[Python-checkins] bpo-33592: Document the C API in PEP 567 (contextvars) (GH-7033)
Miss Islington (bot)
webhook-mailer at python.org
Tue May 22 13:58:05 EDT 2018
https://github.com/python/cpython/commit/afec2d583a06849c5080c6cd40266743c8e04b3e
commit: afec2d583a06849c5080c6cd40266743c8e04b3e
branch: 3.7
author: Miss Islington (bot) <31488909+miss-islington at users.noreply.github.com>
committer: GitHub <noreply at github.com>
date: 2018-05-22T10:58:01-07:00
summary:
bpo-33592: Document the C API in PEP 567 (contextvars) (GH-7033)
(cherry picked from commit b2f5f59ae15564b991f3ca4850e6ad28d9faacbc)
Co-authored-by: Elvis Pranskevichus <elvis at magic.io>
files:
A Doc/c-api/contextvars.rst
M Doc/c-api/concrete.rst
M Doc/whatsnew/3.7.rst
diff --git a/Doc/c-api/concrete.rst b/Doc/c-api/concrete.rst
index 47dab81891d3..9558a4a583cb 100644
--- a/Doc/c-api/concrete.rst
+++ b/Doc/c-api/concrete.rst
@@ -113,5 +113,5 @@ Other Objects
capsule.rst
gen.rst
coro.rst
+ contextvars.rst
datetime.rst
-
diff --git a/Doc/c-api/contextvars.rst b/Doc/c-api/contextvars.rst
new file mode 100644
index 000000000000..4c33ba4f9944
--- /dev/null
+++ b/Doc/c-api/contextvars.rst
@@ -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.
diff --git a/Doc/whatsnew/3.7.rst b/Doc/whatsnew/3.7.rst
index 8324be801491..ac697191b50d 100644
--- a/Doc/whatsnew/3.7.rst
+++ b/Doc/whatsnew/3.7.rst
@@ -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`.)
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