Re: [Boost-users] [crc] bug in boost::crc

Subject: Re: [Boost-users] [crc] bug in boost::crc
From: U.Mutlu (for-gmane_at_[hidden])
Date: 2015-07-09 17:18:00

Hurcan Solter wrote on 07/09/2015 10:21 PM:
> So,you are initializing the crc with a different value(result from previous
> loop) and expecting the same result?

I don't think so, but if you know how to use it correctly let me know pls.

I just wonder why the lib author made such a simple thing so complicated.

The program even gives different results with each run; so there must 
definitely be a bug in the crc library.

> On Thu, Jul 9, 2015 at 8:27 PM, U.Mutlu <for-gmane_at_[hidden]> wrote:
>
>> /*
>>    boost-crc-bug-demo.cpp
>>
>>    Written by U.Mutlu on 2015-07-09-Th
>>
>>    Compile:
>>      g++ -O2 -Wall -std=gnu++11 boost-crc-bug-demo.cpp
>>
>>    Run:
>>      ./a.out
>>
>>    Output:
>>      crc("The quick brown fox jumps over the lazy dog")=414fa339
>>      crc("The quick brown fox ")=88b075e2
>>      crc("The quick brown fox jumps over the lazy dog")=4ac56d0f
>>      ERROR
>>
>>    See also:
>>      http://www.boost.org/doc/libs/1_58_0/libs/crc/crc.html#usage
>>
>>    Conclusion:
>>      It doesn't do what it should and also advertises; ie. there's a bug
>>
>> */
>>
>> #include <boost/crc.hpp>
>> #include <boost/cstdint.hpp>
>> #include <iostream>
>>
>> int main()
>>    {
>>      uint32_t expected;
>>
>>      {
>>      const std::string sTxt = "The quick brown fox jumps over the lazy dog";
>>      boost::crc_optimal<32, 0x04C11DB7, 0xFFFFFFFF, 0xFFFFFFFF, true, true>
>> crc;
>>      crc.process_bytes(sTxt.data(), sTxt.size());
>>      std::cout << "crc(\"" << sTxt << "\")=" << std::hex << crc.checksum()
>> << std::endl;
>>
>>      // save the result for the following test
>>      expected = crc.checksum();
>>      }
>>
>>
>>      // test: doing the same as above, but now in 2 steps, ie. chunk- or
>> blockwise:
>>      std::string sTxt;
>>      uint32_t result = 0xFFFFFFFF;
>>      for (size_t i = 0; i <= 1; ++i)
>>      {
>>      sTxt += !i ? "The quick brown fox "
>>                 : "jumps over the lazy dog";
>>
>>      // using the special ctor for initial remainder stored in "result"
>>      boost::crc_optimal<32, 0x04C11DB7, 0xFFFFFFFF, 0xFFFFFFFF, true, true>
>> crc(result);
>>      crc.process_bytes(sTxt.data(), sTxt.size());
>>      std::cout << "crc(\"" << sTxt << "\")=" << std::hex << crc.checksum()
>> << std::endl;
>>
>>      result = crc.checksum();
>>      }
>>
>>      // eval:
>>      const std::string sRes = result == expected ? "SUCCESS" : "ERROR";
>>      std::cout << sRes << std::endl;
>>
>>      return 0;
>>    }
>>
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>
>
>
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