--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/src/share/vm/gc_implementation/g1/g1BlockOffsetTable.cpp	Thu Jun 05 15:57:56 2008 -0700
@@ -0,0 +1,624 @@
+/*
+ * Copyright 2001-2007 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.
+ *
+ */
+
+#include "incls/_precompiled.incl"
+#include "incls/_g1BlockOffsetTable.cpp.incl"
+
+//////////////////////////////////////////////////////////////////////
+// G1BlockOffsetSharedArray
+//////////////////////////////////////////////////////////////////////
+
+G1BlockOffsetSharedArray::G1BlockOffsetSharedArray(MemRegion reserved,
+                                                   size_t init_word_size) :
+  _reserved(reserved), _end(NULL)
+{
+  size_t size = compute_size(reserved.word_size());
+  ReservedSpace rs(ReservedSpace::allocation_align_size_up(size));
+  if (!rs.is_reserved()) {
+    vm_exit_during_initialization("Could not reserve enough space for heap offset array");
+  }
+  if (!_vs.initialize(rs, 0)) {
+    vm_exit_during_initialization("Could not reserve enough space for heap offset array");
+  }
+  _offset_array = (u_char*)_vs.low_boundary();
+  resize(init_word_size);
+  if (TraceBlockOffsetTable) {
+    gclog_or_tty->print_cr("G1BlockOffsetSharedArray::G1BlockOffsetSharedArray: ");
+    gclog_or_tty->print_cr("  "
+                  "  rs.base(): " INTPTR_FORMAT
+                  "  rs.size(): " INTPTR_FORMAT
+                  "  rs end(): " INTPTR_FORMAT,
+                  rs.base(), rs.size(), rs.base() + rs.size());
+    gclog_or_tty->print_cr("  "
+                  "  _vs.low_boundary(): " INTPTR_FORMAT
+                  "  _vs.high_boundary(): " INTPTR_FORMAT,
+                  _vs.low_boundary(),
+                  _vs.high_boundary());
+  }
+}
+
+void G1BlockOffsetSharedArray::resize(size_t new_word_size) {
+  assert(new_word_size <= _reserved.word_size(), "Resize larger than reserved");
+  size_t new_size = compute_size(new_word_size);
+  size_t old_size = _vs.committed_size();
+  size_t delta;
+  char* high = _vs.high();
+  _end = _reserved.start() + new_word_size;
+  if (new_size > old_size) {
+    delta = ReservedSpace::page_align_size_up(new_size - old_size);
+    assert(delta > 0, "just checking");
+    if (!_vs.expand_by(delta)) {
+      // Do better than this for Merlin
+      vm_exit_out_of_memory(delta, "offset table expansion");
+    }
+    assert(_vs.high() == high + delta, "invalid expansion");
+    // Initialization of the contents is left to the
+    // G1BlockOffsetArray that uses it.
+  } else {
+    delta = ReservedSpace::page_align_size_down(old_size - new_size);
+    if (delta == 0) return;
+    _vs.shrink_by(delta);
+    assert(_vs.high() == high - delta, "invalid expansion");
+  }
+}
+
+bool G1BlockOffsetSharedArray::is_card_boundary(HeapWord* p) const {
+  assert(p >= _reserved.start(), "just checking");
+  size_t delta = pointer_delta(p, _reserved.start());
+  return (delta & right_n_bits(LogN_words)) == (size_t)NoBits;
+}
+
+
+//////////////////////////////////////////////////////////////////////
+// G1BlockOffsetArray
+//////////////////////////////////////////////////////////////////////
+
+G1BlockOffsetArray::G1BlockOffsetArray(G1BlockOffsetSharedArray* array,
+                                       MemRegion mr, bool init_to_zero) :
+  G1BlockOffsetTable(mr.start(), mr.end()),
+  _unallocated_block(_bottom),
+  _array(array), _csp(NULL),
+  _init_to_zero(init_to_zero) {
+  assert(_bottom <= _end, "arguments out of order");
+  if (!_init_to_zero) {
+    // initialize cards to point back to mr.start()
+    set_remainder_to_point_to_start(mr.start() + N_words, mr.end());
+    _array->set_offset_array(0, 0);  // set first card to 0
+  }
+}
+
+void G1BlockOffsetArray::set_space(Space* sp) {
+  _sp = sp;
+  _csp = sp->toContiguousSpace();
+}
+
+// The arguments follow the normal convention of denoting
+// a right-open interval: [start, end)
+void
+G1BlockOffsetArray:: set_remainder_to_point_to_start(HeapWord* start, HeapWord* end) {
+
+  if (start >= end) {
+    // The start address is equal to the end address (or to
+    // the right of the end address) so there are not cards
+    // that need to be updated..
