Module: CRC::Utils

Extended by:
Utils
Included in:
CRC, Utils
Defined in:
lib/crc/_utils.rb,
lib/crc/_byruby.rb

Overview

Utilities.

Instance Method Summary collapse

Instance Method Details

#bitreflect(num, bitsize) ⇒ Object 



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# File 'lib/crc/_utils.rb', line 14

def bitreflect(num, bitsize)
  case
  when bitsize > 128
    bitreflect_reference(num, bitsize)
  when bitsize > 64
    bitreflect128(num) >> (128 - bitsize)
  when bitsize > 32
    bitreflect64(num) >> (64 - bitsize)
  when bitsize > 16
    bitreflect32(num) >> (32 - bitsize)
  when bitsize > 8
    bitreflect16(num) >> (16 - bitsize)
  else
    bitreflect8(num) >> (8 - bitsize)
  end
end

#bitreflect128(n) ⇒ Object 



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# File 'lib/crc/_byruby.rb', line 300

def bitreflect128(n)
  n    = n.to_i
  n    = ((n & 0x55555555555555555555555555555555) <<  1) | ((n >>  1) & 0x55555555555555555555555555555555)
  n    = ((n & 0x33333333333333333333333333333333) <<  2) | ((n >>  2) & 0x33333333333333333333333333333333)
  n    = ((n & 0x0f0f0f0f0f0f0f0f0f0f0f0f0f0f0f0f) <<  4) | ((n >>  4) & 0x0f0f0f0f0f0f0f0f0f0f0f0f0f0f0f0f)
  n    = ((n & 0x00ff00ff00ff00ff00ff00ff00ff00ff) <<  8) | ((n >>  8) & 0x00ff00ff00ff00ff00ff00ff00ff00ff)
  n    = ((n & 0x0000ffff0000ffff0000ffff0000ffff) << 16) | ((n >> 16) & 0x0000ffff0000ffff0000ffff0000ffff)
  n    = ((n & 0x00000000ffffffff00000000ffffffff) << 32) | ((n >> 32) & 0x00000000ffffffff00000000ffffffff)
  return ((n & 0x0000000000000000ffffffffffffffff) << 64) |  (n >> 64) # 0x0000000000000000ffffffffffffffff
end

#bitreflect16(n) ⇒ Object 



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# File 'lib/crc/_byruby.rb', line 273

def bitreflect16(n)
  n    = n.to_i
  n    = ((n & 0x5555) <<  1) | ((n >>  1) & 0x5555)
  n    = ((n & 0x3333) <<  2) | ((n >>  2) & 0x3333)
  n    = ((n & 0x0f0f) <<  4) | ((n >>  4) & 0x0f0f)
  return ((n & 0x00ff) <<  8) |  (n >>  8) # 0x00ff
end

#bitreflect32(n) ⇒ Object 



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# File 'lib/crc/_byruby.rb', line 281

def bitreflect32(n)
  n    = n.to_i
  n    = ((n & 0x55555555) <<  1) | ((n >>  1) & 0x55555555)
  n    = ((n & 0x33333333) <<  2) | ((n >>  2) & 0x33333333)
  n    = ((n & 0x0f0f0f0f) <<  4) | ((n >>  4) & 0x0f0f0f0f)
  n    = ((n & 0x00ff00ff) <<  8) | ((n >>  8) & 0x00ff00ff)
  return ((n & 0x0000ffff) << 16) |  (n >> 16) # 0x0000ffff
end

#bitreflect64(n) ⇒ Object 



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# File 'lib/crc/_byruby.rb', line 290

def bitreflect64(n)
  n    = n.to_i
  n    = ((n & 0x5555555555555555) <<  1) | ((n >>  1) & 0x5555555555555555)
  n    = ((n & 0x3333333333333333) <<  2) | ((n >>  2) & 0x3333333333333333)
  n    = ((n & 0x0f0f0f0f0f0f0f0f) <<  4) | ((n >>  4) & 0x0f0f0f0f0f0f0f0f)
  n    = ((n & 0x00ff00ff00ff00ff) <<  8) | ((n >>  8) & 0x00ff00ff00ff00ff)
  n    = ((n & 0x0000ffff0000ffff) << 16) | ((n >> 16) & 0x0000ffff0000ffff)
  return ((n & 0x00000000ffffffff) << 32) |  (n >> 32) # 0x00000000ffffffff
end

