/*

 * Copyright (c) 2014, 2018, 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 "classfile/javaClasses.hpp"

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

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

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

#include "jfr/leakprofiler/utilities/unifiedOop.hpp"

#include "oops/fieldStreams.hpp"

#include "oops/instanceKlass.hpp"

#include "oops/objArrayOop.inline.hpp"

#include "oops/oopsHierarchy.hpp"

#include "runtime/handles.inline.hpp"

bool EdgeUtils::is_leak_edge(const Edge& edge) {

  return (const Edge*)edge.pointee()->mark() == &edge;

}

bool EdgeUtils::is_root(const Edge& edge) {

  return edge.is_root();

}

static int field_offset(const Edge& edge) {

  assert(!edge.is_root(), "invariant");

  const oop ref_owner = edge.reference_owner();

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

  const oop* reference = UnifiedOop::decode(edge.reference());

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

  assert(!UnifiedOop::is_narrow(reference), "invariant");

  assert(!ref_owner->is_array(), "invariant");

  assert(ref_owner->is_instance(), "invariant");

  const int offset = (int)pointer_delta(reference, ref_owner, sizeof(char));

  assert(offset < (ref_owner->size() * HeapWordSize), "invariant");

  return offset;

}

static const InstanceKlass* field_type(const Edge& edge) {

  assert(!edge.is_root() || !EdgeUtils::is_array_element(edge), "invariant");

  return (const InstanceKlass*)edge.reference_owner_klass();

}

const Symbol* EdgeUtils::field_name_symbol(const Edge& edge) {

  assert(!edge.is_root(), "invariant");

  assert(!is_array_element(edge), "invariant");

  const int offset = field_offset(edge);

  const InstanceKlass* ik = field_type(edge);

  while (ik != NULL) {

    JavaFieldStream jfs(ik);

    while (!jfs.done()) {

      if (offset == jfs.offset()) {

        return jfs.name();

      }

      jfs.next();

    }

    ik = (InstanceKlass*)ik->super();

  }

  return NULL;

}

jshort EdgeUtils::field_modifiers(const Edge& edge) {

  const int offset = field_offset(edge);

  const InstanceKlass* ik = field_type(edge);

  while (ik != NULL) {

    JavaFieldStream jfs(ik);

    while (!jfs.done()) {

      if (offset == jfs.offset()) {

        return jfs.access_flags().as_short();

      }

      jfs.next();

    }

    ik = (InstanceKlass*)ik->super();

  }

  return 0;

}

bool EdgeUtils::is_array_element(const Edge& edge) {

  assert(!edge.is_root(), "invariant");

  const oop ref_owner = edge.reference_owner();

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

  return ref_owner->is_objArray();

}

static int array_offset(const Edge& edge) {

  assert(!edge.is_root(), "invariant");

  const oop ref_owner = edge.reference_owner();

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

  const oop* reference = UnifiedOop::decode(edge.reference());

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

  assert(!UnifiedOop::is_narrow(reference), "invariant");

  assert(ref_owner->is_array(), "invariant");

  const objArrayOop ref_owner_array = static_cast<const objArrayOop>(ref_owner);

  const int offset = (int)pointer_delta(reference, ref_owner_array->base(), heapOopSize);

  assert(offset >= 0 && offset < ref_owner_array->length(), "invariant");

  return offset;

}

int EdgeUtils::array_index(const Edge& edge) {

  return is_array_element(edge) ? array_offset(edge) : 0;

}

int EdgeUtils::array_size(const Edge& edge) {

  if (is_array_element(edge)) {

    const oop ref_owner = edge.reference_owner();

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

    assert(ref_owner->is_objArray(), "invariant");

    return ((objArrayOop)(ref_owner))->length();

  }

  return 0;

}

const Edge* EdgeUtils::root(const Edge& edge) {

  const Edge* current = &edge;

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

  while (parent != NULL) {

    current = parent;

    parent = current->parent();

  }

  return current;

}

// The number of references associated with the leak node;

// can be viewed as the leak node "context".

// Used to provide leak context for a "capped/skipped" reference chain.

static const size_t leak_context = 100;

// The number of references associated with the root node;

// can be viewed as the root node "context".

// Used to provide root context for a "capped/skipped" reference chain.

static const size_t root_context = 100;

// A limit on the reference chain depth to be serialized,

static const size_t max_ref_chain_depth = leak_context + root_context;

const RoutableEdge* skip_to(const RoutableEdge& edge, size_t skip_length) {

  const RoutableEdge* current = &edge;

  const RoutableEdge* parent = current->physical_parent();

  size_t seek = 0;

  while (parent != NULL && seek != skip_length) {

    seek++;

    current = parent;

    parent = parent->physical_parent();

  }

  return current;

}

#ifdef ASSERT

static void validate_skip_target(const RoutableEdge* skip_target) {

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

  assert(skip_target->distance_to_root() + 1 == root_context, "invariant");

  assert(skip_target->is_sentinel(), "invariant");

}

static void validate_new_skip_edge(const RoutableEdge* new_skip_edge, const RoutableEdge* last_skip_edge, size_t adjustment) {

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

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

  if (last_skip_edge != NULL) {

    const RoutableEdge* const target = skip_to(*new_skip_edge->logical_parent(), adjustment);

    validate_skip_target(target->logical_parent());

    return;

