/*

 * Copyright (c) 2003, 2011, 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/loaderConstraints.hpp"

#include "memory/resourceArea.hpp"

#include "oops/oop.inline.hpp"

#include "runtime/handles.inline.hpp"

#include "runtime/safepoint.hpp"

#include "utilities/hashtable.inline.hpp"

LoaderConstraintTable::LoaderConstraintTable(int nof_buckets)

  : Hashtable<klassOop>(nof_buckets, sizeof(LoaderConstraintEntry)) {};

LoaderConstraintEntry* LoaderConstraintTable::new_entry(

                                 unsigned int hash, Symbol* name,

                                 klassOop klass, int num_loaders,

                                 int max_loaders) {

  LoaderConstraintEntry* entry;

  entry = (LoaderConstraintEntry*)Hashtable<klassOop>::new_entry(hash, klass);

  entry->set_name(name);

  entry->set_num_loaders(num_loaders);

  entry->set_max_loaders(max_loaders);

  return entry;

}

void LoaderConstraintTable::free_entry(LoaderConstraintEntry *entry) {

  // decrement name refcount before freeing

  entry->name()->decrement_refcount();

  Hashtable<klassOop>::free_entry(entry);

}

void LoaderConstraintTable::oops_do(OopClosure* f) {

  for (int index = 0; index < table_size(); index++) {

    for (LoaderConstraintEntry* probe = bucket(index);

                                probe != NULL;

                                probe = probe->next()) {

      if (probe->klass() != NULL) {

        f->do_oop((oop*)probe->klass_addr());

      }

      for (int n = 0; n < probe->num_loaders(); n++) {

        if (probe->loader(n) != NULL) {

          f->do_oop(probe->loader_addr(n));

        }

      }

    }

  }

}

// The loaderConstraintTable must always be accessed with the

// SystemDictionary lock held. This is true even for readers as

// entries in the table could be being dynamically resized.

LoaderConstraintEntry** LoaderConstraintTable::find_loader_constraint(

                                    Symbol* name, Handle loader) {

  unsigned int hash = compute_hash(name);

  int index = hash_to_index(hash);

  LoaderConstraintEntry** pp = bucket_addr(index);

  while (*pp) {

    LoaderConstraintEntry* p = *pp;

    if (p->hash() == hash) {

      if (p->name() == name) {

        for (int i = p->num_loaders() - 1; i >= 0; i--) {

          if (p->loader(i) == loader()) {

            return pp;

          }

        }

      }

    }

    pp = p->next_addr();

  }

  return pp;

}

void LoaderConstraintTable::purge_loader_constraints(BoolObjectClosure* is_alive) {

  assert(SafepointSynchronize::is_at_safepoint(), "must be at safepoint");

  // Remove unloaded entries from constraint table

  for (int index = 0; index < table_size(); index++) {

    LoaderConstraintEntry** p = bucket_addr(index);

    while(*p) {

      LoaderConstraintEntry* probe = *p;

      klassOop klass = probe->klass();

      // Remove klass that is no longer alive

      if (klass != NULL && !is_alive->do_object_b(klass)) {

        probe->set_klass(NULL);

        if (TraceLoaderConstraints) {

          ResourceMark rm;

          tty->print_cr("[Purging class object from constraint for name %s,"

                     " loader list:",

                     probe->name()->as_C_string());

          for (int i = 0; i < probe->num_loaders(); i++) {

            tty->print_cr("[   [%d]: %s", i,

                          SystemDictionary::loader_name(probe->loader(i)));

          }

        }

      }

      // Remove entries no longer alive from loader array

      int n = 0;

      while (n < probe->num_loaders()) {

        if (probe->loader(n) != NULL) {

          if (!is_alive->do_object_b(probe->loader(n))) {

            if (TraceLoaderConstraints) {

              ResourceMark rm;

              tty->print_cr("[Purging loader %s from constraint for name %s",

                            SystemDictionary::loader_name(probe->loader(n)),

                            probe->name()->as_C_string()

                            );

            }

            // Compact array

            int num = probe->num_loaders() - 1;

            probe->set_num_loaders(num);

            probe->set_loader(n, probe->loader(num));

            probe->set_loader(num, NULL);

            if (TraceLoaderConstraints) {

              ResourceMark rm;

              tty->print_cr("[New loader list:");

              for (int i = 0; i < probe->num_loaders(); i++) {

                tty->print_cr("[   [%d]: %s", i,

                              SystemDictionary::loader_name(probe->loader(i)));

              }

            }

            continue;  // current element replaced, so restart without

                       // incrementing n

          }

        }

        n++;

      }

      // Check whether entry should be purged

      if (probe->num_loaders() < 2) {

            if (TraceLoaderConstraints) {

              ResourceMark rm;

              tty->print("[Purging complete constraint for name %s\n",

                         probe->name()->as_C_string());

            }

        // Purge entry

        *p = probe->next();

        FREE_C_HEAP_ARRAY(oop, probe->loaders());

        free_entry(probe);

      } else {

#ifdef ASSERT

        if (probe->klass() != NULL) {

          assert(is_alive->do_object_b(probe->klass()), "klass should be live");

