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64 lines
2.0 KiB
64 lines
2.0 KiB
/*-------------------------------------------------------------------------
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*
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* datum.h--
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* POSTGRES abstract data type datum representation definitions.
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*
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*
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* Copyright (c) 1994, Regents of the University of California
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*
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* $Id: datum.h,v 1.5 1997/09/08 21:54:53 momjian Exp $
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*
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*-------------------------------------------------------------------------
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*/
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#ifndef DATUM_H
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#define DATUM_H
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/*--------------------------------------------------------
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* SOME NOT VERY PORTABLE ROUTINES ???
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*--------------------------------------------------------
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*
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* In the implementation of the next routines we assume the following:
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*
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* A) if a type is "byVal" then all the information is stored in the
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* Datum itself (i.e. no pointers involved!). In this case the
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* length of the type is always greater than zero and less than
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* "sizeof(Datum)"
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* B) if a type is not "byVal" and it has a fixed length, then
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* the "Datum" always contain a pointer to a stream of bytes.
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* The number of significant bytes are always equal to the length of thr
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* type.
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* C) if a type is not "byVal" and is of variable length (i.e. it has
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* length == -1) then "Datum" always points to a "struct varlena".
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* This varlena structure has information about the actual length of this
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* particular instance of the type and about its value.
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*/
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/*---------------
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* datumGetSize
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* find the "real" length of a datum
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*/
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extern Size datumGetSize(Datum value, Oid type, bool byVal, Size len);
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/*---------------
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* datumCopy
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* make a copy of a datum.
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*/
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extern Datum datumCopy(Datum value, Oid type, bool byVal, Size len);
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/*---------------
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* datumFree
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* free space that *might* have been palloced by "datumCopy"
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*/
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extern void datumFree(Datum value, Oid type, bool byVal, Size len);
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/*---------------
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* datumIsEqual
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* return true if thwo datums are equal, false otherwise.
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* XXX : See comments in the code for restrictions!
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*/
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extern bool
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datumIsEqual(Datum value1, Datum value2, Oid type,
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bool byVal, Size len);
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#endif /* DATUM_H */
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