Class: Integer

Inherits:
Object
  • Object
show all
Defined in:
lib/ruby-vpi/integer.rb

Overview

NOTE: Because integers are immediate values in Ruby, these methods cannot modify the value of the integer upon which they are invoked. Instead, they return the new value as their result.

Instance Method Summary collapse

Instance Method Details

#extend_sign(aOrigWidth, aExtWidth) ⇒ Object

Performs sign extension on this integer, which has the given width (number of bits), so that the result will have the given extended width (number of bits).



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# File 'lib/ruby-vpi/integer.rb', line 97

def extend_sign aOrigWidth, aExtWidth
  result = self
  maskWidth = aExtWidth - aOrigWidth

  if maskWidth > 0 && result[aOrigWidth - 1] == 1
    result |= (maskWidth.to_mask << aOrigWidth)
  end

  result & aExtWidth.to_mask
end

#length ⇒ Object

Returns the minimum number of bits necessary to represent this integer.



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# File 'lib/ruby-vpi/integer.rb', line 23

def length
  to_s(2).length
end

#limit ⇒ Object

Returns the lowest upper-bound of this integer. This integer cannot reach the limit without occupying more bits in its binary representation.



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# File 'lib/ruby-vpi/integer.rb', line 29

def limit
  length.to_limit
end

#log2 ⇒ Object

Returns the ceiling of the logarithm (base 2) of this positive integer.



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# File 'lib/ruby-vpi/integer.rb', line 11

def log2
  raise "integer must be positive" if self < 0
  bin = to_s(2)

  if bin =~ /^10+$/
    bin.length - 1
  else
    bin.length
  end
end

#mask ⇒ Object Also known as: max

Returns a bit-mask capable of masking this integer.



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# File 'lib/ruby-vpi/integer.rb', line 40

def mask
  length.to_mask
end

#pack(aPackedWidth) ⇒ Object

Transforms this infinite-length Ruby integer into a fixed-length integer (represented in two’s complement form) that has the given width (number of bits).



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# File 'lib/ruby-vpi/integer.rb', line 62

def pack aPackedWidth
  bits = length
  bits += 1 if self > 0 # positive integers also have a sign bit (zero)

  unless aPackedWidth >= bits
    raise ArgumentError, "packed width #{aPackedWidth} must be at least #{bits} for integer #{self}"
  end

  extend_sign(bits, aPackedWidth)
end

#split(aWidth = 8) ⇒ Object

Splits this integer into an array of smaller integers, each of which have the given positive, non-zero width (number of bits). These smaller integers are ordered from left to right, in the same way that humans write unsigned binary numbers; for example:

>> 6.split 1

> [1, 1, 0]

>> 6.split(1).map {|i| i.to_s 2}

> [“1”, “1”, “0”]

>> 6.split 2

> [1, 2]

>> 6.split(2).map {|i| i.to_s 2}

> [“1”, “10”]

Raises:

  • (ArgumentError) 


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# File 'lib/ruby-vpi/integer.rb', line 121

def split aWidth = 8
  raise ArgumentError, "width must be positive and non-zero" unless aWidth > 0

  int, bits = self, length
  mask = aWidth.to_mask
  words = []

  while bits > 0
    words.unshift int & mask
    int >>= aWidth
    bits -= aWidth
  end

  words
end

#to_limit ⇒ Object

Returns the lowest upper-bound of an integer with this number of bits.



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# File 'lib/ruby-vpi/integer.rb', line 34

def to_limit
  2 ** self
end

#to_mask ⇒ Object Also known as: to_max

Returns a bit-mask capable of masking an integer with this number of bits.



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# File 'lib/ruby-vpi/integer.rb', line 45

def to_mask
  to_limit - 1
end

#unpack(aPackedWidth) ⇒ Object

Transforms this fixed-length integer (represented in two’s complement form) that has the given width (number of bits) into an infinite-length Ruby integer.



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# File 'lib/ruby-vpi/integer.rb', line 76

def unpack aPackedWidth
  bits = length

  unless aPackedWidth >= bits
    raise ArgumentError, "packed width #{aPackedWidth} must be at least #{bits} for integer #{self}"
  end

  mask = aPackedWidth.to_mask
  result = self & mask

  if result[aPackedWidth - 1] == 1
    -((-result) & mask)
  else
    result
  end
end