pythongh-110850: Add PyTime_t C API

Add PyTime_t API:

* PyTime_t type.
* PyTime_MIN and PyTime_MAX constants.
* PyTime_AsSecondsDouble(), PyTime_GetMonotonicClock(),
  PyTime_GetPerfCounter() and PyTime_GetSystemClock() functions.

Author: vstinner

Doc/c-api/time.rst

@@ -0,0 +1,132 @@
+.. highlight:: c
+
+PyTime API
+==========
+
+.. versionadded:: 3.13
+
+PyTime API
+----------
+
+The PyTime_t API is written to use timestamp and timeout values stored in
+various formats and to read clocks.
+
+The :c:type:`PyTime_t` type is an integer to support directly common arithmetic
+operations such as ``t1 + t2``.
+
+The PyTime_t API supports a resolution of ``1`` nanosecond. The
+:c:type:`PyTime_t` type is signed to support negative timestamps. The supported
+range is around [-292.3 years; +292.3 years]. Using the Unix epoch (January
+1st, 1970), the supported date range is around [1677-09-21; 2262-04-11].
+
+Time formats:
+
+* Seconds.
+* Seconds as a floating pointer number (C :c:type:`double`).
+* Milliseconds (10\ :sup:`-3` seconds).
+* Microseconds (10\ :sup:`-6` seconds).
+* 100 nanoseconds (10\ :sup:`-7` seconds), used on Windows.
+* Nanoseconds (10\ :sup:`-9` seconds).
+* :c:expr:`timeval` structure, 1 microsecond (10\ :sup:`-6` seconds).
+* :c:expr:`timespec` structure, 1 nanosecond (10\ :sup:`-9` seconds).
+
+Integer overflows are detected and raise :exc:`OverflowError`. Conversion to a
+resolution larger than 1 nanosecond is rounded correctly with the requested
+rounding mode. Available rounding modes:
+
+* Round towards minus infinity (-inf). For example, used to read a clock.
+* Round towards infinity (+inf). For example, used for timeout to wait "at
+  least" N seconds.
+* Round to nearest with ties going to nearest even integer. For example, used
+  to round from a Python float.
+* Round away from zero. For example, used for timeout.
+
+Some functions clamp the result in the range [PyTime_MIN; PyTime_MAX]. The
+caller doesn't have to handle errors and so doesn't need to hold the GIL to
+handle exceptions. For example, ``_PyTime_Add(t1, t2)`` computes ``t1+t2`` and
+clamps the result on overflow.
+
+Clocks:
+
+* System clock
+* Monotonic clock
+* Performance counter
+
+Internally, operations like ``(t * k / q)`` with integers are implemented in a
+way to reduce the risk of integer overflow. Such operation is used to convert a
+clock value expressed in ticks with a frequency to PyTime_t, like
+``QueryPerformanceCounter()`` with ``QueryPerformanceFrequency()`` on Windows.
+
+
+Types
+-----
+
+.. c:type:: PyTime_t
+
+   Timestamp type with subsecond precision: 64-bit signed integer.
+
+   This type can be used to store a duration. Indirectly, it can be used to
+   store a date relative to a reference date, such as the UNIX epoch.
+
+
+Constants
+---------
+
+.. c:var:: PyTime_t PyTime_MIN
+
+   Minimum value of the :c:type:`PyTime_t` type.
+   :c:macro`PyTime_MIN` nanoseconds is around -292.3 years.
+
+.. c:var:: PyTime_t PyTime_MAX
+
+   Maximum value of the :c:type:`PyTime_t` type.
+   :c:macro`PyTime_MAX` nanoseconds is around +292.3 years.
+
+
+Functions
+---------
+
+.. c:function:: double PyTime_AsSecondsDouble(PyTime_t t)
+
+   Convert a timestamp to a number of seconds as a C :c:type:`double`.
+
+   The function cannot fail.
+
+
+.. c:function:: PyTime_t PyTime_GetMonotonicClock(void)
+
+   Get the time of a monotonic clock, i.e. a clock that cannot go backwards.
+   The clock is not affected by system clock updates. The reference point of
+   the returned value is undefined, so that only the difference between the
+   results of consecutive calls is valid.
+
+   If reading the clock fails, silently ignore the error and return 0.
+
+   On integer overflow, silently ignore the overflow and clamp the clock to
+   the [PyTime_MIN; PyTime_MAX] range.
+
+   See also the :func:`time.monotonic` function.
+
+.. c:function:: PyTime_t PyTime_GetPerfCounter(void)
+
+   Get the performance counter: clock with the highest available resolution to
+   measure a short duration.
+
+   If reading the clock fails, silently ignore the error and return 0.
+
+   On integer overflow, silently ignore the overflow and clamp the time to the
+   [PyTime_MIN; PyTime_MAX] range.
+
+   See also the :func:`time.perf_counter` function.
+
+
+.. c:function:: PyTime_t PyTime_GetSystemClock(void)
+
+   Get the current time from the system clock.
+
+   If reading the clock fails, silently ignore the error and return ``0``.
+
+   On integer overflow, silently ignore the overflow and clamp the clock to
+   the [PyTime_MIN; PyTime_MAX] range.
+
+   See also the :func:`time.time` function.

