Add (and use) generic reference counter, to improve signal:noise ratio

in code defining reference-counted objects.

src/core/refcnt.c

@@ -0,0 +1,73 @@
+/*
+ * Copyright (C) 2007 Michael Brown <mbrown@fensystems.co.uk>.
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License as
+ * published by the Free Software Foundation; either version 2 of the
+ * License, or any later version.
+ *
+ * This program is distributed in the hope that it will be useful, but
+ * WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software
+ * Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
+ */
+
+#include <stdlib.h>
+#include <gpxe/refcnt.h>
+
+/** @file
+ *
+ * Reference counting
+ *
+ */
+
+/**
+ * Increment reference count
+ *
+ * @v refcnt		Reference counter, or NULL
+ *
+ * If @c refcnt is NULL, no action is taken.
+ */
+void ref_get ( struct refcnt *refcnt ) {
+
+	if ( ! refcnt )
+		return;
+
+	refcnt->refcnt++;
+
+	DBGC ( refcnt, "REFCNT %p incremented to %d\n",
+	       refcnt, refcnt->refcnt );
+}
+
+/**
+ * Decrement reference count
+ *
+ * @v refcnt		Reference counter, or NULL
+ *
+ * If the reference count decreases below zero, the object's free()
+ * method will be called.
+ *
+ * If @c refcnt is NULL, no action is taken.
+ */
+void ref_put ( struct refcnt *refcnt ) {
+
+	if ( ! refcnt )
+		return;
+
+	refcnt->refcnt--;
+	DBGC ( refcnt, "REFCNT %p decremented to %d\n",
+	       refcnt, refcnt->refcnt );
+
+	if ( refcnt->refcnt >= 0 )
+		return;
+
+	if ( refcnt->free ) {
+		refcnt->free ( refcnt );
+	} else {
+		free ( refcnt );
+	}
+}