Re: Looking to write bitsets to a basic_string

From:
"alex" <alex.shulgin@gmail.com>
Newsgroups:
comp.lang.c++.moderated
Date:
15 Dec 2006 08:24:08 -0500
Message-ID:
<1166184012.474326.280030@79g2000cws.googlegroups.com>
CSAWannabe wrote:

I've got a vector of bitsets with 10 bits in each bitset like this:

        std::vector<std::bitset<10> > m_vctBitSets;

std::bitset<10> bsBitSet = 0xF0;
m_vctBitSets.push_back(bsBitSet);

I want to write the vector bitsets to a std::string.. so that there is
no gap between each bitset,i.e. the second bitset in the vector would
start on bit 11 in the std::string. I could also write them to a
buffer something like unsigned char [x]. But prefer to work with
std::string.


Something like this should do the job:

size_t const bitset_size = 10;
std::string output;
unsigned long data = 0;
size_t size = 0;
for (size_t i = 0; i < vec.size(); ++i)
{
    if (size + bitset_size > sizeof(data) * 8)
    {
        // flush ready bytes
        while (size >= 8)
        {
            output += data & 0xFF; // output lowest byte
            data >>= 8;
            size -= 8;
        }
    }
    data |= vec[i].to_ulong() << bitset_size;
    size += bitset_size;
}

--
Alex Shulgin

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