Adjust date/time functions so that they do a better job of keeping track

of whether the current time is UTC or localtime, and no-op the 'utc' and
'localtime' modifiers accordingly. See
[forum:/info/e7a939e074|forum post e7a939e074].
Also add the datedebug() function, available
only under -DSQLITE_DEBUG, for improved visibility of the DateTime object
during debugging and testing.

FossilOrigin-Name: dc569683748354a6db83438904422e802d3ea780775c48da85b474fff03ca8a1

1 files changed, 60 insertions, 18 deletions

diff --git a/src/date.c b/src/date.c
index 239a772ca..3bb4a8c71 100644
--- a/src/date.c
+++ b/src/date.c
@@ -73,12 +73,12 @@ struct DateTime {
   char validJD;       /* True (1) if iJD is valid */
   char validYMD;      /* True (1) if Y,M,D are valid */
   char validHMS;      /* True (1) if h,m,s are valid */
-  char validTZ;       /* True (1) if tz is valid */
   char nFloor;            /* Days to implement "floor" */
   unsigned rawS      : 1; /* Raw numeric value stored in s */
-  unsigned tzSet     : 1; /* Timezone was set explicitly */
   unsigned isError   : 1; /* An overflow has occurred */
   unsigned useSubsec : 1; /* Display subsecond precision */
+  unsigned isUtc     : 1; /* Time is known to be UTC */
+  unsigned isLocal   : 1; /* Time is known to be localtime */
 };
 
 
@@ -176,6 +176,8 @@ static int parseTimezone(const char *zDate, DateTime *p){
     sgn = +1;
   }else if( c=='Z' || c=='z' ){
     zDate++;
+    p->isLocal = 0;
+    p->isUtc = 1;
     goto zulu_time;
   }else{
     return c!=0;
@@ -188,7 +190,6 @@ static int parseTimezone(const char *zDate, DateTime *p){
   p->tz = sgn*(nMn + nHr*60);
 zulu_time:
   while( sqlite3Isspace(*zDate) ){ zDate++; }
-  p->tzSet = 1;
   return *zDate!=0;
 }
 
@@ -232,7 +233,6 @@ static int parseHhMmSs(const char *zDate, DateTime *p){
   p->m = m;
   p->s = s + ms;
   if( parseTimezone(zDate, p) ) return 1;
-  p->validTZ = (p->tz!=0)?1:0;
   return 0;
 }
 
@@ -279,11 +279,13 @@ static void computeJD(DateTime *p){
   p->validJD = 1;
   if( p->validHMS ){
     p->iJD += p->h*3600000 + p->m*60000 + (sqlite3_int64)(p->s*1000 + 0.5);
-    if( p->validTZ ){
+    if( p->tz ){
       p->iJD -= p->tz*60000;
       p->validYMD = 0;
       p->validHMS = 0;
-      p->validTZ = 0;
+      p->tz = 0;
+      p->isUtc = 1;
+      p->isLocal = 0;
     }
   }
 }
@@ -350,11 +352,14 @@ static int parseYyyyMmDd(const char *zDate, DateTime *p){
   p->M = M;
   p->D = D;
   computeFloor(p);
-  if( p->validTZ ){
+  if( p->tz ){
     computeJD(p);
   }
   return 0;
-}
+};
+
+
+static void clearYMD_HMS_TZ(DateTime *p);  /* Forward declaration */
 
 /*
 ** Set the time to the current time reported by the VFS.
@@ -365,6 +370,9 @@ static int setDateTimeToCurrent(sqlite3_context *context, DateTime *p){
   p->iJD = sqlite3StmtCurrentTime(context);
   if( p->iJD>0 ){
     p->validJD = 1;
+    p->isUtc = 1;
+    p->isLocal = 0;
+    clearYMD_HMS_TZ(p);
     return 0;
   }else{
     return 1;
@@ -503,7 +511,7 @@ static void computeYMD_HMS(DateTime *p){
 static void clearYMD_HMS_TZ(DateTime *p){
   p->validYMD = 0;
   p->validHMS = 0;
-  p->validTZ = 0;
+  p->tz = 0;
 }
 
