Commit bffceab6 authored by Philipp Stephani's avatar Philipp Stephani
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Add conversions to and from struct timespec to module interface.

Time values are a fundamental data type, and such conversions are hard
to implement within modules because of the various forms of time
values in Emacs Lisp.  Adding dedicated conversion functions can
significantly simplify module code dealing with times.

This approach uses nanosecond precision.  While Emacs in theory has
support for higher-precision time values, in practice most languages
and standards, such as POSIX, C, Java, and Go, have settled on
nanosecond-precision integers to represent time.

* src/ Add header for struct timespec.

* src/module-env-27.h: Add module functions for time conversion.

* src/emacs-module.c (module_extract_time, module_make_time): New
(initialize_environment): Use them.

* test/data/emacs-module/mod-test.c (Fmod_test_add_nanosecond): New
test function.
(emacs_module_init): Define it.

* test/src/emacs-module-tests.el (mod-test-add-nanosecond/valid)
(mod-test-add-nanosecond/nil, mod-test-add-nanosecond/invalid): New
unit tests.

* doc/lispref/internals.texi (Module Values): Document time
conversion functions.
parent 5ae407aa
......@@ -1387,6 +1387,38 @@ This function returns the value of a Lisp float specified by
@var{arg}, as a C @code{double} value.
@end deftypefn
@deftypefn Function struct timespec extract_time (emacs_env *@var{env}, emacs_value @var{time})
This function, which is available since Emacs 27, interprets
@var{time} as an Emacs Lisp time value and returns the corresponding
@code{struct timespec}. @xref{Time of Day}. @code{struct timespec}
represents a timestamp with nanosecond precision. It has the
following members:
@table @code
@item time_t tv_sec
Whole number of seconds.
@item long tv_nsec
Fractional seconds as number of nanoseconds, always less than one
@end table
@xref{Elapsed Time,,,libc}.
If @var{time} has higher precision than nanoseconds, then this
function truncates it to nanosecond precision. This function signals
an error if @var{time} (truncated to nanoseconds) cannot be
represented by @code{struct timespec}. For example, if @code{time_t}
is a 32-bit integral type, then a @var{time} value of ten billion
seconds would signal an error, but a @var{time} value of 600
picoseconds would get truncated to zero.
If you need to deal with time values that are not representable by
@code{struct timespec}, or if you want higher precision, call the Lisp
function @code{encode-time} and work with its return value.
@xref{Time Conversion}.
@end deftypefn
@deftypefn Function bool copy_string_contents (emacs_env *@var{env}, emacs_value @var{arg}, char *@var{buf}, ptrdiff_t *@var{len})
This function stores the UTF-8 encoded text of a Lisp string specified
by @var{arg} in the array of @code{char} pointed by @var{buf}, which
......@@ -1452,6 +1484,18 @@ This function takes a @code{double} argument @var{d} and returns the
corresponding Emacs floating-point value.
@end deftypefn
@deftypefn Function emacs_value make_time (emacs_env *@var{env}, struct timespec @var{time})
This function, which is available since Emacs 27, takes a @code{struct
timespec} argument @var{time} and returns the corresponding Emacs
timestamp as a pair @code{(@var{ticks} . @var{hz})}. @xref{Time of
Day}. The return value represents exactly the same timestamp as
@var{time}: all input values are representable, and there is never a
loss of precision. @code{@var{time}.tv_sec} and
@code{@var{time}.tv_nsec} can be arbitrary values. In particular,
there's no requirement that @var{time} be normalized. This means that
@code{@var{time}.tv_nsec} can be negative or larger than 999,999,999.
@end deftypefn
@deftypefn Function emacs_value make_string (emacs_env *@var{env}, const char *@var{str}, ptrdiff_t @var{strlen})
