Backported PyCapsule from 3.1, and converted most uses of
CObject to PyCapsule.
diff --git a/Doc/c-api/capsule.rst b/Doc/c-api/capsule.rst
new file mode 100644
index 0000000..2939314
--- /dev/null
+++ b/Doc/c-api/capsule.rst
@@ -0,0 +1,150 @@
+.. 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 disambiguate.
+
+
+.. 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 disambiguate.
+
+
+.. 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 disambiguate.
+
+
+.. 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.
diff --git a/Doc/c-api/cobject.rst b/Doc/c-api/cobject.rst
index 10f7bba..73fbbf5 100644
--- a/Doc/c-api/cobject.rst
+++ b/Doc/c-api/cobject.rst
@@ -7,8 +7,11 @@
.. index:: object: CObject
-Refer to :ref:`using-cobjects` for more information on using these objects.
+.. warning::
+
+ The CObject API is deprecated as of Python 2.7. Please switch to the new
+ :ref:`capsules` API.
.. ctype:: PyCObject
diff --git a/Doc/c-api/concrete.rst b/Doc/c-api/concrete.rst
index 0595788..5ee611b 100644
--- a/Doc/c-api/concrete.rst
+++ b/Doc/c-api/concrete.rst
@@ -100,6 +100,7 @@
descriptor.rst
slice.rst
weakref.rst
+ capsule.rst
cobject.rst
cell.rst
gen.rst
diff --git a/Doc/data/refcounts.dat b/Doc/data/refcounts.dat
index b902bde..16f0604 100644
--- a/Doc/data/refcounts.dat
+++ b/Doc/data/refcounts.dat
@@ -55,6 +55,45 @@
PyBuffer_New:PyObject*::+1:
PyBuffer_New:int:size::
+PyCapsule_GetContext:void *:::
+PyCapsule_GetContext:PyObject*:self:0:
+
+PyCapsule_GetDestructor:void (*)(PyObject *):::
+PyCapsule_GetDestructor:PyObject*:self:0:
+
+PyCapsule_GetName:const char *:::
+PyCapsule_GetName:PyObject*:self:0:
+
+PyCapsule_GetPointer:void*:::
+PyCapsule_GetPointer:PyObject*:self:0:
+PyCapsule_GetPointer:const char *:name::
+
+PyCapsule_Import:void *:::
+PyCapsule_Import:const char *:name::
+PyCapsule_Import:int:no_block::
+
+PyCapsule_New:PyObject*::+1:
+PyCapsule_New:void*:pointer::
+PyCapsule_New:const char *:name::
+PyCapsule_New::void (* destructor)(PyObject* )::
+
+PyCapsule_SetContext:int:::
+PyCapsule_SetContext:PyObject*:self:0:
+PyCapsule_SetContext:void *:context::
+
+PyCapsule_SetDestructor:int:::
+PyCapsule_SetDestructor:PyObject*:self:0:
+PyCapsule_SetDestructor:void (*)(PyObject *):destructor::
+
+PyCapsule_SetName:int:::
+PyCapsule_SetName:PyObject*:self:0:
+PyCapsule_SetName:const char *:name::
+
+PyCapsule_SetPointer:int:::
+PyCapsule_SetPointer:PyObject*:self:0:
+PyCapsule_SetPointer:void*:pointer::
+
+
PyCObject_AsVoidPtr:void*:::
PyCObject_AsVoidPtr:PyObject*:self:0:
diff --git a/Doc/extending/extending.rst b/Doc/extending/extending.rst
index c7bff3e..5408b88 100644
--- a/Doc/extending/extending.rst
+++ b/Doc/extending/extending.rst
@@ -1060,7 +1060,7 @@
define this symbol).
-.. _using-cobjects:
+.. _using-capsules:
Providing a C API for an Extension Module
=========================================
@@ -1096,23 +1096,40 @@
other extension modules must be exported in a different way.
Python provides a special mechanism to pass C-level information (pointers) from
-one extension module to another one: CObjects. A CObject is a Python data type
-which stores a pointer (:ctype:`void \*`). CObjects can only be created and
+one extension module to another one: Capsules. A Capsule is a Python data type
+which stores a pointer (:ctype:`void \*`). Capsules can only be created and
accessed via their C API, but they can be passed around like any other Python
object. In particular, they can be assigned to a name in an extension module's
namespace. Other extension modules can then import this module, retrieve the
-value of this name, and then retrieve the pointer from the CObject.
