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 1.434 2009/05/11 20:53:29 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,

/*
** Return the default collation sequence for the expression pExpr. If
** there is no default collation type, return 0.
*/
CollSeq *sqlite3ExprCollSeq(Parse *pParse, Expr *pExpr){
  CollSeq *pColl = 0;
  Expr *p = pExpr;
  while( p ){
    int op;
    pColl = p->pColl;
    if( pColl ) break;
    op = p->op;
    if( (op==TK_AGG_COLUMN || op==TK_COLUMN || op==TK_REGISTER) && p->pTab!=0 ){
      /* op==TK_REGISTER && p->pTab!=0 happens when pExpr was originally
      ** a TK_COLUMN but was previously evaluated and cached in a register */

    assert( pToken->dyn==0 );
    pNew->span = *pToken;
    if( pToken->n>=2 
         && ((c = pToken->z[0])=='\'' || c=='"' || c=='[' || c=='`') ){
      sqlite3TokenCopy(db, &pNew->token, pToken);
      if( pNew->token.z ){
        pNew->token.n = sqlite3Dequote((char*)pNew->token.z);
        assert( pNew->token.n==(unsigned)sqlite3Strlen30((char*)pNew->token.z) );
      }
      if( c=='"' ) pNew->flags |= EP_DblQuoted;
    }else{
      pNew->token = *pToken;
    }
    pNew->token.quoted = 0;
  }else if( pLeft ){

**
** This routine is called by the parser to deal with on of those terms.
** It immediately generates code to store the value in a memory location.
** The returns an expression that will code to extract the value from
** that memory location as needed.
*/
Expr *sqlite3RegisterExpr(Parse *pParse, Token *pToken){
  Vdbe *v = pParse->pVdbe;
  Expr *p;
  if( pParse->nested==0 ){
    sqlite3ErrorMsg(pParse, "near \"%T\": syntax error", pToken);
    return sqlite3PExpr(pParse, TK_NULL, 0, 0, 0);
  }
  if( v==0 ) return 0;
  p = sqlite3PExpr(pParse, TK_REGISTER, 0, 0, pToken);
  if( p==0 ){
    return 0;  /* Malloc failed */
  }
  p->iTable = atoi((char*)&pToken->z[1]);
  return p;
}

** Wildcards consisting of a single "?" are assigned the next sequential
** variable number.
**
** Wildcards of the form "?nnn" are assigned the number "nnn".  We make
** sure "nnn" is not too be to avoid a denial of service attack when
** the SQL statement comes from an external source.
**
** Wildcards of the form ":aaa" or "$aaa" are assigned the same number
** as the previous instance of the same wildcard.  Or if this is the first
** instance of the wildcard, the next sequenial variable number is
** assigned.
*/
void sqlite3ExprAssignVarNumber(Parse *pParse, Expr *pExpr){
  Token *pToken;
  sqlite3 *db = pParse->db;

      sqlite3ErrorMsg(pParse, "variable number must be between ?1 and ?%d",
          db->aLimit[SQLITE_LIMIT_VARIABLE_NUMBER]);
    }
    if( i>pParse->nVar ){
      pParse->nVar = i;
    }
  }else{
    /* Wildcards of the form ":aaa" or "$aaa".  Reuse the same variable
    ** number as the prior appearance of the same name, or if the name
    ** has never appeared before, reuse the same variable number
    */
    int i;
    u32 n;
    n = pToken->n;
    for(i=0; i<pParse->nVarExpr; i++){
      Expr *pE;
      if( (pE = pParse->apVarExpr[i])!=0
          && pE->token.n==n
          && memcmp(pE->token.z, pToken->z, n)==0 ){
        pExpr->iTable = pE->iTable;
        break;
      }
    }
    if( i>=pParse->nVarExpr ){
      pExpr->iTable = ++pParse->nVar;
      if( pParse->nVarExpr>=pParse->nVarExprAlloc-1 ){