1 files changed, 132 insertions, 0 deletions
diff --git a/src/backend/storage/page/itemptr.c b/src/backend/storage/page/itemptr.c
new file mode 100644
index 0000000..f40d6c2
--- /dev/null
+++ b/src/backend/storage/page/itemptr.c
@@ -0,0 +1,132 @@
+/*-------------------------------------------------------------------------
+ *
+ * itemptr.c
+ *	  POSTGRES disk item pointer code.
+ *
+ * Portions Copyright (c) 1996-2021, PostgreSQL Global Development Group
+ * Portions Copyright (c) 1994, Regents of the University of California
+ *
+ *
+ * IDENTIFICATION
+ *	  src/backend/storage/page/itemptr.c
+ *
+ *-------------------------------------------------------------------------
+ */
+#include "postgres.h"
+
+#include "storage/itemptr.h"
+
+
+/*
+ * ItemPointerEquals
+ *	Returns true if both item pointers point to the same item,
+ *	 otherwise returns false.
+ *
+ * Note:
+ *	Asserts that the disk item pointers are both valid!
+ */
+bool
+ItemPointerEquals(ItemPointer pointer1, ItemPointer pointer2)
+{
+	/*
+	 * We really want ItemPointerData to be exactly 6 bytes.  This is rather a
+	 * random place to check, but there is no better place.
+	 */
+	StaticAssertStmt(sizeof(ItemPointerData) == 3 * sizeof(uint16),
+					 "ItemPointerData struct is improperly padded");
+
+	if (ItemPointerGetBlockNumber(pointer1) ==
+		ItemPointerGetBlockNumber(pointer2) &&
+		ItemPointerGetOffsetNumber(pointer1) ==
+		ItemPointerGetOffsetNumber(pointer2))
+		return true;
+	else
+		return false;
+}
+
+/*
+ * ItemPointerCompare
+ *		Generic btree-style comparison for item pointers.
+ */
+int32
+ItemPointerCompare(ItemPointer arg1, ItemPointer arg2)
+{
+	/*
+	 * Use ItemPointerGet{Offset,Block}NumberNoCheck to avoid asserting
+	 * ip_posid != 0, which may not be true for a user-supplied TID.
+	 */
+	BlockNumber b1 = ItemPointerGetBlockNumberNoCheck(arg1);
+	BlockNumber b2 = ItemPointerGetBlockNumberNoCheck(arg2);
+
+	if (b1 < b2)
+		return -1;
+	else if (b1 > b2)
+		return 1;
+	else if (ItemPointerGetOffsetNumberNoCheck(arg1) <
+			 ItemPointerGetOffsetNumberNoCheck(arg2))
+		return -1;
+	else if (ItemPointerGetOffsetNumberNoCheck(arg1) >
+			 ItemPointerGetOffsetNumberNoCheck(arg2))
+		return 1;
+	else
+		return 0;
+}
+
+/*
+ * ItemPointerInc
+ *		Increment 'pointer' by 1 only paying attention to the ItemPointer's
+ *		type's range limits and not MaxOffsetNumber and FirstOffsetNumber.
+ *		This may result in 'pointer' becoming !OffsetNumberIsValid.
+ *
+ * If the pointer is already the maximum possible values permitted by the
+ * range of the ItemPointer's types, then do nothing.
+ */
+void
+ItemPointerInc(ItemPointer pointer)
+{
+	BlockNumber blk = ItemPointerGetBlockNumberNoCheck(pointer);
+	OffsetNumber off = ItemPointerGetOffsetNumberNoCheck(pointer);
+
+	if (off == PG_UINT16_MAX)
+	{
+		if (blk != InvalidBlockNumber)
+		{
+			off = 0;
+			blk++;
+		}
+	}
+	else
+		off++;
+
+	ItemPointerSet(pointer, blk, off);
+}
+
+/*
+ * ItemPointerDec
+ *		Decrement 'pointer' by 1 only paying attention to the ItemPointer's
+ *		type's range limits and not MaxOffsetNumber and FirstOffsetNumber.
+ *		This may result in 'pointer' becoming !OffsetNumberIsValid.
+ *
+ * If the pointer is already the minimum possible values permitted by the
+ * range of the ItemPointer's types, then do nothing.  This does rely on
+ * FirstOffsetNumber being 1 rather than 0.
+ */
+void
+ItemPointerDec(ItemPointer pointer)
+{
+	BlockNumber blk = ItemPointerGetBlockNumberNoCheck(pointer);
+	OffsetNumber off = ItemPointerGetOffsetNumberNoCheck(pointer);
+
+	if (off == 0)
+	{
+		if (blk != 0)
+		{
+			off = PG_UINT16_MAX;
+			blk--;
+		}
+	}
+	else
+		off--;
+
+	ItemPointerSet(pointer, blk, off);
+}