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Fold years so even 32-bit systems can handle astronomical stuff past 2038

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This commit is contained in:
Dianne Skoll
2025-05-08 14:14:49 -04:00
parent 4590e746c5
commit ed7c5103ff
3 changed files with 55 additions and 5 deletions
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53
src/funcs.c
View File

@@ -2699,7 +2699,9 @@ static int FTimeStuff(int wantmins, func_info *info)
}
}
if (CalcMinsFromUTC(dse, tim, &mins, &dst)) return E_MKTIME_PROBLEM;
if (CalcMinsFromUTC(dse, tim, &mins, &dst)) {
return E_MKTIME_PROBLEM;
}
RetVal.type = INT_TYPE;
if (wantmins) RETVAL = mins; else RETVAL = dst;
@@ -2751,6 +2753,9 @@ static int FLocalToUTC(func_info *info)
time_t loc_t;
struct tm local, *utc;
int fold_year = -1;
int wkday, isleap;
ASSERT_TYPE(0, DATETIME_TYPE);
FromDSE(DATEPART(ARG(0)), &yr, &mon, &day);
@@ -2767,10 +2772,32 @@ static int FLocalToUTC(func_info *info)
local.tm_isdst = -1;
loc_t = mktime(&local);
if (loc_t == -1) {
return E_MKTIME_PROBLEM;
/* Try folding the year */
wkday = DATEPART(ARG(0)) % 7;
isleap = IsLeapYear(yr);
fold_year = FoldArray[isleap][wkday];
memset(&local, 0, sizeof(local));
local.tm_sec = 0;
local.tm_min = min;
local.tm_hour = hr;
local.tm_mday = day;
local.tm_mon = mon;
local.tm_year = fold_year-1900;
local.tm_isdst = -1;
loc_t = mktime(&local);
if (loc_t == -1) {
/* Still no joy */
return E_MKTIME_PROBLEM;
}
}
utc = gmtime(&loc_t);
/* Unfold the year, if necessary */
if (fold_year > 0) {
utc->tm_year = yr + utc->tm_year - fold_year; /* The two 1900s cancel */
}
dse = DSE(utc->tm_year+1900, utc->tm_mon, utc->tm_mday);
RetVal.type = DATETIME_TYPE;
RETVAL = MINUTES_PER_DAY * dse + utc->tm_hour*60 + utc->tm_min;
@@ -2783,6 +2810,8 @@ static int UTCToLocalHelper(int datetime, int *ret)
time_t utc_t;
struct tm *local, utc;
char const *old_tz;
int fold_year = -1;
int isleap, wkday;
FromDSE(datetime / MINUTES_PER_DAY, &yr, &mon, &day);
hr = (datetime % MINUTES_PER_DAY) / 60;
@@ -2805,16 +2834,34 @@ static int UTCToLocalHelper(int datetime, int *ret)
utc.tm_year = yr-1900;
utc.tm_isdst = 0;
utc_t = mktime(&utc);
if (utc_t == -1) {
/* Try folding the year */
wkday = (datetime / MINUTES_PER_DAY) % 7;
isleap = IsLeapYear(yr);
fold_year = FoldArray[isleap][wkday];
memset(&utc, 0, sizeof(utc));
utc.tm_sec = 0;
utc.tm_min = min;
utc.tm_hour = hr;
utc.tm_mday = day;
utc.tm_mon = mon;
utc.tm_year = fold_year-1900;
utc.tm_isdst = 0;
utc_t = mktime(&utc);
}
tz_set_tz(old_tz);
if (old_tz) {
free( (void *) old_tz);
}
if (utc_t == -1) {
return E_MKTIME_PROBLEM;
}
local = localtime(&utc_t);
if (fold_year > 0) {
local->tm_year = yr + local->tm_year - fold_year; /* The two 1900s cancel */
}
dse = DSE(local->tm_year+1900, local->tm_mon, local->tm_mday);
*ret = MINUTES_PER_DAY * dse + local->tm_hour*60 + local->tm_min;
return OK;

3
src/globals.h
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@@ -244,3 +244,6 @@ EXTERN int SuppressLRM
/* Translatable messages */
extern char const *translatables[];
/* Array for "folding" years to similar years */
extern int FoldArray[2][7];

4
src/main.c
View File

@@ -1561,8 +1561,8 @@ int DoErrMsg(ParsePtr p)
leap year beginning on Saturday. Used to fold back dates which
are too high for the standard Unix representation.
NOTE: This implies that you cannot set BASE > 2012!!!!! */
static int FoldArray[2][7] = {
{2035, 2030, 2031, 2037, 2027, 2033, 2034},
int FoldArray[2][7] = {
{2035, 2030, 2031, 2026, 2027, 2033, 2034},
{2024, 2036, 2020, 2032, 2016, 2028, 2012}
};