# available since Python 3.1!


cdef extern from "Python.h":

    ctypedef struct PyCapsule_Type
    # This subtype of PyObject represents an opaque value, useful for
    # C extension modules who need to pass an opaque value (as a void*
    # pointer) through Python code to other C code. It is often used
    # to make a C function pointer defined in one module available to
    # other modules, so the regular import mechanism can be used to
    # access C APIs defined in dynamically loaded modules.


    ctypedef void (*PyCapsule_Destructor)(object o) noexcept
    # The type of a destructor callback for a capsule.
    #
    # See PyCapsule_New() for the semantics of PyCapsule_Destructor
    # callbacks.


    bint PyCapsule_CheckExact(object o)
    # Return true if its argument is a PyCapsule.


    object PyCapsule_New(void *pointer, const char *name,
                         PyCapsule_Destructor destructor)
    # Return value: New reference.
    #
    # Create a PyCapsule encapsulating the pointer. The pointer
    # argument may not be NULL.
    #
    # On failure, set an exception and return NULL.
    #
    # The name string may either be NULL or a pointer to a valid C
    # string. If non-NULL, this string must outlive the
    # capsule. (Though it is permitted to free it inside the
    # destructor.)
    #
    # If the destructor argument is not NULL, it will be called with
    # the capsule as its argument when it is destroyed.
    #
    # If this capsule will be stored as an attribute of a module, the
    # name should be specified as modulename.attributename. This will
    # enable other modules to import the capsule using
    # PyCapsule_Import().


    void* PyCapsule_GetPointer(object capsule, const char *name) except? NULL
    # Retrieve the pointer stored in the capsule. On failure, set an
    # exception and return NULL.
    #
    # The name parameter must compare exactly to the name stored in
    # the capsule. If the name stored in the capsule is NULL, the name
    # passed in must also be NULL. Python uses the C function strcmp()
    # to compare capsule names.


    PyCapsule_Destructor PyCapsule_GetDestructor(object capsule) except? NULL
    # Return the current destructor stored in the capsule. On failure,
    # set an exception and return NULL.
    #
    # It is legal for a capsule to have a NULL destructor. This makes
    # a NULL return code somewhat ambiguous; use PyCapsule_IsValid()
    # or PyErr_Occurred() to disambiguate.


    const char* PyCapsule_GetName(object capsule) except? NULL
    # Return the current name stored in the capsule. On failure, set
    # an exception and return NULL.
    #
    # It is legal for a capsule to have a NULL name. This makes a NULL
    # return code somewhat ambiguous; use PyCapsule_IsValid() or
    # PyErr_Occurred() to disambiguate.


    void* PyCapsule_GetContext(object capsule) except? NULL
    # Return the current context stored in the capsule. On failure,
    # set an exception and return NULL.
    #
    # It is legal for a capsule to have a NULL context. This makes a
    # NULL return code somewhat ambiguous; use PyCapsule_IsValid() or
    # PyErr_Occurred() to disambiguate.


    bint PyCapsule_IsValid(object capsule, const char *name)
    # Determines whether or not capsule is a valid capsule. A valid
    # capsule is non-NULL, passes PyCapsule_CheckExact(), has a
    # non-NULL pointer stored in it, and its internal name matches the
    # name parameter. (See PyCapsule_GetPointer() for information on
    # how capsule names are compared.)
    #
    # In other words, if PyCapsule_IsValid() returns a true value,
    # calls to any of the accessors (any function starting with
    # PyCapsule_Get()) are guaranteed to succeed.
    #
    # Return a nonzero value if the object is valid and matches the
    # name passed in. Return 0 otherwise. This function will not fail.


    int PyCapsule_SetPointer(object capsule, void *pointer) except -1
    # Set the void pointer inside capsule to pointer. The pointer may
    # not be NULL.
    #
    # Return 0 on success. Return nonzero and set an exception on
    # failure.


    int PyCapsule_SetDestructor(object capsule, PyCapsule_Destructor destructor) except -1
    # Set the destructor inside capsule to destructor.
    #
    # Return 0 on success. Return nonzero and set an exception on
    # failure.


    int PyCapsule_SetName(object capsule, const char *name) except -1
    # Set the name inside capsule to name. If non-NULL, the name must
    # outlive the capsule. If the previous name stored in the capsule
    # was not NULL, no attempt is made to free it.
    #
    # Return 0 on success. Return nonzero and set an exception on
    # failure.


    int PyCapsule_SetContext(object capsule, void *context) except -1
    # Set the context pointer inside capsule to context.  Return 0 on
    # success. Return nonzero and set an exception on failure.


    void* PyCapsule_Import(const char *name, int no_block) except? NULL
    # Import a pointer to a C object from a capsule attribute in a
    # module. The name parameter should specify the full name to the
    # attribute, as in module.attribute. The name stored in the
    # capsule must match this string exactly. If no_block is true,
    # import the module without blocking (using
    # PyImport_ImportModuleNoBlock()). If no_block is false, import
    # the module conventionally (using PyImport_ImportModule()).
    #
    # Return the capsule’s internal pointer on success. On failure,
    # set an exception and return NULL. However, if PyCapsule_Import()
    # failed to import the module, and no_block was true, no exception
    # is set.