+    return;
+  }
+
+  // Write the backskip value for each region.
+  //
+  //    offset
+  //    card             2nd                       3rd
+  //     | +- 1st        |                         |
+  //     v v             v                         v
+  //    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+     +-+-+-+-+-+-+-+-+-+-+-
+  //    |x|0|0|0|0|0|0|0|1|1|1|1|1|1| ... |1|1|1|1|2|2|2|2|2|2| ...
+  //    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+     +-+-+-+-+-+-+-+-+-+-+-
+  //    11              19                        75
+  //      12
+  //
+  //    offset card is the card that points to the start of an object
+  //      x - offset value of offset card
+  //    1st - start of first logarithmic region
+  //      0 corresponds to logarithmic value N_words + 0 and 2**(3 * 0) = 1
+  //    2nd - start of second logarithmic region
+  //      1 corresponds to logarithmic value N_words + 1 and 2**(3 * 1) = 8
+  //    3rd - start of third logarithmic region
+  //      2 corresponds to logarithmic value N_words + 2 and 2**(3 * 2) = 64
+  //
+  //    integer below the block offset entry is an example of
+  //    the index of the entry
+  //
+  //    Given an address,
+  //      Find the index for the address
+  //      Find the block offset table entry
+  //      Convert the entry to a back slide
+  //        (e.g., with today's, offset = 0x81 =>
+  //          back slip = 2**(3*(0x81 - N_words)) = 2**3) = 8
+  //      Move back N (e.g., 8) entries and repeat with the
+  //        value of the new entry
+  //
+  size_t start_card = _array->index_for(start);
+  size_t end_card = _array->index_for(end-1);
+  assert(start ==_array->address_for_index(start_card), "Precondition");
+  assert(end ==_array->address_for_index(end_card)+N_words, "Precondition");
+  set_remainder_to_point_to_start_incl(start_card, end_card); // closed interval
+}
+
+// Unlike the normal convention in this code, the argument here denotes
+// a closed, inclusive interval: [start_card, end_card], cf set_remainder_to_point_to_start()
+// above.
+void
+G1BlockOffsetArray::set_remainder_to_point_to_start_incl(size_t start_card, size_t end_card) {
+  if (start_card > end_card) {
+    return;
+  }
+  assert(start_card > _array->index_for(_bottom), "Cannot be first card");
+  assert(_array->offset_array(start_card-1) <= N_words,
+    "Offset card has an unexpected value");
+  size_t start_card_for_region = start_card;
+  u_char offset = max_jubyte;
+  for (int i = 0; i < BlockOffsetArray::N_powers; i++) {
+    // -1 so that the the card with the actual offset is counted.  Another -1
+    // so that the reach ends in this region and not at the start
+    // of the next.
+    size_t reach = start_card - 1 + (BlockOffsetArray::power_to_cards_back(i+1) - 1);
+    offset = N_words + i;
+    if (reach >= end_card) {
+      _array->set_offset_array(start_card_for_region, end_card, offset);
+      start_card_for_region = reach + 1;
+      break;
+    }
+    _array->set_offset_array(start_card_for_region, reach, offset);
+    start_card_for_region = reach + 1;
+  }
+  assert(start_card_for_region > end_card, "Sanity check");
+  DEBUG_ONLY(check_all_cards(start_card, end_card);)
+}
+
+// The block [blk_start, blk_end) has been allocated;
+// adjust the block offset table to represent this information;
+// right-open interval: [blk_start, blk_end)
+void
+G1BlockOffsetArray::alloc_block(HeapWord* blk_start, HeapWord* blk_end) {
+  mark_block(blk_start, blk_end);
+  allocated(blk_start, blk_end);
+}
+
+// Adjust BOT to show that a previously whole block has been split
+// into two.
+void G1BlockOffsetArray::split_block(HeapWord* blk, size_t blk_size,
+                                     size_t left_blk_size) {
+  // Verify that the BOT shows [blk, blk + blk_size) to be one block.
+  verify_single_block(blk, blk_size);
+  // Update the BOT to indicate that [blk + left_blk_size, blk + blk_size)
+  // is one single block.
