Postgres95 1.01 Distribution - Virgin SourcesPG95-1_01

1 files changed, 60 insertions, 0 deletions

diff --git a/src/backend/storage/off.h b/src/backend/storage/off.h
new file mode 100644
index 00000000000..e5f5cbf5482
--- /dev/null
+++ b/src/backend/storage/off.h
@@ -0,0 +1,60 @@
+/*-------------------------------------------------------------------------
+ *
+ * off.h--
+ *    POSTGRES disk "offset" definitions.
+ *
+ *
+ * Copyright (c) 1994, Regents of the University of California
+ *
+ * $Id: off.h,v 1.1.1.1 1996/07/09 06:21:53 scrappy Exp $
+ *
+ *-------------------------------------------------------------------------
+ */
+#ifndef	OFF_H
+#define OFF_H
+
+#include "c.h"
+#include "machine.h"		/* for BLCKSZ */
+#include "storage/itemid.h"
+
+/*
+ * OffsetNumber:
+ *
+ * this is a 1-based index into the linp (ItemIdData) array in the
+ * header of each disk page.
+ */
+typedef uint16			OffsetNumber;
+
+#define InvalidOffsetNumber	((OffsetNumber) 0)
+#define FirstOffsetNumber	((OffsetNumber) 1)
+#define	MaxOffsetNumber		((OffsetNumber) (BLCKSZ / sizeof(ItemIdData)))
+#define	OffsetNumberMask	(0xffff)		/* valid uint16 bits */
+
+/* ----------------
+ *	support macros
+ * ----------------
+ */
+
+/*
+ * OffsetNumberIsValid --
+ *	True iff the offset number is valid.
+ */
+#define OffsetNumberIsValid(offsetNumber) \
+    ((bool) ((offsetNumber != InvalidOffsetNumber) && \
+	     (offsetNumber <= MaxOffsetNumber)))
+
+/*
+ * OffsetNumberNext --
+ * OffsetNumberPrev --
+ *	Increments/decrements the argument.  These macros look pointless
+ *	but they help us disambiguate the different manipulations on
+ *	OffsetNumbers (e.g., sometimes we substract one from an
+ *	OffsetNumber to move back, and sometimes we do so to form a
+ *	real C array index).
+ */
+#define OffsetNumberNext(offsetNumber) \
+    ((OffsetNumber) (1 + (offsetNumber)))
+#define OffsetNumberPrev(offsetNumber) \
+    ((OffsetNumber) (-1 + (offsetNumber)))
+
+#endif	/* OFF_H */