From: Thomas Lockhart <Thomas.G.Lockhart@jpl.nasa.gov>

Subject: [HACKERS] More date time functions

Here are some additional patches mostly related to the date and time
data types. It includes some type conversion routines to move between
the different date types and some other date manipulation routines such
as date_part(units,datetime).

I noticed Edmund Mergl et al's neat trick for getting function overloading
for builtin functions, so started to use that for the date and time stuff.
Later, if someone figures out how to get function overloading directly
for internal C code, then we can move to that technique.

These patches include documentation updates (don't faint!) for the built-in
man page. Doesn't yet include mention of timestamp, since I don't know
much about it and since it may change a bit to become a _real_ ANSI timestamp
which would include parser support for the declaration syntax (what do you
think, Dan?).

The patches were developed on the 970330 release, but have been rebuilt
off of the 970402 release. The first patch below is to get libpq to compile,
on my Linux box, but is not related to the rest of the patches and you can
choose not to apply that one at this time. Thanks in advance, scrappy!

1 files changed, 80 insertions, 19 deletions

diff --git a/src/backend/utils/adt/nabstime.c b/src/backend/utils/adt/nabstime.c
index 3ae1978b73..8f1420bbd2 100644
--- a/src/backend/utils/adt/nabstime.c
+++ b/src/backend/utils/adt/nabstime.c
@@ -7,7 +7,7 @@
  *
  *
  * IDENTIFICATION
- *    $Header: /cvsroot/pgsql/src/backend/utils/adt/nabstime.c,v 1.21 1997/03/28 07:12:53 scrappy Exp $
+ *    $Header: /cvsroot/pgsql/src/backend/utils/adt/nabstime.c,v 1.22 1997/04/02 18:33:50 scrappy Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -27,6 +27,7 @@
 #ifndef USE_POSIX_TIME
 #include <sys/timeb.h>
 #endif
+#include "utils/builtins.h"
 #include "access/xact.h"
 
 
@@ -90,11 +91,19 @@ printf( "GetCurrentAbsoluteTime- timezone is %s -> %d seconds from UTC\n",
 void
 GetCurrentTime(struct tm *tm)
 {
-    time_t now;
+    abstime2tm( GetCurrentTransactionStartTime(), &CTimeZone, tm);
+
+    return;
+} /* GetCurrentTime() */
+
+
+void
+abstime2tm(AbsoluteTime time, int *tzp, struct tm *tm)
+{
     struct tm *tt;
 
-    now = GetCurrentTransactionStartTime()-CTimeZone;
-    tt = gmtime( &now);
+    if (tzp != NULL) time -= *tzp;
+    tt = gmtime((time_t *) &time);
 
     tm->tm_year = tt->tm_year+1900;
     tm->tm_mon = tt->tm_mon+1;
@@ -105,11 +114,13 @@ GetCurrentTime(struct tm *tm)
     tm->tm_isdst = tt->tm_isdst;
 
     return;
-} /* GetCurrentTime() */
+} /* abstime2tm() */
 
 
-AbsoluteTime tm2abstime( struct tm *tm, int tz);
-
+/* tm2abstime()
+ * Convert a tm structure to abstime.
+ * Note that tm has full year (not 1900-based) and 1-based month.
+ */
 AbsoluteTime
 tm2abstime( struct tm *tm, int tz)
 {
@@ -122,13 +133,13 @@ tm2abstime( struct tm *tm, int tz)
       || tm->tm_hour < 0 || tm->tm_hour >= 24
       || tm->tm_min < 0 || tm->tm_min > 59
       || tm->tm_sec < 0 || tm->tm_sec > 59)
-	return INVALID_ABSTIME;
+	return(INVALID_ABSTIME);
 
     day = (date2j( tm->tm_year, tm->tm_mon, tm->tm_mday) - date2j( 1970, 1, 1));
 
     /* check for time out of range */
     if ((day < MIN_DAYNUM) || (day > MAX_DAYNUM))
-	return INVALID_ABSTIME;
+	return(INVALID_ABSTIME);
 
     /* convert to seconds */
     sec = tm->tm_sec + tz + (tm->tm_min +(day*24 + tm->tm_hour)*60)*60;
@@ -136,7 +147,7 @@ tm2abstime( struct tm *tm, int tz)
     /* check for overflow */
     if ((day == MAX_DAYNUM && sec < 0) ||
       (day == MIN_DAYNUM && sec > 0))
-	return INVALID_ABSTIME;
+	return(INVALID_ABSTIME);
 
     /* daylight correction */
     if (tm->tm_isdst < 0) {		/* unknown; find out */
@@ -147,7 +158,7 @@ tm2abstime( struct tm *tm, int tz)
 
     /* check for reserved values (e.g. "current" on edge of usual range */
     if (!AbsoluteTimeIsReal(sec))
-	return INVALID_ABSTIME;
+	return(INVALID_ABSTIME);
 
     return sec;
 } /* tm2abstime() */
@@ -369,6 +380,16 @@ AbsoluteTimeIsAfter(AbsoluteTime time1, AbsoluteTime time2)
 }
 