+  mark_block(blk + left_blk_size, blk + blk_size);
+}
+
+
+// Action_mark - update the BOT for the block [blk_start, blk_end).
+//               Current typical use is for splitting a block.
+// Action_single - udpate the BOT for an allocation.
+// Action_verify - BOT verification.
+void G1BlockOffsetArray::do_block_internal(HeapWord* blk_start,
+                                           HeapWord* blk_end,
+                                           Action action) {
+  assert(Universe::heap()->is_in_reserved(blk_start),
+         "reference must be into the heap");
+  assert(Universe::heap()->is_in_reserved(blk_end-1),
+         "limit must be within the heap");
+  // This is optimized to make the test fast, assuming we only rarely
+  // cross boundaries.
+  uintptr_t end_ui = (uintptr_t)(blk_end - 1);
+  uintptr_t start_ui = (uintptr_t)blk_start;
+  // Calculate the last card boundary preceding end of blk
+  intptr_t boundary_before_end = (intptr_t)end_ui;
+  clear_bits(boundary_before_end, right_n_bits(LogN));
+  if (start_ui <= (uintptr_t)boundary_before_end) {
+    // blk starts at or crosses a boundary
+    // Calculate index of card on which blk begins
+    size_t    start_index = _array->index_for(blk_start);
+    // Index of card on which blk ends
+    size_t    end_index   = _array->index_for(blk_end - 1);
+    // Start address of card on which blk begins
+    HeapWord* boundary    = _array->address_for_index(start_index);
+    assert(boundary <= blk_start, "blk should start at or after boundary");
+    if (blk_start != boundary) {
+      // blk starts strictly after boundary
+      // adjust card boundary and start_index forward to next card
+      boundary += N_words;
+      start_index++;
+    }
+    assert(start_index <= end_index, "monotonicity of index_for()");
+    assert(boundary <= (HeapWord*)boundary_before_end, "tautology");
+    switch (action) {
+      case Action_mark: {
+        if (init_to_zero()) {
+          _array->set_offset_array(start_index, boundary, blk_start);
+          break;
+        } // Else fall through to the next case
+      }
+      case Action_single: {
+        _array->set_offset_array(start_index, boundary, blk_start);
+        // We have finished marking the "offset card". We need to now
+        // mark the subsequent cards that this blk spans.
+        if (start_index < end_index) {
+          HeapWord* rem_st = _array->address_for_index(start_index) + N_words;
+          HeapWord* rem_end = _array->address_for_index(end_index) + N_words;
+          set_remainder_to_point_to_start(rem_st, rem_end);
+        }
+        break;
+      }
+      case Action_check: {
+        _array->check_offset_array(start_index, boundary, blk_start);
+        // We have finished checking the "offset card". We need to now
+        // check the subsequent cards that this blk spans.
+        check_all_cards(start_index + 1, end_index);
+        break;
+      }
+      default:
+        ShouldNotReachHere();
+    }
+  }
+}
+
+// The card-interval [start_card, end_card] is a closed interval; this
+// is an expensive check -- use with care and only under protection of
+// suitable flag.
+void G1BlockOffsetArray::check_all_cards(size_t start_card, size_t end_card) const {
+
+  if (end_card < start_card) {
+    return;
+  }
+  guarantee(_array->offset_array(start_card) == N_words, "Wrong value in second card");
+  for (size_t c = start_card + 1; c <= end_card; c++ /* yeah! */) {
+    u_char entry = _array->offset_array(c);
+    if (c - start_card > BlockOffsetArray::power_to_cards_back(1)) {
+      guarantee(entry > N_words, "Should be in logarithmic region");
+    }
+    size_t backskip = BlockOffsetArray::entry_to_cards_back(entry);
+    size_t landing_card = c - backskip;
+    guarantee(landing_card >= (start_card - 1), "Inv");
+    if (landing_card >= start_card) {
+      guarantee(_array->offset_array(landing_card) <= entry, "monotonicity");
+    } else {
+      guarantee(landing_card == start_card - 1, "Tautology");
+      guarantee(_array->offset_array(landing_card) <= N_words, "Offset value");
+    }
+  }
+}
+
+// The range [blk_start, blk_end) represents a single contiguous block
+// of storage; modify the block offset table to represent this
+// information; Right-open interval: [blk_start, blk_end)
+// NOTE: this method does _not_ adjust _unallocated_block.
