Class: BERT::Decode

Inherits:
Object
  • Object
show all
Includes:
Types
Defined in:
lib/bert/decode.rb

Constant Summary

Constants included from Types

Types::ATOM, Types::BIN, Types::FLOAT, Types::FUN, Types::INT, Types::LARGE_BIGNUM, Types::LARGE_TUPLE, Types::LIST, Types::MAGIC, Types::MAX_INT, Types::MIN_INT, Types::NEW_FUN, Types::NIL, Types::SMALL_BIGNUM, Types::SMALL_INT, Types::SMALL_TUPLE, Types::STRING

Instance Attribute Summary collapse

Class Method Summary collapse

Instance Method Summary collapse

Constructor Details

#initialize(ins) ⇒ Decode

Returns a new instance of Decode.



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# File 'lib/bert/decode.rb', line 14

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

Instance Attribute Details

#in ⇒ Object

Returns the value of attribute in.



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# File 'lib/bert/decode.rb', line 3

def in
  @in
end

Class Method Details

.decode(string) ⇒ Object 



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# File 'lib/bert/decode.rb', line 10

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

.impl ⇒ Object 



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# File 'lib/bert/decode.rb', line 6

def self.impl
  'Ruby'
end

Instance Method Details

#fail(str) ⇒ Object 



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# File 'lib/bert/decode.rb', line 244

def fail(str)
  raise str
end

#peek(length) ⇒ Object 



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# File 'lib/bert/decode.rb', line 60

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/bert/decode.rb', line 70

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

#peek_2 ⇒ Object 



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# File 'lib/bert/decode.rb', line 74

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

#read(length) ⇒ Object 



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# File 'lib/bert/decode.rb', line 43

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/bert/decode.rb', line 78

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

#read_2 ⇒ Object 



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# File 'lib/bert/decode.rb', line 82

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

#read_4 ⇒ Object 



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# File 'lib/bert/decode.rb', line 86

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

#read_any ⇒ Object 



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# File 'lib/bert/decode.rb', line 19

def read_any
  fail("Bad Magic") unless read_1 == MAGIC
  read_any_raw
end

#read_any_raw ⇒ Object 



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# File 'lib/bert/decode.rb', line 24

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 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/bert/decode.rb', line 94

def read_atom
  fail("Invalid Type, not an atom") unless read_1 == ATOM
  length = read_2
  a = read_string(length)
  case a
    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/bert/decode.rb', line 238

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

#read_complex_type(arity) ⇒ Object 



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# File 'lib/bert/decode.rb', line 177

def read_complex_type(arity)
  case read_any_raw
    when :nil
      nil
    when :true
      true
    when :false
      false
    when :time
      Time.at(read_any_raw * 1_000_000 + read_any_raw, read_any_raw)
    when :regex
      source = read_any_raw
      opts = read_any_raw
      options = 0
      options |= Regexp::EXTENDED if opts.include?(:extended)
      options |= Regexp::IGNORECASE if opts.include?(:caseless)
      options |= Regexp::MULTILINE if opts.include?(:multiline)
      Regexp.new(source, options)
    when :dict
      read_dict
    else
      nil
  end
end

#read_dict ⇒ Object 



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# File 'lib/bert/decode.rb', line 202

def read_dict
  type = read_1
  fail("Invalid dict spec, not an erlang list") unless [LIST, NIL].include?(type)
  if type == LIST
    length = read_4
  else
    length = 0
  end
  hash = {}
  length.times do |i|
    pair = read_any_raw
    hash[pair[0]] = pair[1]
  end
  read_1 if type == LIST
  hash
end

#read_erl_string ⇒ Object 



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# File 'lib/bert/decode.rb', line 224

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

#read_float ⇒ Object 



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# File 'lib/bert/decode.rb', line 145

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/bert/decode.rb', line 111

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/bert/decode.rb', line 132

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/bert/decode.rb', line 156

def read_large_tuple
  fail("Invalid Type, not a small tuple") unless read_1 == LARGE_TUPLE
  read_tuple(read_4)
end

#read_list ⇒ Object 



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# File 'lib/bert/decode.rb', line 230

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
  list
end

#read_nil ⇒ Object 



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# File 'lib/bert/decode.rb', line 219

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

#read_small_bignum ⇒ Object 



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# File 'lib/bert/decode.rb', line 119

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/bert/decode.rb', line 106

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/bert/decode.rb', line 151

def read_small_tuple
  fail("Invalid Type, not a small tuple") unless read_1 == SMALL_TUPLE
  read_tuple(read_1)
end

#read_string(length) ⇒ Object 



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# File 'lib/bert/decode.rb', line 90

def read_string(length)
  read(length)
end

#read_tuple(arity) ⇒ Object 



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# File 'lib/bert/decode.rb', line 161

def read_tuple(arity)
  if arity > 0
    tag = read_any_raw
    if tag == :bert
      read_complex_type(arity)
    else
      tuple = Tuple.new(arity)
      tuple[0] = tag
      (arity - 1).times { |i| tuple[i + 1] = read_any_raw }
      tuple
    end
  else
    Tuple.new
  end
end