 
+/* abstime_finite()
+ */
+bool
+abstime_finite(AbsoluteTime abstime)
+{
+    return((abstime != INVALID_ABSTIME)
+      && (abstime != NOSTART_ABSTIME) && (abstime != NOEND_ABSTIME));
+} /* abstime_datetime() */
+
+
 /*
  *	abstimeeq	- returns 1, iff arguments are equal
  *	abstimene	- returns 1, iff arguments are not equal
@@ -381,7 +402,7 @@ bool
 abstimeeq(AbsoluteTime t1, AbsoluteTime t2)
 {
     if (t1 == INVALID_ABSTIME || t2 == INVALID_ABSTIME)
-	return 0;
+	return(FALSE);
     if (t1 == CURRENT_ABSTIME)
 	t1 = GetCurrentTransactionStartTime();
     if (t2 == CURRENT_ABSTIME)
@@ -394,7 +415,7 @@ bool
 abstimene(AbsoluteTime t1, AbsoluteTime t2)
 { 
     if (t1 == INVALID_ABSTIME || t2 == INVALID_ABSTIME)
-	return 0;
+	return(FALSE);
     if (t1 == CURRENT_ABSTIME)
 	t1 = GetCurrentTransactionStartTime();
     if (t2 == CURRENT_ABSTIME)
@@ -407,7 +428,7 @@ bool
 abstimelt(AbsoluteTime t1, AbsoluteTime t2)
 { 
     if (t1 == INVALID_ABSTIME || t2 == INVALID_ABSTIME)
-	return 0;
+	return(FALSE);
     if (t1 == CURRENT_ABSTIME)
 	t1 = GetCurrentTransactionStartTime();
     if (t2 == CURRENT_ABSTIME)
@@ -420,7 +441,7 @@ bool
 abstimegt(AbsoluteTime t1, AbsoluteTime t2)
 { 
     if (t1 == INVALID_ABSTIME || t2 == INVALID_ABSTIME)
-	return 0;
+	return(FALSE);
     if (t1 == CURRENT_ABSTIME)
 	t1 = GetCurrentTransactionStartTime();
     if (t2 == CURRENT_ABSTIME)
@@ -433,7 +454,7 @@ bool
 abstimele(AbsoluteTime t1, AbsoluteTime t2)
 { 
     if (t1 == INVALID_ABSTIME || t2 == INVALID_ABSTIME)
-	return 0;
+	return(FALSE);
     if (t1 == CURRENT_ABSTIME)
 	t1 = GetCurrentTransactionStartTime();
     if (t2 == CURRENT_ABSTIME)
@@ -446,7 +467,7 @@ bool
 abstimege(AbsoluteTime t1, AbsoluteTime t2)
 { 
     if (t1 == INVALID_ABSTIME || t2 == INVALID_ABSTIME)
-	return 0;
+	return(FALSE);
     if (t1 == CURRENT_ABSTIME)
 	t1 = GetCurrentTransactionStartTime();
     if (t2 == CURRENT_ABSTIME)
@@ -455,6 +476,7 @@ abstimege(AbsoluteTime t1, AbsoluteTime t2)
     return(t1 >= t2);
 }
 
+
 /* datetime_abstime()
  * Convert datetime to abstime.
  */
@@ -480,10 +502,10 @@ datetime_abstime(DateTime *datetime)
 
     } else {
 	if (DATETIME_IS_RELATIVE(*datetime)) {
-	    datetime2tm( SetDateTime(*datetime), tm, &fsec);
+	    datetime2tm( SetDateTime(*datetime), &CTimeZone, tm, &fsec);
 	    result = tm2abstime( tm, 0);
 
-	} else if (datetime2tm( *datetime, tm, &fsec) == 0) {
+	} else if (datetime2tm( *datetime, &CTimeZone, tm, &fsec) == 0) {
 	    result = tm2abstime( tm, 0);
 
 	} else {
@@ -493,3 +515,42 @@ datetime_abstime(DateTime *datetime)
 
     return(result);
 } /* datetime_abstime() */
+
+/* abstime_datetime()
+ * Convert datetime to abstime.
+ */
+DateTime *
+abstime_datetime(AbsoluteTime abstime)
+{
+    DateTime *result;
+
+    if (!PointerIsValid(result = PALLOCTYPE(DateTime)))
+	elog(WARN,"Unable to allocate space to convert abstime to datetime",NULL);
+
+    switch (abstime) {
+    case INVALID_ABSTIME:
+        DATETIME_INVALID(*result);
+	break;
+
+    case NOSTART_ABSTIME:
+        DATETIME_NOBEGIN(*result);
+	break;
+
+    case NOEND_ABSTIME:
+        DATETIME_NOEND(*result);
+	break;
+
+    case EPOCH_ABSTIME:
+        DATETIME_EPOCH(*result);
+	break;
+
+    case CURRENT_ABSTIME:
+        DATETIME_CURRENT(*result);
+	break;
+
+    default:
+        *result = abstime + ((date2j( 1970, 1, 1) - date2j( 2000, 1, 1))*86400);
+    };
+
+    return(result);
+} /* abstime_datetime() */