[C++-sig] Unicode string in different version of libboost-python

Jan. 27, 2015

      Hi,

I'm working on a python wrapper for the lib libexiv2

This is the port to Python 3 of pyexiv2 written for Python 2

I've two machines, one 32 bits with these versions:

vincent@tiemoko:~$ dpkg --list | grep libboost
ii libboost-python-dev         1.48.0.2            Boost.Python Library 
development files (default version)
ii libboost-python1.46-dev     1.46.1-7ubuntu3     Boost.Python Library 
development files
ii libboost-python1.46.1       1.46.1-7ubuntu3     Boost.Python Library
ii libboost-python1.48.0       1.48.0-3            Boost.Python Library
ii libboost1.46-dev            1.46.1-7ubuntu3     Boost C++ Libraries 
development files

and one 64 bits (this is my main devel machine):

vincent@djoliba:~$ dpkg --list | grep libboost
ii  libboost-date-time1.54.0:amd64  1.54.0-4ubuntu3.1   amd64  set of 
date-time libraries
ii  libboost-python-dev             1.54.0.1ubuntu1     amd64 
Boost.Python Library
ii  libboost-python1.54-dev:amd64   1.54.0-4ubuntu3.1   amd64 
Boost.Python Library development files
ii  libboost-python1.54.0:amd64     1.54.0-4ubuntu3.1   amd64 
Boost.Python Library
rc  libboost-serialization1.46.1    1.46.1-7ubuntu3     amd64 
serialization library for C++
ii  libboost-system1.54.0:amd64     1.54.0-4ubuntu3.1   amd64 Operating 
system (e.g. diagnostics support) library
ii  libboost1.54-dev                1.54.0-4ubuntu3.1   amd64  Boost C++ 
Libraries development files

It's seems these different versions have different behaviours with the 
python string.

On the more recent version, I encode my python string in utf-8 before 
send it to the wrapper and that's works fine.

On the 32 bits machine I've this error:
TypeError: No registered converter was able to produce a C++ rvalue of 
type std::string from this Python object of type bytes

If I send directly the unicode string to the wrapper, without encoding, 
that's solve the problem.

Example:

python:

# xmp tag values are embedded into a list
value = ['déjà vu']
try:
     tag._setArrayValue([v.encode('utf-8') for v in value])
except TypeError:
     # old libboost-python version
     tag._setArrayValue(value)

-------------------------------------------------------------------------
exiv2wrapper_python.cpp

#include "exiv2wrapper.hpp"

#include "exiv2/exv_conf.h"
#include "exiv2/version.hpp"

#include <boost/python.hpp>

using namespace boost::python;

using namespace exiv2wrapper;

BOOST_PYTHON_MODULE(libexiv2python)
{
     scope().attr("exiv2_version_info") = \
         boost::python::make_tuple(EXIV2_MAJOR_VERSION,
                                   EXIV2_MINOR_VERSION,
                                   EXIV2_PATCH_VERSION);

register_exception_translator<Exiv2::Error>(&translateExiv2Error);

     // Swallow all warnings and error messages written by libexiv2 to 
stderr
     // (if it was compiled with DEBUG or without SUPPRESS_WARNINGS).
     // See https://bugs.launchpad.net/pyexiv2/+bug/507620.
     std::cerr.rdbuf(NULL);

     [skip]

         .def("_setArrayValue", &XmpTag::setArrayValue)

---------------------------------------------------------------------------
exiv2wrapper.cpp

#include "exiv2wrapper.hpp"

#include "boost/python/stl_iterator.hpp"

#include <fstream>

     [skip]

  void XmpTag::setArrayValue(const boost::python::list& values)
{
     // Reset the value
     _datum->setValue(0);

     for(boost::python::stl_input_iterator<std::string> iterator(values);
         iterator != boost::python::stl_input_iterator<std::string>();
         ++iterator)
     {
         _datum->setValue(*iterator);
     }
}
-------------------------------------------------------------------------

Is this difference into two versions is normal ?

I can adapt my python code for that, but how to know the version of 
libboost ?

Here I use "dpkg --list | grep libboost" but that's for debian 
pacckaging system only and my lib must be run on any os (Windows include).

Thanks for all advices.

Vincent

[C++-sig] Unicode string in different version of libboost-python

Vincent Vande Vyvre