--- /dev/null	2013-09-25 08:54:24.969970990 +0200
+++ new/src/share/vm/gc_implementation/g1/g1BiasedArray.hpp	2013-09-25 10:56:23.144317113 +0200
@@ -0,0 +1,181 @@
+/*
+ * Copyright (c) 2013, Oracle and/or its affiliates. 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 Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
+ * or visit www.oracle.com if you need additional information or have any
+ * questions.
+ *
+ */
+
+#ifndef SHARE_VM_GC_IMPLEMENTATION_G1_G1BIASEDARRAY_HPP
+#define SHARE_VM_GC_IMPLEMENTATION_G1_G1BIASEDARRAY_HPP
+
+#include "utilities/debug.hpp"
+#include "memory/allocation.inline.hpp"
+
+// Implements the common base functionality for arrays that contain provisions
+// for accessing its elements using a biased index.
+// The element type is defined by the instantiating the template.
+class G1BiasedMappedArrayBase VALUE_OBJ_CLASS_SPEC {
+  friend class VMStructs;
+public:
+  typedef size_t idx_t;
+protected:
+  address _base;          // the real base address
+  size_t _length;         // the length of the array
+  address _biased_base;   // base address biased by "bias" elements
+  size_t _bias;           // the bias, i.e. the offset biased_base is located to the right in elements
+  uint _shift_by;         // the amount of bits to shift right when mapping to an index of the array.
+
+protected:
+
+  G1BiasedMappedArrayBase() : _base(NULL), _length(0), _biased_base(NULL),
+    _bias(0), _shift_by(0) { }
+
+  // Allocate a new array, generic version.
+  static address create_new_base_array(size_t length, size_t elem_size) {
+    assert(length > 0, "just checking");
+    assert(elem_size > 0, "just checking");
+    return NEW_C_HEAP_ARRAY(u_char, length * elem_size, mtGC);
+  }
+
+  // Initialize the members of this class. The biased start address of this array
+  // is the bias (in elements) multiplied by the element size.
+  void initialize_base(address base, size_t length, size_t bias, size_t elem_size, uint shift_by) {
+    assert(base != NULL, "just checking");
+    assert(length > 0, "just checking");
+    assert(shift_by < sizeof(uintptr_t) * 8, err_msg("Shifting by %zd, larger than word size?", shift_by));
+    _base = base;
+    _length = length;
+    _biased_base = base - (bias * elem_size);
+    _bias = bias;
+    _shift_by = shift_by;
+  }
+
+  // Allocate and initialize this array to cover the heap addresses in the range
+  // of [bottom, end).
+  void initialize(HeapWord* bottom, HeapWord* end, size_t target_elem_size_in_bytes, size_t mapping_granularity_in_bytes) {
+    assert(mapping_granularity_in_bytes > 0, "just checking");
+    assert(is_power_of_2(mapping_granularity_in_bytes),
+      err_msg("mapping granularity must be power of 2, is %zd", mapping_granularity_in_bytes));
+    assert((uintptr_t)bottom % mapping_granularity_in_bytes == 0,
+      err_msg("bottom mapping area address must be a multiple of mapping granularity %zd, is "PTR_FORMAT,
+        mapping_granularity_in_bytes, bottom));
+    assert((uintptr_t)end % mapping_granularity_in_bytes == 0,
+      err_msg("end mapping area address must be a multiple of mapping granularity %zd, is "PTR_FORMAT,
+        mapping_granularity_in_bytes, end));
+    size_t num_target_elems = (end - bottom) / (mapping_granularity_in_bytes / HeapWordSize);
+    idx_t bias = (uintptr_t)bottom / mapping_granularity_in_bytes;
+    address base = create_new_base_array(num_target_elems, target_elem_size_in_bytes);
+    initialize_base(base, num_target_elems, bias, target_elem_size_in_bytes, log2_intptr(mapping_granularity_in_bytes));
+  }
+
+  size_t bias() const { return _bias; }
+  uint shift_by() const { return _shift_by; }
+
+  void verify_index(idx_t index) const PRODUCT_RETURN;
+  void verify_biased_index(idx_t biased_index) const PRODUCT_RETURN;
+  void verify_biased_index_inclusive_end(idx_t biased_index) const PRODUCT_RETURN;
+
+public:
+   // Return the length of the array in elements.
+   size_t length() const { return _length; }
+};
+
+// Array that provides biased access and mapping from (valid) addresses in the
+// heap into this array.
+template<class T>
+class G1BiasedMappedArray : public G1BiasedMappedArrayBase {
+public:
+  typedef G1BiasedMappedArrayBase::idx_t idx_t;
+
+  T* base() const { return (T*)G1BiasedMappedArrayBase::_base; }
+  // Return the element of the given array at the given index. Assume
+  // the index is valid. This is a convenience method that does sanity
+  // checking on the index.
+  T get_by_index(idx_t index) const {
+    verify_index(index);
+    return this->base()[index];
+  }
+
+  // Set the element of the given array at the given index to the
+  // given value. Assume the index is valid. This is a convenience
+  // method that does sanity checking on the index.
+  void set_by_index(idx_t index, T value) {
+    verify_index(index);
+    this->base()[index] = value;
+  }
+
+  // The raw biased base pointer.
+  T* biased_base() const { return (T*)G1BiasedMappedArrayBase::_biased_base; }
+
+  // Return the element of the given array that covers the given word in the
+  // heap. Assumes the index is valid.
+  T get_by_address(HeapWord* value) const {
+    idx_t biased_index = ((uintptr_t)value) >> this->shift_by();
+    this->verify_biased_index(biased_index);
+    return biased_base()[biased_index];
+  }
+
+  // Set the value of the array entry that corresponds to the given array.
+  void set_by_address(HeapWord * address, T value) {
+    idx_t biased_index = ((uintptr_t)address) >> this->shift_by();
+    this->verify_biased_index(biased_index);
+    biased_base()[biased_index] = value;    
+  }
+
+protected:
+  // Returns the address of the element the given address maps to
+  T* address_mapped_to(HeapWord* address) {
+    idx_t biased_index = ((uintptr_t)address) >> this->shift_by();
+    this->verify_biased_index_inclusive_end(biased_index);
+    return biased_base() + biased_index;
+  }
+
+public:
+  // Return the smallest address (inclusive) in the heap that this array covers.
+  HeapWord* bottom_address_mapped() const {
+    return (HeapWord*) ((uintptr_t)this->bias() << this->shift_by());
+  }
+
+  // Return the highest address (exclusive) in the heap that this array covers.
+  HeapWord* end_address_mapped() const {
+    return (HeapWord*) ((uintptr_t)(this->bias() + this->length()) << this->shift_by());
+  }
+
+protected:
+  virtual T default_value() const = 0;
+  // Set all elements of the given array to the given value.
+  void clear() {
+    T value = default_value();
+    for (idx_t i = 0; i < length(); i++) {
+      set_by_index(i, value);
+    }
+  }
+public:
+  G1BiasedMappedArray() {}
+
+  // Allocate and initialize this array to cover the heap addresses in the range
+  // of [bottom, end).
+  void initialize(HeapWord* bottom, HeapWord* end, size_t mapping_granularity) {
+    G1BiasedMappedArrayBase::initialize(bottom, end, sizeof(T), mapping_granularity);
+    this->clear();
+  }
+};
+
+#endif // SHARE_VM_GC_IMPLEMENTATION_G1_G1BIASEDARRAY_HPP