func.c

SQLite 2.8.6 源代码,用来在Linux/Unix/Windows上编译安装.它是一个小型的数据库,但是非常好用,速度也快,一般的数据库查询之类的操作据统计比MySQL,PostgreSQL

  CountCtx *p;
  p = sqlite_aggregate_context(context, sizeof(*p));
  if( (argc==0 || argv[0]) && p ){
    p->n++;
  }
}   
static void countFinalize(sqlite_func *context){
  CountCtx *p;
  p = sqlite_aggregate_context(context, sizeof(*p));
  sqlite_set_result_int(context, p ? p->n : 0);
}

/*
** This function tracks state information for the min() and max()
** aggregate functions.
*/
typedef struct MinMaxCtx MinMaxCtx;
struct MinMaxCtx {
  char *z;         /* The best so far */
  char zBuf[28];   /* Space that can be used for storage */
};

/*
** Routines to implement min() and max() aggregate functions.
*/
static void minStep(sqlite_func *context, int argc, const char **argv){
  MinMaxCtx *p;
  p = sqlite_aggregate_context(context, sizeof(*p));
  if( p==0 || argc<1 || argv[0]==0 ) return;
  if( p->z==0 || sqliteCompare(argv[0],p->z)<0 ){
    int len;
    if( p->z && p->z!=p->zBuf ){
      sqliteFree(p->z);
    }
    len = strlen(argv[0]);
    if( len < sizeof(p->zBuf) ){
      p->z = p->zBuf;
    }else{
      p->z = sqliteMalloc( len+1 );
      if( p->z==0 ) return;
    }
    strcpy(p->z, argv[0]);
  }
}
static void maxStep(sqlite_func *context, int argc, const char **argv){
  MinMaxCtx *p;
  p = sqlite_aggregate_context(context, sizeof(*p));
  if( p==0 || argc<1 || argv[0]==0 ) return;
  if( p->z==0 || sqliteCompare(argv[0],p->z)>0 ){
    int len;
    if( p->z && p->z!=p->zBuf ){
      sqliteFree(p->z);
    }
    len = strlen(argv[0]);
    if( len < sizeof(p->zBuf) ){
      p->z = p->zBuf;
    }else{
      p->z = sqliteMalloc( len+1 );
      if( p->z==0 ) return;
    }
    strcpy(p->z, argv[0]);
  }
}
static void minMaxFinalize(sqlite_func *context){
  MinMaxCtx *p;
  p = sqlite_aggregate_context(context, sizeof(*p));
  if( p && p->z ){
    sqlite_set_result_string(context, p->z, strlen(p->z));
  }
  if( p && p->z && p->z!=p->zBuf ){
    sqliteFree(p->z);
  }
}

/****************************************************************************
** Time and date functions.
**
** 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.
**
** This implement requires years to be expressed as a 4-digit number
** which means that only dates between 0000-01-01 and 9999-12-31 can
** be represented, even though julian day numbers allow a much wider
** range of dates.
**
** The Gregorian calendar system is used for all dates and times,
** even those that predate the Gregorian calendar.  Historians usually
** use the Julian calendar for dates prior to 1582-10-15 and for some
** dates afterwards, depending on locale.  Beware of this difference.
**
** The conversion algorithms are implemented based on descriptions
** in the following text:
**
**      Jean Meeus
**      Astronomical Algorithms, 2nd Edition, 1998
**      ISBM 0-943396-61-1
**      Willmann-Bell, Inc
**      Richmond, Virginia (USA)
*/
#ifndef SQLITE_OMIT_DATETIME_FUNCS

/*
** Convert N digits from zDate into an integer.  Return
** -1 if zDate does not begin with N digits.
*/
static int getDigits(const char *zDate, int N){
  int val = 0;
  while( N-- ){
    if( !isdigit(*zDate) ) return -1;
    val = val*10 + *zDate - '0';
    zDate++;
  }
  return val;
}

