Add the unixepoch() function and the 'auto' and 'julianday' modifiers.

FossilOrigin-Name: 559fdc0aa76f4c207f99f7b0cee42043b402dc388165817529d9963b115a798c

src/date.c

@@ -662,6 +662,45 @@ static int parseModifier(
   int rc = 1;
   double r;
   switch(sqlite3UpperToLower[(u8)z[0]] ){
+    case 'a': {
+      /*
+      **    auto
+      **
+      ** If rawS is available, then interpret as a julian day number, or
+      ** a unix timestamp, depending on its magnitude.
+      */
+      if( sqlite3_stricmp(z, "auto")==0 ){
+        if( !p->rawS || p->validJD ){
+          rc = 0;
+          p->rawS = 0;
+        }else if( p->s>=-210866760000 && p->s<=253402300799 ){
+          r = p->s*1000.0 + 210866760000000.0;
+          clearYMD_HMS_TZ(p);
+          p->iJD = (sqlite3_int64)(r + 0.5);
+          p->validJD = 1;
+          p->rawS = 0;
+          rc = 0;
+        }
+      }
+      break;
+    }
+    case 'j': {
+      /*
+      **    julianday
+      **
+      ** Always interpret the prior number as a julian-day value.  If this
+      ** is not the first modifier, or if the prior argument is not a numeric
+      ** value in the allowed range of julian day numbers understood by
+      ** SQLite (0..5373484.5) then the result will be NULL.
+      */
+      if( sqlite3_stricmp(z, "julianday")==0 ){
+        if( p->validJD && p->rawS ){
+          rc = 0;
+          p->rawS = 0;
+        }
+      }
+      break;
+    }
 #ifndef SQLITE_OMIT_LOCALTIME
     case 'l': {
       /*    localtime
@@ -926,6 +965,24 @@ static void juliandayFunc(
   }
 }
 
+/*
+**    unixepoch( TIMESTRING, MOD, MOD, ...)
+**
+** Return the number of seconds (including fractional seconds) since
+** the unix epoch of 1970-01-01 00:00:00 GMT.
+*/
+static void unixepochFunc(
+  sqlite3_context *context,
+  int argc,
+  sqlite3_value **argv
+){
+  DateTime x;
+  if( isDate(context, argc, argv, &x)==0 ){
+    computeJD(&x);
+    sqlite3_result_int64(context, x.iJD/1000 - 21086676*(i64)10000);
+  }
+}
+
 /*
 **    datetime( TIMESTRING, MOD, MOD, ...)
 **
@@ -1202,6 +1259,7 @@ void sqlite3RegisterDateTimeFunctions(void){
   static FuncDef aDateTimeFuncs[] = {
 #ifndef SQLITE_OMIT_DATETIME_FUNCS
     PURE_DATE(julianday,        -1, 0, 0, juliandayFunc ),
+    PURE_DATE(unixepoch,        -1, 0, 0, unixepochFunc ),
     PURE_DATE(date,             -1, 0, 0, dateFunc      ),
     PURE_DATE(time,             -1, 0, 0, timeFunc      ),
     PURE_DATE(datetime,         -1, 0, 0, datetimeFunc  ),