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Change current-time back to list form

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Change current-time and related functions back to using the
traditional list form.  Also, add a new boolean variable
current-time-list that lets people try out (TICKS . HZ) form,
with the goal of smoothing the transition.
* src/timefns.c (CURRENT_TIME_LIST): Change default back to true.
(current-time-list): New boolean Lisp variable, which defaults to
CURRENT_TIME_LIST.  All uses of CURRENT_TIME_LIST changed to
use current_time_list, and all documentation changed.
This commit is contained in:
Paul Eggert 2022-04-28 12:50:39 -07:00
parent a41a181db5
commit 083d2708f9
6 changed files with 86 additions and 41 deletions
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9
doc/lispintro/emacs-lisp-intro.texi
View file

@ -15343,9 +15343,12 @@ nil
100
@end group
@group
(1351051674579989697 . 1000000000)
(1173477761000000000 . 1000000000)
(1351050967734791805 . 1000000000)
(20615 27034 579989 697000)
(17905 55681 0 0)
(20615 26327 734791 805000)@footnote{If @code{current-time-list} is
@code{nil} the three timestamps are @code{(1351051674579989697
. 1000000000)}, @code{(1173477761000000000 . 1000000000)}, and
@code{(1351050967734791805 . 1000000000)}, respectively.}
13188
"-rw-r--r--"
@end group

24
doc/lispref/files.texi
View file

@ -1423,9 +1423,9 @@ For example, here are the file attributes for @file{files.texi}:
@group
(file-attributes "files.texi" 'string)
@result{} (nil 1 "lh" "users"
(1351023123050040152 . 1000000000)
(1310720023000000000 . 1000000000)
(1351023659902289872 . 1000000000)
(20614 64019 50040 152000)
(20000 23 0 0)
(20614 64555 902289 872000)
122295 "-rw-rw-rw-"
t 6473924464520138
1014478468)
@ -1449,14 +1449,20 @@ is owned by the user with name @samp{lh}.
@item "users"
is in the group with name @samp{users}.
@item (1351023123050040152 . 1000000000)
was last accessed on October 23, 2012, at 20:12:03.050040152 UTC.
@item (20614 64019 50040 152000)
was last accessed on October 23, 2012, at 20:12:03.050040152 UTC@.
(This timestamp is @code{(1351023123050040152 . 1000000000)}
if @code{current-time-list} is @code{nil}.)
@item (1310720023000000000 . 1000000000)
was last modified on July 15, 2001, at 08:53:43.000000000 UTC.
@item (20000 23 0 0)
was last modified on July 15, 2001, at 08:53:43.000000000 UTC@.
(This timestamp is @code{(1310720023000000000 . 1000000000)}
if @code{current-time-list} is @code{nil}.)
@item (1351023659902289872 . 1000000000)
last had its status changed on October 23, 2012, at 20:20:59.902289872 UTC.
@item (20614 64555 902289 872000)
last had its status changed on October 23, 2012, at 20:20:59.902289872 UTC@.
(This timestamp is @code{(1351023659902289872 . 1000000000)}
if @code{current-time-list} is @code{nil}.)
@item 122295
is 122295 bytes long. (It may not contain 122295 characters, though,

4
doc/lispref/intro.texi
View file

@ -503,9 +503,11 @@ if the information is not available.
@example
@group
emacs-build-time
@result{} (1650228902637038831 . 1000000000)
@result{} (25194 55894 8547 617000)
@end group
@end example
(This timestamp is @code{(1651169878008547617 . 1000000000)}
if @code{current-time-list} was @code{nil} when Emacs was built.)
@end defvar
@defvar emacs-version

29
doc/lispref/os.texi
View file

@ -1359,6 +1359,10 @@ This represents the number of seconds using the formula:
@tex
$high \times 2^{16} + low + micro \times 10^{-6} + pico \times 10^{-12}$.
@end tex
If @code{current-time-list} is @code{t},
some functions may default to returning two- or
three-element lists, with omitted @var{micro} and @var{pico}
components defaulting to zero.
On all current machines @var{pico} is a multiple of 1000, but this
may change as higher-resolution clocks become available.
@end itemize
@ -1410,15 +1414,28 @@ The operating system limits the range of time and zone values.
@end example
@end defun
@defvar current-time-list
This boolean variable is a transition aid. If @code{t},
@code{current-time} and related functions return timestamps in list
form, typically @code{(@var{high} @var{low} @var{micro} @var{pico})};
otherwise, they use @code{(@var{ticks} . @var{hz})} form. Currently
this variable defaults to @code{t}, for behavior compatible with
previous Emacs versions. Developers are encourage to test
timestamp-related code with this variable set to @code{nil}, as it
will default to @code{nil} in a future Emacs version, and will be
removed in some version after that.
@end defvar
@defun current-time
This function returns the current time as a Lisp timestamp.
The timestamp has the form @code{(@var{ticks} . @var{hz})} where
If @code{current-time-list} is @code{nil},
the timestamp has the form @code{(@var{ticks} . @var{hz})} where
@var{ticks} counts clock ticks and @var{hz} is the clock ticks per second.
In Emacs 28 and earlier, the returned timestamp had the list form
@code{(@var{high} @var{low} @var{usec} @var{psec})}. You can use
@code{(time-convert nil 'list)} to return the current time in this
older form. @xref{Time Conversion}.
Otherwise, the timestamp has the list form
@code{(@var{high} @var{low} @var{usec} @var{psec})}.
You can use @code{(time-convert nil t)} or @code{(time-convert nil 'list)}
to obtain a particular form regardless of the value of
@code{current-time-list}. @xref{Time Conversion}.
@end defun
@defun float-time &optional time

