drh
dd5baa95e8
transfering built-in functions over to the user-define function mechanism. (CVS 399) FossilOrigin-Name: c4f9e017b449d4036fa8d2bf77b931d4c31d74f7
134 lines
3.7 KiB
C
134 lines
3.7 KiB
C
/*
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** 2002 February 23
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**
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** The author disclaims copyright to this source code. In place of
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** a legal notice, here is a blessing:
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**
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** May you do good and not evil.
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** May you find forgiveness for yourself and forgive others.
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** May you share freely, never taking more than you give.
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**
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*************************************************************************
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** This file contains the C functions that implement various SQL
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** functions of SQLite.
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**
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** There is only one exported symbol in this file - the function
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** sqliteRegisterBuildinFunctions() found at the bottom of the file.
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** All other code has file scope.
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**
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** $Id: func.c,v 1.5 2002/02/27 19:50:59 drh Exp $
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*/
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#include <ctype.h>
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#include <math.h>
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#include <stdlib.h>
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#include "sqlite.h"
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/*
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** Implementation of the upper() and lower() SQL functions.
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*/
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static void upperFunc(sqlite_func *context, int argc, const char **argv){
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char *z;
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int i;
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if( argc<1 || argv[0]==0 ) return;
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z = sqlite_set_result_string(context, argv[0], -1);
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if( z==0 ) return;
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for(i=0; z[i]; i++){
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if( islower(z[i]) ) z[i] = toupper(z[i]);
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}
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}
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static void lowerFunc(sqlite_func *context, int argc, const char **argv){
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char *z;
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int i;
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if( argc<1 || argv[0]==0 ) return;
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z = sqlite_set_result_string(context, argv[0], -1);
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if( z==0 ) return;
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for(i=0; z[i]; i++){
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if( isupper(z[i]) ) z[i] = tolower(z[i]);
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}
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}
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/*
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** An instance of the following structure holds the context of a
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** sum() or avg() aggregate computation.
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*/
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typedef struct SumCtx SumCtx;
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struct SumCtx {
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double sum; /* Sum of terms */
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};
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/*
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** Routines used to compute the sum or average.
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*/
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static void sumStep(sqlite_func *context, int argc, const char **argv){
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SumCtx *p;
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double x;
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if( argc<1 ) return;
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p = sqlite_aggregate_context(context, sizeof(*p));
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if( p==0 ) return;
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x = argv[0] ? atof(argv[0]) : 0.0;
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p->sum += x;
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}
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static void sumFinalize(sqlite_func *context){
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SumCtx *p;
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p = sqlite_aggregate_context(context, sizeof(*p));
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if( p ){
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sqlite_set_result_double(context, p->sum);
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}
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}
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static void avgFinalize(sqlite_func *context){
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SumCtx *p;
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double rN;
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p = sqlite_aggregate_context(context, sizeof(*p));
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rN = sqlite_aggregate_count(context);
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if( p && rN>0.0 ){
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sqlite_set_result_double(context, p->sum/rN);
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}
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}
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/*
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** An instance of the following structure holds the context of a
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** variance or standard deviation computation.
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*/
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typedef struct StdDevCtx StdDevCtx;
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struct StdDevCtx {
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double sum; /* Sum of terms */
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double sum2; /* Sum of the squares of terms */
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};
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/*
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** Routines used to compute the standard deviation as an aggregate.
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*/
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static void stdDevStep(sqlite_func *context, int argc, const char **argv){
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StdDevCtx *p;
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double x;
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if( argc<1 ) return;
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p = sqlite_aggregate_context(context, sizeof(*p));
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if( p==0 ) return;
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x = argv[0] ? atof(argv[0]) : 0.0;
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p->sum += x;
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p->sum2 += x*x;
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}
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static void stdDevFinalize(sqlite_func *context){
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double rN = sqlite_aggregate_count(context);
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StdDevCtx *p = sqlite_aggregate_context(context, sizeof(*p));
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if( p && rN>1.0 ){
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sqlite_set_result_double(context,
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sqrt((p->sum2 - p->sum*p->sum/rN)/(rN-1.0)));
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}
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}
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/*
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** This function registered all of the above C functions as SQL
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** functions. This should be the only routine in this file with
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** external linkage.
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*/
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void sqliteRegisterBuildinFunctions(sqlite *db){
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sqlite_create_function(db, "upper", 1, upperFunc, 0);
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sqlite_create_function(db, "lower", 1, lowerFunc, 0);
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sqlite_create_aggregate(db, "stddev", 1, stdDevStep, stdDevFinalize, 0);
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sqlite_create_aggregate(db, "x_sum", 1, sumStep, sumFinalize, 0);
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sqlite_create_aggregate(db, "x_avg", 1, sumStep, avgFinalize, 0);
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}
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