/*
 * Copyright (c) 2017, Red Hat, Inc. and/or its affiliates.
 *
 * 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 "oops/oop.hpp"
#include "oops/oop.inline.hpp"
#include "utilities/copy.hpp"
#include "gc/shared/collectedHeap.hpp"
#include "epsilonCollectedHeap.hpp"
#include "epsilonBarrierSet.hpp"

jint EpsilonCollectedHeap::initialize() {
  CollectedHeap::pre_initialize();

  size_t max_byte_size = _policy->max_heap_byte_size();
  size_t align = _policy->heap_alignment();

  ReservedSpace heap_rs = Universe::reserve_heap(max_byte_size,  align);

  _start = (HeapWord *) heap_rs.base();
  _current = _start;
  _end = (HeapWord *) (heap_rs.base() + heap_rs.size());
  size_t size = pointer_delta(_end, _start);

  initialize_reserved_region(_start, _end);
  os::commit_memory((char*)_start, size*HeapWordSize, align, false);

  EpsilonBarrierSet* bs = new EpsilonBarrierSet();
  set_barrier_set(bs);

  log_info(gc)("Initialized with " SIZE_FORMAT "M non-resizable heap.", size*HeapWordSize / M);

  return JNI_OK;
}

HeapWord* EpsilonCollectedHeap::allocate_work(size_t size) {
  do {
    HeapWord* obj = (HeapWord *) _current;
    if (pointer_delta(_end, obj) >= size) {
      HeapWord* new_current = obj + size;
      HeapWord* result = (HeapWord*)Atomic::cmpxchg_ptr(new_current, &_current, obj);
      if (result != obj) {
        continue;
      }
      assert(is_object_aligned((intptr_t)obj), "object is aligned");
      assert(is_object_aligned((intptr_t)new_current), "current is aligned");
      return obj;
    } else {
      return NULL;
    }
  } while (true);
}

HeapWord* EpsilonCollectedHeap::allocate_new_tlab(size_t size) {
  return allocate_work(size);
}

HeapWord* EpsilonCollectedHeap::mem_allocate(size_t size, bool *gc_overhead_limit_was_exceeded) {
  *gc_overhead_limit_was_exceeded = false;
  return allocate_work(size);
}

void EpsilonCollectedHeap::collect(GCCause::Cause cause) {
  log_warning(gc)("GC was triggered with cause \"%s\". Ignoring.", GCCause::to_string(cause));
}

void EpsilonCollectedHeap::do_full_collection(bool clear_all_soft_refs) {
  log_warning(gc)("Full GC was triggered. Ignoring.");
}

void EpsilonCollectedHeap::safe_object_iterate(ObjectClosure *cl) {
  HeapWord* mark = _start;
  while (mark < _current) {
    oop obj = oop(mark);
    cl->do_object(obj);
    mark += obj->size();
  }
}