postgresql/src/include/access/tupmacs.h

/*-------------------------------------------------------------------------
 *
 * tupmacs.h--
 *	  Tuple macros used by both index tuples and heap tuples.
 *
 *
 * Copyright (c) 1994, Regents of the University of California
 *
 * $Id: tupmacs.h,v 1.2 1997/09/07 04:56:17 momjian Exp $
 *
 *-------------------------------------------------------------------------
 */
#ifndef TUPMACS_H
#define TUPMACS_H

/*
 * check to see if the ATT'th bit of an array of 8-bit bytes is set.
 */
#define att_isnull(ATT, BITS) (!((BITS)[(ATT) >> 3] & (1 << ((ATT) & 0x07))))

/*
 * given a AttributeTupleForm and a pointer into a tuple's data
 * area, return the correct value or pointer.
 *
 * We return a 4 byte (char *) value in all cases.	If the attribute has
 * "byval" false or has variable length, we return the same pointer
 * into the tuple data area that we're passed.  Otherwise, we return
 * the 1, 2, or 4 bytes pointed to by it, properly extended to 4
 * bytes, depending on the length of the attribute.
 *
 * note that T must already be properly LONGALIGN/SHORTALIGN'd for
 * this to work correctly.
 *
 * the double-cast is to stop gcc from (correctly) complaining about
 * casting integer types with size < sizeof(char *) to (char *).
 * sign-extension may get weird if you use an integer type that
 * isn't the same size as (char *) for the first cast.  (on the other
 * hand, it's safe to use another type for the (foo *)(T).)
 *
 * attbyval seems to be fairly redundant.  We have to return a pointer if
 * the value is longer than 4 bytes or has variable length; returning the
 * value would be useless.	In fact, for at least the variable length case,
 * the caller assumes we return a pointer regardless of attbyval.
 * I would eliminate attbyval altogether, but I don't know how.  -BRYANH.
 */
#define fetchatt(A, T) \
 ((*(A))->attbyval && (*(A))->attlen != -1 \
  ? ((*(A))->attlen > sizeof(int16) \
	 ? (char *) (long) *((int32 *)(T)) \
	 : ((*(A))->attlen < sizeof(int16) \
		? (char *) (long) *((char *)(T)) \
		: (char *) (long) *((int16 *)(T)))) \
  : (char *) (T))

#endif