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Performance improve to the 'localtime' and 'utc' modifiers for date/time

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functions.

FossilOrigin-Name: 85cb6014751a0572d28ebd839331d5d7a78de45c9e522adcd834a8a85746f32e
This commit is contained in:
drh
2022-02-10 15:40:40 +00:00
parent 522608d3a2
commit eadccaa926
4 changed files with 71 additions and 71 deletions
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112
src/date.c
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@@ -544,67 +544,56 @@ static int osLocaltime(time_t *t, struct tm *pTm){
#ifndef SQLITE_OMIT_LOCALTIME
/*
** Compute the difference (in milliseconds) between localtime and UTC
** (a.k.a. GMT) for the time value p where p is in UTC. If no error occurs,
** return this value and set *pRc to SQLITE_OK.
**
** Or, if an error does occur, set *pRc to SQLITE_ERROR. The returned value
** is undefined in this case.
** Assuming the input DateTime is UTC, move it to its localtime equivalent.
*/
static sqlite3_int64 localtimeOffset(
DateTime *p, /* Date at which to calculate offset */
sqlite3_context *pCtx, /* Write error here if one occurs */
int *pRc /* OUT: Error code. SQLITE_OK or ERROR */
static int toLocaltime(
DateTime *p, /* Date at which to calculate offset */
sqlite3_context *pCtx /* Write error here if one occurs */
){
DateTime x, y;
time_t t;
struct tm sLocal;
int iYearDiff;
/* Initialize the contents of sLocal to avoid a compiler warning. */
memset(&sLocal, 0, sizeof(sLocal));
x = *p;
computeYMD_HMS(&x);
if( x.Y<1971 || x.Y>=2038 ){
computeJD(p);
if( p->iJD<21086676000*(i64)10000 /* 1970-01-01 */
|| p->iJD>21301414560*(i64)10000 /* 2038-01-18 */
){
/* EVIDENCE-OF: R-55269-29598 The localtime_r() C function normally only
** works for years between 1970 and 2037. For dates outside this range,
** SQLite attempts to map the year into an equivalent year within this
** range, do the calculation, then map the year back.
*/
x.Y = 2000;
x.M = 1;
x.D = 1;
x.h = 0;
x.m = 0;
x.s = 0.0;
} else {
int s = (int)(x.s + 0.5);
x.s = s;
DateTime x = *p;
computeYMD_HMS(&x);
iYearDiff = (2000 + x.Y%4) - x.Y;
x.Y += iYearDiff;
x.validJD = 0;
computeJD(&x);
t = (time_t)(x.iJD/1000 - 21086676*(i64)10000);
}else{
iYearDiff = 0;
t = (time_t)(p->iJD/1000 - 21086676*(i64)10000);
}
x.tz = 0;
x.validJD = 0;
computeJD(&x);
t = (time_t)(x.iJD/1000 - 21086676*(i64)10000);
if( osLocaltime(&t, &sLocal) ){
sqlite3_result_error(pCtx, "local time unavailable", -1);
*pRc = SQLITE_ERROR;
return 0;
return SQLITE_ERROR;
}
y.Y = sLocal.tm_year + 1900;
y.M = sLocal.tm_mon + 1;
y.D = sLocal.tm_mday;
y.h = sLocal.tm_hour;
y.m = sLocal.tm_min;
y.s = sLocal.tm_sec;
y.validYMD = 1;
y.validHMS = 1;
y.validJD = 0;
y.rawS = 0;
y.validTZ = 0;
y.isError = 0;
computeJD(&y);
*pRc = SQLITE_OK;
return y.iJD - x.iJD;
p->Y = sLocal.tm_year + 1900 - iYearDiff;
p->M = sLocal.tm_mon + 1;
p->D = sLocal.tm_mday;
p->h = sLocal.tm_hour;
p->m = sLocal.tm_min;
p->s = sLocal.tm_sec;
p->validYMD = 1;
p->validHMS = 1;
p->validJD = 0;
p->rawS = 0;
p->validTZ = 0;
p->isError = 0;
return SQLITE_OK;
}
#endif /* SQLITE_OMIT_LOCALTIME */
@@ -713,9 +702,7 @@ static int parseModifier(
** show local time.
*/
if( sqlite3_stricmp(z, "localtime")==0 && sqlite3NotPureFunc(pCtx) ){
computeJD(p);
p->iJD += localtimeOffset(p, pCtx, &rc);
clearYMD_HMS_TZ(p);
rc = toLocaltime(p, pCtx);
}
break;
}
@@ -741,18 +728,31 @@ static int parseModifier(
#ifndef SQLITE_OMIT_LOCALTIME
else if( sqlite3_stricmp(z, "utc")==0 && sqlite3NotPureFunc(pCtx) ){
if( p->tzSet==0 ){
sqlite3_int64 c1;
i64 iOrigJD; /* Original localtime */
i64 iGuess; /* Guess at the corresponding utc time */
int cnt = 0; /* Safety to prevent infinite loop */
int iErr; /* Guess is off by this much */
computeJD(p);
c1 = localtimeOffset(p, pCtx, &rc);
if( rc==SQLITE_OK ){
p->iJD -= c1;
clearYMD_HMS_TZ(p);
p->iJD += c1 - localtimeOffset(p, pCtx, &rc);
}
iGuess = iOrigJD = p->iJD;
iErr = 0;
do{
DateTime new;
memset(&new, 0, sizeof(new));
iGuess -= iErr;
new.iJD = iGuess;
new.validJD = 1;
rc = toLocaltime(&new, pCtx);
if( rc ) return rc;
computeJD(&new);
iErr = new.iJD - iOrigJD;
}while( iErr && cnt++<3 );
memset(p, 0, sizeof(*p));
p->iJD = iGuess;
p->validJD = 1;
p->tzSet = 1;
}else{
rc = SQLITE_OK;
}
rc = SQLITE_OK;
}
#endif
break;