2009.04.06 15:35 "[Tiff] Writing tiff to in-memory buffer", by Christian Henning

Hi there, I'm extending my code to allow writing to an in-memory buffer using std::stringstream. I'm using stringstream successfully with libpng and libjpeg. Though, I thought libtiff can do that too. I'm actually pretty sure it can and the fault is on my side. Please consider the following code:

static tsize_t read_proc( thandle_t fd
                        , tdata_t buf
                        , tsize_t size
                        )
{

    return size;
}

static tsize_t write_proc( thandle_t handle
                         , tdata_t   buf
                         , tsize_t   size

                         )
{
    std::ostream* os = reinterpret_cast< std::ostream* >( handle );

    boost::gil::detail::io_error_if( os->write( reinterpret_cast<char

const*>( buf )
             , static_cast<std::streamsize>( size )

                          ).bad() == true
               , "ostream_device: Cannot write."

             );

    return size;
}

static toff_t seek_proc( thandle_t handle
                       , toff_t off
                       , int i
                       )
{
    std::ostream* os = reinterpret_cast< std::ostream* >( handle );

    os->seekp( off
             , i == SEEK_SET
             ? std::ios::beg
             : ( i == SEEK_CUR
                 ? std::ios::cur
                 : std::ios::end )
              );

    return off;
}

static int close_proc( thandle_t handle )
{
    std::ostream* os = reinterpret_cast< std::ostream* >( handle );
    os->operator<< ( std::flush );

    return 0;
}

static toff_t size_proc( thandle_t handle )
{
    return 0;
}

void error_handler( const char* module, const char* fmt, va_list ap )
{
}

int main()
{

    TIFFSetErrorHandler(&error_handler);

    stringstream ss( ios_base::in | ios_base::out | ios_base::binary );

    TIFF* t = TIFFClientOpen( "dummy"
                            , "w"

                            , &ss
                            , &read_proc
                            , &write_proc
                            , &seek_proc
                            , &close_proc
                            , &size_proc

                            , NULL
                            , NULL
                            );
}

TIFFClientOpen returns zero while the error handler tells me:

"Not a TIFF or MDI file, bad magic number %d (0x%x)"

I'm using libtiff version 3 something.

Someone any idea what I'm doing wrong here?

Thanks,
Christian