drh
d3a149efca
function interface. (CVS 393) FossilOrigin-Name: 2198109712ccf988f93db5740a4f248e80fb9f5d
101 lines
2.6 KiB
C
101 lines
2.6 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 1.2 2002/02/24 17:12:54 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(void *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(void *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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** 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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int n; /* Number of terms seen so far */
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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(void *stddev, int argc, char **argv){
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StdDevCtx *p;
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double x;
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if( argc<1 ) return 0;
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if( stddev==0 ){
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p = malloc( sizeof(*p) );
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p->n = 0;
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p->sum = 0.0;
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p->sum2 = 0.0;
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}else{
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p = (StdDevCtx*)stddev;
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}
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x = atof(argv[0]);
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p->sum += x;
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p->sum2 += x*x;
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p->n++;
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return p;
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}
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static void stdDevFinalize(void *stddev, void *context){
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StdDevCtx *p = (StdDevCtx*)stddev;
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if( context && p && p->n>1 ){
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double rN = p->n;
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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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if( stddev ) free(stddev);
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}
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/*
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** This file registered all of the above C functions as SQL
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** functions.
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*/
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void sqliteRegisterBuildinFunctions(sqlite *db){
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sqlite_create_function(db, "upper", 1, upperFunc);
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sqlite_create_function(db, "lower", 1, lowerFunc);
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sqlite_create_aggregate(db, "stddev", 1, stdDevStep, stdDevFinalize);
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}
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