Class: ABI::Codec

Inherits:
Object
  • Object
show all
Defined in:
lib/abicoder/codec.rb

Overview

Contract ABI encoding and decoding.

See Also:

Defined Under Namespace

Classes: DecodingError, EncodingError, ValueError, ValueOutOfBounds

Instance Method Summary collapse

Instance Method Details

#decode_abi(types, data, raise_errors = false) ⇒ Object

Decodes multiple arguments using the head/tail mechanism.



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# File 'lib/abicoder/codec.rb', line 169

def decode_abi( types, data, raise_errors = false )
  ## for convenience check if types is a String
  ##   otherwise assume ABI::Type already
  types = types.map { |type| type.is_a?( String ) ? Type.parse( type ) : type }

  outputs = [nil] * types.size
  start_positions = [nil] * types.size + [data.size]

  # TODO: refactor, a reverse iteration will be better
  pos = 0
  types.each_with_index do |t, i|
    # If a type is static, grab the data directly, otherwise record its
    # start position
    if t.dynamic?

      if raise_errors && pos>data.size-1
        raise DecodingError, "Position out of bounds #{pos}>#{data.size-1}"
      end

      start_positions[i] = Utils.big_endian_to_int(data[pos, 32])

      if raise_errors && start_positions[i]>data.size-1
        raise DecodingError, "Start position out of bounds #{start_positions[i]}>#{data.size-1}"
      end

      j = i - 1
      while j >= 0 && start_positions[j].nil?
        start_positions[j] = start_positions[i]
        j -= 1
      end

      pos += 32
    else
      outputs[i] = zero_padding data, pos, t.size, start_positions
      pos += t.size
    end
  end

  # We add a start position equal to the length of the entire data for
  # convenience.
  j = types.size - 1
  while j >= 0 && start_positions[j].nil?
    start_positions[j] = start_positions[types.size]
    j -= 1
  end

  if raise_errors && pos > data.size
    raise DecodingError, "Not enough data for head"
  end


  types.each_with_index do |t, i|
    if t.dynamic?
      offset, next_offset = start_positions[i, 2]
      if offset<=data.size && next_offset<=data.size
        outputs[i] = data[offset...next_offset]
      end
    end
  end

  if raise_errors && outputs.include?(nil)
    raise DecodingError, "Not all data can be parsed"
  end

  types.zip(outputs).map {|(type, out)| decode_type(type, out) }
end

#decode_primitive_type(type, data) ⇒ Object 



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# File 'lib/abicoder/codec.rb', line 297

def decode_primitive_type(type, data)
  case type.base
  when 'address'
    Utils.encode_hex data[12..-1]
  when 'string', 'bytes'
    if type.sub.empty? # dynamic
      if data.length==32
        data[0..32]
      else
        size = Utils.big_endian_to_int data[0,32]
        data[32..-1][0,size]
      end
    else # fixed
      data[0, type.sub.to_i]
    end
  when 'hash'
    data[(32 - type.sub.to_i), type.sub.to_i]
  when 'uint'
    Utils.big_endian_to_int data
  when 'int'
    u = Utils.big_endian_to_int data
    u >= 2**(type.sub.to_i-1) ? (u - 2**type.sub.to_i) : u
  when 'ufixed'
    high, low = type.sub.split('x').map(&:to_i)
    Utils.big_endian_to_int(data) * 1.0 / 2**low
  when 'fixed'
    high, low = type.sub.split('x').map(&:to_i)
    u = Utils.big_endian_to_int data
    i = u >= 2**(high+low-1) ? (u - 2**(high+low)) : u
    i * 1.0 / 2**low
  when 'bool'
    data[-1] == BYTE_ONE
  else
    raise DecodingError, "Unknown primitive type: #{type.base}"
  end
end

