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+/*
+ * This file is part of NetSurf, http://netsurf-browser.org/
+ * Licensed under the GNU General Public License,
+ *                http://www.opensource.org/licenses/gpl-license
+ * Copyright 2006, 2007 Daniel Silverstone <dsilvers@digital-scurf.org>
+ */
+
+/** \file
+ * Ring list structure.
+ *
+ * Rings are structures which have an r_next pointer and an r_prev
+ * pointer which are always initialised and always point at the next
+ * or previous element respectively.
+ *
+ * The degenerate case of a single element in the ring simply points
+ * at itself in both directions. A zero element ring is NULL.
+ *
+ * Some of the ring functions are specific to the fetcher but may be
+ * of use to others and are thus included here.
+ */
+
+#ifndef _NETSURF_UTILS_RING_H_
+#define _NETSURF_UTILS_RING_H_
+
+
+/** Insert the given item into the specified ring.
+ * Assumes that the element is zeroed as appropriate.
+ */
+#define RING_INSERT(ring,element) \
+	/*LOG(("RING_INSERT(%s, %p(%s))", #ring, element, element->host));*/ \
+	if (ring) { \
+		element->r_next = ring; \
+		element->r_prev = ring->r_prev; \
+		ring->r_prev = element; \
+		element->r_prev->r_next = element; \
+	} else \
+		ring = element->r_prev = element->r_next = element
+
+/** Remove the given element from the specified ring.
+ * Will zero the element as needed
+ */
+#define RING_REMOVE(ring, element) \
+	/*LOG(("RING_REMOVE(%s, %p(%s)", #ring, element, element->host));*/ \
+	if (element->r_next != element ) { \
+		/* Not the only thing in the ring */ \
+		element->r_next->r_prev = element->r_prev; \
+		element->r_prev->r_next = element->r_next; \
+		if (ring == element) ring = element->r_next; \
+	} else { \
+		/* Only thing in the ring */ \
+		ring = 0; \
+	} \
+	element->r_next = element->r_prev = 0
+
+/** Find the element (by hostname) in the given ring, leave it in the
+ * provided element variable
+ */
+#define RING_FINDBYHOST(ring, element, hostname) \
+	/*LOG(("RING_FINDBYHOST(%s, %s)", #ring, hostname));*/ \
+	if (ring) { \
+		bool found = false; \
+		element = ring; \
+		do { \
+			if (strcasecmp(element->host, hostname) == 0) { \
+				found = true; \
+				break; \
+			} \
+			element = element->r_next; \
+		} while (element != ring); \
+		if (!found) element = 0; \
+	} else element = 0
+
+/** Measure the size of a ring and put it in the supplied variable */
+#define RING_GETSIZE(ringtype, ring, sizevar) \
+	/*LOG(("RING_GETSIZE(%s)", #ring));*/ \
+	if (ring) { \
+		ringtype *p = ring; \
+		sizevar = 0; \
+		do { \
+			sizevar++; \
+			p = p->r_next; \
+		} while (p != ring); \
+	} else sizevar = 0
+
+/** Count the number of elements in the ring which match the provided hostname */
+#define RING_COUNTBYHOST(ringtype, ring, sizevar, hostname) \
+	/*LOG(("RING_COUNTBYHOST(%s, %s)", #ring, hostname));*/ \
+	if (ring) { \
+		ringtype *p = ring; \
+		sizevar = 0; \
+		do { \
+			if (strcasecmp(p->host, hostname) == 0) \
+				sizevar++; \
+			p = p->r_next; \
+		} while (p != ring); \
+	} else sizevar = 0
+
+#endif