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add GMT option to seconds->date

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This commit is contained in:
Matthew Flatt 2010-08-25 10:45:12 -06:00
parent bc1aeef3c0
commit a04403a316
2 changed files with 47 additions and 21 deletions
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20
collects/scribblings/reference/time.scrbl
View File

@ -15,13 +15,19 @@ The value of @racket[(current-seconds)] increases as time passes
seconds can be compared with a time returned by
@racket[file-or-directory-modify-seconds].}
@defproc[(seconds->date [secs-n exact-integer?]) date?]{
@defproc[(seconds->date [secs-n exact-integer?]
[local-time? any/c #t])
date?]{
Takes @racket[secs-n], a platform-specific time in seconds returned by
@racket[current-seconds] or @racket[file-or-directory-modify-seconds],
and returns an instance of the @racket[date] structure type. If
@racket[secs-n] is too small or large, the @exnraise[exn:fail].
The resulting @racket[date] reflects the time according to the local
time zone if @racket[local-time?] is @racket[#t], otherwise it
reflects a date in GMT.
The value returned by @racket[current-seconds] or
@racket[file-or-directory-modify-seconds] is not portable among
platforms. Convert a time in seconds using @racket[seconds->date] when
@ -44,9 +50,15 @@ Represents a date. For the @racket[second] field, values of
leap-seconds. The @racket[year-day] field reaches @racket[365] only in
leap years.
The @racket[time-zone-offset] field reports the number of seconds east
of GMT for the current time zone (e.g., Pacific Standard Time is
@racket[-28800]), an exact integer.
The @racket[dst?] field is @racket[#t] if the date reflects a
daylight-saving adjustment. The @racket[time-zone-offset] field
reports the number of seconds east of GMT for the current time zone
(e.g., Pacific Standard Time is @racket[-28800]), including any
daylight-saving adjustment (e.g., Pacific Daylight Time is
@racket[-25200]). When a @racket[date] record is generated by
@racket[seconds->date] with @racket[#f] as the second argument, then
the @racket[dst?] and @racket[time-zone-offset] fields are
@racket[#f] and @racket[0], respectively.
The value produced for the @racket[time-zone-offset] field tends to be
sensitive to the value of the @envvar{TZ} environment variable,

48
src/racket/src/fun.c
View File

@ -470,7 +470,7 @@ scheme_init_fun (Scheme_Env *env)
scheme_add_global_constant("seconds->date",
scheme_make_prim_w_arity(seconds_to_date,
"seconds->date",
1, 1),
1, 2),
env);
#endif
@ -8770,6 +8770,7 @@ static int month_offsets[12] = { 0, 31, 59, 90,
static Scheme_Object *seconds_to_date(int argc, Scheme_Object **argv)
{
UNBUNDLE_TIME_TYPE lnow;
int get_gmt;
int hour, min, sec, month, day, year, wday, yday, dst;
long tzoffset;
#ifdef USE_MACTIME
@ -8777,7 +8778,7 @@ static Scheme_Object *seconds_to_date(int argc, Scheme_Object **argv)
DateTimeRec localTime;
#else
# ifdef USE_PALMTIME
# define CHECK_TIME_T UInt32
# define CHECK_TIME_T UInt32
DateTimeType localTime;
# else
# define CHECK_TIME_T time_t
@ -8793,6 +8794,11 @@ static Scheme_Object *seconds_to_date(int argc, Scheme_Object **argv)
scheme_wrong_type("seconds->date", "exact integer", 0, argc, argv);
return NULL;
}
if (argc > 1)
get_gmt = SCHEME_FALSEP(argv[1]);
else
get_gmt = 0;
if (scheme_get_time_val(secs, &lnow)
&& ((UNBUNDLE_TIME_TYPE)(now = (CHECK_TIME_T)lnow)) == lnow) {
@ -8805,7 +8811,10 @@ static Scheme_Object *seconds_to_date(int argc, Scheme_Object **argv)
# ifdef USE_PALMTIME
TimSecondsToDateTime(lnow, &localTime) ;
# else
localTime = localtime(&now);
if (get_gmt)
localTime = gmtime(&now);
else
localTime = localtime(&now);
success = !!localTime;
# endif
#endif
@ -8816,7 +8825,7 @@ static Scheme_Object *seconds_to_date(int argc, Scheme_Object **argv)
# define mzDOW(localTime) localTime.dayOfWeek - 1
# else
# define mzDOW(localTime) localTime.weekDay
#endif
# endif
hour = localTime.hour;
min = localTime.minute;
@ -8831,7 +8840,7 @@ static Scheme_Object *seconds_to_date(int argc, Scheme_Object **argv)
yday = month_offsets[localTime.month - 1] + localTime.day - 1;
/* If month > 2, is it a leap-year? */
if (localTime.month > 2) {
#ifdef USE_MACTIME
# ifdef USE_MACTIME
unsigned long ttime;
DateTimeRec tester;
@ -8845,11 +8854,11 @@ static Scheme_Object *seconds_to_date(int argc, Scheme_Object **argv)
if (tester.month == 2)
/* It is a leap-year */
yday++;
#else
# else
/* PalmOS: */
if (DaysInMonth(2, year) > 28)
yday++;
#endif
# endif
}
# ifdef USE_MACTIME
@ -8882,32 +8891,37 @@ static Scheme_Object *seconds_to_date(int argc, Scheme_Object **argv)
wday = localTime->tm_wday;
yday = localTime->tm_yday;
dst = localTime->tm_isdst;
if (get_gmt)
dst = 0;
else
dst = localTime->tm_isdst;
tzoffset = 0;
if (!get_gmt) {
# ifdef USE_TIMEZONE_VAR
tzoffset = -MSC_IZE(timezone);
tzoffset = -MSC_IZE(timezone);
# endif
# ifdef USE_TOD_FOR_TIMEZONE
{
{
struct timezone xtz;
struct timeval xtv;
gettimeofday(&xtv, &xtz);
tzoffset = -(xtz.tz_minuteswest * 60);
}
}
# endif
# ifdef USE_TIMEZONE_VAR_W_DLS
tzoffset = -(MSCBOR_IZE(timezone) - (dst ? 3600 : 0));
tzoffset = -(MSCBOR_IZE(timezone) - (dst ? 3600 : 0));
# endif
# ifdef USE_TIMEZONE_AND_ALTZONE_VAR
if (dst)
tzoffset = -altzone;
else
tzoffset = -timezone;
if (dst)
tzoffset = -altzone;
else
tzoffset = -timezone;
# endif
# ifdef USE_TM_GMTOFF_FIELD
tzoffset = localTime->tm_gmtoff;
tzoffset = localTime->tm_gmtoff;
# endif
}
#endif