1
  value = (value - (1 << 32)) if negative
  value = Fixnum.induced_from(value)
end

#read_large_bignum ⇒ Object 



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# File 'lib/erlectricity/decoder.rb', line 134

def read_large_bignum
  fail("Invalid Type, not a large bignum") unless read_1 == LARGE_BIGNUM
  size = read_4
  sign = read_1
  bytes = read_string(size).unpack("C" * size)
  added = bytes.zip((0..bytes.length).to_a).inject(0) do |result, byte_index|
    byte, index = *byte_index
    value = (byte * (256 ** index))
    sign != 0 ? (result - value) : (result + value)
  end
  Bignum.induced_from(added)
end

#read_large_tuple ⇒ Object 



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# File 'lib/erlectricity/decoder.rb', line 177

def read_large_tuple
  fail("Invalid Type, not a small tuple") unless read_1 == LARGE_TUPLE
  arity = read_4
  (0...arity).map { |i| read_any_raw }
end

#read_list ⇒ Object 



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# File 'lib/erlectricity/decoder.rb', line 194

def read_list
  fail("Invalid Type, not an erlang list") unless read_1 == LIST
  length = read_4
  list = (0...length).map { |i| read_any_raw }
  read_1
  Erlectricity::List.new(list)
end

#read_new_reference ⇒ Object 



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# File 'lib/erlectricity/decoder.rb', line 153

def read_new_reference
  fail("Invalid Type, not a new-style reference") unless read_1 == NEW_REF
  size = read_2
  node = read_atom
  creation = read_1
  id = (0...size).map { |i| read_4 }
  NewReference.new(node, creation, id)
end

#read_nil ⇒ Object 



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# File 'lib/erlectricity/decoder.rb', line 183

def read_nil
  fail("Invalid Type, not a nil list") unless read_1 == NIL
  Erlectricity::List.new([])
end

#read_pid ⇒ Object 



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# File 'lib/erlectricity/decoder.rb', line 162

def read_pid
  fail("Invalid Type, not a pid") unless read_1 == PID
  node = read_atom
  id = read_4
  serial = read_4
  creation = read_1
  Pid.new(node, id, serial, creation)
end

#read_small_bignum ⇒ Object 



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# File 'lib/erlectricity/decoder.rb', line 121

def read_small_bignum
  fail("Invalid Type, not a small bignum") unless read_1 == SMALL_BIGNUM
  size = read_1
  sign = read_1
  bytes = read_string(size).unpack("C" * size)
  added = bytes.zip((0..bytes.length).to_a).inject(0) do |result, byte_index|
    byte, index = *byte_index
    value = (byte * (256 ** index))
    sign != 0 ? (result - value) : (result + value)
  end
  Bignum.induced_from(added)
end

#read_small_int ⇒ Object 



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# File 'lib/erlectricity/decoder.rb', line 108

def read_small_int
  fail("Invalid Type, not a small int") unless read_1 == SMALL_INT
  read_1
end

#read_small_tuple ⇒ Object 



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# File 'lib/erlectricity/decoder.rb', line 171

def read_small_tuple
  fail("Invalid Type, not a small tuple") unless read_1 == SMALL_TUPLE
  arity = read_1
  (0...arity).map { |i| read_any_raw }
end

#read_string(length) ⇒ Object 



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# File 'lib/erlectricity/decoder.rb', line 88

def read_string(length)
  read(length)
end