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/*-------------------------------------------------------------------------
*
* datum.h
* POSTGRES abstract data type datum representation definitions.
*
*
* Copyright (c) 1994, Regents of the University of California
*
* $Id: datum.h,v 1.9 1999/02/13 23:22:16 momjian Exp $
*
*-------------------------------------------------------------------------
*/
#ifndef DATUM_H
#define DATUM_H
/*--------------------------------------------------------
* SOME NOT VERY PORTABLE ROUTINES ???
*--------------------------------------------------------
*
* In the implementation of the next routines we assume the following:
*
* A) if a type is "byVal" then all the information is stored in the
* Datum itself (i.e. no pointers involved!). In this case the
* length of the type is always greater than zero and less than
* "sizeof(Datum)"
* B) if a type is not "byVal" and it has a fixed length, then
* the "Datum" always contain a pointer to a stream of bytes.
* The number of significant bytes are always equal to the length of thr
* type.
* C) if a type is not "byVal" and is of variable length (i.e. it has
* length == -1) then "Datum" always points to a "struct varlena".
* This varlena structure has information about the actual length of this
* particular instance of the type and about its value.
*/
/*---------------
* datumGetSize
* find the "real" length of a datum
*/
extern Size datumGetSize(Datum value, Oid type, bool byVal, Size len);
/*---------------
* datumCopy
* make a copy of a datum.
*/
extern Datum datumCopy(Datum value, Oid type, bool byVal, Size len);
/*---------------
* datumFree
* free space that *might* have been palloced by "datumCopy"
*/
extern void datumFree(Datum value, Oid type, bool byVal, Size len);
/*---------------
* datumIsEqual
* return true if thwo datums are equal, false otherwise.
* XXX : See comments in the code for restrictions!
*/
extern bool datumIsEqual(Datum value1, Datum value2, Oid type,
bool byVal, Size len);
#endif /* DATUM_H */
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