bpo-33592: Document the C API in PEP 567 (contextvars) (GH-7033)

This commit is contained in:
Elvis Pranskevichus 2018-05-22 13:31:56 -04:00 committed by Yury Selivanov
parent 2a6d5da1d3
commit b2f5f59ae1
3 changed files with 131 additions and 2 deletions

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@ -113,5 +113,5 @@ Other Objects
capsule.rst
gen.rst
coro.rst
contextvars.rst
datetime.rst

125
Doc/c-api/contextvars.rst Normal file
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@ -0,0 +1,125 @@
.. highlightlang:: c
.. _contextvarsobjects:
Context Variables Objects
-------------------------
.. versionadded:: 3.7
This section details the public C API for the :mod:`contextvars` module.
.. c:type:: PyContext
The C structure used to represent a :class:`contextvars.Context`
object.
.. c:type:: PyContextVar
The C structure used to represent a :class:`contextvars.ContextVar`
object.
.. c:type:: PyContextToken
The C structure used to represent a :class:`contextvars.Token` object.
.. c:var:: PyTypeObject PyContext_Type
The type object representing the *context* type.
.. c:var:: PyTypeObject PyContextVar_Type
The type object representing the *context variable* type.
.. c:var:: PyTypeObject PyContextToken_Type
The type object representing the *context variable token* type.
Type-check macros:
.. c:function:: int PyContext_CheckExact(PyObject *o)
Return true if *o* is of type :c:data:`PyContext_Type`. *o* must not be
*NULL*. This function always succeeds.
.. c:function:: int PyContextVar_CheckExact(PyObject *o)
Return true if *o* is of type :c:data:`PyContextVar_Type`. *o* must not be
*NULL*. This function always succeeds.
.. c:function:: int PyContextToken_CheckExact(PyObject *o)
Return true if *o* is of type :c:data:`PyContextToken_Type`.
*o* must not be *NULL*. This function always succeeds.
Context object management functions:
.. c:function:: PyContext *PyContext_New(void)
Create a new empty context object. Returns ``NULL`` if an error
has occurred.
.. c:function:: PyContext *PyContext_Copy(PyContext *ctx)
Create a shallow copy of the passed *ctx* context object.
Returns ``NULL`` if an error has occurred.
.. c:function:: PyContext *PyContext_CopyCurrent(void)
Create a shallow copy of the current thread context.
Returns ``NULL`` if an error has occurred.
.. c:function:: int PyContext_Enter(PyContext *ctx)
Set *ctx* as the current context for the current thread.
Returns ``0`` on success, and ``-1`` on error.
.. c:function:: int PyContext_Exit(PyContext *ctx)
Deactivate the *ctx* context and restore the previous context as the
current context for the current thread. Returns ``0`` on success,
and ``-1`` on error.
.. c:function:: int PyContext_ClearFreeList()
Clear the context variable free list. Return the total number of
freed items. This function always succeeds.
Context variable functions:
.. c:function:: PyContextVar *PyContextVar_New(const char *name, PyObject *def)
Create a new ``ContextVar`` object. The *name* parameter is used
for introspection and debug purposes. The *def* parameter may optionally
specify the default value for the context variable. If an error has
occurred, this function returns ``NULL``.
.. c:function:: int PyContextVar_Get(PyContextVar *var, PyObject *default_value, PyObject **value)
Get the value of a context variable. Returns ``-1`` if an error has
occurred during lookup, and ``0`` if no error occurred, whether or not
a value was found.
If the context variable was found, *value* will be a pointer to it.
If the context variable was *not* found, *value* will point to:
- *default_value*, if not ``NULL``;
- the default value of *var*, if not ``NULL``;
- ``NULL``
If the value was found, the function will create a new reference to it.
.. c:function:: PyContextToken *PyContextVar_Set(PyContextVar *var, PyObject *value)
Set the value of *var* to *value* in the current context. Returns a
pointer to a :c:type:`PyContextToken` object, or ``NULL`` if an error
has occurred.
.. c:function:: int PyContextVar_Reset(PyContextVar *var, PyContextToken *token)
Reset the state of the *var* context variable to that it was in before
:c:func:`PyContextVar_Set` that returned the *token* was called.
This function returns ``0`` on success and ``-1`` on error.

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@ -515,7 +515,8 @@ New Modules
contextvars
-----------
The new :mod:`contextvars` module and a set of new C APIs introduce
The new :mod:`contextvars` module and a set of
:ref:`new C APIs <contextvarsobjects>` introduce
support for *context variables*. Context variables are conceptually
similar to thread-local variables. Unlike TLS, context variables
support asynchronous code correctly.
@ -1543,6 +1544,9 @@ A new API for thread-local storage has been implemented. See
:ref:`thread-specific-storage-api` for a complete reference.
(Contributed by Masayuki Yamamoto in :issue:`25658`.)
The new :ref:`context variables <whatsnew37-pep567>` functionality
exposes a number of :ref:`new C APIs <contextvarsobjects>`.
The new :c:func:`PyImport_GetModule` function returns the previously
imported module with the given name.
(Contributed by Eric Snow in :issue:`28411`.)