Class: BTC::ScriptNumber

Inherits:
Object
  • Object
show all
Defined in:
lib/btcruby/script/script_number.rb

Constant Summary collapse

DEFAULT_MAX_SIZE = 
4
INT64_MAX = 
0x7fffffffffffffff
INT64_MIN = 
- 1

Class Method Summary collapse

Instance Method Summary collapse

Constructor Details

#initialize(integer: nil, boolean: nil, data: nil, hex: nil, require_minimal: true, max_size: DEFAULT_MAX_SIZE) ⇒ ScriptNumber

Returns a new instance of ScriptNumber.



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# File 'lib/btcruby/script/script_number.rb', line 17

def initialize(integer: nil, boolean: nil, data: nil, hex: nil, require_minimal: true, max_size: DEFAULT_MAX_SIZE)
  if integer
    assert(integer >= INT64_MIN && integer <= INT64_MAX, "Integer must be within int64 range")
    @integer = integer
  elsif boolean == false || boolean == true
    @integer = boolean ? 1 : 0
  elsif data || hex
    data ||= BTC.from_hex(hex)
    if data.bytesize > max_size
      raise ScriptNumberError, "script number overflow (#{data.bytesize} > #{max_size})"
    end
    if require_minimal && data.bytesize > 0
      # Check that the number is encoded with the minimum possible
      # number of bytes.
      #
      # If the most-significant-byte - excluding the sign bit - is zero
      # then we're not minimal. Note how this test also rejects the
      # negative-zero encoding, 0x80.
      if (data.bytes.last & 0x7f) == 0
        # One exception: if there's more than one byte and the most
        # significant bit of the second-most-significant-byte is set
        # it would conflict with the sign bit. An example of this case
        # is +-255, which encode to 0xff00 and 0xff80 respectively.
        # (big-endian).
        if data.bytesize <= 1 || (data.bytes[data.bytesize - 2] & 0x80) == 0
          raise ScriptNumberError, "non-minimally encoded script number"
        end
      end
    end
    @integer = self.class.decode_integer(data)
  else
    raise ArgumentError
  end
end

Class Method Details

.decode_integer(data) ⇒ Object 



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# File 'lib/btcruby/script/script_number.rb', line 124

def self.decode_integer(data)
  return 0 if data.empty?

  result = 0

  bytes = data.bytes
  bytes.each_with_index do |byte, i|
    result |= bytes[i] << 8*i
  end

  # If the input vector's most significant byte is 0x80, remove it from
  # the result's msb and return a negative.
  if (bytes.last & 0x80) != 0
    return -(result & ~(0x80 << (8 * (bytes.size - 1))));
  end
  return result
end

.encode_integer(value) ⇒ Object 



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# File 'lib/btcruby/script/script_number.rb', line 142

def self.encode_integer(value)
  return "".b if value == 0

  result = []
  negative = value < 0
  absvalue = negative ? -value : value

  while absvalue != 0
    result.push(absvalue & 0xff)
    absvalue >>= 8
  end

  # - If the most significant byte is >= 0x80 and the value is positive, push a
  # new zero-byte to make the significant byte < 0x80 again.
  #
  # - If the most significant byte is >= 0x80 and the value is negative, push a
  # new 0x80 byte that will be popped off when converting to an integral.
  #
  # - If the most significant byte is < 0x80 and the value is negative, add
  # 0x80 to it, since it will be subtracted and interpreted as a negative when
  # converting to an integral.

  if (result.last & 0x80) != 0
    result.push(negative ? 0x80 : 0)
  elsif negative
    result[result.size - 1] = result.last | 0x80
  end

  BTC.data_from_bytes(result)
end

Instance Method Details

#!=(other) ⇒ Object 



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# File 'lib/btcruby/script/script_number.rb', line 55

def !=(other); @integer != other.to_i; end

#*(other) ⇒ Object 



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# File 'lib/btcruby/script/script_number.rb', line 73

def *(other)
  # TODO: add asserts to check that result fits within int64 limits
  self.class.new(integer: @integer * other.to_i)
end

#+(other) ⇒ Object 



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# File 'lib/btcruby/script/script_number.rb', line 61

def +(other); self.class.new(integer: @integer + other.to_i); end

#+@ ⇒ Object 



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# File 'lib/btcruby/script/script_number.rb', line 64

def +@
  self
end

#-(other) ⇒ Object 



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# File 'lib/btcruby/script/script_number.rb', line 62

def -(other); self.class.new(integer: @integer - other.to_i); end

#-@ ⇒ Object 



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# File 'lib/btcruby/script/script_number.rb', line 68

def -@
  assert(@integer > INT64_MIN && @integer <= INT64_MAX, "Integer will not be within int64 range after negation")
  self.class.new(integer: -@integer)
end

#/(other) ⇒ Object 



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# File 'lib/btcruby/script/script_number.rb', line 78

def /(other)
  # TODO: add asserts to check that result fits within int64 limits
  self.class.new(integer: @integer / other.to_i)
end

#<(other) ⇒ Object 



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# File 'lib/btcruby/script/script_number.rb', line 57

def  <(other); @integer  < other.to_i; end

#<<(other) ⇒ Object 



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# File 'lib/btcruby/script/script_number.rb', line 83

def <<(other)
  # TODO: add asserts to check that result fits within int64 limits
  assert(other >= 0, "Shift amount must not be negative")
  a = @integer.abs
  r = a << other.to_i
  if a != @integer
    r = -r
  end
  self.class.new(integer: r)
end

#<=(other) ⇒ Object 



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# File 'lib/btcruby/script/script_number.rb', line 56

def <=(other); @integer <= other.to_i; end

#==(other) ⇒ Object

Operators



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# File 'lib/btcruby/script/script_number.rb', line 54

def ==(other); @integer == other.to_i; end

#>(other) ⇒ Object 



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# File 'lib/btcruby/script/script_number.rb', line 59

def  >(other); @integer  > other.to_i; end

#>=(other) ⇒ Object 



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# File 'lib/btcruby/script/script_number.rb', line 58

def >=(other); @integer >= other.to_i; end

#>>(other) ⇒ Object 



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# File 'lib/btcruby/script/script_number.rb', line 94

def >>(other)
  # TODO: add asserts to check that result fits within int64 limits
  assert(other >= 0, "Shift amount must not be negative")
  a = @integer.abs
  r = a >> other.to_i
  if a != @integer
    r = -r
  end
  self.class.new(integer: r)
end

#assert(condition, message) ⇒ Object 



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# File 'lib/btcruby/script/script_number.rb', line 173

def assert(condition, message)
  raise message if !condition
end

#data ⇒ Object 



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# File 'lib/btcruby/script/script_number.rb', line 116

def data
  self.class.encode_integer(@integer)
end

#to_hex ⇒ Object 



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# File 'lib/btcruby/script/script_number.rb', line 120

def to_hex
  BTC.to_hex(data)
end

#to_i ⇒ Object

Conversion Methods



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# File 'lib/btcruby/script/script_number.rb', line 108

def to_i
  @integer
end

#to_s ⇒ Object 



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# File 'lib/btcruby/script/script_number.rb', line 112

def to_s
  @integer.to_s
end