More cleanups of the include files

- centralizing to simplify the -I's required to compile

src/include/utils/datum.h

@@ -0,0 +1,64 @@
+/*-------------------------------------------------------------------------
+ *
+ * datum.h--
+ *    POSTGRES abstract data type datum representation definitions.
+ *
+ *
+ * Copyright (c) 1994, Regents of the University of California
+ *
+ * $Id: datum.h,v 1.1 1996/08/28 01:58:48 scrappy Exp $
+ *
+ *-------------------------------------------------------------------------
+ */
+#ifndef	DATUM_H
+#define	DATUM_H
+
+#include "postgres.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 */