        }

        for (n = 0; n < probe->num_loaders(); n++) {

          if (probe->loader(n) != NULL) {

            assert(is_alive->do_object_b(probe->loader(n)), "loader should be live");

          }

        }

#endif

        // Go to next entry

        p = probe->next_addr();

      }

    }

  }

}

bool LoaderConstraintTable::add_entry(Symbol* class_name,

                                      klassOop klass1, Handle class_loader1,

                                      klassOop klass2, Handle class_loader2) {

  int failure_code = 0; // encode different reasons for failing

  if (klass1 != NULL && klass2 != NULL && klass1 != klass2) {

    failure_code = 1;

  } else {

    klassOop klass = klass1 != NULL ? klass1 : klass2;

    LoaderConstraintEntry** pp1 = find_loader_constraint(class_name,

                                                         class_loader1);

    if (*pp1 != NULL && (*pp1)->klass() != NULL) {

      if (klass != NULL) {

        if (klass != (*pp1)->klass()) {

          failure_code = 2;

        }

      } else {

        klass = (*pp1)->klass();

      }

    }

    LoaderConstraintEntry** pp2 = find_loader_constraint(class_name,

                                                         class_loader2);

    if (*pp2 != NULL && (*pp2)->klass() != NULL) {

      if (klass != NULL) {

        if (klass != (*pp2)->klass()) {

          failure_code = 3;

        }

      } else {

        klass = (*pp2)->klass();

      }

    }

    if (failure_code == 0) {

      if (*pp1 == NULL && *pp2 == NULL) {

        unsigned int hash = compute_hash(class_name);

        int index = hash_to_index(hash);

        LoaderConstraintEntry* p;

        p = new_entry(hash, class_name, klass, 2, 2);

        p->set_loaders(NEW_C_HEAP_ARRAY(oop, 2));

        p->set_loader(0, class_loader1());

        p->set_loader(1, class_loader2());

        p->set_klass(klass);

        p->set_next(bucket(index));

        set_entry(index, p);

        if (TraceLoaderConstraints) {

          ResourceMark rm;

          tty->print("[Adding new constraint for name: %s, loader[0]: %s,"

                     " loader[1]: %s ]\n",

                     class_name->as_C_string(),

                     SystemDictionary::loader_name(class_loader1()),

                     SystemDictionary::loader_name(class_loader2())

                     );

        }

      } else if (*pp1 == *pp2) {

        /* constraint already imposed */

        if ((*pp1)->klass() == NULL) {

          (*pp1)->set_klass(klass);

          if (TraceLoaderConstraints) {

            ResourceMark rm;

            tty->print("[Setting class object in existing constraint for"

                       " name: %s and loader %s ]\n",

                       class_name->as_C_string(),

                       SystemDictionary::loader_name(class_loader1())

                       );

          }

        } else {

          assert((*pp1)->klass() == klass, "loader constraints corrupted");

        }

      } else if (*pp1 == NULL) {

        extend_loader_constraint(*pp2, class_loader1, klass);

      } else if (*pp2 == NULL) {

        extend_loader_constraint(*pp1, class_loader2, klass);

      } else {

        merge_loader_constraints(pp1, pp2, klass);

      }

    }

  }

  if (failure_code != 0 && TraceLoaderConstraints) {

    ResourceMark rm;

    const char* reason = "";

    switch(failure_code) {

    case 1: reason = "the class objects presented by loader[0] and loader[1]"

              " are different"; break;

    case 2: reason = "the class object presented by loader[0] does not match"

              " the stored class object in the constraint"; break;

    case 3: reason = "the class object presented by loader[1] does not match"

              " the stored class object in the constraint"; break;

    default: reason = "unknown reason code";

    }

    tty->print("[Failed to add constraint for name: %s, loader[0]: %s,"

               " loader[1]: %s, Reason: %s ]\n",

               class_name->as_C_string(),

               SystemDictionary::loader_name(class_loader1()),

               SystemDictionary::loader_name(class_loader2()),

               reason

               );

  }

  return failure_code == 0;

}

// return true if the constraint was updated, false if the constraint is

// violated

bool LoaderConstraintTable::check_or_update(instanceKlassHandle k,

                                                   Handle loader,

                                                   Symbol* name) {

  LoaderConstraintEntry* p = *(find_loader_constraint(name, loader));

  if (p && p->klass() != NULL && p->klass() != k()) {

    if (TraceLoaderConstraints) {

      ResourceMark rm;

      tty->print("[Constraint check failed for name %s, loader %s: "

                 "the presented class object differs from that stored ]\n",

                 name->as_C_string(),

                 SystemDictionary::loader_name(loader()));

    }

    return false;

  } else {

    if (p && p->klass() == NULL) {

      p->set_klass(k());

      if (TraceLoaderConstraints) {

        ResourceMark rm;

        tty->print("[Updating constraint for name %s, loader %s, "

                   "by setting class object ]\n",

                   name->as_C_string(),

                   SystemDictionary::loader_name(loader()));

      }

    }

    return true;

