--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/src/share/vm/gc_implementation/concurrentMarkSweep/freeChunk.hpp	Mon Jun 09 11:51:19 2008 -0400
@@ -0,0 +1,137 @@
+/*
+ * Copyright 2001-2005 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.
+ *
+ */
+
+//
+// Free block maintenance for Concurrent Mark Sweep Generation
+//
+// The main data structure for free blocks are
+// . an indexed array of small free blocks, and
+// . a dictionary of large free blocks
+//
+
+// No virtuals in FreeChunk (don't want any vtables).
+
+// A FreeChunk is merely a chunk that can be in a doubly linked list
+// and has a size field. NOTE: FreeChunks are distinguished from allocated
+// objects in two ways (by the sweeper), depending on whether the VM is 32 or
+// 64 bits.
+// In 32 bits or 64 bits without CompressedOops, the second word (prev) has the
+// LSB set to indicate a free chunk; allocated objects' klass() pointers
+// don't have their LSB set. The corresponding bit in the CMSBitMap is
+// set when the chunk is allocated. There are also blocks that "look free"
+// but are not part of the free list and should not be coalesced into larger
+// free blocks. These free blocks have their two LSB's set.
+
+class FreeChunk VALUE_OBJ_CLASS_SPEC {
+  friend class VMStructs;
+  // For 64 bit compressed oops, the markOop encodes both the size and the
+  // indication that this is a FreeChunk and not an object.
+  volatile size_t   _size;
+  FreeChunk* _prev;
+  FreeChunk* _next;
+
+  markOop mark()     const volatile { return (markOop)_size; }
+  void set_mark(markOop m)          { _size = (size_t)m; }
+
+ public:
+  NOT_PRODUCT(static const size_t header_size();)
+
+  // Returns "true" if the address indicates that the block represents
+  // a free chunk.
+  static bool indicatesFreeChunk(const HeapWord* addr) {
+    // Force volatile read from addr because value might change between
+    // calls.  We really want the read of _mark and _prev from this pointer
+    // to be volatile but making the fields volatile causes all sorts of
+    // compilation errors.
+    return ((volatile FreeChunk*)addr)->isFree();
+  }
+
+  bool isFree() const volatile {
+    LP64_ONLY(if (UseCompressedOops) return mark()->is_cms_free_chunk(); else)
+    return (((intptr_t)_prev) & 0x1) == 0x1;
+  }
+  bool cantCoalesce() const {
+    assert(isFree(), "can't get coalesce bit on not free");
+    return (((intptr_t)_prev) & 0x2) == 0x2;
+  }
+  void dontCoalesce() {
+    // the block should be free
+    assert(isFree(), "Should look like a free block");
+    _prev = (FreeChunk*)(((intptr_t)_prev) | 0x2);
+  }
+  FreeChunk* prev() const {
+    return (FreeChunk*)(((intptr_t)_prev) & ~(0x3));
+  }
+
+  debug_only(void* prev_addr() const { return (void*)&_prev; })
+
+  size_t size() const volatile {
+    LP64_ONLY(if (UseCompressedOops) return mark()->get_size(); else )
+    return _size;
+  }
+  void setSize(size_t sz) {
+    LP64_ONLY(if (UseCompressedOops) set_mark(markOopDesc::set_size_and_free(sz)); else )
+    _size = sz;
+  }
+
+  FreeChunk* next()   const { return _next; }
+
+  void linkAfter(FreeChunk* ptr) {
+    linkNext(ptr);
+    if (ptr != NULL) ptr->linkPrev(this);
+  }
+  void linkAfterNonNull(FreeChunk* ptr) {
+    assert(ptr != NULL, "precondition violation");
+    linkNext(ptr);
+    ptr->linkPrev(this);
+  }
+  void linkNext(FreeChunk* ptr) { _next = ptr; }
+  void linkPrev(FreeChunk* ptr) {
+     LP64_ONLY(if (UseCompressedOops) _prev = ptr; else)
+     _prev = (FreeChunk*)((intptr_t)ptr | 0x1);
+  }
+  void clearPrev()              { _prev = NULL; }
+  void clearNext()              { _next = NULL; }
+  void markNotFree() {
+   LP64_ONLY(if (UseCompressedOops) set_mark(markOopDesc::prototype());)
+   // Also set _prev to null
+   _prev = NULL;
+  }
+
+  // Return the address past the end of this chunk
+  HeapWord* end() const { return ((HeapWord*) this) + size(); }
+
+  // debugging
+  void verify()             const PRODUCT_RETURN;
+  void verifyList()         const PRODUCT_RETURN;
+  void mangleAllocated(size_t size) PRODUCT_RETURN;
+  void mangleFreed(size_t size)     PRODUCT_RETURN;
+};
+
+// Alignment helpers etc.
+#define numQuanta(x,y) ((x+y-1)/y)
+enum AlignmentConstants {
+  MinChunkSize = numQuanta(sizeof(FreeChunk), MinObjAlignmentInBytes) * MinObjAlignment
+};
+