SQLite

** This file contains the C functions that implement date and time
** functions for SQLite.  
**
** There is only one exported symbol in this file - the function
** sqlite3RegisterDateTimeFunctions() found at the bottom of the file.
** All other code has file scope.
**
** $Id: date.c,v 1.95 2008/12/09 04:59:00 shane Exp $
**
** SQLite processes all times and dates as Julian Day numbers.  The
** dates and times are stored as the number of days since noon
** in Greenwich on November 24, 4714 B.C. according to the Gregorian
** calendar system. 
**
** 1970-01-01 00:00:00 is JD 2440587.5

typedef struct DateTime DateTime;
struct DateTime {
  sqlite3_int64 iJD; /* The julian day number times 86400000 */
  int Y, M, D;       /* Year, month, and day */
  int h, m;          /* Hour and minutes */
  int tz;            /* Timezone offset in minutes */
  double s;          /* Seconds */
  char validYMD;     /* True (1) if Y,M,D are valid */
  char validHMS;     /* True (1) if h,m,s are valid */
  char validJD;      /* True (1) if iJD is valid */
  char validTZ;      /* True (1) if tz is valid */
};


/*
** Convert zDate into one or more integers.  Additional arguments
** come in groups of 5 as follows:
**

  }
  p->validJD = 0;
  p->validHMS = 1;
  p->h = h;
  p->m = m;
  p->s = s + ms;
  if( parseTimezone(zDate, p) ) return 1;
  p->validTZ = (p->tz!=0)?1:0;
  return 0;
}

/*
** Convert from YYYY-MM-DD HH:MM:SS to julian day.  We always assume
** that the YYYY-MM-DD is according to the Gregorian calendar.
**

  }
  if( M<=2 ){
    Y--;
    M += 12;
  }
  A = Y/100;
  B = 2 - A + (A/4);
  X1 = 36525*(Y+4716)/100;
  X2 = 306001*(M+1)/10000;
  p->iJD = (sqlite3_int64)((X1 + X2 + D + B - 1524.5 ) * 86400000);
  p->validJD = 1;
  if( p->validHMS ){
    p->iJD += p->h*3600000 + p->m*60000 + (sqlite3_int64)(p->s*1000);
    if( p->validTZ ){
      p->iJD -= p->tz*60000;
      p->validYMD = 0;
      p->validHMS = 0;
      p->validTZ = 0;
    }
  }

  int Z, A, B, C, D, E, X1;
  if( p->validYMD ) return;
  if( !p->validJD ){
    p->Y = 2000;
    p->M = 1;
    p->D = 1;
  }else{
    Z = (int)((p->iJD + 43200000)/86400000);
    A = (int)((Z - 1867216.25)/36524.25);
    A = Z + 1 + A - (A/4);
    B = A + 1524;
    C = (int)((B - 122.1)/365.25);
    D = (36525*C)/100;
    E = (int)((B-D)/30.6001);
    X1 = (int)(30.6001*E);
    p->D = B - D - X1;
    p->M = E<14 ? E-1 : E-13;
    p->Y = p->M>2 ? C - 4716 : C - 4715;
  }
  p->validYMD = 1;
}

/*
** Compute the Hour, Minute, and Seconds from the julian day number.
*/
static void computeHMS(DateTime *p){
  int s;
  if( p->validHMS ) return;
  computeJD(p);
  s = (int)((p->iJD + 43200000) % 86400000);
  p->s = s/1000.0;
  s = (int)p->s;
  p->s -= s;
  p->h = s/3600;
  s -= p->h*3600;
  p->m = s/60;
  p->s += s - p->m*60;
  p->validHMS = 1;
}

#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.
*/
static sqlite3_int64 localtimeOffset(DateTime *p){
  DateTime x, y;
  time_t t;
  x = *p;
  computeYMD_HMS(&x);
  if( x.Y<1971 || x.Y>=2038 ){
    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;
  }
  x.tz = 0;
  x.validJD = 0;
  computeJD(&x);
  t = x.iJD/1000 - 210866760000LL;
#ifdef HAVE_LOCALTIME_R
  {
    struct tm sLocal;
    localtime_r(&t, &sLocal);
    y.Y = sLocal.tm_year + 1900;
    y.M = sLocal.tm_mon + 1;
    y.D = sLocal.tm_mday;

      /*
      **    unixepoch
      **
      ** Treat the current value of p->iJD as the number of
      ** seconds since 1970.  Convert to a real julian day number.
      */
      if( strcmp(z, "unixepoch")==0 && p->validJD ){
        p->iJD = p->iJD*10/864000 + 210866760000000LL;
        clearYMD_HMS_TZ(p);
        rc = 0;
      }
#ifndef SQLITE_OMIT_LOCALTIME
      else if( strcmp(z, "utc")==0 ){
        sqlite3_int64 c1;
        computeJD(p);
        c1 = localtimeOffset(p);
        p->iJD -= c1;
        clearYMD_HMS_TZ(p);
        p->iJD += c1 - localtimeOffset(p);
        rc = 0;
      }
#endif
      break;
    }
    case 'w': {
      /*
      **    weekday N
      **
      ** Move the date to the same time on the next occurrence of
      ** weekday N where 0==Sunday, 1==Monday, and so forth.  If the
      ** date is already on the appropriate weekday, this is a no-op.
      */
      if( strncmp(z, "weekday ", 8)==0 && getValue(&z[8],&r)>0
                 && (n=(int)r)==r && n>=0 && r<7 ){
        sqlite3_int64 Z;
        computeYMD_HMS(p);
        p->validTZ = 0;
        p->validJD = 0;
        computeJD(p);
        Z = ((p->iJD + 129600000)/86400000) % 7;
        if( Z>n ) Z -= 7;