#decode_type(type, arg) ⇒ Object 



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# File 'lib/abicoder/codec.rb', line 253

def decode_type(type, arg)
  return nil if arg.nil? || arg.empty?
  if type.kind_of?( Tuple ) && type.dims.empty?
    arg ? decode_abi(type.types, arg) : []
  elsif %w(string bytes).include?(type.base) && type.sub.empty?
    l = Utils.big_endian_to_int arg[0,32]
    data = arg[32..-1]
    data[0, l]
  elsif !type.dims.empty? && (l = type.dims.last)>0 # static-sized arrays
    subtype = type.subtype
    if subtype.dynamic?
      start_positions = (0...l).map {|i| Utils.big_endian_to_int(arg[32*i, 32]) }
      start_positions.push arg.size

      outputs = (0...l).map {|i| arg[start_positions[i]...start_positions[i+1]] }

      outputs.map {|out| decode_type(subtype, out) }
    else
      (0...l).map {|i| decode_type(subtype, arg[subtype.size*i, subtype.size]) }
    end

  elsif type.dynamic?
    l = Utils.big_endian_to_int arg[0,32]
    raise DecodingError, "Too long length: #{l}" if l>100000
    subtype = type.subtype

    if subtype.dynamic?
      raise DecodingError, "Not enough data for head" unless arg.size >= 32 + 32*l

      start_positions = (1..l).map {|i| 32+Utils.big_endian_to_int(arg[32*i, 32]) }
      start_positions.push arg.size

      outputs = (0...l).map {|i| arg[start_positions[i]...start_positions[i+1]] }

      outputs.map {|out| decode_type(subtype, out) }
    else
      (0...l).map {|i| decode_type(subtype, arg[32 + subtype.size*i, subtype.size]) }
    end

  else
    decode_primitive_type type, arg
  end
end

#decode_typed_data(type_name, data) ⇒ Object 



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# File 'lib/abicoder/codec.rb', line 249

def decode_typed_data( type_name, data )
  decode_primitive_type Type.parse(type_name), data
end

#encode_abi(types, args) ⇒ Object

Encodes multiple arguments using the head/tail mechanism.



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# File 'lib/abicoder/codec.rb', line 18

def encode_abi(types, args)
  ## for convenience check if types is a String
  ##   otherwise assume ABI::Type already
  types = types.map { |type| type.is_a?( String ) ? Type.parse( type ) : type }

  head_size = (0...args.size)
    .map {|i| types[i].size || 32 }
    .reduce(0, &:+)

  head, tail = '', ''
  args.each_with_index do |arg, i|
    if types[i].dynamic?
      head += encode_type(Type.size_type, head_size + tail.size)
      tail += encode_type(types[i], arg)
    else
      head += encode_type(types[i], arg)
    end
  end

  "#{head}#{tail}"
end

#encode_primitive_type(type, arg) ⇒ Object 



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# File 'lib/abicoder/codec.rb', line 82

def encode_primitive_type(type, arg)
  case type.base
  when 'uint'
    begin
      real_size = type.sub.to_i
      i = get_uint arg

      raise ValueOutOfBounds, arg unless i >= 0 && i < 2**real_size
      Utils.zpad_int i
    rescue EncodingError
      raise ValueOutOfBounds, arg
    end
  when 'bool'
    raise ArgumentError, "arg is not bool: #{arg}" unless arg.instance_of?(TrueClass) || arg.instance_of?(FalseClass)
    Utils.zpad_int(arg ? 1 : 0)
  when 'int'
    begin
      real_size = type.sub.to_i
      i = get_int arg

      raise ValueOutOfBounds, arg unless i >= -2**(real_size-1) && i < 2**(real_size-1)
      Utils.zpad_int(i % 2**type.sub.to_i)
    rescue EncodingError
      raise ValueOutOfBounds, arg
    end
  when 'string'
    if arg.encoding.name == 'UTF-8'
      arg = arg.b
    else
      begin
        arg.unpack('U*')
      rescue ArgumentError
        raise ValueError, "string must be UTF-8 encoded"
      end
    end

