Class: BinaryCodec::Amount

Inherits:
SerializedType show all
Defined in:
lib/binary-codec/types/amount.rb

Constant Summary collapse

DEFAULT_AMOUNT_HEX = 
"4000000000000000".freeze
ZERO_CURRENCY_AMOUNT_HEX = 
"8000000000000000".freeze
NATIVE_AMOUNT_BYTE_LENGTH = 
8
CURRENCY_AMOUNT_BYTE_LENGTH = 
48
MAX_IOU_PRECISION = 
16
MIN_IOU_EXPONENT = 
-96
MAX_IOU_EXPONENT = 
80
MAX_DROPS = 
BigDecimal("1e17")
MIN_XRP = 
BigDecimal("1e-6")

Instance Attribute Summary

Attributes inherited from SerializedType

#bytes

Class Method Summary collapse

Instance Method Summary collapse

Methods inherited from SerializedType

from_bytes, from_hex, from_json, get_type_by_name, #to_byte_sink, #to_bytes, #to_hex, #to_s

Constructor Details

#initialize(bytes = nil) ⇒ Amount 



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# File 'lib/binary-codec/types/amount.rb', line 22

def initialize(bytes = nil)
  if bytes.nil?
    bytes = hex_to_bytes(DEFAULT_AMOUNT_HEX)
  end

  @bytes = bytes
end

Class Method Details

.from(value) ⇒ Amount

Construct an amount from an IOU, MPT, or string amount



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# File 'lib/binary-codec/types/amount.rb', line 34

def self.from(value)
  return value if value.is_a?(Amount)

  amount = Array.new(8, 0) # Equivalent to a Uint8Array of 8 zeros

  if value.is_a?(String)
    Amount.assert_xrp_is_valid(value)

    number = value.to_i # Use to_i for equivalent BigInt handling

    int_buf = [Array.new(4, 0), Array.new(4, 0)]
    BinaryCodec.write_uint32be(int_buf[0], (number >> 32) & 0xFFFFFFFF, 0)
    BinaryCodec.write_uint32be(int_buf[1], number & 0xFFFFFFFF, 0)

    amount = int_buf.flatten

    amount[0] |= 0x40

    return Amount.new(amount)
  end

  if is_amount_object_iou?(value)
    number = BigDecimal(value[:value])
    self.assert_iou_is_valid(number)

    if number.zero?
      amount[0] |= 0x80
    else
      scale = number.frac.to_s('F').split('.').last.size
      unscaled_value = (number * (10**scale)).to_i
      int_string = unscaled_value.abs.to_s.ljust(16, '0')
      num = int_string.to_i

      int_buf = [Array.new(4, 0), Array.new(4, 0)]
      BinaryCodec.write_uint32be(int_buf[0], (num >> 32) & 0xFFFFFFFF)
      BinaryCodec.write_uint32be(int_buf[1], num & 0xFFFFFFFF)

      amount = int_buf.flatten

      amount[0] |= 0x80

      if number > 0
        amount[0] |= 0x40
      end

      exponent = number.exponent - 16
      exponent_byte = 97 + exponent
      amount[0] |= exponent_byte >> 2
      amount[1] |= (exponent_byte & 0x03) << 6
    end

    currency = Currency.from(value[:currency]).to_bytes
    issuer = AccountId.from(value[:issuer]).to_bytes

    return Amount.new(amount + currency + issuer)
  end

end

.from_parser(parser) ⇒ Amount

Read an amount from a BinaryParser



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# File 'lib/binary-codec/types/amount.rb', line 97

def self.from_parser(parser)
  is_iou = parser.peek & 0x80 != 0
  return Amount.new(parser.read(48)) if is_iou

  # The amount can be either MPT or XRP at this point
  is_mpt = parser.peek & 0x20 != 0
  num_bytes = is_mpt ? 33 : 8
  Amount.new(parser.read(num_bytes))
end

Instance Method Details

#to_json ⇒ Hash, String

The JSON representation of this Amount



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# File 'lib/binary-codec/types/amount.rb', line 110

def to_json
  if is_native?
    bytes = @bytes.dup # Duplicate the bytes to avoid mutation
    is_positive = (bytes[0] & 0x40) != 0
    sign = is_positive ? '' : '-'
    bytes[0] &= 0x3f

    msb = BinaryCodec.read_uint32be(bytes[0, 4])
    lsb = BinaryCodec.read_uint32be(bytes[4, 4])
    num = (msb << 32) | lsb

    return "#{sign}#{num}"
  end

  if is_iou?
    parser = BinaryParser.new(to_s)
    mantissa = parser.read(8)
    currency = Currency.from_parser(parser)
    issuer = AccountId.from_parser(parser)

    b1 = mantissa[0]
    b2 = mantissa[1]

    is_positive = (b1 & 0x40) != 0
    sign = is_positive ? '' : '-'
    exponent = ((b1 & 0x3f) << 2) + ((b2 & 0xff) >> 6) - 97

    mantissa[0] = 0
    mantissa[1] &= 0x3f
    value = BigDecimal("#{sign}#{bytes_to_hex(mantissa).to_i(16)}") * BigDecimal("1e#{exponent}")
    self.class.assert_iou_is_valid(value)

    return {
      "value" => value.to_s('F'),
      "currency" => currency.to_json,
      "issuer" => issuer.to_json
    }.to_s
  end

  if is_mpt?
    parser = BinaryParser.new(to_s)
    leading_byte = parser.read(1)
    amount = parser.read(8)
    mpt_id = Hash192.from_parser(parser)

    is_positive = (leading_byte[0] & 0x40) != 0
    sign = is_positive ? '' : '-'

    msb = read_uint32be(amount[0, 4])
    lsb = read_uint32be(amount[4, 4])
    num = (msb << 32) | lsb

    return {
      value: "#{sign}#{num}",
      mpt_issuance_id: mpt_id.to_s
    }.to_s
  end

  raise 'Invalid amount to construct JSON'
end