SQLite

** 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"

/*

  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);
}

**    May you find forgiveness for yourself and forgive others.
**    May you share freely, never taking more than you give.
**
*************************************************************************
** This header file defines the interface that the SQLite library
** presents to client programs.
**
** @(#) $Id: sqlite.h.in,v 1.28 2002/02/27 19:50:59 drh Exp $
*/
#ifndef _SQLITE_H_
#define _SQLITE_H_
#include <stdarg.h>     /* Needed for the definition of va_list */

/*
** The version of the SQLite library.

  void (*xFinalize)(sqlite_func*),       /* Called once to get final result */
  void *pUserData           /* Available via the sqlite_user_data() call */
);

/*
** The user function implementations call one of the following four routines
** in order to return their results.  The first parameter to each of these
** routines is a copy of the first argument to xFunc() or xFinialize().
** The second parameter to these routines is the result to be returned.
** A NULL can be passed as the second parameter to sqlite_set_result_string()
** in order to return a NULL result.
**
** The 3rd argument to _string and _error is the number of characters to
** take from the string.  If this argument is negative, then all characters
** up to and including the first '\000' are used.

** sqlite_create_aggregate() routines used to register user functions
** is available to the implementation of the function using this
** call.
*/
void *sqlite_user_data(sqlite_func*);

/*
** Aggregate functions use the following routine to allocate
** a structure for storing their state.  The first time this routine
** is called for a particular aggregate, a new structure of size nBytes
** is allocated, zeroed, and returned.  On subsequent calls (for the
** same aggregate instance) the same buffer is returned.  The implementation
** of the aggregate can use the returned buffer to accumulate data.
**
** The buffer allocated is freed automatically be SQLite.
*/
void *sqlite_aggregate_context(sqlite_func*, int nBytes);

/*
** The next routine returns the number of calls to xStep for a particular
** aggregate function instance.  The current call to xStep counts so this
** routine always returns at least 1.
*/
int sqlite_aggregate_count(sqlite_func*);

#ifdef __cplusplus
}  /* End of the 'extern "C"' block */
#endif

#endif /* _SQLITE_H_ */

** type to the other occurs as necessary.
** 
** Most of the code in this file is taken up by the sqliteVdbeExec()
** function which does the work of interpreting a VDBE program.
** But other routines are also provided to help in building up
** a program instruction by instruction.
**
** $Id: vdbe.c,v 1.125 2002/02/27 19:50:59 drh Exp $
*/
#include "sqliteInt.h"
#include <ctype.h>

/*
** The following global variable is incremented every time a cursor
** moves, either by the OP_MoveTo or the OP_Next opcode.  The test

** This routine is defined here in vdbe.c because it depends on knowing
** the internals of the sqlite_func structure which is only defined in that
** one source file.
*/
void *sqlite_aggregate_context(sqlite_func *p, int nByte){
  assert( p && p->pFunc && p->pFunc->xStep );
  if( p->pAgg==0 ){
    if( nByte<=NBFS ){
      p->pAgg = (void*)p->z;
    }else{
      p->pAgg = sqliteMalloc( nByte );
    }
  }
  return p->pAgg;
}

/*
** Return the number of times the Step function of a user-defined 
** aggregate has been called.

static void AggReset(Agg *pAgg){
  int i;
  HashElem *p;
  for(p = sqliteHashFirst(&pAgg->hash); p; p = sqliteHashNext(p)){
    AggElem *pElem = sqliteHashData(p);
    assert( pAgg->apFunc!=0 );
    for(i=0; i<pAgg->nMem; i++){
      Mem *pMem = &pElem->aMem[i];
      if( pAgg->apFunc[i] && (pMem->s.flags & STK_AggCtx)!=0 ){
        sqlite_func ctx;
        ctx.s.flags = STK_Null;
        ctx.z = 0;
        ctx.pAgg = pMem->z;
        ctx.cnt = pMem->s.i;
        ctx.isStep = 0;
        ctx.isError = 0;
        (*pAgg->apFunc[i]->xFinalize)(&ctx);
        if( pMem->z!=0 && pMem->z!=pMem->s.z ){
          sqliteFree(pMem->z);
        }
      }else if( pMem->s.flags & STK_Dyn ){
        sqliteFree(pMem->z);
      }
    }
    sqliteFree(pElem);
  }
  sqliteHashClear(&pAgg->hash);
  sqliteFree(pAgg->apFunc);
  pAgg->apFunc = 0;

      if( Stringify(p, i) ) goto no_mem;
    }
  }
  i = aStack[p->tos].i;
  VERIFY( if( i<0 || i>=p->agg.nMem ) goto bad_instruction; )
  ctx.pFunc = (UserFunc*)pOp->p3;
  pMem = &p->agg.pCurrent->aMem[i];
  ctx.z = pMem->s.z;
  ctx.pAgg = pMem->z;
  ctx.cnt = ++pMem->s.i;
  ctx.isError = 0;
  ctx.isStep = 1;
  (ctx.pFunc->xStep)(&ctx, n, (const char**)&zStack[p->tos-n]);
  pMem->z = ctx.pAgg;
  pMem->s.flags = STK_AggCtx;