bpo-31784: Implement PEP 564: add time.time_ns() (#3989)

Add new time functions:

* time.clock_gettime_ns()
* time.clock_settime_ns()
* time.monotonic_ns()
* time.perf_counter_ns()
* time.process_time_ns()
* time.time_ns()

Add new _PyTime functions:

* _PyTime_FromTimespec()
* _PyTime_FromNanosecondsObject()
* _PyTime_FromTimeval()

Other changes:

* Add also os.times() tests to test_os.
* pytime_fromtimeval() and pytime_fromtimeval() now return
  _PyTime_MAX or _PyTime_MIN on overflow, rather than undefined
  behaviour
* _PyTime_FromNanoseconds() parameter type changes from long long to
  _PyTime_t

2 files changed, 84 insertions, 6 deletions

diff --git a/Doc/library/time.rst b/Doc/library/time.rst
index 253df73..4ffb4d2 100644
--- a/Doc/library/time.rst
+++ b/Doc/library/time.rst
@@ -185,7 +185,7 @@ Functions
    .. versionadded:: 3.3
 
 
-.. function:: clock_gettime(clk_id)
+.. function:: clock_gettime(clk_id) -> float
 
    Return the time of the specified clock *clk_id*.  Refer to
    :ref:`time-clock-id-constants` for a list of accepted values for *clk_id*.
@@ -195,7 +195,16 @@ Functions
    .. versionadded:: 3.3
 
 
-.. function:: clock_settime(clk_id, time)
+.. function:: clock_gettime_ns(clk_id) -> int
+
+   Similar to :func:`clock_gettime` but return time as nanoseconds.
+
+   Availability: Unix.
+
+   .. versionadded:: 3.7
+
+
+.. function:: clock_settime(clk_id, time: float)
 
    Set the time of the specified clock *clk_id*.  Currently,
    :data:`CLOCK_REALTIME` is the only accepted value for *clk_id*.
@@ -205,6 +214,15 @@ Functions
    .. versionadded:: 3.3
 
 
+.. function:: clock_settime_ns(clk_id, time: int)
+
+   Similar to :func:`clock_settime` but set time with nanoseconds.
+
+   Availability: Unix.
+
+   .. versionadded:: 3.7
+
+
 .. function:: ctime([secs])
 
    Convert a time expressed in seconds since the epoch to a string representing
@@ -267,7 +285,7 @@ Functions
    The earliest date for which it can generate a time is platform-dependent.
 
 
-.. function:: monotonic()
+.. function:: monotonic() -> float
 
    Return the value (in fractional seconds) of a monotonic clock, i.e. a clock
    that cannot go backwards.  The clock is not affected by system clock updates.
@@ -287,7 +305,13 @@ Functions
       The function is now always available.
 
 
-.. function:: perf_counter()
+.. function:: monotonic_ns() -> int
+
+   Similar to :func:`monotonic`, but return time as nanoseconds.
+
+   .. versionadded:: 3.7
+
+.. function:: perf_counter() -> float
 
    .. index::
       single: benchmarking
@@ -300,8 +324,14 @@ Functions
 
    .. versionadded:: 3.3
 
+.. function:: perf_counter_ns() -> int
+
+   Similar to :func:`perf_counter`, but return time as nanoseconds.
+
+   .. versionadded:: 3.7
 
-.. function:: process_time()
+
+.. function:: process_time() -> float
 
    .. index::
       single: CPU time
@@ -316,6 +346,12 @@ Functions
 
    .. versionadded:: 3.3
 
+.. function:: process_time_ns() -> int
+
+   Similar to :func:`process_time` but return time as nanoseconds.
+
+   .. versionadded:: 3.7
+
 .. function:: sleep(secs)
 
    Suspend execution of the calling thread for the given number of seconds.
@@ -541,7 +577,7 @@ Functions
    :class:`struct_time`, or having elements of the wrong type, a
    :exc:`TypeError` is raised.
 
-.. function:: time()
+.. function:: time() -> float
 
    Return the time in seconds since the epoch_ as a floating point
    number. The specific date of the epoch and the handling of
@@ -567,6 +603,13 @@ Functions
    of the calendar date may be accessed as attributes.
 
 
+.. function:: time_ns() -> int
+
+   Similar to :func:`time` but returns time as an integer number of nanoseconds
+   since the epoch_.
+
+   .. versionadded:: 3.7
+
 .. function:: tzset()
 
    Reset the time conversion rules used by the library routines. The environment
diff --git a/Doc/whatsnew/3.7.rst b/Doc/whatsnew/3.7.rst
index d5836d5..eb64c6a 100644
--- a/Doc/whatsnew/3.7.rst
+++ b/Doc/whatsnew/3.7.rst
@@ -159,6 +159,32 @@ effort will be made to add such support.
        PEP written by Erik M. Bray; implementation by Masayuki Yamamoto.
 
 
+PEP 564: Add new time functions with nanosecond resolution
+----------------------------------------------------------
+
+Add six new "nanosecond" variants of existing functions to the :mod:`time`
+module:
+
+* :func:`time.clock_gettime_ns`
+* :func:`time.clock_settime_ns`
+* :func:`time.monotonic_ns`
+* :func:`time.perf_counter_ns`
+* :func:`time.process_time_ns`
+* :func:`time.time_ns`
+
+While similar to the existing functions without the ``_ns`` suffix, they
+provide nanosecond resolution: they return a number of nanoseconds as a Python
+``int``.
+
+The ``time.time_ns()`` resolution is 3 times better than the ``time.time()``
+resolution on Linux and Windows.
+
+.. seealso::
+
+    :pep:`564` -- Add new time functions with nanosecond resolution
+       PEP written and implemented by Victor Stinner
+
+
 Other Language Changes
 ======================
 
@@ -313,6 +339,15 @@ separately.  (Contributed by Barry Warsaw in :issue:`1198569`.)
 time
 ----
 
+The :pep:`564` added six new functions with nanosecond resolution:
+
+* :func:`time.clock_gettime_ns`
+* :func:`time.clock_settime_ns`
+* :func:`time.monotonic_ns`
+* :func:`time.perf_counter_ns`
+* :func:`time.process_time_ns`
+* :func:`time.time_ns`
+
 Add new clock identifiers:
 
 * :data:`time.CLOCK_BOOTTIME` (Linux): Identical to