SQLite

**    May you find forgiveness for yourself and forgive others.
**    May you share freely, never taking more than you give.
**
*************************************************************************
** This file contains routines used for analyzing expressions and
** for generating VDBE code that evaluates expressions in SQLite.
**
** $Id: expr.c,v 1.423 2009/03/24 15:31:28 drh Exp $
*/
#include "sqliteInt.h"

/*
** Return the 'affinity' of the expression pExpr if any.
**
** If pExpr is a column, a reference to a column via an 'AS' alias,

  pNew->iAgg = -1;
  pNew->span.z = (u8*)"";
  if( pToken ){
    int c;
    assert( pToken->dyn==0 );
    pNew->span = *pToken;
 
    /* The pToken->z value is read-only.  But the new expression
    ** node created here might be passed to sqlite3DequoteExpr() which
    ** will attempt to modify pNew->token.z.  Hence, if the token
    ** is quoted, make a copy now so that DequoteExpr() will change
    ** the copy rather than the original text.
    */
    if( pToken->n>=2 
         && ((c = pToken->z[0])=='\'' || c=='"' || c=='[' || c=='`') ){
      sqlite3TokenCopy(db, &pNew->token, pToken);
    }else{
      pNew->token = *pToken;
      pNew->flags |= EP_Dequoted;
      VVA_ONLY( pNew->vvaFlags |= EVVA_ReadOnlyToken; )
    }
  }else if( pLeft ){
    if( pRight ){
      if( pRight->span.dyn==0 && pLeft->span.dyn==0 ){
        sqlite3ExprSpan(pNew, &pLeft->span, &pRight->span);
      }
      if( pRight->flags & EP_ExpCollate ){

/*
** The Expr.token field might be a string literal that is quoted.
** If so, remove the quotation marks.
*/
void sqlite3DequoteExpr(sqlite3 *db, Expr *p){
  if( !ExprHasAnyProperty(p, EP_Dequoted) ){
    ExprSetProperty(p, EP_Dequoted);
    assert( (p->vvaFlags & EVVA_ReadOnlyToken)==0 );
    sqlite3Dequote((char*)p->token.z);
  }
}

/*
** Return the number of bytes allocated for the expression structure 
** passed as the first argument. This is always one of EXPR_FULLSIZE,

/*
** 2001 September 15
**
** 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.
**
*************************************************************************
** Internal interface definitions for SQLite.
**
** @(#) $Id: sqliteInt.h,v 1.847 2009/03/24 15:31:28 drh Exp $
*/
#ifndef _SQLITEINT_H_
#define _SQLITEINT_H_

/*
** Include the configuration header output by 'configure' if we're using the
** autoconf-based build

** If the EP_TokenOnly flag is set in Expr.flags, then only EXPR_TOKENONLYSIZE
** bytes of space are allocated for the expression structure. This is enough
** space to store all fields up to and including the "Token token;" field.
*/
struct Expr {
  u8 op;                 /* Operation performed by this node */
  char affinity;         /* The affinity of the column or 0 if not a column */
  VVA_ONLY(u8 vvaFlags;) /* Flags used for VV&A only.  EVVA_* below. */
  u16 flags;             /* Various flags.  EP_* See below */
  Token token;           /* An operand token */

  /* If the EP_TokenOnly flag is set in the Expr.flags mask, then no
  ** space is allocated for the fields below this point. An attempt to
  ** access them will result in a segfault or malfunction. 
  *********************************************************************/

#define EP_IntValue   0x0800  /* Integer value contained in iTable */
#define EP_xIsSelect  0x1000  /* x.pSelect is valid (otherwise x.pList is) */

#define EP_Reduced    0x2000  /* Expr struct is EXPR_REDUCEDSIZE bytes only */
#define EP_TokenOnly  0x4000  /* Expr struct is EXPR_TOKENONLYSIZE bytes only */
#define EP_SpanOnly   0x8000  /* Expr struct is EXPR_SPANONLYSIZE bytes only */

/*
** The following are the meanings of bits in the Expr.vvaFlags field.
** This information is only used when SQLite is compiled with
** SQLITE_DEBUG defined.
*/
#ifndef NDEBUG
#define EVVA_ReadOnlyToken  0x01  /* Expr.token.z is read-only */
#endif

/*
** These macros can be used to test, set, or clear bits in the 
** Expr.flags field.
*/
#define ExprHasProperty(E,P)     (((E)->flags&(P))==(P))
#define ExprHasAnyProperty(E,P)  (((E)->flags&(P))!=0)
#define ExprSetProperty(E,P)     (E)->flags|=(P)