/*

 * Copyright (c) 2014, 2019, 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 "jfr/leakprofiler/chains/edgeStore.hpp"

#include "jfr/leakprofiler/chains/edgeUtils.hpp"

#include "oops/oop.inline.hpp"

StoredEdge::StoredEdge() : Edge() {}

StoredEdge::StoredEdge(const Edge* parent, const oop* reference) : Edge(parent, reference), _gc_root_id(0), _skip_length(0) {}

StoredEdge::StoredEdge(const Edge& edge) : Edge(edge), _gc_root_id(0), _skip_length(0) {}

StoredEdge::StoredEdge(const StoredEdge& edge) : Edge(edge), _gc_root_id(edge._gc_root_id), _skip_length(edge._skip_length) {}

void StoredEdge::operator=(const StoredEdge& edge) {

  Edge::operator=(edge);

  _gc_root_id = edge._gc_root_id;

  _skip_length = edge._skip_length;

}

traceid EdgeStore::_edge_id_counter = 0;

EdgeStore::EdgeStore() : _edges(NULL) {

  _edges = new EdgeHashTable(this);

}

EdgeStore::~EdgeStore() {

  assert(_edges != NULL, "invariant");

  delete _edges;

}

bool EdgeStore::is_empty() const {

  return !_edges->has_entries();

}

void EdgeStore::on_link(EdgeEntry* entry) {

  assert(entry != NULL, "invariant");

  assert(entry->id() == 0, "invariant");

  entry->set_id(++_edge_id_counter);

}

bool EdgeStore::on_equals(uintptr_t hash, const EdgeEntry* entry) {

  assert(entry != NULL, "invariant");

  assert(entry->hash() == hash, "invariant");

  return true;

}

void EdgeStore::on_unlink(EdgeEntry* entry) {

  assert(entry != NULL, "invariant");

  // nothing

}

#ifdef ASSERT

bool EdgeStore::contains(const oop* reference) const {

  return get(reference) != NULL;

}

#endif

StoredEdge* EdgeStore::get(const oop* reference) const {

  assert(reference != NULL, "invariant");

  EdgeEntry* const entry = _edges->lookup_only((uintptr_t)reference);

  return entry != NULL ? entry->literal_addr() : NULL;

}

StoredEdge* EdgeStore::put(const oop* reference) {

  assert(reference != NULL, "invariant");

  const StoredEdge e(NULL, reference);

  assert(NULL == _edges->lookup_only((uintptr_t)reference), "invariant");

  EdgeEntry& entry = _edges->put((uintptr_t)reference, e);

  return entry.literal_addr();

}

traceid EdgeStore::get_id(const Edge* edge) const {

  assert(edge != NULL, "invariant");

  EdgeEntry* const entry = _edges->lookup_only((uintptr_t)edge->reference());

  assert(entry != NULL, "invariant");

  return entry->id();

}

traceid EdgeStore::gc_root_id(const Edge* edge) const {

  assert(edge != NULL, "invariant");

  const traceid gc_root_id = static_cast<const StoredEdge*>(edge)->gc_root_id();

  if (gc_root_id != 0) {

    return gc_root_id;

  }

  // not cached

  assert(edge != NULL, "invariant");

  const Edge* const root = EdgeUtils::root(*edge);

  assert(root != NULL, "invariant");

  assert(root->parent() == NULL, "invariant");

  return get_id(root);

}

static const Edge* get_skip_ancestor(const Edge** current, size_t distance_to_root, size_t* skip_length) {

  assert(distance_to_root >= EdgeUtils::root_context, "invariant");

  assert(*skip_length == 0, "invariant");

  *skip_length = distance_to_root - (EdgeUtils::root_context - 1);

  const Edge* const target = EdgeUtils::ancestor(**current, *skip_length);

  assert(target != NULL, "invariant");

  assert(target->distance_to_root() + 1 == EdgeUtils::root_context, "invariant");

  return target;

}

bool EdgeStore::put_skip_edge(StoredEdge** previous, const Edge** current, size_t distance_to_root) {

  assert(*previous != NULL, "invariant");

  assert((*previous)->parent() == NULL, "invariant");

  assert(*current != NULL, "invariant");

  assert((*current)->distance_to_root() == distance_to_root, "invariant");

  if (distance_to_root < EdgeUtils::root_context) {

    // nothing to skip

    return false;