    if type.sub.empty? # variable length type
      raise ValueOutOfBounds, "Integer invalid or out of range: #{arg.size}" if arg.size >= TT256
      size = Utils.zpad_int arg.size
      value = Utils.rpad arg, BYTE_ZERO, Utils.ceil32(arg.size)
      "#{size}#{value}"
    else # fixed length type
      sub = type.sub.to_i
      raise ValueOutOfBounds, "invalid string length #{sub}" if arg.size > sub
      raise ValueOutOfBounds, "invalid string length #{sub}" if sub < 0 || sub > 32
      Utils.rpad(arg, BYTE_ZERO, 32)
    end
  when 'bytes'
    raise EncodingError, "Expecting string: #{arg}" unless arg.instance_of?(String)
    arg = arg.b

    if type.sub.empty? # variable length type
      raise ValueOutOfBounds, "Integer invalid or out of range: #{arg.size}" if arg.size >= TT256
      size = Utils.zpad_int arg.size
      value = Utils.rpad arg, BYTE_ZERO, Utils.ceil32(arg.size)
      "#{size}#{value}"
    else # fixed length type
      sub = type.sub.to_i
      raise ValueOutOfBounds, "invalid bytes length #{sub}" if arg.size > sub
      raise ValueOutOfBounds, "invalid bytes length #{sub}" if sub < 0 || sub > 32
      Utils.rpad(arg, BYTE_ZERO, 32)
    end
  when 'address'
    if arg.is_a?(Integer)
      Utils.zpad_int arg
    elsif arg.size == 20
      Utils.zpad arg, 32
    elsif arg.size == 40
      Utils.zpad_hex arg
    elsif arg.size == 42 && arg[0,2] == '0x'
      Utils.zpad_hex arg[2..-1]
    else
      raise EncodingError, "Could not parse address: #{arg}"
    end
  else
    raise EncodingError, "Unhandled type: #{type.base} #{type.sub}"
  end
end

#encode_type(type, arg) ⇒ String

Encodes a single value (static or dynamic).

Parameters:

  • type (ABI::Type) —

    value type

  • arg (Object) —

    value

Returns:

  • (String) —

    encoded bytes



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# File 'lib/abicoder/codec.rb', line 48

def encode_type(type, arg)
  if ['string', 'bytes'].include?(type.base) && type.sub.empty?
    encode_primitive_type type, arg
  elsif type.dynamic?
    raise ArgumentError, "arg must be an array" unless arg.instance_of?(Array)

    head, tail = '', ''
    if type.dims.last == 0
      head += encode_type(Type.size_type, arg.size)
    else
      raise ArgumentError, "Wrong array size: found #{arg.size}, expecting #{type.dims.last}" unless arg.size == type.dims.last
    end

    sub_type = type.subtype
    sub_size = type.subtype.size
    arg.size.times do |i|
      if sub_size.nil?
        head += encode_type(Type.size_type, 32*arg.size + tail.size)
        tail += encode_type(sub_type, arg[i])
      else
        head += encode_type(sub_type, arg[i])
      end
    end

    "#{head}#{tail}"
  else # static type
    if type.dims.empty?
      encode_primitive_type type, arg
    else
      arg.map {|x| encode_type(type.subtype, x) }.join
    end
  end
end

#min_data_size(types) ⇒ Object 



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# File 'lib/abicoder/codec.rb', line 162

def min_data_size( types )
  types.size*32
end

#zero_padding(data, pos, count, start_positions) ⇒ Object 



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# File 'lib/abicoder/codec.rb', line 237

def zero_padding( data, pos, count, start_positions )
  if pos >= data.size
    start_positions[start_positions.size-1] += count
    "\x00"*count
  elsif pos + count > data.size
    start_positions[start_positions.size-1] += ( count - (data.size-pos))
    data[pos,data.size-pos] + "\x00"*( count - (data.size-pos))
  else
    data[pos, count]
  end
end