where.c

在VC6环境下开发

#include "eDbInit.h"

int eDbExprSplit(CExpr *aCE, Expr *pExpr, int nSlot, int base);

WhereExpr aCExpr;
#define ARRAYSIZE(X)  (sizeof(X)/sizeof(X[0]))
/*
** This routine is used to divide the WHERE expression into subexpressions
** separated by the OR operator.
**
** aSlot[] is an array of subexpressions structures.
** There are nSlot spaces left in this array.  This routine attempts to
** split pExpr into subexpressions and fills aSlot[] with those subexpressions.
** The return value is the number of slots filled.
*/

int eDbDealwithWhereClause(SrcList *pSrc,Expr *pWhere){
	int nExpr;
	int n;
	memset(&aCExpr,0,sizeof(aCExpr));
	n = ARRAYSIZE(aCExpr.a);
	nExpr = eDbExprSplit(aCExpr.a,pWhere,n,0);
	aCExpr.nExpr = nExpr;	
	return eDb_OK;
}
/*
** Generate code for a boolean expression such that a jump is made
** to the label "dest" if the expression is false but execution
** continues straight thru if the expression is true.
**
** If the expression evaluates to NULL (neither true nor false) then
** jump if jumpIfNull is true or fall through if jumpIfNull is false.
*/
int eDbExprSplit(CExpr *aCE, Expr *pExpr, int nSlot, int base){
	int nExpr;
	int cnt;
	if( pExpr==0 || nSlot<1 ) return 0;
	if( nSlot==1 ){
		aCE[0].pExpr = pExpr;
		return 1;
	}
	switch( pExpr->op ){
		case TK_AND: {			
			nExpr = eDbExprSplit(aCE, pExpr->pLeft, nSlot, base);
			aCE[nExpr-1].op = TK_AND;			
			aCE[nExpr-1].next = nExpr + base;
			cnt = nExpr-1;
			nExpr += eDbExprSplit(&aCE[nExpr], pExpr->pRight, nSlot-nExpr, nExpr+base);			
			aCE[cnt].go = nExpr + base;
			break;
		}
		case TK_OR: {
			nExpr = eDbExprSplit(aCE, pExpr->pLeft, nSlot, base);
			aCE[nExpr-1].op = TK_OR;
			aCE[nExpr-1].next = nExpr + base;
			cnt = nExpr-1;
			nExpr += eDbExprSplit(&aCE[nExpr], pExpr->pRight, nSlot-nExpr, nExpr+base);
			aCE[cnt].go = nExpr + base;
			break;
		}
		case TK_LT:
		case TK_LE:
		case TK_GT:
		case TK_GE:
		case TK_NE:
		case TK_EQ:{
			aCE[0].pExpr = pExpr;
			return 1;
			break;
		}
		default: {
			assert(0);
		}
	}
	return nExpr;
}