SQLite

**   drh@hwaci.com
**   http://www.hwaci.com/drh/
**
*************************************************************************
** This file contains routines used for analyzing expressions and
** for generating VDBE code that evaluates expressions.
**
** $Id: expr.c,v 1.18 2000/06/21 13:59:11 drh Exp $
** $Id: expr.c,v 1.19 2000/08/28 15:51:44 drh Exp $
*/
#include "sqliteInt.h"

/*
** Walk an expression tree.  Return 1 if the expression is constant
** and 0 if it involves variables.
*/

  } aFunc[] = {
     { "count",  5, FN_Count },
     { "min",    3, FN_Min   },
     { "max",    3, FN_Max   },
     { "sum",    3, FN_Sum   },
     { "avg",    3, FN_Avg   },
     { "fcnt",   4, FN_Fcnt  },  /* Used for testing only */
     { "length", 6, FN_Length},
     { "substr", 6, FN_Substr},
  };
  int i;
  for(i=0; i<ArraySize(aFunc); i++){
    if( aFunc[i].len==pToken->n 
     && sqliteStrNICmp(pToken->z, aFunc[i].zName, aFunc[i].len)==0 ){
       return aFunc[i].id;
    }

        case FN_Avg:
        case FN_Sum: {
          no_such_func = !allowAgg;
          too_many_args = n>1;
          too_few_args = n<1;
          is_agg = 1;
          break;
        }
        case FN_Length: {
          too_few_args = n<1;
          too_many_args = n>1;
          break;
        }
        case FN_Substr: {
          too_few_args = n<3;
          too_many_args = n>3;
          break;
        }
        /* The "fcnt(*)" function always returns the number of fetch
        ** operations that have occurred so far while processing the
        ** SQL statement.  This information can be used by test procedures
        ** to verify that indices are being used properly to minimize
        ** searching.  All arguments to fcnt() are ignored.  fcnt() has
        ** no use (other than testing) that we are aware of.
        */
        case FN_Fcnt: {
          n = 0;
          break;
        }
      
        default: break;
      }
      if( no_such_func ){
        sqliteSetNString(&pParse->zErrMsg, "no such function: ", -1,
           pExpr->token.z, pExpr->token.n, 0);
        pParse->nErr++;
        nErr++;

      break;
    }
    case TK_FUNCTION: {
      int id = pExpr->iColumn;
      int op;
      int i;
      ExprList *pList = pExpr->pList;
      switch( id ){
      if( id==FN_Fcnt ){
        sqliteVdbeAddOp(v, OP_Fcnt, 0, 0, 0, 0);
        break;
      }
      op = id==FN_Min ? OP_Min : OP_Max;
      for(i=0; i<pList->nExpr; i++){
        sqliteExprCode(pParse, pList->a[i].pExpr);
        if( i>0 ){
          sqliteVdbeAddOp(v, op, 0, 0, 0, 0);
        case FN_Fcnt: {
          sqliteVdbeAddOp(v, OP_Fcnt, 0, 0, 0, 0);
          break;
        }
        case FN_Min: 
        case FN_Max: {
          op = id==FN_Min ? OP_Min : OP_Max;
          for(i=0; i<pList->nExpr; i++){
            sqliteExprCode(pParse, pList->a[i].pExpr);
            if( i>0 ){
              sqliteVdbeAddOp(v, op, 0, 0, 0, 0);
            }
          }
          break;
        }
        case FN_Length: {
          sqliteExprCode(pParse, pList->a[0].pExpr);
          sqliteVdbeAddOp(v, OP_Strlen, 0, 0, 0, 0);
          break;
        }
        case FN_Substr: {
          for(i=0; i<pList->nExpr; i++){
            sqliteExprCode(pParse, pList->a[i].pExpr);
          }
          sqliteVdbeAddOp(v, OP_Substr, 0, 0, 0, 0);
          break;
        }
        default: {
          /* Can't happen! */
          break;
        }
      }
      break;
    }
    case TK_SELECT: {
      sqliteVdbeAddOp(v, OP_MemLoad, pExpr->iColumn, 0, 0, 0);
      break;

** Author contact information:
**   drh@hwaci.com
**   http://www.hwaci.com/drh/
**
*************************************************************************
** Internal interface definitions for SQLite.
**
** @(#) $Id: sqliteInt.h,v 1.29 2000/08/02 13:47:42 drh Exp $
** @(#) $Id: sqliteInt.h,v 1.30 2000/08/28 15:51:44 drh Exp $
*/
#include "sqlite.h"
#include "dbbe.h"
#include "vdbe.h"
#include "parse.h"
#include <gdbm.h>
#include <stdio.h>

#define FN_Unknown    0
#define FN_Count      1
#define FN_Min        2
#define FN_Max        3
#define FN_Sum        4
#define FN_Avg        5
#define FN_Fcnt       6
#define FN_Length     7
#define FN_Substr     8

/*
** Forward references to structures
*/
typedef struct Column Column;
typedef struct Table Table;
typedef struct Index Index;

** inplicit conversion from one 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 1.38 2000/08/02 12:26:29 drh Exp $
** $Id: vdbe.c,v 1.39 2000/08/28 15:51:44 drh Exp $
*/
#include "sqliteInt.h"
#include <unistd.h>

/*
** SQL is translated into a sequence of instructions to be
** executed by a virtual machine.  Each instruction is an instance

  "String",         "Null",           "Pop",            "Dup",
  "Pull",           "Add",            "AddImm",         "Subtract",
  "Multiply",       "Divide",         "Min",            "Max",
  "Like",           "Glob",           "Eq",             "Ne",
  "Lt",             "Le",             "Gt",             "Ge",
  "IsNull",         "NotNull",        "Negative",       "And",
  "Or",             "Not",            "Concat",         "Noop",
  "Strlen",         "Substr",       
};

/*
** Given the name of an opcode, return its number.  Return 0 if
** there is no match.
**
** This routine is used for testing and debugging.

