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hotspot/src/share/vm/memory/memRegion.cpp

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+/*
+ * Copyright 2000-2004 Sun Microsystems, Inc.  All Rights Reserved.
+ * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
+ *
+ * This code is free software; you can redistribute it and/or modify it
+ * under the terms of the GNU General Public License version 2 only, as
+ * published by the Free Software Foundation.
+ *
+ * This code 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
+ * version 2 for more details (a copy is included in the LICENSE file that
+ * accompanied this code).
+ *
+ * You should have received a copy of the GNU General Public License version
+ * 2 along with this work; if not, write to the Free Software Foundation,
+ * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
+ *
+ * Please contact Sun Microsystems, Inc., 4150 Network Circle, Santa Clara,
+ * CA 95054 USA or visit www.sun.com if you need additional information or
+ * have any questions.
+ *
+ */
+
+// A very simple data structure representing a contigous word-aligned
+// region of address space.
+
+#include "incls/_precompiled.incl"
+#include "incls/_memRegion.cpp.incl"
+
+MemRegion MemRegion::intersection(const MemRegion mr2) const {
+  MemRegion res;
+  HeapWord* res_start = MAX2(start(), mr2.start());
+  HeapWord* res_end   = MIN2(end(),   mr2.end());
+  if (res_start < res_end) {
+    res.set_start(res_start);
+    res.set_end(res_end);
+  }
+  return res;
+}
+
+MemRegion MemRegion::_union(const MemRegion mr2) const {
+  // If one region is empty, return the other
+  if (is_empty()) return mr2;
+  if (mr2.is_empty()) return MemRegion(start(), end());
+
+  // Otherwise, regions must overlap or be adjacent
+  assert(((start() <= mr2.start()) && (end() >= mr2.start())) ||
+         ((mr2.start() <= start()) && (mr2.end() >= start())),
+             "non-adjacent or overlapping regions");
+  MemRegion res;
+  HeapWord* res_start = MIN2(start(), mr2.start());
+  HeapWord* res_end   = MAX2(end(),   mr2.end());
+  res.set_start(res_start);
+  res.set_end(res_end);
+  return res;
+}
+
+MemRegion MemRegion::minus(const MemRegion mr2) const {
+  // There seem to be 6 cases:
+  //                  |this MemRegion|
+  // |strictly below|
+  //   |overlap beginning|
+  //                    |interior|
+  //                        |overlap ending|
+  //                                   |strictly above|
+  //              |completely overlapping|
+  // We can't deal with an interior case because it would
+  // produce two disjoint regions as a result.
+  // We aren't trying to be optimal in the number of tests below,
+  // but the order is important to distinguish the strictly cases
+  // from the overlapping cases.
+  if (mr2.end() <= start()) {
+    // strictly below
+    return MemRegion(start(), end());
+  }
+  if (mr2.start() <= start() && mr2.end() <= end()) {
+    // overlap beginning
+    return MemRegion(mr2.end(), end());
+  }
+  if (mr2.start() >= end()) {
+    // strictly above
+    return MemRegion(start(), end());
+  }
+  if (mr2.start() >= start() && mr2.end() >= end()) {
+    // overlap ending
+    return MemRegion(start(), mr2.start());
+  }
+  if (mr2.start() <= start() && mr2.end() >= end()) {
+    // completely overlapping
+    return MemRegion();
+  }
+  if (mr2.start() > start() && mr2.end() < end()) {
+    // interior
+    guarantee(false, "MemRegion::minus, but interior");
+    return MemRegion();
+  }
+  ShouldNotReachHere();
+  return MemRegion();
+}