Module: CRC::Aux

Defined in:
lib/crc/_aux.rb,
lib/crc/codegen.rb,
lib/crc/_combine.rb

Overview

Internal using module.

Class Method Summary collapse

Class Method Details

.combine(crc1, crc2, len2, bitsize, polynomial, initial_crc, reflect_input, reflect_output, xor_output) ⇒ Object 



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# File 'lib/crc/_combine.rb', line 57

def self.combine(crc1, crc2, len2,
                 bitsize, polynomial, initial_crc,
                 reflect_input, reflect_output, xor_output)
  return crc1 unless len2 > 1

  crc1 ^= initial_crc

  odd = []
  even = []
  if reflect_output
    odd << Utils.bitreflect(polynomial, bitsize)
    col = 1
    (bitsize - 1).times do
      odd << col
      col <<= 1
    end
  else
    col = 2
    (bitsize - 1).times do
      odd << col
      col <<= 1
    end
    odd << polynomial
  end

  Aux.gf2_matrix_square(bitsize, even, odd)
  Aux.gf2_matrix_square(bitsize, odd, even)

  while true
    Aux.gf2_matrix_square(bitsize, even, odd)
    if len2[0] == 1
      crc1 = Aux.gf2_matrix_times(even, crc1)
    end
    len2 >>= 1
    break unless len2 > 0

    Aux.gf2_matrix_square(bitsize, odd, even)
    if len2[0] == 1
      crc1 = Aux.gf2_matrix_times(odd, crc1)
    end
    len2 >>= 1;
    break unless len2 > 0
  end

  crc1 ^ crc2
end

.digest(num, bitsize) ⇒ Object 



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# File 'lib/crc/_aux.rb', line 13

def self.digest(num, bitsize)
  DIGEST(num, bitsize) { |n| n.chr(Encoding::BINARY) }
end

.DIGEST(num, bitsize) ⇒ Object 



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# File 'lib/crc/_aux.rb', line 6

def self.DIGEST(num, bitsize)
  bits = (bitsize + 7) / 8 * 8
  seq = ""
  (bits - 8).step(0, -8) { |i| seq << yield((num >> i) & 0xff) }
  seq
end

.dump_banner(line_prefix, crcname, algorithm) ⇒ Object 



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# File 'lib/crc/codegen.rb', line 841

def self.dump_banner(line_prefix, crcname, algorithm)
  case algorithm
  when ALGORITHM_BITBYBIT
    algorithm = "bit-by-bit"
  when ALGORITHM_BITBYBIT_FAST
    algorithm = "bit-by-bit-fast"
  when ALGORITHM_HALFBYTE_TABLE
    algorithm = "halfbyte-table"
  when ALGORITHM_STANDARD_TABLE
    algorithm = "standard-table"
  when ALGORITHM_SLICING_BY_4, ALGORITHM_SLICING_BY_8, ALGORITHM_SLICING_BY_16
    algorithm = "slicing-by-#{algorithm} (with byte-order free), based Intel's slicing-by-8"
  else
    raise ArgumentError, "out of algorithm code (given #{algorithm})"
  end
  ("A CRC calculator for \#{crcname}.\n\nThis code is auto generated by <https://rubygems.org/gems/crc>.\n\n* License:: Creative Commons License Zero (CC0 / Public Domain)\n        See <https://creativecommons.org/publicdomain/zero/1.0/>\n* Version:: crc-\#{CRC::VERSION} (powered by \#{RUBY_DESCRIPTION})\n* Generated at:: \#{Time.now.strftime \"%Y-%m-%d\"}\n* Algorithm:: \#{algorithm}\n* Need available memory:: about 1 MiB\n  EOS\nend\n").gsub!(/^(?!$)/, " ").gsub!(/^/) { line_prefix }.chomp!

.export_slicing_table(table, baseindent, indentsize, tableprefix, tablesuffix, elementprefix, elementsuffix, lineinelements, &hexnum) ⇒ Object 



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# File 'lib/crc/codegen.rb', line 870

def self.export_slicing_table(table, baseindent, indentsize, tableprefix, tablesuffix, elementprefix, elementsuffix, lineinelements, &hexnum)
  indent = ->(n = 0) { baseindent + (" " * (indentsize * n)) }
  tableprefix &&= "#{indent[0]}#{tableprefix}\n"
  tablesuffix &&= "\n#{indent[0]}#{tablesuffix}"
  if table[0].kind_of?(Array)
    ("\#{tableprefix}\#{indent[1]}\#{elementprefix}\n\#{\ntable = table.map { |tt|\n  tt = tt.map(&hexnum)\n  %(\#{indent[2]}\#{tt.each_slice(lineinelements).map { |ttt| ttt.join(\", \") }.join(\",\\n\#{indent[2]}\")}\\n)\n}.join(\"\#{indent[1]}\#{elementsuffix},\\n\#{indent[1]}\#{elementprefix}\\n\").chomp!\n}\n\#{indent[1]}\#{elementsuffix}\#{tablesuffix}\n    TABLE2\n  else\n    table = table.map(&hexnum)\n    %(\#{indent[1]}\#{table.each_slice(lineinelements).map { |ttt| ttt.join(\", \") }.join(\",\\n\#{indent[1]}\")}\\n).chomp!\n  end\nend\n").chomp!

.gf2_matrix_square(bitsize, square, matrix) ⇒ Object 



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# File 'lib/crc/_combine.rb', line 49

def self.gf2_matrix_square(bitsize, square, matrix)
  bitsize.times do |n|
    square[n] = gf2_matrix_times(matrix, matrix[n])
  end

  nil
end

.gf2_matrix_times(matrix, vector) ⇒ Object 



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# File 'lib/crc/_combine.rb', line 38

def self.gf2_matrix_times(matrix, vector)
  sum = 0
  matrix.each do |m|
    break unless vector > 0
    sum ^= m unless vector[0] == 0
    vector >>= 1
  end

  sum
end

.hexdigest(num, bitsize) ⇒ Object 



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# File 'lib/crc/_aux.rb', line 17

def self.hexdigest(num, bitsize)
  DIGEST(num, bitsize) { |n| "%02X" % n }
end

.slide_to_head(bitsize, state, polynomial, bitmask) ⇒ Object

call-seq:

slide_to_head(bitsize, state, polynomial, bitmask) { |padded_state, padded_polynomial, shift_input, off_msb, carries_mask, padding_size| padded_new_state } -> new_state

YIELD(padded_state, padded_polynomial, shift_input, off_msb, carries_mask, padding_size) -> padded_new_state



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# File 'lib/crc/_aux.rb', line 27

def self.slide_to_head(bitsize, state, polynomial, bitmask)
  pad = bitsize & 0x07
  if pad == 0
    yield(state, polynomial, bitsize - 8, bitsize - 1, bitmask >> 1, 0)
  else
    pad = 8 - pad
    yield(state << pad, polynomial << pad, bitsize - 8 + pad, bitsize - 1 + pad, (bitmask << pad >> 1) | 0x7f, pad) >> pad
  end
end