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 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.

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 *

 * 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.

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#ifndef SHARE_OOPS_COMPRESSEDOOPS_INLINE_HPP

#define SHARE_OOPS_COMPRESSEDOOPS_INLINE_HPP

#include "gc/shared/collectedHeap.hpp"

#include "memory/universe.hpp"

#include "oops/oop.hpp"

// Functions for encoding and decoding compressed oops.

// If the oops are compressed, the type passed to these overloaded functions

// is narrowOop.  All functions are overloaded so they can be called by

// template functions without conditionals (the compiler instantiates via

// the right type and inlines the appropriate code).

// Algorithm for encoding and decoding oops from 64 bit pointers to 32 bit

// offset from the heap base.  Saving the check for null can save instructions

// in inner GC loops so these are separated.

namespace CompressedOops {

  inline bool is_null(oop obj)       { return obj == NULL; }

  inline bool is_null(narrowOop obj) { return obj == 0; }

  inline oop decode_not_null(narrowOop v) {

    assert(!is_null(v), "narrow oop value can never be zero");

    address base = Universe::narrow_oop_base();

    int    shift = Universe::narrow_oop_shift();

    oop result = (oop)(void*)((uintptr_t)base + ((uintptr_t)v << shift));

    assert(check_obj_alignment(result), "address not aligned: " INTPTR_FORMAT, p2i((void*) result));

    return result;

  }

  inline oop decode(narrowOop v) {

    return is_null(v) ? (oop)NULL : decode_not_null(v);

  }

  inline narrowOop encode_not_null(oop v) {

    assert(!is_null(v), "oop value can never be zero");

    assert(check_obj_alignment(v), "Address not aligned");

    assert(Universe::heap()->is_in_reserved(v), "Address not in heap");

    address base = Universe::narrow_oop_base();

    int    shift = Universe::narrow_oop_shift();

    uint64_t  pd = (uint64_t)(pointer_delta((void*)v, (void*)base, 1));

    assert(OopEncodingHeapMax > pd, "change encoding max if new encoding");

    uint64_t result = pd >> shift;

    assert((result & CONST64(0xffffffff00000000)) == 0, "narrow oop overflow");

    assert(decode(result) == v, "reversibility");

    return (narrowOop)result;

  }

  inline narrowOop encode(oop v) {

    return is_null(v) ? (narrowOop)0 : encode_not_null(v);

  }

  // No conversions needed for these overloads

  inline oop decode_not_null(oop v)             { return v; }

  inline oop decode(oop v)                      { return v; }

  inline narrowOop encode_not_null(narrowOop v) { return v; }

  inline narrowOop encode(narrowOop v)          { return v; }

}

#endif // SHARE_OOPS_COMPRESSEDOOPS_INLINE_HPP