67 lines
1.8 KiB
Ruby
67 lines
1.8 KiB
Ruby
# frozen_string_literal: true
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module TTFunk # rubocop: disable Style/Documentation # false positive
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# Bit crunching utility methods.
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module BinUtils
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# Turn a bunch of small integers into one big integer. Assumes big-endian.
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#
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# @param arr [Array<Integer>]
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# @param bit_width [Integer] bit width of the elements
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# @return [Integer]
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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
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# Slice a big integer into a bunch of small integers. Assumes big-endian.
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#
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# @param value [Integer]
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# @param bit_width [Integer] bit width of the elements
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# @param slice_count [Integer] number of elements to slice into. This is
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# needed for cases where top bits are zero.
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# @return [Array<Integer>]
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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
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# Two's compliment to an integer.
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#
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# @param num [Integer]
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# @param bit_width [Integer] number width
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# @return [Integer]
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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
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# Turns a (sorted) sequence of values into a series of two-element arrays
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# where the first element is the start and the second is the length.
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#
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# @param values [Array<Integer>]
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# @return [Array<Array(Integer, Integer)>]
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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
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end
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BinUtils.extend(BinUtils)
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end
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