1 files changed, 108 insertions, 0 deletions

diff --git a/mps/code/ring.h b/mps/code/ring.h
new file mode 100644
index 00000000000..43c71600ec0
--- /dev/null
+++ b/mps/code/ring.h
@@ -0,0 +1,108 @@
+/* impl.h.ring: RING INTERFACE
+ *
+ * $HopeName: MMsrc!ring.h(MMdevel_pekka_locus.1) $
+ * Copyright (C) 1999 Harlequin Limited.  All rights reserved.
+ */
+
+
+#ifndef ring_h
+#define ring_h
+
+#include "check.h"
+#include "mpmtypes.h"
+
+
+/* RingStruct -- double-ended queue structure
+ *
+ * .ring: The ring structure is used as a field in other structures
+ * in order to link them together into "rings".  See impl.c.ring.
+ */
+
+typedef struct RingStruct *Ring;
+typedef struct RingStruct {     /* double-ended queue structure */
+  Ring next, prev;              /* links to next and prev element */
+} RingStruct;
+
+
+#define RingNONE ((Ring)0)
+
+extern Bool RingCheck(Ring ring);
+extern Bool RingCheckSingle(Ring ring);
+extern Bool RingIsSingle(Ring ring);
+
+/* .ring.init: */
+extern void (RingInit)(Ring ring);
+#define RingInit(ring) \
+  BEGIN \
+    Ring _ring = (ring); \
+    AVER(_ring != NULL); \
+    _ring->next = _ring; \
+    _ring->prev = _ring; \
+    AVER(RingCheck(_ring)); \
+  END
+
+/* .ring.finish: */
+extern void (RingFinish)(Ring ring);
+#define RingFinish(ring) \
+  BEGIN \
+    Ring _ring = (ring); \
+    AVER(RingCheckSingle(_ring)); \
+    _ring->next = RingNONE; \
+    _ring->prev = RingNONE; \
+  END
+
+/* .ring.append: */
+extern void (RingAppend)(Ring ring, Ring new);
+#define RingAppend(ring, new) \
+  BEGIN \
+    Ring _ring = (ring), _new = (new); \
+    AVER(RingCheck(_ring)); \
+    AVER(RingCheckSingle(_new)); \
+    _new->prev = _ring->prev; \
+    _new->next = _ring; \
+    _ring->prev->next = _new; \
+    _ring->prev = _new; \
+  END
+
+/* .ring.insert: */
+extern void (RingInsert)(Ring ring, Ring new);
+#define RingInsert(ring, new) \
+  BEGIN \
+    Ring _ring = (ring), _new = (new); \
+    AVER(RingCheck(_ring)); \
+    AVER(RingCheckSingle(_new)); \
+    _new->prev = _ring; \
+    _new->next = _ring->next; \
+    _ring->next->prev = _new; \
+    _ring->next = _new; \
+  END
+
+/* .ring.remove: */
+extern void (RingRemove)(Ring old);
+#define RingRemove(old) \
+  BEGIN \
+    Ring _old = (old); \
+    AVER(RingCheck(_old)); \
+    AVER(!RingIsSingle(_old)); \
+    _old->next->prev = _old->prev; \
+    _old->prev->next = _old->next; \
+    _old->next = _old; \
+    _old->prev = _old; \
+  END
+
+/* .ring.next: */
+extern Ring (RingNext)(Ring ring);
+#define RingNext(ring)  ((ring)->next)
+
+/* .ring.elt: See design.mps.ring.elt */
+#define RING_ELT(type, field, node) \
+   ((type)((char *)(node) - (size_t)(&((type)0)->field)))
+
+/* .ring.for: See design.mps.ring.for */
+#define RING_FOR(node, ring, next) \
+  for(node = RingNext(ring), next = RingNext(node); \
+      node != (ring); \
+      node = (next), next = RingNext(node))
+
+
+#endif /* ring_h */