This function creates an Emacs string from C text string pointed by
@var{str} whose length in bytes, not including the terminating null
......@@ -1910,6 +1910,9 @@ returns a regexp that never matches anything, which is an identity for
this operation. Previously, the empty string was returned in this
** New module environment functions 'make_time' and 'extract_time' to
convert between timespec structures and Emacs Lisp time values.
* Changes in Emacs 27.1 on Non-Free Operating Systems
......@@ -77,6 +77,7 @@ To add a new module function, proceed as follows:
#include <stdint.h>
#include <stdio.h>
#include <stdlib.h>
#include <time.h>
#include "lisp.h"
#include "dynlib.h"
......@@ -737,6 +738,20 @@ module_process_input (emacs_env *env)
return emacs_process_input_continue;
static struct timespec
module_extract_time (emacs_env *env, emacs_value value)
MODULE_FUNCTION_BEGIN ((struct timespec) {0});
return lisp_time_argument (value_to_lisp (value));
static emacs_value
module_make_time (emacs_env *env, struct timespec time)
return lisp_to_value (env, make_lisp_time (time));
/* Subroutines. */
......@@ -1140,6 +1155,8 @@ initialize_environment (emacs_env *env, struct emacs_env_private *priv)
env->vec_size = module_vec_size;
env->should_quit = module_should_quit;
env->process_input = module_process_input;
env->extract_time = module_extract_time;
env->make_time = module_make_time;
Vmodule_environments = Fcons (make_mint_ptr (env), Vmodule_environments);
return env;
......@@ -22,6 +22,7 @@ along with GNU Emacs. If not, see <>. */
#include <stdint.h>
#include <stddef.h>
#include <time.h>
#ifndef __cplusplus
#include <stdbool.h>
......@@ -2,3 +2,9 @@
function should quit. */
enum emacs_process_input_result (*process_input) (emacs_env *env)
struct timespec (*extract_time) (emacs_env *env, emacs_value value)
emacs_value (*make_time) (emacs_env *env, struct timespec time)
......@@ -366,6 +366,18 @@ Fmod_test_sleep_until (emacs_env *env, ptrdiff_t nargs, emacs_value *args,
return env->intern (env, "finished");
static emacs_value
Fmod_test_add_nanosecond (emacs_env *env, ptrdiff_t nargs, emacs_value *args,
void *data)
assert (nargs == 1);
struct timespec time = env->extract_time (env, args[0]);
assert (time.tv_nsec >= 0);
assert (time.tv_nsec < 2000000000); /* possible leap second */
return env->make_time (env, time);
/* Lisp utilities for easier readability (simple wrappers). */
/* Provide FEATURE to Emacs. */
......@@ -434,6 +446,7 @@ emacs_module_init (struct emacs_runtime *ert)
DEFUN ("mod-test-invalid-finalizer", Fmod_test_invalid_finalizer, 0, 0,
DEFUN ("mod-test-sleep-until", Fmod_test_sleep_until, 2, 2, NULL, NULL);
DEFUN ("mod-test-add-nanosecond", Fmod_test_add_nanosecond, 1, 1, NULL, NULL);
#undef DEFUN
......@@ -310,4 +310,32 @@ Interactively, you can try hitting \\[keyboard-quit] to quit."
(ert-deftest mod-test-add-nanosecond/valid ()
(dolist (input (list
;; Some realistic examples.
(current-time) (time-to-seconds)
(encode-time 12 34 5 6 7 2019 t)
;; Various legacy timestamp forms.
'(123 456) '(123 456 789) '(123 456 789 6000)
;; Corner case: this will result in a nanosecond
;; value of 1000000000 after addition. The module
;; code should handle this correctly.
'(123 65535 999999 999000)
;; Seconds since the epoch.
123 123.45
;; New (TICKS . HZ) format.
'(123456789 . 1000000000)))
(ert-info ((format "input: %s" input))
(should (time-equal-p (mod-test-add-nanosecond input)
(time-add input '(0 0 0 1000)))))))
(ert-deftest mod-test-add-nanosecond/nil ()
(should (<= (float-time (mod-test-add-nanosecond nil))
(+ (float-time) 1e-9))))
(ert-deftest mod-test-add-nanosecond/invalid ()
(dolist (input '(1.0e+INF 1.0e-INF 0.0e+NaN (123) (123.45 6 7) "foo" [1 2]))
(ert-info ((format "input: %s" input))
(should-error (mod-test-add-nanosecond input)))))
;;; emacs-module-tests.el ends here
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