Question

我试图计算CRC32-C校验和值。我提到了很多在线CRC计算器和许多网站，用于编写我自己的crc校验和计算器。我没有得到预期的结果。仅限我的研究＆＃34; http://crccalc.com/＆＃34;给出了我的预期价值。

我看到有很多方法有表，没有表..等似乎没有什么对我有用，我上传简单的方法程序，我用来计算crc

POLY_LENGTH = 32

def convertobin(input_message):
    input_message = bin(input_message[::-1])
    return input_message

def find_xor(polynomial, input_message):
    # print polynomial
    print input_message
    xor = polynomial ^ input_message
    return xor

def find_crc(polynomial, packet):
    print len(packet)
    input_messageInBin = bin(int(packet,16))[2:]
    print input_messageInBin, type(input_messageInBin)
    input_messageInBin = input_messageInBin + '0'*31
    inputMessageLength = len(input_messageInBin)
    firstTime = 1
    remainder = 0
    startmarker = 0
    control = 1
    diff = 0
    stopmarker = 0
    import pdb; pdb.set_trace()
    while control:
        if len(input_messageInBin) > (startmarker + 32) :
            if firstTime:
                inputString = input_messageInBin[0:POLY_LENGTH]
                stopmarker = POLY_LENGTH - 1
                xor = find_xor(polynomial, int(inputString,2))

                xor_bits_length = len(bin(xor)) - 2
                remainder = str(bin(xor))[2:]
                diff = POLY_LENGTH - xor_bits_length
                firstTime = 0
                startmarker = startmarker + diff - 1
            else:
                diff_bits = input_messageInBin[stopmarker+1:stopmarker+diff+1]
                inputString = remainder + diff_bits
                print "--------------------------------------------------------"
                print "Total number of different bits are: ", diff
                print "remainder + diff_bits : ", remainder, "+", diff_bits
                print "XOR of :"
                print inputString
                print bin(polynomial)[2:]
                xor = find_xor(polynomial, int(inputString,2))
                xor_bits_length = len(bin(xor)) - 2
                remainder = str(bin(xor))[2:]
                print remainder
                print "--------------------------------------------------------"
                diff = POLY_LENGTH - xor_bits_length
                stopmarker = stopmarker + diff
                startmarker = startmarker + diff

        else:
            control = 0
            remainder = remainder + input_messageInBin[startmarker:stopmarker]
            print stopmarker
            print startmarker

    return remainder
val = find_crc(0x1EDC6F41, 'FFFFFFFFFFFFFFFFFFFF0F0FB01013F2E8FAF0421208')
print val

我试图让这个工作。感谢有人为此提供解决方案

Answer 1

据我测试模块使用CRC-32C（令人讨厌的错误ceph对象），最好的是crccheck，它不像大多数实现那样需要SSE4。

>>> from crccheck.crc import Crc32c
>>> Crc32c().process(b'kwarunek').finalhex()
'aa862086'

http://crccalc.com/会得到相同的结果。

编辑：十六进制值的计算

crccheck能够为十六进制值计算校验和，只需要将值作为字节传递 - method for large integers：

x = int('FFFFFFFFFFFFFFFFFFFF0F0FB01013F2E8FAF0421208', 16)
nbytes, rem = divmod(x.bit_length(), 8)
if rem: nbytes += 1
prepared = x.to_bytes(nbytes, 'big')

Crc32c().process(prepared).finalhex()

Python的CRC校验和计算

1 个答案: