/*-------------------------------------------------------------------------
 *
 * attnum.h--
 *	  POSTGRES attribute number definitions.
 *
 *
 * Copyright (c) 1994, Regents of the University of California
 *
 * $Id: attnum.h,v 1.6 1997/09/08 02:34:02 momjian Exp $
 *
 *-------------------------------------------------------------------------
 */
#ifndef ATTNUM_H
#define ATTNUM_H


/*
 * user defined attribute numbers start at 1.	-ay 2/95
 */
typedef int16 AttrNumber;

#define InvalidAttrNumber		0

/* ----------------
 *		support macros
 * ----------------
 */
/*
 * AttributeNumberIsValid --
 *		True iff the attribute number is valid.
 */
#define AttributeNumberIsValid(attributeNumber) \
	((bool) ((attributeNumber) != InvalidAttrNumber))

/*
 * AttrNumberIsForUserDefinedAttr --
 *		True iff the attribute number corresponds to an user defined attribute.
 */
#define AttrNumberIsForUserDefinedAttr(attributeNumber) \
	((bool) ((attributeNumber) > 0))

/*
 * AttrNumberGetAttrOffset --
 *		Returns the attribute offset for an attribute number.
 *
 * Note:
 *		Assumes the attribute number is for an user defined attribute.
 */
#define AttrNumberGetAttrOffset(attNum) \
	 (AssertMacro(AttrNumberIsForUserDefinedAttr(attNum)) ? \
	  ((attNum - 1)) : 0)

/*
 * AttributeOffsetGetAttributeNumber --
 *		Returns the attribute number for an attribute offset.
 */
#define AttrOffsetGetAttrNumber(attributeOffset) \
	 ((AttrNumber) (1 + attributeOffset))

#endif							/* ATTNUM_H */