Class: MrbParser::CRC

Inherits:
Object
  • Object
show all
Defined in:
lib/mrb_parser/crc.rb

Overview

calculate CRC

an Ruby port of src/crc.c in mruby

Constant Summary collapse

CRC_16_CCITT =

x^16+x^12+x^5+1

0x11021
CRC_XOR_PATTERN = 
(CRC_16_CCITT << 8)
CRC_CARRY_BIT = 
0x01000000
CHAR_BIT = 
8

Class Method Summary collapse

Class Method Details

.calc_crc_16_ccitt(data0, nbytes, crc) ⇒ Object 



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# File 'lib/mrb_parser/crc.rb', line 15

def self.calc_crc_16_ccitt(data0, nbytes, crc)
  data = data0.unpack("C*")
  crcwk = crc << 8
  for ibyte in 0...nbytes
    crcwk |= data[ibyte]
    for ibit in 0...CHAR_BIT
      crcwk <<= 1
      carry = crcwk & CRC_CARRY_BIT
      if carry.nonzero?
        crcwk ^= CRC_XOR_PATTERN
      end
    end
  end
  return crcwk >> 8
end