Ticket #10809: test.cpp

#include <sstream>

#include <boost/iostreams/slice.hpp>
#include <boost/iostreams/stream.hpp>

void runTest(bool doSeek)
{
    namespace io = boost::iostreams;
    typedef io::restriction<std::istream> SlicedStreamDev;

    std::istringstream data;
    data.str("foo bar");
    // Seek to start of "bar", and restrict to a single character
    int offset = 4;
    int length = 1;
    data.seekg(offset);
    io::stream<SlicedStreamDev> restrictedStream(SlicedStreamDev(data, offset, length));
    if (doSeek)
        restrictedStream.seekg(0); // Seek to beginning of restricted stream - should do nothing.

    // Should dump the entire contents of the restricted stream (ie, "b") to
    // the screen.  This doesn't work if seekg(0) has been called above
    std::cout << restrictedStream.rdbuf() << "\n";
}


int main()
{
    runTest(false);
    runTest(true);

    // Here's part of what's happening behind the scenes:
    std::istringstream data;
    data.str("foo bar");
    {
        // boost::iostreams::seek with std::streambuf calls the following, which
        // fails according to C++11 standard N3242, section 27.8.2.4 (table 130)
        std::streambuf::pos_type result = data.rdbuf()->pubseekoff(4, std::ios::cur, std::ios::in | std::ios::out);
        std::cout << "istringstream pubseekoff() result: " << result << "\n";
    }

    {
        // The following also does not work in libstdc++, since istringstream
        // has no output pointer set in the streambuf, so passing std::ios::out
        // doesn't make sense (note implications for boost::iostreams::seek,
        // which passes (std::ios::in | std::ios::out) by default!)
        std::streambuf::pos_type result = data.rdbuf()->pubseekoff(4, std::ios::beg, std::ios::in | std::ios::out);
        std::cout << "pubseekoff() result: " << result << "\n";
    }

    return 0;
}