  }

  size_t skip_length = 0;

  const Edge* const skip_ancestor = get_skip_ancestor(current, distance_to_root, &skip_length);

  assert(skip_ancestor != NULL, "invariant");

  (*previous)->set_skip_length(skip_length);

  // lookup target

  StoredEdge* stored_target = get(skip_ancestor->reference());

  if (stored_target != NULL) {

    (*previous)->set_parent(stored_target);

    // linked to existing, complete

    return true;

  }

  assert(stored_target == NULL, "invariant");

  stored_target = put(skip_ancestor->reference());

  assert(stored_target != NULL, "invariant");

  (*previous)->set_parent(stored_target);

  *previous = stored_target;

  *current = skip_ancestor->parent();

  return false;

}

static void link_edge(const StoredEdge* current_stored, StoredEdge** previous) {

  assert(current_stored != NULL, "invariant");

  assert(*previous != NULL, "invariant");

  assert((*previous)->parent() == NULL, "invariant");

  (*previous)->set_parent(current_stored);

}

static const StoredEdge* find_closest_skip_edge(const StoredEdge* edge, size_t* distance) {

  assert(edge != NULL, "invariant");

  assert(distance != NULL, "invariant");

  const StoredEdge* current = edge;

  *distance = 1;

  while (current != NULL && !current->is_skip_edge()) {

    ++(*distance);

    current = current->parent();

  }

  return current;

}

void EdgeStore::link_with_existing_chain(const StoredEdge* current_stored, StoredEdge** previous, size_t previous_length) {

  assert(current_stored != NULL, "invariant");

  assert((*previous)->parent() == NULL, "invariant");

  size_t distance_to_skip_edge; // including the skip edge itself

  const StoredEdge* const closest_skip_edge = find_closest_skip_edge(current_stored, &distance_to_skip_edge);

  if (closest_skip_edge == NULL) {

    // no found skip edge implies root

    if (distance_to_skip_edge + previous_length <= EdgeUtils::max_ref_chain_depth) {

      link_edge(current_stored, previous);

      return;

    }

    assert(current_stored->distance_to_root() == distance_to_skip_edge - 2, "invariant");

    put_skip_edge(previous, reinterpret_cast<const Edge**>(&current_stored), distance_to_skip_edge - 2);

    return;

  }

  assert(closest_skip_edge->is_skip_edge(), "invariant");

  if (distance_to_skip_edge + previous_length <= EdgeUtils::leak_context) {

    link_edge(current_stored, previous);

    return;

  }

  // create a new skip edge with derived information from closest skip edge

  (*previous)->set_skip_length(distance_to_skip_edge + closest_skip_edge->skip_length());

  (*previous)->set_parent(closest_skip_edge->parent());

}

StoredEdge* EdgeStore::link_new_edge(StoredEdge** previous, const Edge** current) {

  assert(*previous != NULL, "invariant");

  assert((*previous)->parent() == NULL, "invariant");

  assert(*current != NULL, "invariant");

  assert(!contains((*current)->reference()), "invariant");

  StoredEdge* const stored_edge = put((*current)->reference());

  assert(stored_edge != NULL, "invariant");

  link_edge(stored_edge, previous);

  return stored_edge;

}

bool EdgeStore::put_edges(StoredEdge** previous, const Edge** current, size_t limit) {

  assert(*previous != NULL, "invariant");

  assert(*current != NULL, "invariant");

  size_t depth = 1;

  while (*current != NULL && depth < limit) {

    StoredEdge* stored_edge = get((*current)->reference());

    if (stored_edge != NULL) {

      link_with_existing_chain(stored_edge, previous, depth);

      return true;

    }

    stored_edge = link_new_edge(previous, current);

    assert((*previous)->parent() != NULL, "invariant");

    *previous = stored_edge;

    *current = (*current)->parent();

    ++depth;

  }

  return NULL == *current;

}

// Install the immediate edge into the mark word of the leak candidate object

StoredEdge* EdgeStore::associate_leak_context_with_candidate(const Edge* edge) {

  assert(edge != NULL, "invariant");

  assert(!contains(edge->reference()), "invariant");

  StoredEdge* const leak_context_edge = put(edge->reference());

  oop sample_object = edge->pointee();

  assert(sample_object != NULL, "invariant");

  assert(NULL == sample_object->mark().to_pointer(), "invariant");

  sample_object->set_mark(markWord::from_pointer(leak_context_edge));

  return leak_context_edge;

}

/*

 * The purpose of put_chain() is to reify the edge sequence

 * discovered during heap traversal with a normalized logical copy.

