python/src/object/function.cpp

// Copyright David Abrahams 2001. Permission to copy, use,
// modify, sell and distribute this software is granted provided this
// copyright notice appears in all copies. This software is provided
// "as is" without express or implied warranty, and with no claim as
// to its suitability for any purpose.

#include <boost/python/object/function.hpp>
#include <boost/python/object/function_object.hpp>
#include <boost/python/object/function_handle.hpp>
#include <boost/python/errors.hpp>
#include <boost/python/str.hpp>
#include <boost/python/object_attributes.hpp>
#include <boost/python/args.hpp>
#include <boost/python/refcount.hpp>
#include <boost/python/extract.hpp>

#include <algorithm>
#include <cstring>

namespace boost { namespace python { namespace objects { 

extern PyTypeObject function_type;

function::function(
    py_function const& implementation
    , unsigned min_arity
    , unsigned max_arity
    , python::detail::keyword const* names_and_defaults
    , unsigned num_keywords
    )
    : m_fn(implementation)
      , m_min_arity(min_arity)
      // was using std::max here, but a problem with MinGW-2.95 and
      // our <boost/numeric/...> directory prevents it.
      , m_max_arity(max_arity > min_arity ? max_arity : min_arity)
{
    if (names_and_defaults != 0)
    {
        unsigned keyword_offset
            = m_max_arity > num_keywords ? m_max_arity - num_keywords : 0;


        unsigned tuple_size = num_keywords ? m_max_arity : 0;
        m_arg_names = object(handle<>(PyTuple_New(tuple_size)));

        if (num_keywords != 0)
        {
            for (unsigned j = 0; j < keyword_offset; ++j)
                PyTuple_SET_ITEM(m_arg_names.ptr(), j, incref(Py_None));
        }
        
        for (unsigned i = 0; i < num_keywords; ++i)
        {
            PyTuple_SET_ITEM(
                m_arg_names.ptr()
                , i + keyword_offset
                , expect_non_null(
                    PyString_FromString(const_cast<char*>(names_and_defaults[i].name))
                    )
                );
        }
    }
    
    PyObject* p = this;
    if (function_type.ob_type == 0)
    {
        function_type.ob_type = &PyType_Type;
        ::PyType_Ready(&function_type);
    }
    PyObject_INIT(p, &function_type);
}

function::~function()
{
}

PyObject* function::call(PyObject* args, PyObject* keywords) const
{
    std::size_t nargs = PyTuple_GET_SIZE(args);
    std::size_t nkeywords = keywords ? PyDict_Size(keywords) : 0;
    std::size_t total_args = nargs + nkeywords;
    
    function const* f = this;

    // Try overloads looking for a match
    do
    {
        // Check for a plausible number of arguments
        if (total_args >= f->m_min_arity && total_args <= f->m_max_arity)
        {
            // This will be the args that actually get passed
            handle<> args2(allow_null(borrowed(args)));

            if (nkeywords > 0) // Keyword arguments were supplied
            {
                if (f->m_arg_names.ptr() == Py_None) // this overload doesn't accept keywords
                {
                    args2 = handle<>(); // signal failure
                }
                else
                {
                    std::size_t max_args
                        = static_cast<std::size_t>(PyTuple_Size(f->m_arg_names.ptr()));

                    // "all keywords are none" is a special case
                    // indicating we will accept any number of keyword
                    // arguments
                    if (max_args == 0)
                    {
                        // no argument preprocessing
                    }
                    else if (max_args < total_args)
                    {
                        args2 = handle<>();
                    }
                    else
                    {
                        // build a new arg tuple
                        args2 = handle<>(PyTuple_New(total_args));

                        // Fill in the positional arguments
                        for (std::size_t i = 0; i < nargs; ++i)
                            PyTuple_SET_ITEM(args2.get(), i, incref(PyTuple_GET_ITEM(args, i)));

                        // Grab remaining arguments by name from the keyword dictionary
                        for (std::size_t j = nargs; j < total_args; ++j)
                        {
                            PyObject* value = PyDict_GetItem(
                                keywords, PyTuple_GET_ITEM(f->m_arg_names.ptr(), j));
                        
                            if (!value)
                            {
                                PyErr_Clear();
                                args2 = handle<>();
                                break;
                            }
                            PyTuple_SET_ITEM(args2.get(), j, incref(value));
                        }
                    }
                }
            }
            
            // Call the function.  Pass keywords in case it's a
            // function accepting any number of keywords
            PyObject* result = args2 ? f->m_fn(args2.get(), keywords) : 0;
            
            // If the result is NULL but no error was set, m_fn failed
            // the argument-matching test.