+void
+G1BlockOffsetArray::single_block(HeapWord* blk_start, HeapWord* blk_end) {
+  do_block_internal(blk_start, blk_end, Action_single);
+}
+
+// Mark the BOT such that if [blk_start, blk_end) straddles a card
+// boundary, the card following the first such boundary is marked
+// with the appropriate offset.
+// NOTE: this method does _not_ adjust _unallocated_block or
+// any cards subsequent to the first one.
+void
+G1BlockOffsetArray::mark_block(HeapWord* blk_start, HeapWord* blk_end) {
+  do_block_internal(blk_start, blk_end, Action_mark);
+}
+
+void G1BlockOffsetArray::join_blocks(HeapWord* blk1, HeapWord* blk2) {
+  HeapWord* blk1_start = Universe::heap()->block_start(blk1);
+  HeapWord* blk2_start = Universe::heap()->block_start(blk2);
+  assert(blk1 == blk1_start && blk2 == blk2_start,
+         "Must be block starts.");
+  assert(blk1 + _sp->block_size(blk1) == blk2, "Must be contiguous.");
+  size_t blk1_start_index = _array->index_for(blk1);
+  size_t blk2_start_index = _array->index_for(blk2);
+  assert(blk1_start_index <= blk2_start_index, "sanity");
+  HeapWord* blk2_card_start = _array->address_for_index(blk2_start_index);
+  if (blk2 == blk2_card_start) {
+    // blk2 starts a card.  Does blk1 start on the prevous card, or futher
+    // back?
+    assert(blk1_start_index < blk2_start_index, "must be lower card.");
+    if (blk1_start_index + 1 == blk2_start_index) {
+      // previous card; new value for blk2 card is size of blk1.
+      _array->set_offset_array(blk2_start_index, (u_char) _sp->block_size(blk1));
+    } else {
+      // Earlier card; go back a card.
+      _array->set_offset_array(blk2_start_index, N_words);
+    }
+  } else {
+    // blk2 does not start a card.  Does it cross a card?  If not, nothing
+    // to do.
+    size_t blk2_end_index =
+      _array->index_for(blk2 + _sp->block_size(blk2) - 1);
+    assert(blk2_end_index >= blk2_start_index, "sanity");
+    if (blk2_end_index > blk2_start_index) {
+      // Yes, it crosses a card.  The value for the next card must change.
+      if (blk1_start_index + 1 == blk2_start_index) {
+        // previous card; new value for second blk2 card is size of blk1.
+        _array->set_offset_array(blk2_start_index + 1,
+                                 (u_char) _sp->block_size(blk1));
+      } else {
+        // Earlier card; go back a card.
+        _array->set_offset_array(blk2_start_index + 1, N_words);
+      }
+    }
+  }
+}
+
+HeapWord* G1BlockOffsetArray::block_start_unsafe(const void* addr) {
+  assert(_bottom <= addr && addr < _end,
+         "addr must be covered by this Array");
+  // Must read this exactly once because it can be modified by parallel
+  // allocation.
+  HeapWord* ub = _unallocated_block;
+  if (BlockOffsetArrayUseUnallocatedBlock && addr >= ub) {
+    assert(ub < _end, "tautology (see above)");
+    return ub;
+  }
+  // Otherwise, find the block start using the table.
+  HeapWord* q = block_at_or_preceding(addr, false, 0);
+  return forward_to_block_containing_addr(q, addr);
+}
+
+// This duplicates a little code from the above: unavoidable.
+HeapWord*
+G1BlockOffsetArray::block_start_unsafe_const(const void* addr) const {
+  assert(_bottom <= addr && addr < _end,
+         "addr must be covered by this Array");
+  // Must read this exactly once because it can be modified by parallel
+  // allocation.
+  HeapWord* ub = _unallocated_block;
+  if (BlockOffsetArrayUseUnallocatedBlock && addr >= ub) {
+    assert(ub < _end, "tautology (see above)");
+    return ub;
+  }
+  // Otherwise, find the block start using the table.
+  HeapWord* q = block_at_or_preceding(addr, false, 0);
+  HeapWord* n = q + _sp->block_size(q);
+  return forward_to_block_containing_addr_const(q, n, addr);
+}
+
+
+HeapWord*
+G1BlockOffsetArray::forward_to_block_containing_addr_slow(HeapWord* q,
+                                                          HeapWord* n,
+                                                          const void* addr) {
+  // We're not in the normal case.  We need to handle an important subcase
+  // here: LAB allocation.  An allocation previously recorded in the
+  // offset table was actually a lab allocation, and was divided into
+  // several objects subsequently.  Fix this situation as we answer the
+  // query, by updating entries as we cross them.
