1 files changed, 65 insertions, 0 deletions
diff --git a/contrib/pageinspect/fsmfuncs.c b/contrib/pageinspect/fsmfuncs.c
new file mode 100644
index 0000000..23b192b
--- /dev/null
+++ b/contrib/pageinspect/fsmfuncs.c
@@ -0,0 +1,65 @@
+/*-------------------------------------------------------------------------
+ *
+ * fsmfuncs.c
+ *	  Functions to investigate FSM pages
+ *
+ * These functions are restricted to superusers for the fear of introducing
+ * security holes if the input checking isn't as water-tight as it should.
+ * You'd need to be superuser to obtain a raw page image anyway, so
+ * there's hardly any use case for using these without superuser-rights
+ * anyway.
+ *
+ * Copyright (c) 2007-2023, PostgreSQL Global Development Group
+ *
+ * IDENTIFICATION
+ *	  contrib/pageinspect/fsmfuncs.c
+ *
+ *-------------------------------------------------------------------------
+ */
+
+#include "postgres.h"
+
+#include "funcapi.h"
+#include "lib/stringinfo.h"
+#include "miscadmin.h"
+#include "pageinspect.h"
+#include "storage/fsm_internals.h"
+#include "utils/builtins.h"
+
+/*
+ * Dumps the contents of a FSM page.
+ */
+PG_FUNCTION_INFO_V1(fsm_page_contents);
+
+Datum
+fsm_page_contents(PG_FUNCTION_ARGS)
+{
+	bytea	   *raw_page = PG_GETARG_BYTEA_P(0);
+	StringInfoData sinfo;
+	Page		page;
+	FSMPage		fsmpage;
+	int			i;
+
+	if (!superuser())
+		ereport(ERROR,
+				(errcode(ERRCODE_INSUFFICIENT_PRIVILEGE),
+				 errmsg("must be superuser to use raw page functions")));
+
+	page = get_page_from_raw(raw_page);
+
+	if (PageIsNew(page))
+		PG_RETURN_NULL();
+
+	fsmpage = (FSMPage) PageGetContents(page);
+
+	initStringInfo(&sinfo);
+
+	for (i = 0; i < NodesPerPage; i++)
+	{
+		if (fsmpage->fp_nodes[i] != 0)
+			appendStringInfo(&sinfo, "%d: %d\n", i, fsmpage->fp_nodes[i]);
+	}
+	appendStringInfo(&sinfo, "fp_next_slot: %d\n", fsmpage->fp_next_slot);
+
+	PG_RETURN_TEXT_P(cstring_to_text_with_len(sinfo.data, sinfo.len));
+}