/*
** Parse times of the form HH:MM:SS or HH:MM.  Store the
** result (in days) in *prJD.
**
** Return 1 if there is a parsing error and 0 on success.
*/
static int parseHhMmSs(const char *zDate, double *prJD){
  int h, m, s;
  h = getDigits(zDate, 2);
  if( h<0 || zDate[2]!=':' ) return 1;
  zDate += 3;
  m = getDigits(zDate, 2);
  if( m<0 || m>59 ) return 1;
  zDate += 2;
  if( *zDate==':' ){
    s = getDigits(&zDate[1], 2);
    if( s<0 || s>59 ) return 1;
    zDate += 3;
  }else{
    s = 0;
  }
  while( isspace(*zDate) ){ zDate++; }
  *prJD = (h*3600.0 + m*60.0 + s)/86400.0;
  return 0;
}

/*
** Parse dates of the form
**
**     YYYY-MM-DD HH:MM:SS
**     YYYY-MM-DD HH:MM
**     YYYY-MM-DD
**
** Write the result as a julian day number in *prJD.  Return 0
** on success and 1 if the input string is not a well-formed
** date.
*/
static int parseYyyyMmDd(const char *zDate, double *prJD){
  int Y, M, D;
  double rTime;
  int A, B, X1, X2;

  Y = getDigits(zDate, 4);
  if( Y<0 || zDate[4]!='-' ) return 1;
  zDate += 5;
  M = getDigits(zDate, 2);
  if( M<=0 || M>12 || zDate[2]!='-' ) return 1;
  zDate += 3;
  D = getDigits(zDate, 2);
  if( D<=0 || D>31 ) return 1;
  zDate += 2;
  while( isspace(*zDate) ){ zDate++; }
  if( isdigit(*zDate) ){
    if( parseHhMmSs(zDate, &rTime) ) return 1;
  }else if( *zDate==0 ){
    rTime = 0.0;
  }else{ 
    return 1;
  }

  /* The year, month, and day are now stored in Y, M, and D.  Convert
  ** these into the Julian Day number.  See Meeus page 61.
  */
  if( M<=2 ){
    Y--;
    M += 12;
  }
  A = Y/100;
  B = 2 - A + (A/4);
  X1 = 365.25*(Y+4716);
  X2 = 30.6001*(M+1);
  *prJD = X1 + X2 + D + B - 1524.5 + rTime;
  return 0;
}

/*
** Attempt to parse the given string into a Julian Day Number.  Return
** the number of errors.
**
** The following are acceptable forms for the input string:
**
**      YYYY-MM-DD
**      YYYY-MM-DD HH:MM
**      YYYY-MM-DD HH:MM:SS
**      HH:MM
**      HH:MM:SS
**      DDDD.DD 
**      now
*/
static int parseDateOrTime(const char *zDate, double *prJD){
  int i;
  for(i=0; isdigit(zDate[i]); i++){}
  if( i==4 && zDate[i]=='-' ){
    return parseYyyyMmDd(zDate, prJD);
  }else if( i==2 && zDate[i]==':' ){
    return parseHhMmSs(zDate, prJD);
  }else if( i==0 && sqliteStrICmp(zDate,"now")==0 ){
    return sqliteOsCurrentTime(prJD);
  }else if( sqliteIsNumber(zDate) ){
    *prJD = atof(zDate);
    return 0;
  }
  return 1;
}

/*
** A structure for holding date and time.
*/
typedef struct DateTime DateTime;
struct DateTime {
  double rJD;    /* The julian day number */
  int Y, M, D;   /* Year, month, and day */
  int h, m, s;   /* Hour minute and second */
};

/*
** Break up a julian day number into year, month, day, hour, minute, second.
** This function assume the Gregorian calendar - even for dates prior
** to the invention of the Gregorian calendar in 1582.
**
** See Meeus page 63.
**
** If mode==1 only the year, month, and day are computed.  If mode==2
** then only the hour, minute, and second are computed.  If mode==3 then
** everything is computed.  If mode==0, this routine is a no-op.
*/
static void decomposeDate(DateTime *p, int mode){
  int Z;
  Z = p->rJD + 0.5;
  if( mode & 1 ){
    int A, B, C, D, E, X1;
    A = (Z - 1867216.25)/36524.25;
    A = Z + 1 + A - (A/4);
    B = A + 1524;
    C = (B - 122.1)/365.25;
    D = 365.25*C;
    E = (B-D)/30.6001;
    X1 = 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;
  }
  if( mode & 2 ){
    p->s = (p->rJD + 0.5 - Z)*86400.0;
    p->h = p->s/3600;
    p->s -= p->h*3600;
    p->m = p->s/60;
    p->s -= p->m*60;
  }
}