+  size_t next_index = _array->index_for(n) + 1;
+  HeapWord* next_boundary = _array->address_for_index(next_index);
+  if (csp() != NULL) {
+    if (addr >= csp()->top()) return csp()->top();
+    while (next_boundary < addr) {
+      while (n <= next_boundary) {
+        q = n;
+        oop obj = oop(q);
+        if (obj->klass() == NULL) return q;
+        n += obj->size();
+      }
+      assert(q <= next_boundary && n > next_boundary, "Consequence of loop");
+      // [q, n) is the block that crosses the boundary.
+      alloc_block_work2(&next_boundary, &next_index, q, n);
+    }
+  } else {
+    while (next_boundary < addr) {
+      while (n <= next_boundary) {
+        q = n;
+        oop obj = oop(q);
+        if (obj->klass() == NULL) return q;
+        n += _sp->block_size(q);
+      }
+      assert(q <= next_boundary && n > next_boundary, "Consequence of loop");
+      // [q, n) is the block that crosses the boundary.
+      alloc_block_work2(&next_boundary, &next_index, q, n);
+    }
+  }
+  return forward_to_block_containing_addr_const(q, n, addr);
+}
+
+HeapWord* G1BlockOffsetArray::block_start_careful(const void* addr) const {
+  assert(_array->offset_array(0) == 0, "objects can't cross covered areas");
+
+  assert(_bottom <= addr && addr < _end,
+         "addr must be covered by this Array");
+  // Must read this exactly once because it can be modified by parallel
+  // allocation.
+  HeapWord* ub = _unallocated_block;
+  if (BlockOffsetArrayUseUnallocatedBlock && addr >= ub) {
+    assert(ub < _end, "tautology (see above)");
+    return ub;
+  }
+
+  // Otherwise, find the block start using the table, but taking
+  // care (cf block_start_unsafe() above) not to parse any objects/blocks
+  // on the cards themsleves.
+  size_t index = _array->index_for(addr);
+  assert(_array->address_for_index(index) == addr,
+         "arg should be start of card");
+
+  HeapWord* q = (HeapWord*)addr;
+  uint offset;
+  do {
+    offset = _array->offset_array(index--);
+    q -= offset;
+  } while (offset == N_words);
+  assert(q <= addr, "block start should be to left of arg");
+  return q;
+}
+
+// Note that the committed size of the covered space may have changed,
+// so the table size might also wish to change.
+void G1BlockOffsetArray::resize(size_t new_word_size) {
+  HeapWord* new_end = _bottom + new_word_size;
+  if (_end < new_end && !init_to_zero()) {
+    // verify that the old and new boundaries are also card boundaries
+    assert(_array->is_card_boundary(_end),
+           "_end not a card boundary");
+    assert(_array->is_card_boundary(new_end),
+           "new _end would not be a card boundary");
+    // set all the newly added cards
+    _array->set_offset_array(_end, new_end, N_words);
+  }
+  _end = new_end;  // update _end
+}
+
+void G1BlockOffsetArray::set_region(MemRegion mr) {
+  _bottom = mr.start();
+  _end = mr.end();
+}
+
+//
+//              threshold_
+//              |   _index_
+//              v   v
+//      +-------+-------+-------+-------+-------+
+//      | i-1   |   i   | i+1   | i+2   | i+3   |
+//      +-------+-------+-------+-------+-------+
+//       ( ^    ]
+//         block-start
+//
+void G1BlockOffsetArray::alloc_block_work2(HeapWord** threshold_, size_t* index_,
+                                           HeapWord* blk_start, HeapWord* blk_end) {
+  // For efficiency, do copy-in/copy-out.
