/*
** 2002 February 23
**
** The author disclaims copyright to this source code. In place of
** a legal notice, here is a blessing:
**
** May you do good and not evil.
** May you find forgiveness for yourself and forgive others.
** May you share freely, never taking more than you give.
**
*************************************************************************
** This file contains the C functions that implement various SQL
** functions of SQLite.
**
** There is only one exported symbol in this file - the function
** sqliteRegisterBuildinFunctions() found at the bottom of the file.
** All other code has file scope.
**
** $Id: func.c,v 1.5 2002/02/27 19:50:59 drh Exp $
*/
#include <ctype.h>
#include <math.h>
#include <stdlib.h>
#include "sqlite.h"
/*
** Implementation of the upper() and lower() SQL functions.
*/
static void upperFunc(sqlite_func *context, int argc, const char **argv){
char *z;
int i;
if( argc<1 || argv[0]==0 ) return;
z = sqlite_set_result_string(context, argv[0], -1);
if( z==0 ) return;
for(i=0; z[i]; i++){
if( islower(z[i]) ) z[i] = toupper(z[i]);
}
}
static void lowerFunc(sqlite_func *context, int argc, const char **argv){
char *z;
int i;
if( argc<1 || argv[0]==0 ) return;
z = sqlite_set_result_string(context, argv[0], -1);
if( z==0 ) return;
for(i=0; z[i]; i++){
if( isupper(z[i]) ) z[i] = tolower(z[i]);
}
}
/*
** An instance of the following structure holds the context of a
** sum() or avg() aggregate computation.
*/
typedef struct SumCtx SumCtx;
struct SumCtx {
double sum; /* Sum of terms */
};
/*
** Routines used to compute the sum or average.
*/
static void sumStep(sqlite_func *context, int argc, const char **argv){
SumCtx *p;
double x;
if( argc<1 ) return;
p = sqlite_aggregate_context(context, sizeof(*p));
if( p==0 ) return;
x = argv[0] ? atof(argv[0]) : 0.0;
p->sum += x;
}
static void sumFinalize(sqlite_func *context){
SumCtx *p;
p = sqlite_aggregate_context(context, sizeof(*p));
if( p ){
sqlite_set_result_double(context, p->sum);
}
}
static void avgFinalize(sqlite_func *context){
SumCtx *p;
double rN;
p = sqlite_aggregate_context(context, sizeof(*p));
rN = sqlite_aggregate_count(context);
if( p && rN>0.0 ){
sqlite_set_result_double(context, p->sum/rN);
}
}
/*
** An instance of the following structure holds the context of a
** variance or standard deviation computation.
*/
typedef struct StdDevCtx StdDevCtx;
struct StdDevCtx {
double sum; /* Sum of terms */
double sum2; /* Sum of the squares of terms */
};
/*
** Routines used to compute the standard deviation as an aggregate.
*/
static void stdDevStep(sqlite_func *context, int argc, const char **argv){
StdDevCtx *p;
double x;
if( argc<1 ) return;
p = sqlite_aggregate_context(context, sizeof(*p));
if( p==0 ) return;
x = argv[0] ? atof(argv[0]) : 0.0;
p->sum += x;
p->sum2 += x*x;
}
static void stdDevFinalize(sqlite_func *context){
double rN = sqlite_aggregate_count(context);
StdDevCtx *p = sqlite_aggregate_context(context, sizeof(*p));
if( p && rN>1.0 ){
sqlite_set_result_double(context,
sqrt((p->sum2 - p->sum*p->sum/rN)/(rN-1.0)));
}
}
/*
** 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 sqliteRegisterBuildinFunctions(sqlite *db){
sqlite_create_function(db, "upper", 1, upperFunc, 0);
sqlite_create_function(db, "lower", 1, lowerFunc, 0);
sqlite_create_aggregate(db, "stddev", 1, stdDevStep, stdDevFinalize, 0);
sqlite_create_aggregate(db, "x_sum", 1, sumStep, sumFinalize, 0);
sqlite_create_aggregate(db, "x_avg", 1, sumStep, avgFinalize, 0);
}