+value of this name, and then retrieve the pointer from the Capsule.
-There are many ways in which CObjects can be used to export the C API of an
-extension module. Each name could get its own CObject, or all C API pointers
-could be stored in an array whose address is published in a CObject. And the
+There are many ways in which Capsules can be used to export the C API of an
+extension module. Each function could get its own Capsule, or all C API pointers
+could be stored in an array whose address is published in a Capsule. And the
various tasks of storing and retrieving the pointers can be distributed in
different ways between the module providing the code and the client modules.
+Whichever method you choose, it's important to name your Capsules properly.
+The function :cfunc:`PyCapsule_New` takes a name parameter
+(:ctype:`const char \*`); you're permitted to pass in a *NULL* name, but
+we strongly encourage you to specify a name. Properly named Capsules provide
+a degree of runtime type-safety; there is no feasible way to tell one unnamed
+Capsule from another.
+
+In particular, Capsules used to expose C APIs should be given a name following
+this convention::
+
+ modulename.attributename
+
+The convenience function :cfunc:`PyCapsule_Import` makes it easy to
+load a C API provided via a Capsule, but only if the Capsule's name
+matches this convention. This behavior gives C API users a high degree
+of certainty that the Capsule they load contains the correct C API.
+
The following example demonstrates an approach that puts most of the burden on
the writer of the exporting module, which is appropriate for commonly used
library modules. It stores all C API pointers (just one in the example!) in an
-array of :ctype:`void` pointers which becomes the value of a CObject. The header
+array of :ctype:`void` pointers which becomes the value of a Capsule. The header
file corresponding to the module provides a macro that takes care of importing
the module and retrieving its C API pointers; client modules only have to call
this macro before accessing the C API.
@@ -1174,8 +1191,8 @@
/* Initialize the C API pointer array */
PySpam_API[PySpam_System_NUM] = (void *)PySpam_System;
- /* Create a CObject containing the API pointer array's address */
- c_api_object = PyCObject_FromVoidPtr((void *)PySpam_API, NULL);
+ /* Create a Capsule containing the API pointer array's address */
+ c_api_object = PyCapsule_New((void *)PySpam_API, "spam._C_API", NULL);
if (c_api_object != NULL)
PyModule_AddObject(m, "_C_API", c_api_object);
@@ -1217,28 +1234,14 @@
#define PySpam_System \
(*(PySpam_System_RETURN (*)PySpam_System_PROTO) PySpam_API[PySpam_System_NUM])
- /* Return -1 and set exception on error, 0 on success. */
+ /* Return -1 on error, 0 on success.
+ * PyCapsule_Import will set an exception if there's an error.
+ */
static int
import_spam(void)
{
- PyObject *c_api_object;
- PyObject *module;
-
- module = PyImport_ImportModule("spam");
- if (module == NULL)
- return -1;
-
- c_api_object = PyObject_GetAttrString(module, "_C_API");
- if (c_api_object == NULL) {
- Py_DECREF(module);
- return -1;
- }
- if (PyCObject_Check(c_api_object))
- PySpam_API = (void **)PyCObject_AsVoidPtr(c_api_object);
-
- Py_DECREF(c_api_object);
- Py_DECREF(module);
- return 0;
+ PySpam_API = (void **)PyCapsule_Import("spam._C_API", 0);
+ return (PySpam_API != NULL) ? 0 : -1;
}
#endif
@@ -1270,11 +1273,11 @@
rather complicated. However, the basic structure is the same for each function
that is exported, so it has to be learned only once.
-Finally it should be mentioned that CObjects offer additional functionality,
+Finally it should be mentioned that Capsules offer additional functionality,
which is especially useful for memory allocation and deallocation of the pointer
-stored in a CObject. The details are described in the Python/C API Reference
-Manual in the section :ref:`cobjects` and in the implementation of CObjects (files
-:file:`Include/cobject.h` and :file:`Objects/cobject.c` in the Python source
+stored in a Capsule. The details are described in the Python/C API Reference
+Manual in the section :ref:`capsules` and in the implementation of Capsules (files
+:file:`Include/pycapsule.h` and :file:`Objects/pycapsule.c` in the Python source
code distribution).
.. rubric:: Footnotes