+  HeapWord* threshold = *threshold_;
+  size_t    index = *index_;
+
+  assert(blk_start != NULL && blk_end > blk_start,
+         "phantom block");
+  assert(blk_end > threshold, "should be past threshold");
+  assert(blk_start <= threshold, "blk_start should be at or before threshold")
+  assert(pointer_delta(threshold, blk_start) <= N_words,
+         "offset should be <= BlockOffsetSharedArray::N");
+  assert(Universe::heap()->is_in_reserved(blk_start),
+         "reference must be into the heap");
+  assert(Universe::heap()->is_in_reserved(blk_end-1),
+         "limit must be within the heap");
+  assert(threshold == _array->_reserved.start() + index*N_words,
+         "index must agree with threshold");
+
+  DEBUG_ONLY(size_t orig_index = index;)
+
+  // Mark the card that holds the offset into the block.  Note
+  // that _next_offset_index and _next_offset_threshold are not
+  // updated until the end of this method.
+  _array->set_offset_array(index, threshold, blk_start);
+
+  // We need to now mark the subsequent cards that this blk spans.
+
+  // Index of card on which blk ends.
+  size_t end_index   = _array->index_for(blk_end - 1);
+
+  // Are there more cards left to be updated?
+  if (index + 1 <= end_index) {
+    HeapWord* rem_st  = _array->address_for_index(index + 1);
+    // Calculate rem_end this way because end_index
+    // may be the last valid index in the covered region.
+    HeapWord* rem_end = _array->address_for_index(end_index) +  N_words;
+    set_remainder_to_point_to_start(rem_st, rem_end);
+  }
+
+  index = end_index + 1;
+  // Calculate threshold_ this way because end_index
+  // may be the last valid index in the covered region.
+  threshold = _array->address_for_index(end_index) + N_words;
+  assert(threshold >= blk_end, "Incorrect offset threshold");
+
+  // index_ and threshold_ updated here.
+  *threshold_ = threshold;
+  *index_ = index;
+
+#ifdef ASSERT
+  // The offset can be 0 if the block starts on a boundary.  That
+  // is checked by an assertion above.
+  size_t start_index = _array->index_for(blk_start);
+  HeapWord* boundary    = _array->address_for_index(start_index);
+  assert((_array->offset_array(orig_index) == 0 &&
+          blk_start == boundary) ||
+          (_array->offset_array(orig_index) > 0 &&
+         _array->offset_array(orig_index) <= N_words),
+         "offset array should have been set");
+  for (size_t j = orig_index + 1; j <= end_index; j++) {
+    assert(_array->offset_array(j) > 0 &&
+           _array->offset_array(j) <=
+             (u_char) (N_words+BlockOffsetArray::N_powers-1),
+           "offset array should have been set");
+  }
+#endif
+}
+
+//////////////////////////////////////////////////////////////////////
+// G1BlockOffsetArrayContigSpace
+//////////////////////////////////////////////////////////////////////
+
+HeapWord*
+G1BlockOffsetArrayContigSpace::block_start_unsafe(const void* addr) {
+  assert(_bottom <= addr && addr < _end,
+         "addr must be covered by this Array");
+  HeapWord* q = block_at_or_preceding(addr, true, _next_offset_index-1);
+  return forward_to_block_containing_addr(q, addr);
+}
+
+HeapWord*
+G1BlockOffsetArrayContigSpace::
+block_start_unsafe_const(const void* addr) const {
+  assert(_bottom <= addr && addr < _end,
+         "addr must be covered by this Array");
+  HeapWord* q = block_at_or_preceding(addr, true, _next_offset_index-1);
+  HeapWord* n = q + _sp->block_size(q);
+  return forward_to_block_containing_addr_const(q, n, addr);
+}
+
+G1BlockOffsetArrayContigSpace::
+G1BlockOffsetArrayContigSpace(G1BlockOffsetSharedArray* array,
+                              MemRegion mr) :
+  G1BlockOffsetArray(array, mr, true)
+{
+  _next_offset_threshold = NULL;
+  _next_offset_index = 0;
+}
+
+HeapWord* G1BlockOffsetArrayContigSpace::initialize_threshold() {
+  assert(!Universe::heap()->is_in_reserved(_array->_offset_array),
+         "just checking");
+  _next_offset_index = _array->index_for(_bottom);
+  _next_offset_index++;
+  _next_offset_threshold =
+    _array->address_for_index(_next_offset_index);
+  return _next_offset_threshold;
+}
+
+void G1BlockOffsetArrayContigSpace::zero_bottom_entry() {
+  assert(!Universe::heap()->is_in_reserved(_array->_offset_array),
+         "just checking");
+  size_t bottom_index = _array->index_for(_bottom);
+  assert(_array->address_for_index(bottom_index) == _bottom,
+         "Precondition of call");
+  _array->set_offset_array(bottom_index, 0);
+}