            // This assumes that all other error-reporters are
            // well-behaved and never return NULL to python without
            // setting an error.
            if (result != 0 || PyErr_Occurred())
                return result;
        }
        f = f->m_overloads.get();
    }
    while (f);
    // None of the overloads matched; time to generate the error message
    argument_error(args, keywords);
    return 0;
}

void function::argument_error(PyObject* args, PyObject* keywords) const
{
    // This function needs to be improved to do better error reporting.
    PyErr_BadArgument();
}

void function::add_overload(handle<function> const& overload_)
{
    function* parent = this;
    
    while (parent->m_overloads)
        parent = parent->m_overloads.get();

    parent->m_overloads = overload_;

    // If we have no documentation, get the docs from the overload
    if (!m_doc)
        m_doc = overload_->m_doc;
}

namespace
{
  char const* const binary_operator_names[] =
  {
      "add__",
      "and__",
      "div__",
      "divmod__",
      "eq__",
      "floordiv__",
      "ge__",
      "gt__",
      "le__",
      "lshift__",
      "lt__",
      "mod__",
      "mul__",
      "ne__",
      "or__",
      "pow__",
      "radd__",
      "rand__",
      "rdiv__",
      "rdivmod__", 
      "rfloordiv__",
      "rlshift__",
      "rmod__",
      "rmul__",
      "ror__",
      "rpow__", 
      "rrshift__",
      "rshift__",
      "rsub__",
      "rtruediv__",
      "rxor__",
      "sub__",
      "truediv__", 
      "xor__"
  };

  struct less_cstring
  {
      bool operator()(char const* x, char const* y) const
      {
          return BOOST_CSTD_::strcmp(x,y) < 0;
      }
  };
  
  inline bool is_binary_operator(char const* name)
  {
      return name[0] == '_'
          && name[1] == '_'
          && std::binary_search(
              &binary_operator_names[0]
              , binary_operator_names + sizeof(binary_operator_names)/sizeof(*binary_operator_names)
              , name + 2
              , less_cstring()
              );
  }

  // Something for the end of the chain of binary operators
  PyObject* not_implemented_impl(PyObject*, PyObject*)
  {
      Py_INCREF(Py_NotImplemented);
      return Py_NotImplemented;
  }
  
  handle<function> not_implemented_function()
  {
      static object keeper(
          function_object(&not_implemented_impl, 2, 3
                          , python::detail::keyword_range())
          );
      return handle<function>(borrowed(downcast<function>(keeper.ptr())));
  }
}

void function::add_to_namespace(
    object const& name_space, char const* name_, object const& attribute)
{
    str const name(name_);
    PyObject* const ns = name_space.ptr();
    
    if (attribute.ptr()->ob_type == &function_type)
    {
        function* new_func = downcast<function>(attribute.ptr());
        PyObject* dict = 0;
        
        if (PyClass_Check(ns))
            dict = ((PyClassObject*)ns)->cl_dict;
        else if (PyType_Check(ns))
            dict = ((PyTypeObject*)ns)->tp_dict;
        else
            dict = PyObject_GetAttrString(ns, "__dict__");

        if (dict == 0)
            throw_error_already_set();

        // This isn't quite typesafe. We'll shoot first by assuming
        // the thing is a function*, then ask questions later. The code works nicer that way.
        handle<function> existing(
            allow_null(downcast<function>(::PyObject_GetItem(dict, name.ptr())))
            );
        
        if (existing)
        {
            if (existing->ob_type == &function_type)
            {
                new_func->add_overload(existing);
            }
            else if (existing->ob_type == &PyStaticMethod_Type)
            {
                char const* name_space_name = extract<char const*>(name_space.attr("__name__"));
                
                ::PyErr_Format(
                    PyExc_RuntimeError
                    , "Boost.Python - All overloads must be exported "
                      "before calling \'class_<...>(\"%s\").staticmethod(\"%s\")\'"
                    , name_space_name
                    , name_
                    );
                throw_error_already_set();
            }
        }
        else if (is_binary_operator(name_))
        {
            // Binary operators need an additional overload which
            // returns NotImplemented, so that Python will try the
            // __rxxx__ functions on the other operand. We add this
            // when no overloads for the operator already exist.
            new_func->add_overload(not_implemented_function());
        }

        // A function is named the first time it is added to a namespace.
        if (new_func->name().ptr() == Py_None)
            new_func->m_name = name;
    }

    // The PyObject_GetAttrString() call above left an active error
    PyErr_Clear();
    if (PyObject_SetAttr(ns, name.ptr(), attribute.ptr()) < 0)
        throw_error_already_set();
}

void function::add_to_namespace(
    object const& name_space, char const* name_, object const& attribute, char const* doc)
{
    add_to_namespace(name_space, name_, attribute);
    if (doc != 0)
    {
        object attr_copy(attribute);
        attr_copy.attr("__doc__") = doc;
    }
}

BOOST_PYTHON_DECL void add_to_namespace(
    object const& name_space, char const* name, object const& attribute)
{
    function::add_to_namespace(name_space, name, attribute);
}

