in reply to computing CRC32 in Perl and C

gri6507:

In the C version, you're including the string terminator '\0' in your calculation. Try sizeof(s)-1.

...roboticus

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Re^2: computing CRC32 in Perl and C
by gri6507 (Deacon) on Dec 13, 2007 at 20:31 UTC
    I don't think this is it. I changed from mCrc = crc(s, sizeof(s), mLookup, &mMask); to mCrc = crc(s, sizeof(s)-1, mLookup, &mMask); and now, even though the results are different, they still don't agree. 
    perl try.pl
CRC for 'Hello Word. How are you?' is 0x8487fb61


gcc try.c; ./a.out
CRC for 'Hello Word. How are you?' is 0x7b78049e

    [download]
    I have a feeling the problem is the poly, or the reflections, or the initial poly or something like that - I just can't figure out what.
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      Okay ... here are a couple other things to try:

      • Are you scanning through the bits in the correct order? I notice you're scanning LSB to MSB . Is that what the CRC wants?
      • Try calculating a single character to see if your initial conditions match up.
      ...roboticus
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