  }

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

  // only one level of logical indirection

  validate_skip_target(new_skip_edge->logical_parent());

}

#endif // ASSERT

static void install_logical_route(const RoutableEdge* new_skip_edge, size_t skip_target_distance) {

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

  assert(!new_skip_edge->is_skip_edge(), "invariant");

  assert(!new_skip_edge->processed(), "invariant");

  const RoutableEdge* const skip_target = skip_to(*new_skip_edge, skip_target_distance);

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

  new_skip_edge->set_skip_edge(skip_target);

  new_skip_edge->set_skip_length(skip_target_distance);

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

  assert(new_skip_edge->logical_parent() == skip_target, "invariant");

}

static const RoutableEdge* find_last_skip_edge(const RoutableEdge& edge, size_t& distance) {

  assert(distance == 0, "invariant");

  const RoutableEdge* current = &edge;

  while (current != NULL) {

    if (current->is_skip_edge() && current->skip_edge()->is_sentinel()) {

      return current;

    }

    current = current->physical_parent();

    ++distance;

  }

  return current;

}

static void collapse_overlapping_chain(const RoutableEdge& edge,

                                       const RoutableEdge* first_processed_edge,

                                       size_t first_processed_distance) {

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

  // first_processed_edge is already processed / written

  assert(first_processed_edge->processed(), "invariant");

  assert(first_processed_distance + 1 <= leak_context, "invariant");

  // from this first processed edge, attempt to fetch the last skip edge

  size_t last_skip_edge_distance = 0;

  const RoutableEdge* const last_skip_edge = find_last_skip_edge(*first_processed_edge, last_skip_edge_distance);

  const size_t distance_discovered = first_processed_distance + last_skip_edge_distance + 1;

  if (distance_discovered <= leak_context || (last_skip_edge == NULL && distance_discovered <= max_ref_chain_depth)) {

    // complete chain can be accommodated without modification

    return;

  }

  // backtrack one edge from existing processed edge

  const RoutableEdge* const new_skip_edge = skip_to(edge, first_processed_distance - 1);

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

  assert(!new_skip_edge->processed(), "invariant");

  assert(new_skip_edge->parent() == first_processed_edge, "invariant");

  size_t adjustment = 0;

  if (last_skip_edge != NULL) {

    assert(leak_context - 1 > first_processed_distance - 1, "invariant");

    adjustment = leak_context - first_processed_distance - 1;

    assert(last_skip_edge_distance + 1 > adjustment, "invariant");

    install_logical_route(new_skip_edge, last_skip_edge_distance + 1 - adjustment);

  } else {

    install_logical_route(new_skip_edge, last_skip_edge_distance + 1 - root_context);

    new_skip_edge->logical_parent()->set_skip_length(1); // sentinel

  }

  DEBUG_ONLY(validate_new_skip_edge(new_skip_edge, last_skip_edge, adjustment);)

}

static void collapse_non_overlapping_chain(const RoutableEdge& edge,

                                           const RoutableEdge* first_processed_edge,

                                           size_t first_processed_distance) {

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

  assert(!first_processed_edge->processed(), "invariant");

  // this implies that the first "processed" edge is the leak context relative "leaf"

  assert(first_processed_distance + 1 == leak_context, "invariant");

  const size_t distance_to_root = edge.distance_to_root();

  if (distance_to_root + 1 <= max_ref_chain_depth) {

    // complete chain can be accommodated without constructing a skip edge

    return;

  }

  install_logical_route(first_processed_edge, distance_to_root + 1 - first_processed_distance - root_context);

  first_processed_edge->logical_parent()->set_skip_length(1); // sentinel

  DEBUG_ONLY(validate_new_skip_edge(first_processed_edge, NULL, 0);)

}

static const RoutableEdge* processed_edge(const RoutableEdge& edge, size_t& distance) {

  assert(distance == 0, "invariant");

  const RoutableEdge* current = &edge;

  while (current != NULL && distance < leak_context - 1) {

    if (current->processed()) {

      return current;

    }

    current = current->physical_parent();

    ++distance;

  }

  assert(distance <= leak_context - 1, "invariant");

  return current;

}

/*

 * Some vocabulary:

 * -----------

 * "Context" is an interval in the chain, it is associcated with an edge and it signifies a number of connected edges.

 * "Processed / written" means an edge that has already been serialized.

 * "Skip edge" is an edge that contains additional information for logical routing purposes.

 * "Skip target" is an edge used as a destination for a skip edge

 */

void EdgeUtils::collapse_chain(const RoutableEdge& edge) {

  assert(is_leak_edge(edge), "invariant");

  // attempt to locate an already processed edge inside current leak context (if any)

  size_t first_processed_distance = 0;

  const RoutableEdge* const first_processed_edge = processed_edge(edge, first_processed_distance);

  if (first_processed_edge == NULL) {

    return;

  }

  if (first_processed_edge->processed()) {

    collapse_overlapping_chain(edge, first_processed_edge, first_processed_distance);

  } else {

    collapse_non_overlapping_chain(edge, first_processed_edge, first_processed_distance);

  }

  assert(edge.logical_distance_to_root() + 1 <= max_ref_chain_depth, "invariant");

}