| .. highlightlang:: c |
| |
| .. _capsules: |
| |
| Capsules |
| -------- |
| |
| .. index:: object: Capsule |
| |
| Refer to :ref:`using-capsules` for more information on using these objects. |
| |
| |
| .. ctype:: PyCapsule |
| |
| This subtype of :ctype:`PyObject` represents an opaque value, useful for C |
| extension modules who need to pass an opaque value (as a :ctype:`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. |
| |
| .. ctype:: PyCapsule_Destructor |
| |
| The type of a destructor callback for a capsule. Defined as:: |
| |
| typedef void (*PyCapsule_Destructor)(PyObject *); |
| |
| See :cfunc:`PyCapsule_New` for the semantics of PyCapsule_Destructor |
| callbacks. |
| |
| |
| .. cfunction:: int PyCapsule_CheckExact(PyObject *p) |
| |
| Return true if its argument is a :ctype:`PyCapsule`. |
| |
| |
| .. cfunction:: PyObject* PyCapsule_New(void *pointer, const char *name, PyCapsule_Destructor destructor) |
| |
| Create a :ctype:`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 :cfunc:`PyCapsule_Import`. |
| |
| |
| .. cfunction:: void* PyCapsule_GetPointer(PyObject *capsule, const char *name) |
| |
| 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 :cfunc:`strcmp` to compare capsule |
| names. |
| |
| |
| .. cfunction:: PyCapsule_Destructor PyCapsule_GetDestructor(PyObject *capsule) |
| |
| 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 :cfunc:`PyCapsule_IsValid` or |
| :cfunc:`PyErr_Occurred` to disambugate. |
| |
| |
| .. cfunction:: void* PyCapsule_GetContext(PyObject *capsule) |
| |
| 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 :cfunc:`PyCapsule_IsValid` or |
| :cfunc:`PyErr_Occurred` to disambugate. |
| |
| |
| .. cfunction:: const char* PyCapsule_GetName(PyObject *capsule) |
| |
| 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 :cfunc:`PyCapsule_IsValid` or |
| :cfunc:`PyErr_Occurred` to disambugate. |
| |
| |
| .. cfunction:: void* PyCapsule_Import(const char *name, int no_block) |
| |
| 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 :cfunc:`PyImport_ImportModuleNoBlock`). If *no_block* is false, |
| import the module conventionally (using :cfunc:`PyImport_ImportModule`). |
| |
| Return the capsule's internal *pointer* on success. On failure, set an |
| exception and return *NULL*. However, if :cfunc:`PyCapsule_Import` failed to |
| import the module, and *no_block* was true, no exception is set. |
| |
| .. cfunction:: int PyCapsule_IsValid(PyObject *capsule, const char *name) |
| |
| Determines whether or not *capsule* is a valid capsule. A valid capsule is |
| non-*NULL*, passes :cfunc:`PyCapsule_CheckExact`, has a non-*NULL* pointer |
| stored in it, and its internal name matches the *name* parameter. (See |
| :cfunc:`PyCapsule_GetPointer` for information on how capsule names are |
| compared.) |
| |
| In other words, if :cfunc:`PyCapsule_IsValid` returns a true value, calls to |
| any of the accessors (any function starting with :cfunc:`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. |
| |
| .. cfunction:: int PyCapsule_SetContext(PyObject *capsule, void *context) |
| |
| Set the context pointer inside *capsule* to *context*. |
| |
| Return 0 on success. Return nonzero and set an exception on failure. |
| |
| .. cfunction:: int PyCapsule_SetDestructor(PyObject *capsule, PyCapsule_Destructor destructor) |
| |
| Set the destructor inside *capsule* to *destructor*. |
| |
| Return 0 on success. Return nonzero and set an exception on failure. |
| |
| .. cfunction:: int PyCapsule_SetName(PyObject *capsule, const char *name) |
| |
| 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. |
| |
| .. cfunction:: int PyCapsule_SetPointer(PyObject *capsule, void *pointer) |
| |
| 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. |