        Stringify(p, tos);
        if( i>=0 && i<p->nSet && !SetTest(&p->aSet[i], p->zStack[tos]) ){
          pc = pOp->p2 - 1;
        }
        PopStack(p, 1);
        break;
      }

      /* Opcode: Length * * *
      **
      ** Interpret the top of the stack as a string.  Replace the top of
      ** stack with an integer which is the length of the string.
      */
      case OP_Strlen: {
        int tos = p->tos;
        int len;
        if( tos<0 ) goto not_enough_stack;
        Stringify(p, tos);
        len = p->aStack[tos].n-1;
        PopStack(p, 1);
        p->tos++;
        p->aStack[tos].i = len;
        p->aStack[tos].flags = STK_Int;
        break;
      }

      /* Opcode: Substr P1 P2 *
      **
      ** This operation pops between 1 and 3 elements from the stack and
      ** pushes back a single element.  The bottom-most element popped from
      ** the stack is a string and the element pushed back is also a string.
      ** The other two elements popped are integers.  The integers are taken
      ** from the stack only if P1 and/or P2 are 0.  When P1 or P2 are
      ** not zero, the value of the operand is used rather than the integer
      ** from the stack.  In the sequel, we will use P1 and P2 to describe
      ** the two integers, even if those integers are really taken from the
      ** stack.
      **
      ** The string pushed back onto the stack is a substring of the string
      ** that was popped.  There are P2 characters in the substring.  The
      ** first character of the substring is the P1-th character of the
      ** original string where the left-most character is 1 (not 0).  If P1
      ** is negative, then counting begins at the right instead of at the
      ** left.
      */
      case OP_Substr: {
        int cnt;
        int start;
        int n;
        char *z;

        if( pOp->p2==0 ){
          if( p->tos<0 ) goto not_enough_stack;
          Integerify(p, p->tos);
          cnt = p->aStack[p->tos].i;
          PopStack(p, 1);
        }else{
          cnt = pOp->p2;
        }
        if( pOp->p1==0 ){
          if( p->tos<0 ) goto not_enough_stack;
          Integerify(p, p->tos);
          start = p->aStack[p->tos].i;
          PopStack(p, 1);
        }else{
          start = pOp->p1;
        }
        if( p->tos<0 ) goto not_enough_stack;
        Stringify(p, p->tos);
        n = p->aStack[p->tos].n - 1;
        if( start<0 ){
          start += n;
          if( start<0 ){
            cnt += start;
            start = 0;
          }
        }
        if( cnt<0 ) cnt = 0;
        if( cnt > n ){
          cnt = n;
        }
        z = sqliteMalloc( cnt+1 );
        if( z==0 ) goto no_mem;
        strncpy(z, p->zStack[p->tos], cnt);
        z[cnt] = 0;
        PopStack(p, 1);
        p->tos++;
        p->zStack[p->tos] = z;
        p->aStack[p->tos].n = cnt + 1;
        p->aStack[p->tos].flags = STK_Str|STK_Dyn;
        break;
      }

      /* An other opcode is illegal...
      */
      default: {
        sprintf(zBuf,"%d",pOp->opcode);
        sqliteSetString(pzErrMsg, "unknown opcode ", zBuf, 0);
        rc = SQLITE_INTERNAL;

*************************************************************************
** Header file for the Virtual DataBase Engine (VDBE)
**
** This header defines the interface to the virtual database engine
** or VDBE.  The VDBE implements an abstract machine that runs a
** simple program to access and modify the underlying database.
**
** $Id: vdbe.h,v 1.11 2000/07/28 14:32:50 drh Exp $
** $Id: vdbe.h,v 1.12 2000/08/28 15:51:45 drh Exp $
*/
#ifndef _SQLITE_VDBE_H_
#define _SQLITE_VDBE_H_
#include <stdio.h>

/*
** A single VDBE is an opaque structure named "Vdbe".  Only routines

#define OP_Negative           83
#define OP_And                84
#define OP_Or                 85
#define OP_Not                86
#define OP_Concat             87
#define OP_Noop               88

#define OP_Strlen             89
#define OP_Substr             90

#define OP_MAX                88
#define OP_MAX                90

/*
** Prototypes for the VDBE interface.  See comments on the implementation
** for a description of what each of these routines does.
*/
Vdbe *sqliteVdbeCreate(Dbbe*);
int sqliteVdbeAddOp(Vdbe*,int,int,int,const char*,int);