Doc/c-api/utilities.rst

@@ -20,4 +20,5 @@ and parsing function arguments and constructing Python values from C values.
    hash.rst
    reflection.rst
    codec.rst
+   time.rst
    perfmaps.rst

Doc/whatsnew/3.13.rst

@@ -1181,6 +1181,16 @@ New Features
   :exc:`KeyError` if the key missing.
   (Contributed by Stefan Behnel and Victor Stinner in :gh:`111262`.)
 
+* Add PyTime_t C API:
+
+  * :c:type:`PyTime_t` type.
+  * :c:var:`PyTime_MIN` and :c:var:`PyTime_MAX` constants.
+  * :c:func:`PyTime_AsSecondsDouble`, :c:func:`PyTime_GetMonotonicClock`,
+    :c:func:`PyTime_GetPerfCounter` and :c:func:`PyTime_GetSystemClock`
+    functions.
+
+  (Contributed by Victor Stinner in :gh:`110850`.)
+
 
 Porting to Python 3.13
 ----------------------

Include/Python.h

@@ -97,6 +97,7 @@
 #include "weakrefobject.h"
 #include "structseq.h"
 #include "cpython/picklebufobject.h"
+#include "cpython/pytime.h"
 #include "codecs.h"
 #include "pyerrors.h"
 #include "pythread.h"

Include/cpython/pytime.h

@@ -0,0 +1,98 @@
+// The PyTime_t API is written to use timestamp and timeout values stored in
+// various formats and to read clocks.
+//
+// The PyTime_t type is an integer to support directly common arithmetic
+// operations like t1 + t2.
+//
+// The PyTime_t API supports a resolution of 1 nanosecond. The PyTime_t type
+// is signed to support negative timestamps. The supported range is around
+// [-292.3 years; +292.3 years]. Using the Unix epoch (January 1st, 1970), the
+// supported date range is around [1677-09-21; 2262-04-11].
+//
+// Formats:
+//
+// * seconds
+// * seconds as a floating pointer number (C double)
+// * milliseconds (10^-3 seconds)
+// * microseconds (10^-6 seconds)
+// * 100 nanoseconds (10^-7 seconds)
+// * nanoseconds (10^-9 seconds)
+// * timeval structure, 1 microsecond resolution (10^-6 seconds)
+// * timespec structure, 1 nanosecond resolution (10^-9 seconds)
+//
+// Integer overflows are detected and raise OverflowError. Conversion to a
+// resolution worse than 1 nanosecond is rounded correctly with the requested
+// rounding mode. There are 4 rounding modes: floor (towards -inf), ceiling
+// (towards +inf), half even and up (away from zero).
+//
+// Some functions clamp the result in the range [PyTime_MIN; PyTime_MAX], so
+// the caller doesn't have to handle errors and doesn't need to hold the GIL.
+// For example, _PyTime_Add(t1, t2) computes t1+t2 and clamp the result on
+// overflow.
+//
+// Clocks:
+//
+// * System clock
+// * Monotonic clock
+// * Performance counter
+//
+// Operations like (t * k / q) with integers are implemented in a way to reduce
+// the risk of integer overflow. Such operation is used to convert a clock
+// value expressed in ticks with a frequency to PyTime_t, like
+// QueryPerformanceCounter() with QueryPerformanceFrequency().
+
+#ifndef Py_LIMITED_API
+#ifndef Py_PYTIME_H
+#define Py_PYTIME_H
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+// PyTime_t: Python timestamp with subsecond precision. It can be used to store
+// a duration, and so indirectly a date relative to a reference date, such as
+// the UNIX epoch.
+typedef int64_t PyTime_t;
+
+// PyTime_MIN nanoseconds is around -292.3 years
+#define PyTime_MIN INT64_MIN
+
+// PyTime_MAX nanoseconds is around +292.3 years
+#define PyTime_MAX INT64_MAX
+
+// Convert a timestamp to a number of seconds as a C double.
+// The function cannot fail.
+PyAPI_FUNC(double) PyTime_AsSecondsDouble(PyTime_t t);
+
+// Get the time of a monotonic clock, i.e. a clock that cannot go backwards.
+// The clock is not affected by system clock updates. The reference point of
+// the returned value is undefined, so that only the difference between the
+// results of consecutive calls is valid.
+//
+// If reading the clock fails, silently ignore the error and return 0.
+//
+// On integer overflow, silently ignore the overflow and clamp the time to the
+// [PyTime_MIN; PyTime_MAX] range.
+PyAPI_FUNC(PyTime_t) PyTime_GetMonotonicClock(void);
+
+// Get the performance counter: clock with the highest available resolution to
+// measure a short duration.
+//
+// If reading the clock fails, silently ignore the error and return 0.
+//
+// On integer overflow, silently ignore the overflow and clamp the time to the
+// [PyTime_MIN; PyTime_MAX] range.
+PyAPI_FUNC(PyTime_t) PyTime_GetPerfCounter(void);
+
+// Get the current time from the system clock.
+//
+// If reading the clock fails, silently ignore the error and return 0.
+//
+// On integer overflow, silently ignore the overflow and clamp the time to the
+// [PyTime_MIN; PyTime_MAX] range.
+PyAPI_FUNC(PyTime_t) PyTime_GetSystemClock(void);
+
+#ifdef __cplusplus
+}
+#endif
+#endif /* Py_PYTIME_H */
+#endif /* Py_LIMITED_API */