Module: Eth::Abi::Decoder

Extended by:
Decoder
Included in:
Decoder
Defined in:
lib/eth/abi/decoder.rb

Overview

Provides a utility module to assist decoding ABIs.

Class Method Summary collapse

Instance Method Summary collapse

Class Method Details

.primitive_type(type, data) ⇒ String

Decodes primitive types.

Parameters:

  • type (Eth::Abi::Type) —

    type to be decoded.

  • data (String) —

    encoded primitive type data string.

Returns:

  • (String) —

    the decoded data for the type.

Raises:



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# File 'lib/eth/abi/decoder.rb', line 129

def primitive_type(type, data)
  case type.base_type
  when "address"

    # decoded address with 0x-prefix
    Address.new(Util.bin_to_hex data[12..-1]).to_s.downcase
  when "string", "bytes"
    if type.sub_type.empty?
      size = Util.deserialize_big_endian_to_int data[0, 32]

      # decoded dynamic-sized array
      decoded = data[32..-1][0, size]
      decoded.force_encoding(Encoding::UTF_8)
      decoded
    else

      # decoded static-sized array
      data[0, type.sub_type.to_i]
    end
  when "hash"

    # decoded hash
    data[(32 - type.sub_type.to_i), type.sub_type.to_i]
  when "uint"

    # decoded unsigned integer
    Util.deserialize_big_endian_to_int data
  when "int"
    u = Util.deserialize_big_endian_to_int data
    i = u >= 2 ** (type.sub_type.to_i - 1) ? (u - 2 ** 256) : u

    # decoded integer
    i
  when "ureal", "ufixed"
    high, low = type.sub_type.split("x").map(&:to_i)

    # decoded unsigned fixed point numeric
    Util.deserialize_big_endian_to_int(data) * 1.0 / 2 ** low
  when "real", "fixed"
    high, low = type.sub_type.split("x").map(&:to_i)
    u = Util.deserialize_big_endian_to_int data
    i = u >= 2 ** (high + low - 1) ? (u - 2 ** (high + low)) : u

    # decoded fixed point numeric
    i * 1.0 / 2 ** low
  when "bool"

    # decoded boolean
    data[-1] == Constant::BYTE_ONE
  else
    raise DecodingError, "Unknown primitive type: #{type.base_type}"
  end
end

.type(type, arg) ⇒ String

Decodes a specific value, either static or dynamic.

Parameters:

  • type (Eth::Abi::Type) —

    type to be decoded.

  • arg (String) —

    encoded type data string.

Returns:

  • (String) —

    the decoded data for the type.

Raises:



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# File 'lib/eth/abi/decoder.rb', line 33

def type(type, arg)
  if %w(string bytes).include?(type.base_type) and type.sub_type.empty?
    # Case: decoding a string/bytes
    if type.dimensions.empty?
      l = Util.deserialize_big_endian_to_int arg[0, 32]
      data = arg[32..-1]
      raise DecodingError, "Wrong data size for string/bytes object" unless data.size == Util.ceil32(l)

      # decoded strings and bytes
      data[0, l]
      # Case: decoding array of string/bytes
    else
      l = Util.deserialize_big_endian_to_int arg[0, 32]
      raise DecodingError, "Wrong data size for dynamic array" unless arg.size >= 32 + 32 * l

      # Decode each element of the array
      (1..l).map do |i|
        pointer = Util.deserialize_big_endian_to_int arg[i * 32, 32] # Pointer to the size of the array's element
        raise DecodingError, "Offset out of bounds" if pointer < 32 * l || pointer > arg.size - 64
        data_l = Util.deserialize_big_endian_to_int arg[32 + pointer, 32] # length of the element
        raise DecodingError, "Offset out of bounds" if pointer + 32 + Util.ceil32(data_l) > arg.size
        type(Type.parse(type.base_type), arg[pointer + 32, Util.ceil32(data_l) + 32])
      end
    end
  elsif type.base_type == "tuple" && type.dimensions.empty?
    offset = 0
    result = []
    raise DecodingError, "Cannot decode tuples without known components" if type.components.nil?
    type.components.each_with_index do |c, i|
      if c.dynamic?
        pointer = Util.deserialize_big_endian_to_int arg[offset, 32]
        next_offset = if i + 1 < type.components.size
            Util.deserialize_big_endian_to_int arg[offset + 32, 32]
          else
            arg.size
          end
        raise DecodingError, "Offset out of bounds" if pointer > arg.size || next_offset > arg.size || next_offset < pointer
        result << type(c, arg[pointer, next_offset - pointer])
        offset += 32
      else
        size = c.size
        raise DecodingError, "Offset out of bounds" if offset + size > arg.size
        result << type(c, arg[offset, size])
        offset += size
      end
    end
    result
  elsif type.dynamic?
    l = Util.deserialize_big_endian_to_int arg[0, 32]
    nested_sub = type.nested_sub