 * This copy consist of two sub-sequences and a connecting link (skip edge).

 *

 * "current" can be thought of as the cursor (search) edge, it is not in the edge store.

 * "previous" is always an edge in the edge store.

 * The leak context edge is the edge adjacent to the leak candidate object, always an edge in the edge store.

 */

void EdgeStore::put_chain(const Edge* chain, size_t length) {

  assert(chain != NULL, "invariant");

  assert(chain->distance_to_root() + 1 == length, "invariant");

  StoredEdge* const leak_context_edge = associate_leak_context_with_candidate(chain);

  assert(leak_context_edge != NULL, "invariant");

  assert(leak_context_edge->parent() == NULL, "invariant");

  if (1 == length) {

    return;

  }

  const Edge* current = chain->parent();

  assert(current != NULL, "invariant");

  StoredEdge* previous = leak_context_edge;

  // a leak context is the sequence of (limited) edges reachable from the leak candidate

  if (put_edges(&previous, &current, EdgeUtils::leak_context)) {

    // complete

    assert(previous != NULL, "invariant");

    put_chain_epilogue(leak_context_edge, EdgeUtils::root(*previous));

    return;

  }

  const size_t distance_to_root = length > EdgeUtils::leak_context ? length - 1 - EdgeUtils::leak_context : length - 1;

  assert(current->distance_to_root() == distance_to_root, "invariant");

  // a skip edge is the logical link

  // connecting the leak context sequence with the root context sequence

  if (put_skip_edge(&previous, &current, distance_to_root)) {

    // complete

    assert(previous != NULL, "invariant");

    assert(previous->is_skip_edge(), "invariant");

    assert(previous->parent() != NULL, "invariant");

    put_chain_epilogue(leak_context_edge, EdgeUtils::root(*previous->parent()));

    return;

  }

  assert(current->distance_to_root() < EdgeUtils::root_context, "invariant");

  // a root context is the sequence of (limited) edges reachable from the root

  put_edges(&previous, &current, EdgeUtils::root_context);

  assert(previous != NULL, "invariant");

  put_chain_epilogue(leak_context_edge, EdgeUtils::root(*previous));

}

void EdgeStore::put_chain_epilogue(StoredEdge* leak_context_edge, const Edge* root) const {

  assert(leak_context_edge != NULL, "invariant");

  assert(root != NULL, "invariant");

  store_gc_root_id_in_leak_context_edge(leak_context_edge, root);

  assert(leak_context_edge->distance_to_root() + 1 <= EdgeUtils::max_ref_chain_depth, "invariant");

}

// To avoid another traversal to resolve the root edge id later,

// cache it in the immediate leak context edge for fast retrieval.

void EdgeStore::store_gc_root_id_in_leak_context_edge(StoredEdge* leak_context_edge, const Edge* root) const {

  assert(leak_context_edge != NULL, "invariant");

  assert(leak_context_edge->gc_root_id() == 0, "invariant");

  assert(root != NULL, "invariant");

  assert(root->parent() == NULL, "invariant");

  assert(root->distance_to_root() == 0, "invariant");

  const StoredEdge* const stored_root = static_cast<const StoredEdge*>(root);

  traceid root_id = stored_root->gc_root_id();

  if (root_id == 0) {

    root_id = get_id(root);

    stored_root->set_gc_root_id(root_id);

  }

  assert(root_id != 0, "invariant");

  leak_context_edge->set_gc_root_id(root_id);

  assert(leak_context_edge->gc_root_id() == stored_root->gc_root_id(), "invariant");

}