text: /*-------------------------------------------------------------------------
   *
   * datum.h
   *	  POSTGRES Datum (abstract data type) manipulation routines.
   *
   * These routines are driven by the 'typbyval' and 'typlen' information,
   * which must previously have been obtained by the caller for the datatype
   * of the Datum.  (We do it this way because in most situations the caller
   * can look up the info just once and use it for many per-datum operations.)
   *
   * Portions Copyright (c) 1996-2010, PostgreSQL Global Development Group
   * Portions Copyright (c) 1994, Regents of the University of California
   *
   * $PostgreSQL: pgsql/src/include/utils/datum.h,v 1.26 2010/01/02 16:58:10 momjian Exp $
   *
   *-------------------------------------------------------------------------
   */
  #ifndef DATUM_H
  #define DATUM_H
  
  /*
   * datumGetSize - find the "real" length of a datum
   */
  extern Size datumGetSize(Datum value, bool typByVal, int typLen);
  
  /*
   * datumCopy - make a copy of a datum.
   *
   * If the datatype is pass-by-reference, memory is obtained with palloc().
   */
  extern Datum datumCopy(Datum value, bool typByVal, int typLen);
  
  /*
   * datumFree - free a datum previously allocated by datumCopy, if any.
   *
   * Does nothing if datatype is pass-by-value.
   */
  extern void datumFree(Datum value, bool typByVal, int typLen);
  
  /*
   * datumIsEqual
   * return true if two datums of the same type are equal, false otherwise.
   *
   * XXX : See comments in the code for restrictions!
   */
  extern bool datumIsEqual(Datum value1, Datum value2,
  			 bool typByVal, int typLen);
  
  #endif   /* DATUM_H */
  