    if nested_sub.dynamic?
      raise DecodingError, "Wrong data size for dynamic array" unless arg.size >= 32 + 32 * l
      offsets = (0...l).map do |i|
        off = Util.deserialize_big_endian_to_int arg[32 + 32 * i, 32]
        raise DecodingError, "Offset out of bounds" if off < 32 * l || off > arg.size - 64
        off
      end
      offsets.map { |off| type(nested_sub, arg[32 + off..]) }
    else
      raise DecodingError, "Wrong data size for dynamic array" unless arg.size >= 32 + nested_sub.size * l
      # decoded dynamic-sized arrays with static sub-types
      (0...l).map { |i| type(nested_sub, arg[32 + nested_sub.size * i, nested_sub.size]) }
    end
  elsif !type.dimensions.empty?
    l = type.dimensions.first
    nested_sub = type.nested_sub

    if nested_sub.dynamic?
      raise DecodingError, "Wrong data size for static array" unless arg.size >= 32 * l
      offsets = (0...l).map do |i|
        off = Util.deserialize_big_endian_to_int arg[32 * i, 32]
        raise DecodingError, "Offset out of bounds" if off < 32 * l || off > arg.size - 32
        off
      end
      offsets.each_with_index.map do |off, i|
        size = (i + 1 < offsets.length ? offsets[i + 1] : arg.size) - off
        type(nested_sub, arg[off, size])
      end
    else
      # decoded static-size arrays with static sub-types
      (0...l).map { |i| type(nested_sub, arg[nested_sub.size * i, nested_sub.size]) }
    end
  else

    # decoded primitive types
    primitive_type type, arg
  end
end

Instance Method Details

#primitive_type(type, data) ⇒ String

Decodes primitive types.

Parameters:

  • type (Eth::Abi::Type) —

    type to be decoded.

  • data (String) —

    encoded primitive type data string.

Returns:

  • (String) —

    the decoded data for the type.

Raises:



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# File 'lib/eth/abi/decoder.rb', line 129

def primitive_type(type, data)
  case type.base_type
  when "address"

    # decoded address with 0x-prefix
    Address.new(Util.bin_to_hex data[12..-1]).to_s.downcase
  when "string", "bytes"
    if type.sub_type.empty?
      size = Util.deserialize_big_endian_to_int data[0, 32]

      # decoded dynamic-sized array
      decoded = data[32..-1][0, size]
      decoded.force_encoding(Encoding::UTF_8)
      decoded
    else

      # decoded static-sized array
      data[0, type.sub_type.to_i]
    end
  when "hash"

    # decoded hash
    data[(32 - type.sub_type.to_i), type.sub_type.to_i]
  when "uint"

    # decoded unsigned integer
    Util.deserialize_big_endian_to_int data
  when "int"
    u = Util.deserialize_big_endian_to_int data
    i = u >= 2 ** (type.sub_type.to_i - 1) ? (u - 2 ** 256) : u

    # decoded integer
    i
  when "ureal", "ufixed"
    high, low = type.sub_type.split("x").map(&:to_i)

    # decoded unsigned fixed point numeric
    Util.deserialize_big_endian_to_int(data) * 1.0 / 2 ** low
  when "real", "fixed"
    high, low = type.sub_type.split("x").map(&:to_i)
    u = Util.deserialize_big_endian_to_int data
    i = u >= 2 ** (high + low - 1) ? (u - 2 ** (high + low)) : u

    # decoded fixed point numeric
    i * 1.0 / 2 ** low
  when "bool"

    # decoded boolean
    data[-1] == Constant::BYTE_ONE
  else
    raise DecodingError, "Unknown primitive type: #{type.base_type}"
  end
end

#type(type, arg) ⇒ String

Decodes a specific value, either static or dynamic.