BOOST_PYTHON_DECL void add_to_namespace(
    object const& name_space, char const* name, object const& attribute, char const* doc)
{
    function::add_to_namespace(name_space, name, attribute, doc);    
}


namespace
{
  struct bind_return
  {
      bind_return(PyObject*& result, function const* f, PyObject* args, PyObject* keywords)
          : m_result(result)
            , m_f(f)
            , m_args(args)
            , m_keywords(keywords)
      {}

      void operator()() const
      {
          m_result = m_f->call(m_args, m_keywords);
      }
      
   private:
      PyObject*& m_result;
      function const* m_f;
      PyObject* m_args;
      PyObject* m_keywords;
  };
}

extern "C"
{
    // Stolen from Python's funcobject.c
    static PyObject *
    function_descr_get(PyObject *func, PyObject *obj, PyObject *type_)
    {
        if (obj == Py_None)
            obj = NULL;
        return PyMethod_New(func, obj, type_);
    }

    static void
    function_dealloc(PyObject* p)
    {
        delete static_cast<function*>(p);
    }

    static PyObject *
    function_call(PyObject *func, PyObject *args, PyObject *kw)
    {
        PyObject* result = 0;
        handle_exception(bind_return(result, static_cast<function*>(func), args, kw));
        return result;
    }

    //
    // Here we're using the function's tp_getset rather than its
    // tp_members to set up __doc__ and __name__, because tp_members
    // really depends on having a POD object type (it relies on
    // offsets). It might make sense to reformulate function as a POD
    // at some point, but this is much more expedient.
    //
    static PyObject* function_get_doc(PyObject* op, void*)
    {
        function* f = downcast<function>(op);
        return python::incref(f->doc().ptr());
    }
    
    static int function_set_doc(PyObject* op, PyObject* doc, void*)
    {
        function* f = downcast<function>(op);
        f->doc(doc ? object(python::detail::borrowed_reference(doc)) : object());
        return 0;
    }
    
    static PyObject* function_get_name(PyObject* op, void*)
    {
        function* f = downcast<function>(op);
        if (f->name().ptr() == Py_None)
            return PyString_InternFromString("<unnamed Boost.Python function>");
        else
            return python::incref(f->name().ptr());
    }
}
    
static PyGetSetDef function_getsetlist[] = {
    {"__name__", (getter)function_get_name, 0 },
    {"__doc__", (getter)function_get_doc, (setter)function_set_doc},
    {NULL} /* Sentinel */
};

PyTypeObject function_type = {
    PyObject_HEAD_INIT(0)
    0,
    "Boost.Python.function",
    sizeof(function),
    0,
    (destructor)function_dealloc,               /* tp_dealloc */
    0,                                  /* tp_print */
    0,                                  /* tp_getattr */
    0,                                  /* tp_setattr */
    0,                                  /* tp_compare */
    0, //(reprfunc)func_repr,                   /* tp_repr */
    0,                                  /* tp_as_number */
    0,                                  /* tp_as_sequence */
    0,                                  /* tp_as_mapping */
    0,                                  /* tp_hash */
    function_call,                              /* tp_call */
    0,                                  /* tp_str */
    0, // PyObject_GenericGetAttr,            /* tp_getattro */
    0, // PyObject_GenericSetAttr,            /* tp_setattro */
    0,                                  /* tp_as_buffer */
    Py_TPFLAGS_DEFAULT /* | Py_TPFLAGS_HAVE_GC */,/* tp_flags */
    0,                                  /* tp_doc */
    0, // (traverseproc)func_traverse,          /* tp_traverse */
    0,                                  /* tp_clear */
    0,                                  /* tp_richcompare */
    0, //offsetof(PyFunctionObject, func_weakreflist), /* tp_weaklistoffset */
    0,                                  /* tp_iter */
    0,                                  /* tp_iternext */
    0,                                  /* tp_methods */
    0, // func_memberlist,              /* tp_members */
    function_getsetlist,                /* tp_getset */
    0,                                  /* tp_base */
    0,                                  /* tp_dict */
    function_descr_get,                 /* tp_descr_get */
    0,                                  /* tp_descr_set */
    0, //offsetof(PyFunctionObject, func_dict),      /* tp_dictoffset */
    0,                                      /* tp_init */
    0,                                      /* tp_alloc */
    0,
    0                                       /* tp_new */
};

object function_object(
    py_function const& f, unsigned min_arity, unsigned max_arity
    , python::detail::keyword_range const& keywords)
{
    return python::object(
        python::detail::new_non_null_reference(
            new function(
                f, min_arity, max_arity, keywords.first, keywords.second - keywords.first)));
}

object function_object(
    py_function const& f
    , unsigned arity
    , python::detail::keyword_range const& kw)
{
    return function_object(f, arity, arity, kw);
}

object function_object(py_function const& f, unsigned arity)
{
    return function_object(f, arity, arity, python::detail::keyword_range());
}


handle<> function_handle_impl(py_function const& f, unsigned min_arity, unsigned max_arity)
{
    return python::handle<>(
        allow_null(
            new function(f, min_arity, max_arity, 0, 0)));
}

}

namespace detail
{
  object BOOST_PYTHON_DECL make_raw_function(objects::py_function f, std::size_t min_args)
  {
      static keyword k;
    
      return objects::function_object(
          f
          , min_args
          , std::numeric_limits<std::size_t>::max()
          , keyword_range(&k,&k));
  }
}

}} // namespace boost::python::objects