/*
** Check to see that all arguments are valid date strings.  If any 
** argument is not a valid date string, return 0.  If all arguments
** are valid, return 1 and write into *p->rJD the sum of the julian day
** numbers for all date strings.
**
** A "valid" date string is one that is accepted by parseDateOrTime().
**
** The mode argument is passed through to decomposeDate() in order to
** fill in the year, month, day, hour, minute, and second of the *p
** structure, if desired.
*/
static int isDate(int argc, const char **argv, DateTime *p, int mode){
  double r;
  int i;
  p->rJD = 0.0;
  for(i=0; i<argc; i++){
    if( argv[i]==0 ) return 0;
    if( parseDateOrTime(argv[i], &r) ) return 0;
    p->rJD += r;
  }
  decomposeDate(p, mode);
  return 1;
}


/*
** The following routines implement the various date and time functions
** of SQLite.
*/
static void juliandayFunc(sqlite_func *context, int argc, const char **argv){
  DateTime x;
  if( isDate(argc, argv, &x, 0) ){
    sqlite_set_result_double(context, x.rJD);
  }
}
static void timestampFunc(sqlite_func *context, int argc, const char **argv){
  DateTime x;
  if( isDate(argc, argv, &x, 3) ){
    char zBuf[100];
    sprintf(zBuf, "%04d-%02d-%02d %02d:%02d:%02d",x.Y, x.M, x.D, x.h, x.m, x.s);
    sqlite_set_result_string(context, zBuf, -1);
  }
}
static void timeFunc(sqlite_func *context, int argc, const char **argv){
  DateTime x;
  if( isDate(argc, argv, &x, 2) ){
    char zBuf[100];
    sprintf(zBuf, "%02d:%02d:%02d", x.h, x.m, x.s);
    sqlite_set_result_string(context, zBuf, -1);
  }
}
static void dateFunc(sqlite_func *context, int argc, const char **argv){
  DateTime x;
  if( isDate(argc, argv, &x, 1) ){
    char zBuf[100];
    sprintf(zBuf, "%04d-%02d-%02d", x.Y, x.M, x.D);
    sqlite_set_result_string(context, zBuf, -1);
  }
}
static void yearFunc(sqlite_func *context, int argc, const char **argv){
  DateTime x;
  if( isDate(argc, argv, &x, 1) ){
    sqlite_set_result_int(context, x.Y);
  }
}
static void monthFunc(sqlite_func *context, int argc, const char **argv){
  DateTime x;
  if( isDate(argc, argv, &x, 1) ){
    sqlite_set_result_int(context, x.M);
  }
}
static void dayofweekFunc(sqlite_func *context, int argc, const char **argv){
  DateTime x;
  if( isDate(argc, argv, &x, 0) ){
    int Z = x.rJD + 1.5;
    sqlite_set_result_int(context, Z % 7);
  }
}
static void dayofmonthFunc(sqlite_func *context, int argc, const char **argv){
  DateTime x;
  if( isDate(argc, argv, &x, 1) ){
    sqlite_set_result_int(context, x.D);
  }
}
static void secondFunc(sqlite_func *context, int argc, const char **argv){
  DateTime x;
  if( isDate(argc, argv, &x, 2) ){
    sqlite_set_result_int(context, x.s);
  }
}
static void minuteFunc(sqlite_func *context, int argc, const char **argv){
  DateTime x;
  if( isDate(argc, argv, &x, 2) ){
    sqlite_set_result_int(context, x.m);
  }
}
static void hourFunc(sqlite_func *context, int argc, const char **argv){
  DateTime x;
  if( isDate(argc, argv, &x, 2) ){
    sqlite_set_result_int(context, x.h);
  }
}
#endif /* !defined(SQLITE_OMIT_DATETIME_FUNCS) */
/***************************************************************************/