15
etc/NEWS
View file

@ -203,12 +203,15 @@ use the new 'tamil-itrans-digits' and 'tamil-inscript-digits' input
methods instead.
+++
** current-time and related functions now yield (TICKS . HZ) timestamps.
Previously they yielded timestamps of the forms (HI LO US PS), (HI LO
US) or (HI LO), which were less regular and less efficient and which
lacked information about clock resolution. This long-planned change
was documented in Emacs 27. To convert a timestamp X to the old
4-element list form, you can use (time-convert X 'list).
** New variable current-time-list governing default timestamp form.
Functions like current-time now yield (TICKS . HZ) timestamps if this
new variable is nil. The variable defaults to t, which means these
functions default to timestamps of the forms (HI LO US PS), (HI LO US)
or (HI LO), which are less regular and less efficient. This is part
of a long-planned change first documented in Emacs 27. Developers are
encourage to test timestamp-related code with this variable set to
nil, as it will default to nil in a future Emacs version and will be
removed some time after that.
* Changes in Emacs 29.1

46
src/timefns.c
View file

@ -69,11 +69,11 @@ enum { TM_YEAR_BASE = 1900 };
# define FASTER_TIMEFNS 1
#endif
/* current-time etc. generate (TICKS . HZ) timestamps.
To change that to the old 4-element list format (HI LO US PS),
compile with -DCURRENT_TIME_LIST=1. */
/* current-time-list defaults to t, typically generating (HI LO US PS)
timestamps. To change the default to nil, generating (TICKS . HZ)
timestamps, compile with -DCURRENT_TIME_LIST=0. */
#ifndef CURRENT_TIME_LIST
enum { CURRENT_TIME_LIST = false };
enum { CURRENT_TIME_LIST = true };
#endif
#if FIXNUM_OVERFLOW_P (1000000000)
@ -568,7 +568,7 @@ lisp_time_seconds (struct lisp_time t)
Lisp_Object
make_lisp_time (struct timespec t)
{
if (CURRENT_TIME_LIST)
if (current_time_list)
{
time_t s = t.tv_sec;
int ns = t.tv_nsec;
@ -1171,13 +1171,13 @@ time_arith (Lisp_Object a, Lisp_Object b, bool subtract)
}
/* Return an integer if the timestamp resolution is 1,
otherwise the (TICKS . HZ) form if !CURRENT_TIME_LIST or if
otherwise the (TICKS . HZ) form if !current_time_list or if
either input used (TICKS . HZ) form or the result can't be expressed
exactly in (HI LO US PS) form, otherwise the (HI LO US PS) form
for backward compatibility. */
return (EQ (hz, make_fixnum (1))
? ticks
: (!CURRENT_TIME_LIST
: (!current_time_list
|| aform == TIMEFORM_TICKS_HZ
|| bform == TIMEFORM_TICKS_HZ
|| !trillion_factor (hz))
@ -1716,7 +1716,7 @@ usage: (encode-time TIME &rest OBSOLESCENT-ARGUMENTS) */)
time_error (mktime_errno);
if (EQ (hz, make_fixnum (1)))
return (CURRENT_TIME_LIST
return (current_time_list
? list2 (hi_time (value), lo_time (value))
: INT_TO_INTEGER (value));
else
@ -1747,7 +1747,7 @@ bits, and USEC and PSEC are the microsecond and picosecond counts. */)
struct lisp_time t;
enum timeform input_form = decode_lisp_time (time, false, &t, 0);
if (NILP (form))
form = CURRENT_TIME_LIST ? Qlist : Qt;
form = current_time_list ? Qlist : Qt;
if (EQ (form, Qlist))
return ticks_hz_list4 (t.ticks, t.hz);
if (EQ (form, Qinteger))
@ -1762,14 +1762,15 @@ bits, and USEC and PSEC are the microsecond and picosecond counts. */)
DEFUN ("current-time", Fcurrent_time, Scurrent_time, 0, 0, 0,
doc: /* Return the current time, as the number of seconds since 1970-01-01 00:00:00.
The time is returned as a pair of integers (TICKS . HZ), where TICKS
counts clock ticks and HZ is the clock ticks per second.
If the variable `current-time-list' is nil, the time is returned as a
pair of integers (TICKS . HZ), where TICKS counts clock ticks and HZ
is the clock ticks per second. Otherwise, the time is returned as a
list of integers (HIGH LOW USEC PSEC) where HIGH has the most
significant bits of the seconds, LOW has the least significant 16
bits, and USEC and PSEC are the microsecond and picosecond counts.
In Emacs 28 and earlier, the returned timestamp had the form (HIGH LOW
USEC PSEC), where HIGH is the most significant bits of the seconds,
LOW the least significant 16 bits, and USEC and PSEC are the
microsecond and picosecond counts. Use \(time-convert nil \\='list)
if you need this older timestamp form. */)
You can use `time-convert' to get a particular timestamp form
regardless of the value of `current-time-list'. */)
(void)
{
return make_lisp_time (current_timespec ());
@ -2025,6 +2026,19 @@ syms_of_timefns (void)
DEFSYM (Qencode_time, "encode-time");
DEFVAR_BOOL ("current-time-list", current_time_list,
doc: /* Whether `current-time' should return list or (TICKS . HZ) form.
This boolean variable is a transition aid. If t, `current-time' and
related functions return timestamps in list form, typically
\(HIGH LOW USEC PSEC); otherwise, they use (TICKS . HZ) form.
Currently this variable defaults to t, for behavior compatible with
previous Emacs versions. Developers are encourage to test
timestamp-related code with this variable set to nil, as it will
default to nil in a future Emacs version, and will be removed in some
version after that. */);
current_time_list = CURRENT_TIME_LIST;
defsubr (&Scurrent_time);
#ifdef CLOCKS_PER_SEC
defsubr (&Scurrent_cpu_time);