        clearYMD_HMS_TZ(p);
        p->iJD += tx.iJD;
        rc = 0;
        break;
      }
      z += n;
      while( isspace(*(u8*)z) ) z++;
      n = (int)strlen(z);
      if( n>10 || n<3 ) break;
      if( z[n-1]=='s' ){ z[n-1] = 0; n--; }
      computeJD(p);
      rc = 0;
      if( n==3 && strcmp(z,"day")==0 ){
        p->iJD += (sqlite3_int64)(r*86400000.0 + 0.5);
      }else if( n==4 && strcmp(z,"hour")==0 ){
        p->iJD += (sqlite3_int64)(r*(86400000.0/24.0) + 0.5);
      }else if( n==6 && strcmp(z,"minute")==0 ){
        p->iJD += (sqlite3_int64)(r*(86400000.0/(24.0*60.0)) + 0.5);
      }else if( n==6 && strcmp(z,"second")==0 ){
        p->iJD += (sqlite3_int64)(r*(86400000.0/(24.0*60.0*60.0)) + 0.5);
      }else if( n==5 && strcmp(z,"month")==0 ){
        int x, y;
        computeYMD_HMS(p);
        p->M += (int)r;
        x = p->M>0 ? (p->M-1)/12 : (p->M-12)/12;
        p->Y += x;
        p->M -= x*12;
        p->validJD = 0;
        computeJD(p);
        y = (int)r;
        if( y!=r ){
          p->iJD += (sqlite3_int64)((r - y)*30.0*86400000.0 + 0.5);
        }
      }else if( n==4 && strcmp(z,"year")==0 ){
        computeYMD_HMS(p);
        p->Y += (int)r;
        p->validJD = 0;
        computeJD(p);
      }else{
        rc = 1;
      }
      clearYMD_HMS_TZ(p);
      break;

  const unsigned char *z;
  int eType;
  memset(p, 0, sizeof(*p));
  if( argc==0 ){
    setDateTimeToCurrent(context, p);
  }else if( (eType = sqlite3_value_type(argv[0]))==SQLITE_FLOAT
                   || eType==SQLITE_INTEGER ){
    p->iJD = (sqlite3_int64)(sqlite3_value_double(argv[0])*86400000.0 + 0.5);
    p->validJD = 1;
  }else{
    z = sqlite3_value_text(argv[0]);
    if( !z || parseDateOrTime(context, (char*)z, p) ){
      return 1;
    }
  }

static void strftimeFunc(
  sqlite3_context *context,
  int argc,
  sqlite3_value **argv
){
  DateTime x;
  u64 n;
  size_t i,j;
  char *z;
  sqlite3 *db;
  const char *zFmt = (const char*)sqlite3_value_text(argv[0]);
  char zBuf[100];
  if( zFmt==0 || isDate(context, argc-1, argv+1, &x) ) return;
  db = sqlite3_context_db_handle(context);
  for(i=0, n=1; zFmt[i]; i++, n++){

  }
  if( n<sizeof(zBuf) ){
    z = zBuf;
  }else if( n>(u64)db->aLimit[SQLITE_LIMIT_LENGTH] ){
    sqlite3_result_error_toobig(context);
    return;
  }else{
    z = sqlite3DbMallocRaw(db, (int)n);
    if( z==0 ){
      sqlite3_result_error_nomem(context);
      return;
    }
  }
  computeJD(&x);
  computeYMD_HMS(&x);

        case 'j': {
          int nDay;             /* Number of days since 1st day of year */
          DateTime y = x;
          y.validJD = 0;
          y.M = 1;
          y.D = 1;
          computeJD(&y);
          nDay = (int)((x.iJD-y.iJD+43200000)/86400000);
          if( zFmt[i]=='W' ){
            int wd;   /* 0=Monday, 1=Tuesday, ... 6=Sunday */
            wd = (int)(((x.iJD+43200000)/86400000)%7);
            sqlite3_snprintf(3, &z[j],"%02d",(nDay+7-wd)/7);
            j += 2;
          }else{
            sqlite3_snprintf(4, &z[j],"%03d",nDay+1);
            j += 3;
          }
          break;

        case 's': {
          sqlite3_snprintf(30,&z[j],"%d",
                           (int)(x.iJD/1000.0 - 210866760000.0));
          j += strlen(&z[j]);
          break;
        }
        case 'S':  sqlite3_snprintf(3,&z[j],"%02d",(int)x.s); j+=2; break;
        case 'w':  z[j++] = (char)(((x.iJD+129600000)/86400000) % 7) + '0'; break;
        case 'Y':  sqlite3_snprintf(5,&z[j],"%04d",x.Y); j+=strlen(&z[j]);break;
        default:   z[j++] = '%'; break;
      }
    }
  }
  z[j] = 0;
  sqlite3_result_text(context, z, -1,