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

Subject: Re: [Boost-users] [crc] bug in boost::crc
From: Hurcan Solter (hsolter_at_[hidden])
Date: 2015-07-09 16:21:30

So,you are initializing the crc with a different value(result from previous
loop) and expecting the same result?

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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