Module: Tem::Builders::Abi::Impl

Defined in:
lib/tem/builders/abi.rb

Overview

Implementation code for the ABI methods.

Class Method Summary collapse

Class Method Details

.check_number_range(number, length, is_signed) ⇒ Object

Checks the range of a number for fixed-length encoding.



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# File 'lib/tem/builders/abi.rb', line 444

def self.check_number_range(number, length, is_signed)
  range = 1 << (8 * length)
  if is_signed      
    min_value, max_value = -(range >> 1), (range >> 1) - 1
  else
    min_value, max_value = 0, range - 1
  end
  
  exception_string = "Number #{number} exceeds #{min_value}-#{max_value}"
  raise exception_string if number < min_value or number > max_value
end

.number_from_array(array, offset, length, is_signed, is_big_endian) ⇒ Object

Reads a variable-length number serialized to an array.

The source is indicated by the array and offset parameters. The number’s length is given in bytes.



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# File 'lib/tem/builders/abi.rb', line 381

def self.number_from_array(array, offset, length, is_signed, is_big_endian)
  # Read the raw number from the array.    
  number = 0
  if is_big_endian
    0.upto length - 1 do |i|
      number = (number << 8) | array[offset + i]
    end
  else
    (length - 1).downto 0 do |i|
      number = (number << 8) | array[offset + i]
    end
  end
  
  if is_signed  # Add the sign if necessary.
    range = 1 << (8 * length)
    max_value = (range >> 1) - 1
    number -= range if number > max_value
  end
      
  number
end

.number_to_array(number, length, is_signed, is_big_endian) ⇒ Object

Writes a fixed or variable-length number to an array.

The source is indicated by the array and offset parameters. The number’s length is given in bytes.



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# File 'lib/tem/builders/abi.rb', line 407

def self.number_to_array(number, length, is_signed, is_big_endian)
  bytes = []
  if number.kind_of? OpenSSL::BN  # OpenSSL key material
    if is_signed and number < 0  # normalize number
      range = OpenSSL::BN.new("1") << (8 * length)
      number += range
    end
    
    length ||= [number.num_bytes, 1].max
    v = 0
    (length * 8 - 1).downto 0 do |i|
      v = (v << 1) | (number.bit_set?(i) ? 1 : 0)
      if i & 7 == 0
        bytes << v
        v = 0
      end
    end
    bytes.reverse! unless is_big_endian
  else  # Ruby number.
    if length
      length.times do
        bytes << (number & 0xFF)
        number >>= 8
      end
    else
      loop do
        bytes << (number & 0xFF)
        number >>= 8
        break if number == 0
      end
    end
    bytes.reverse! if is_big_endian
  end    
  bytes
end

.string_from_array(array, offset, length) ⇒ Object

Reads a variable-length string serialized to an array.

The source is indicated by the array and offset parameters. The number’s length is given in bytes.



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# File 'lib/tem/builders/abi.rb', line 460

def self.string_from_array(array, offset, length)
  array[offset, length].pack('C*')
end

.string_to_array(array_or_string, length) ⇒ Object

Writes a fixed or variable-length string to an array.

The source is indicated by the array and offset parameters. The number’s length is given in bytes.



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# File 'lib/tem/builders/abi.rb', line 468

def self.string_to_array(array_or_string, length)
  if array_or_string.respond_to? :to_str
    # array_or_string is String-like
    string = array_or_string.to_str
    array = string.unpack('C*')
  else
    # array_or_string is Array-like
    array = array_or_string
  end
  
  if length and array.length > length
    raise "Cannot fit #{array_or_string.inspect} into a #{length}-byte string"       
  end
  # Pad the array with zeros up to the fixed length.
  length ||= 0
  array << 0 while array.length < length
  array
end