/*

 * Copyright (c) 2012, 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.

 *

 */

#include "precompiled.hpp"

#include "memory/allocation.hpp"

#include "memory/metachunk.hpp"

#include "utilities/copy.hpp"

#include "utilities/debug.hpp"

//

// Future modification

//

// The Metachunk can conceivable be replaced by the Chunk in

// allocation.hpp.  Note that the latter Chunk is the space for

// allocation (allocations from the chunk are out of the space in

// the Chunk after the header for the Chunk) where as Metachunks

// point to space in a VirtualSpace.  To replace Metachunks with

// Chunks, change Chunks so that they can be allocated out of a VirtualSpace.

const size_t metadata_chunk_initialize = 0xf7f7f7f7;

size_t Metachunk::_overhead =

  Chunk::aligned_overhead_size(sizeof(Metachunk)) / BytesPerWord;

// Metachunk methods

Metachunk* Metachunk::initialize(MetaWord* ptr, size_t word_size) {

  // Set bottom, top, and end.  Allow space for the Metachunk itself

  Metachunk* chunk = (Metachunk*) ptr;

  MetaWord* chunk_bottom = ptr + _overhead;

  chunk->set_bottom(ptr);

  chunk->set_top(chunk_bottom);

  MetaWord* chunk_end = ptr + word_size;

  assert(chunk_end > chunk_bottom, "Chunk must be too small");

  chunk->set_end(chunk_end);

  chunk->set_next(NULL);

  chunk->set_word_size(word_size);

#ifdef ASSERT

  size_t data_word_size = pointer_delta(chunk_end, chunk_bottom, sizeof(MetaWord));

  Copy::fill_to_words((HeapWord*) chunk_bottom, data_word_size, metadata_chunk_initialize);

#endif

  return chunk;

}

MetaWord* Metachunk::allocate(size_t word_size) {

  MetaWord* result = NULL;

  // If available, bump the pointer to allocate.

  if (free_word_size() >= word_size) {

    result = _top;

    _top = _top + word_size;

  }

  return result;

}

// _bottom points to the start of the chunk including the overhead.

  return pointer_delta(_top, _bottom, sizeof(MetaWord));

}

  return pointer_delta(_end, _top, sizeof(MetaWord));

}

  return pointer_delta(_end, _bottom, sizeof(MetaWord));

}

void Metachunk::print_on(outputStream* st) const {

  st->print_cr("Metachunk:"

               " bottom " PTR_FORMAT " top " PTR_FORMAT

               " end " PTR_FORMAT " size " SIZE_FORMAT,

               bottom(), top(), end(), word_size());

}

#ifndef PRODUCT

void Metachunk::mangle() {

  // Mangle the payload of the chunk and not the links that

  // maintain list of chunks.

  HeapWord* start = (HeapWord*)(bottom() + overhead());

  size_t word_size = capacity_word_size() - overhead();

  Copy::fill_to_words(start, word_size, metadata_chunk_initialize);

}

#endif // PRODUCT

void Metachunk::verify() {

#ifdef ASSERT

  // Cannot walk through the blocks unless the blocks have

  // headers with sizes.

  assert(_bottom <= _top &&

         _top <= _end,

         "Chunk has been smashed");

#endif

  return;

}