Parameters:

  • type (Eth::Abi::Type) —

    type to be decoded.

  • arg (String) —

    encoded type data string.

Returns:

  • (String) —

    the decoded data for the type.

Raises:



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# File 'lib/eth/abi/decoder.rb', line 33

def type(type, arg)
  if %w(string bytes).include?(type.base_type) and type.sub_type.empty?
    # Case: decoding a string/bytes
    if type.dimensions.empty?
      l = Util.deserialize_big_endian_to_int arg[0, 32]
      data = arg[32..-1]
      raise DecodingError, "Wrong data size for string/bytes object" unless data.size == Util.ceil32(l)

      # decoded strings and bytes
      data[0, l]
      # Case: decoding array of string/bytes
    else
      l = Util.deserialize_big_endian_to_int arg[0, 32]
      raise DecodingError, "Wrong data size for dynamic array" unless arg.size >= 32 + 32 * l

      # Decode each element of the array
      (1..l).map do |i|
        pointer = Util.deserialize_big_endian_to_int arg[i * 32, 32] # Pointer to the size of the array's element
        raise DecodingError, "Offset out of bounds" if pointer < 32 * l || pointer > arg.size - 64
        data_l = Util.deserialize_big_endian_to_int arg[32 + pointer, 32] # length of the element
        raise DecodingError, "Offset out of bounds" if pointer + 32 + Util.ceil32(data_l) > arg.size
        type(Type.parse(type.base_type), arg[pointer + 32, Util.ceil32(data_l) + 32])
      end
    end
  elsif type.base_type == "tuple" && type.dimensions.empty?
    offset = 0
    result = []
    raise DecodingError, "Cannot decode tuples without known components" if type.components.nil?
    type.components.each_with_index do |c, i|
      if c.dynamic?
        pointer = Util.deserialize_big_endian_to_int arg[offset, 32]
        next_offset = if i + 1 < type.components.size
            Util.deserialize_big_endian_to_int arg[offset + 32, 32]
          else
            arg.size
          end
        raise DecodingError, "Offset out of bounds" if pointer > arg.size || next_offset > arg.size || next_offset < pointer
        result << type(c, arg[pointer, next_offset - pointer])
        offset += 32
      else
        size = c.size
        raise DecodingError, "Offset out of bounds" if offset + size > arg.size
        result << type(c, arg[offset, size])
        offset += size
      end
    end
    result
  elsif type.dynamic?
    l = Util.deserialize_big_endian_to_int arg[0, 32]
    nested_sub = type.nested_sub

    if nested_sub.dynamic?
      raise DecodingError, "Wrong data size for dynamic array" unless arg.size >= 32 + 32 * l
      offsets = (0...l).map do |i|
        off = Util.deserialize_big_endian_to_int arg[32 + 32 * i, 32]
        raise DecodingError, "Offset out of bounds" if off < 32 * l || off > arg.size - 64
        off
      end
      offsets.map { |off| type(nested_sub, arg[32 + off..]) }
    else
      raise DecodingError, "Wrong data size for dynamic array" unless arg.size >= 32 + nested_sub.size * l
      # decoded dynamic-sized arrays with static sub-types
      (0...l).map { |i| type(nested_sub, arg[32 + nested_sub.size * i, nested_sub.size]) }
    end
  elsif !type.dimensions.empty?
    l = type.dimensions.first
    nested_sub = type.nested_sub

    if nested_sub.dynamic?
      raise DecodingError, "Wrong data size for static array" unless arg.size >= 32 * l
      offsets = (0...l).map do |i|
        off = Util.deserialize_big_endian_to_int arg[32 * i, 32]
        raise DecodingError, "Offset out of bounds" if off < 32 * l || off > arg.size - 32
        off
      end
      offsets.each_with_index.map do |off, i|
        size = (i + 1 < offsets.length ? offsets[i + 1] : arg.size) - off
        type(nested_sub, arg[off, size])
      end
    else
      # decoded static-size arrays with static sub-types
      (0...l).map { |i| type(nested_sub, arg[nested_sub.size * i, nested_sub.size]) }
    end
  else

    # decoded primitive types
    primitive_type type, arg
  end
end