Module: TTFunk::BinUtils

Extended by:
BinUtils
Included in:
BinUtils
Defined in:
lib/ttfunk/bin_utils.rb,
lib/ttfunk/bin_utils.rb

Overview

Bit crunching utility methods.

Instance Method Summary collapse

Instance Method Details

#rangify(values) ⇒ Array<Array(Integer, Integer)>

Turns a (sorted) sequence of values into a series of two-element arrays where the first element is the start and the second is the length.

Parameters:

  • values (Array<Integer>)

Returns:

  • (Array<Array(Integer, Integer)>)
Source Code
lib/ttfunk/bin_utils.rb, line 60
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def rangify(values)

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  values

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    .slice_when { |a, b| b - a > 1 }

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    .map { |span| [span.first, span.length - 1] }

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end

#slice_int(value, bit_width:, slice_count:) ⇒ Array<Integer>

Slice a big integer into a bunch of small integers. Assumes big-endian.

Parameters:

  • value (Integer)
  • bit_width (Integer) —

    bit width of the elements

  • slice_count (Integer) —

    number of elements to slice into. This is needed for cases where top bits are zero.

Returns:

  • (Array<Integer>)
Source Code
lib/ttfunk/bin_utils.rb, line 30
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def slice_int(value, bit_width:, slice_count:)

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  mask = (2**bit_width) - 1

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  Array.new(slice_count) do |i|

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    (value >> (bit_width * i)) & mask

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  end

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end







    
      

  

  
    #stitch_int(arr, bit_width:)  ⇒ Integer 
  

  

  


  

    
Turn a bunch of small integers into one big integer. Assumes big-endian.



  





  

Parameters:


    
  
    
  • 
      
        arr
      
      
        (Array<Integer>)
      
      
      
    
    • 
  
    
  • 
      
        bit_width
      
      
        (Integer)
      
      
      
        —
        
    bit width of the elements
    

    
      
    
    • 
  




Returns:


    
  
    
  • 
      
      
        (Integer)
      
      
      
    
    • 
  







  Source Code
  
lib/ttfunk/bin_utils.rb, line 13

  
13
def stitch_int(arr, bit_width:)

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  value = 0

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  arr.each_with_index do |element, index|

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    value |= element << (bit_width * index)

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  end

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  value

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end







    
      

  

  
    #twos_comp_to_int(num, bit_width:)  ⇒ Integer 
  

  

  


  

    
Two’s compliment to an integer.



  





  

Parameters:


    
  
    
  • 
      
        num
      
      
        (Integer)
      
      
      
    
    • 
  
    
  • 
      
        bit_width
      
      
        (Integer)
      
      
      
        —
        
    number width
    

    
      
    
    • 
  




Returns:


    
  
    
  • 
      
      
        (Integer)
      
      
      
    
    • 
  







  Source Code
  
lib/ttfunk/bin_utils.rb, line 43

  
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def twos_comp_to_int(num, bit_width:)

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  if num >> (bit_width - 1) == 1

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    # we want all ones

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    mask = (2**bit_width) - 1

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    # find 2's complement, i.e. flip bits (xor with mask) and add 1

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    -((num ^ mask) + 1)

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  else

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    num

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  end

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end