 #ifndef SQLITE_OMIT_LOCALTIME
@@ -635,7 +643,7 @@ static int toLocaltime(
   p->validHMS = 1;
   p->validJD = 0;
   p->rawS = 0;
-  p->validTZ = 0;
+  p->tz = 0;
   p->isError = 0;
   return SQLITE_OK;
 }
@@ -793,7 +801,9 @@ static int parseModifier(
       ** show local time.
       */
       if( sqlite3_stricmp(z, "localtime")==0 && sqlite3NotPureFunc(pCtx) ){
-        rc = toLocaltime(p, pCtx);
+        rc = p->isLocal ? SQLITE_OK : toLocaltime(p, pCtx);
+        p->isUtc = 0;
+        p->isLocal = 1;
       }
       break;
     }
@@ -818,7 +828,7 @@ static int parseModifier(
       }
 #ifndef SQLITE_OMIT_LOCALTIME
       else if( sqlite3_stricmp(z, "utc")==0 && sqlite3NotPureFunc(pCtx) ){
-        if( p->tzSet==0 ){
+        if( p->isUtc==0 ){
           i64 iOrigJD;              /* Original localtime */
           i64 iGuess;               /* Guess at the corresponding utc time */
           int cnt = 0;              /* Safety to prevent infinite loop */
@@ -841,7 +851,8 @@ static int parseModifier(
           memset(p, 0, sizeof(*p));
           p->iJD = iGuess;
           p->validJD = 1;
-          p->tzSet = 1;
+          p->isUtc = 1;
+          p->isLocal = 0;
         }
         rc = SQLITE_OK;
       }
@@ -861,7 +872,7 @@ static int parseModifier(
                && r>=0.0 && r<7.0 && (n=(int)r)==r ){
         sqlite3_int64 Z;
         computeYMD_HMS(p);
-        p->validTZ = 0;
+        p->tz = 0;
         p->validJD = 0;
         computeJD(p);
         Z = ((p->iJD + 129600000)/86400000) % 7;
@@ -901,7 +912,7 @@ static int parseModifier(
       p->h = p->m = 0;
       p->s = 0.0;
       p->rawS = 0;
-      p->validTZ = 0;
+      p->tz = 0;
       p->validJD = 0;
       if( sqlite3_stricmp(z,"month")==0 ){
         p->D = 1;
@@ -1674,9 +1685,7 @@ static void timediffFunc(
     d1.iJD = d2.iJD - d1.iJD;
     d1.iJD += (u64)1486995408 * (u64)100000;
   }
-  d1.validYMD = 0;
-  d1.validHMS = 0;
-  d1.validTZ = 0;
+  clearYMD_HMS_TZ(&d1);
   computeYMD_HMS(&d1);
   sqlite3StrAccumInit(&sRes, 0, 0, 0, 100);
   sqlite3_str_appendf(&sRes, "%c%04d-%02d-%02d %02d:%02d:%06.3f",
@@ -1745,6 +1754,36 @@ static void currentTimeFunc(
 }
 #endif
 
+#if !defined(SQLITE_OMIT_DATETIME_FUNCS) && defined(SQLITE_DEBUG)
+/*
+**   datedebug(...)
+**
+** This routine returns JSON that describes the internal DateTime object.
+** Used for debugging and testing only.  Subject to change.
+*/
+static void datedebugFunc(
+  sqlite3_context *context,
+  int argc,
+  sqlite3_value **argv
+){
+  DateTime x;
+  if( isDate(context, argc, argv, &x)==0 ){
+    char *zJson;
+    zJson = sqlite3_mprintf(
+      "{iJD:%lld,Y:%d,M:%d,D:%d,h:%d,m:%d,tz:%d,"
+      "s:%.3f,validJD:%d,validYMS:%d,validHMS:%d,"
+      "nFloor:%d,rawS:%d,isError:%d,useSubsec:%d,"
+      "isUtc:%d,isLocal:%d}",
+      x.iJD, x.Y, x.M, x.D, x.h, x.m, x.tz,
+      x.s, x.validJD, x.validYMD, x.validHMS,
+      x.nFloor, x.rawS, x.isError, x.useSubsec,
+      x.isUtc, x.isLocal);
+    sqlite3_result_text(context, zJson, -1, sqlite3_free);
+  }
+}
+#endif /* !SQLITE_OMIT_DATETIME_FUNCS && SQLITE_DEBUG */
+
+
 /*
 ** This function registered all of the above C functions as SQL
 ** functions.  This should be the only routine in this file with
@@ -1760,6 +1799,9 @@ void sqlite3RegisterDateTimeFunctions(void){
     PURE_DATE(datetime,         -1, 0, 0, datetimeFunc  ),
     PURE_DATE(strftime,         -1, 0, 0, strftimeFunc  ),
     PURE_DATE(timediff,          2, 0, 0, timediffFunc  ),
+#ifdef SQLITE_DEBUG
+    PURE_DATE(datedebug,        -1, 0, 0, datedebugFunc ),
+#endif
     DFUNCTION(current_time,      0, 0, 0, ctimeFunc     ),
     DFUNCTION(current_timestamp, 0, 0, 0, ctimestampFunc),
     DFUNCTION(current_date,      0, 0, 0, cdateFunc     ),