#bitreflect8(n) ⇒ Object 



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# File 'lib/crc/_byruby.rb', line 266

def bitreflect8(n)
  n    = n.to_i
  n    = ((n & 0x55) <<  1) | ((n >>  1) & 0x55)
  n    = ((n & 0x33) <<  2) | ((n >>  2) & 0x33)
  return ((n & 0x0f) <<  4) |  (n >>  4) # 0x0f
end

#bitreflect_reference(num, bitsize) ⇒ Object 



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# File 'lib/crc/_utils.rb', line 8

def bitreflect_reference(num, bitsize)
  n = 0
  bitsize.times { n <<= 1; n |= (num & 0x01); num >>= 1 }
  n
end

#build_reflect_table(bitsize, polynomial, unfreeze = false, slice: 16) ⇒ Object 



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# File 'lib/crc/_utils.rb', line 58

def build_reflect_table(bitsize, polynomial, unfreeze = false, slice: 16)
  polynomial = bitreflect(polynomial, bitsize)
  table = []

  table << (t = [])
  256.times do |b|
    8.times { b = (b[0] == 0) ? (b >> 1) : ((b >> 1) ^ polynomial) }
    t << b
  end
  t.freeze unless unfreeze

  (1...slice).step do
    tt = table[-1]
    table << (t = [])
    256.times do |b|
      t << (table[0][tt[b] & 0xff] ^ (tt[b] >> 8))
    end
    t.freeze unless unfreeze
  end

  table.freeze unless unfreeze
  table
end

#build_table(bitsize, polynomial, unfreeze = false, slice: 16) ⇒ Object 



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# File 'lib/crc/_utils.rb', line 31

def build_table(bitsize, polynomial, unfreeze = false, slice: 16)
  bitmask = ~(~0 << bitsize)
  table = []
  Aux.slide_to_head(bitsize, 0, bitmask & polynomial, bitmask) do |xx, poly, csh, head, carries, pad|
    table << (t = [])
    256.times do |b|
      b <<= csh
      8.times { b = (b[head] == 0) ? (b << 1) : (((carries & b) << 1) ^ poly) }
      t << b
    end
    t.freeze unless unfreeze

    carries8 = carries >> 7
    (1...slice).step do
      tt = table[-1]
      table << (t = [])
      256.times do |b|
        t << (table[0][tt[b] >> csh] ^ ((carries8 & tt[b]) << 8))
      end
      t.freeze unless unfreeze
    end
    0
  end
  table.freeze unless unfreeze
  table
end

#export_table(table, bitsize, linewidth, indentsize = 2) ⇒ Object 



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# File 'lib/crc/_utils.rb', line 82

def export_table(table, bitsize, linewidth, indentsize = 2)
  bitsize0 = bitsize.to_i
  indent = " " * indentsize.to_i
  case
  when bitsize0 > 64 || bitsize0 < 1
    raise "invalid bitsize (expected to 1..64, but given #{bitsize})"
  when bitsize0 > 32
    packformat = "Q>"
    hexwidth = 16
  when bitsize0 > 16
    packformat = "N"
    hexwidth = 8
  when bitsize0 > 8
    packformat = "n"
    hexwidth = 4
  else # when bitsize0 > 0
    packformat = "C"
    hexwidth = 2
  end
  table = table.to_a.pack("#{packformat}*").unpack("H*")[0]
  table.gsub!(/(?<=\w)(?=\w{#{hexwidth}}{#{linewidth}}+$)/, "\n")
  table.gsub!(/(?<=\w)(?=\w{#{hexwidth}}+$)/, " ")
  table.gsub!(/(?<=\w)(?=\s|$)/, ",")
  table.gsub!(/(?:(?<=^)|(?<=\s))(?=\w)/, "0x")
  table.gsub!(/^/, "#{indent}  ")
  <<-EOS
#{indent}TABLE = [
#{table}
#{indent}].freeze
  EOS
end