/*
** This function registered all of the above C functions as SQL
** functions.  This should be the only routine in this file with
** external linkage.
*/
void sqliteRegisterBuiltinFunctions(sqlite *db){
  static struct {
     char *zName;
     int nArg;
     int dataType;
     void (*xFunc)(sqlite_func*,int,const char**);
  } aFuncs[] = {
    { "min",       -1, SQLITE_ARGS,    minFunc    },
    { "min",        0, 0,              0          },
    { "max",       -1, SQLITE_ARGS,    maxFunc    },
    { "max",        0, 0,              0          },
    { "length",     1, SQLITE_NUMERIC, lengthFunc },
    { "substr",     3, SQLITE_TEXT,    substrFunc },
    { "abs",        1, SQLITE_NUMERIC, absFunc    },
    { "round",      1, SQLITE_NUMERIC, roundFunc  },
    { "round",      2, SQLITE_NUMERIC, roundFunc  },
    { "upper",      1, SQLITE_TEXT,    upperFunc  },
    { "lower",      1, SQLITE_TEXT,    lowerFunc  },
    { "coalesce",  -1, SQLITE_ARGS,    ifnullFunc },
    { "coalesce",   0, 0,              0          },
    { "coalesce",   1, 0,              0          },
    { "ifnull",     2, SQLITE_ARGS,    ifnullFunc },
    { "random",    -1, SQLITE_NUMERIC, randomFunc },
    { "like",       2, SQLITE_NUMERIC, likeFunc   },
    { "glob",       2, SQLITE_NUMERIC, globFunc   },
    { "nullif",     2, SQLITE_ARGS,    nullifFunc },
    { "sqlite_version",0,SQLITE_TEXT,  versionFunc},
    { "quote",      1, SQLITE_ARGS,    quoteFunc  },
#ifndef SQLITE_OMIT_DATETIME_FUNCS
    { "julianday", -1, SQLITE_NUMERIC, juliandayFunc   },
    { "timestamp", -1, SQLITE_TEXT,    timestampFunc   },
    { "time",      -1, SQLITE_TEXT,    timeFunc        },
    { "date",      -1, SQLITE_TEXT,    dateFunc        },
    { "year",      -1, SQLITE_NUMERIC, yearFunc        },
    { "month",     -1, SQLITE_NUMERIC, monthFunc       },
    { "dayofmonth",-1, SQLITE_NUMERIC, dayofmonthFunc  },
    { "dayofweek", -1, SQLITE_NUMERIC, dayofweekFunc   },
    { "hour",      -1, SQLITE_NUMERIC, hourFunc        },
    { "minute",    -1, SQLITE_NUMERIC, minuteFunc      },
    { "second",    -1, SQLITE_NUMERIC, secondFunc      },
#endif
#ifdef SQLITE_SOUNDEX
    { "soundex",    1, SQLITE_TEXT,    soundexFunc},
#endif
#ifdef SQLITE_TEST
    { "randstr",    2, SQLITE_TEXT,    randStr    },
#endif
  };
  static struct {
    char *zName;
    int nArg;
    int dataType;
    void (*xStep)(sqlite_func*,int,const char**);
    void (*xFinalize)(sqlite_func*);
  } aAggs[] = {
    { "min",    1, 0,              minStep,      minMaxFinalize },
    { "max",    1, 0,              maxStep,      minMaxFinalize },
    { "sum",    1, SQLITE_NUMERIC, sumStep,      sumFinalize    },
    { "avg",    1, SQLITE_NUMERIC, sumStep,      avgFinalize    },
    { "count",  0, SQLITE_NUMERIC, countStep,    countFinalize  },
    { "count",  1, SQLITE_NUMERIC, countStep,    countFinalize  },
#if 0
    { "stddev", 1, SQLITE_NUMERIC, stdDevStep,   stdDevFinalize },
#endif
  };
  int i;

  for(i=0; i<sizeof(aFuncs)/sizeof(aFuncs[0]); i++){
    sqlite_create_function(db, aFuncs[i].zName,
           aFuncs[i].nArg, aFuncs[i].xFunc, 0);
    if( aFuncs[i].xFunc ){
      sqlite_function_type(db, aFuncs[i].zName, aFuncs[i].dataType);
    }
  }
  sqlite_create_function(db, "last_insert_rowid", 0, 
           last_insert_rowid, db);
  sqlite_function_type(db, "last_insert_rowid", SQLITE_NUMERIC);
  for(i=0; i<sizeof(aAggs)/sizeof(aAggs[0]); i++){
    sqlite_create_aggregate(db, aAggs[i].zName,
           aAggs[i].nArg, aAggs[i].xStep, aAggs[i].xFinalize, 0);
    sqlite_function_type(db, aAggs[i].zName, aAggs[i].dataType);
  }
}