  }

}

klassOop LoaderConstraintTable::find_constrained_klass(Symbol* name,

                                                       Handle loader) {

  LoaderConstraintEntry *p = *(find_loader_constraint(name, loader));

  if (p != NULL && p->klass() != NULL) {

    if (Klass::cast(p->klass())->oop_is_instance() && !instanceKlass::cast(p->klass())->is_loaded()) {

      // Only return fully loaded classes.  Classes found through the

      // constraints might still be in the process of loading.

      return NULL;

    }

    return p->klass();

  }

  // No constraints, or else no klass loaded yet.

  return NULL;

}

void LoaderConstraintTable::ensure_loader_constraint_capacity(

                                                     LoaderConstraintEntry *p,

                                                    int nfree) {

    if (p->max_loaders() - p->num_loaders() < nfree) {

        int n = nfree + p->num_loaders();

        oop* new_loaders = NEW_C_HEAP_ARRAY(oop, n);

        memcpy(new_loaders, p->loaders(), sizeof(oop) * p->num_loaders());

        p->set_max_loaders(n);

        FREE_C_HEAP_ARRAY(oop, p->loaders());

        p->set_loaders(new_loaders);

    }

}

void LoaderConstraintTable::extend_loader_constraint(LoaderConstraintEntry* p,

                                                     Handle loader,

                                                     klassOop klass) {

  ensure_loader_constraint_capacity(p, 1);

  int num = p->num_loaders();

  p->set_loader(num, loader());

  p->set_num_loaders(num + 1);

  if (TraceLoaderConstraints) {

    ResourceMark rm;

    tty->print("[Extending constraint for name %s by adding loader[%d]: %s %s",

               p->name()->as_C_string(),

               num,

               SystemDictionary::loader_name(loader()),

               (p->klass() == NULL ? " and setting class object ]\n" : " ]\n")

               );

  }

  if (p->klass() == NULL) {

    p->set_klass(klass);

  } else {

    assert(klass == NULL || p->klass() == klass, "constraints corrupted");

  }

}

void LoaderConstraintTable::merge_loader_constraints(

                                                   LoaderConstraintEntry** pp1,

                                                   LoaderConstraintEntry** pp2,

                                                   klassOop klass) {

  // make sure *pp1 has higher capacity

  if ((*pp1)->max_loaders() < (*pp2)->max_loaders()) {

    LoaderConstraintEntry** tmp = pp2;

    pp2 = pp1;

    pp1 = tmp;

  }

  LoaderConstraintEntry* p1 = *pp1;

  LoaderConstraintEntry* p2 = *pp2;

  ensure_loader_constraint_capacity(p1, p2->num_loaders());

  for (int i = 0; i < p2->num_loaders(); i++) {

    int num = p1->num_loaders();

    p1->set_loader(num, p2->loader(i));

    p1->set_num_loaders(num + 1);

  }

  if (TraceLoaderConstraints) {

    ResourceMark rm;

    tty->print_cr("[Merged constraints for name %s, new loader list:",

                  p1->name()->as_C_string()

                  );

    for (int i = 0; i < p1->num_loaders(); i++) {

      tty->print_cr("[   [%d]: %s", i,

                    SystemDictionary::loader_name(p1->loader(i)));

    }

    if (p1->klass() == NULL) {

      tty->print_cr("[... and setting class object]");

    }

  }

  // p1->klass() will hold NULL if klass, p2->klass(), and old

  // p1->klass() are all NULL.  In addition, all three must have

  // matching non-NULL values, otherwise either the constraints would

  // have been violated, or the constraints had been corrupted (and an

  // assertion would fail).

  if (p2->klass() != NULL) {

    assert(p2->klass() == klass, "constraints corrupted");

  }

  if (p1->klass() == NULL) {

    p1->set_klass(klass);

  } else {

    assert(p1->klass() == klass, "constraints corrupted");

  }

  *pp2 = p2->next();

  FREE_C_HEAP_ARRAY(oop, p2->loaders());

  free_entry(p2);

  return;

}

void LoaderConstraintTable::verify(Dictionary* dictionary,

                                   PlaceholderTable* placeholders) {

  Thread *thread = Thread::current();

  for (int cindex = 0; cindex < _loader_constraint_size; cindex++) {

    for (LoaderConstraintEntry* probe = bucket(cindex);

                                probe != NULL;

                                probe = probe->next()) {

      if (probe->klass() != NULL) {

        instanceKlass* ik = instanceKlass::cast(probe->klass());

        guarantee(ik->name() == probe->name(), "name should match");

        Symbol* name = ik->name();

        Handle loader(thread, ik->class_loader());

        unsigned int d_hash = dictionary->compute_hash(name, loader);

        int d_index = dictionary->hash_to_index(d_hash);

        klassOop k = dictionary->find_class(d_index, d_hash, name, loader);

        if (k != NULL) {

          // We found the class in the system dictionary, so we should

          // make sure that the klassOop matches what we already have.

          guarantee(k == probe->klass(), "klass should be in dictionary");

        } else {

          // If we don't find the class in the system dictionary, it

          // has to be in the placeholders table.

          unsigned int p_hash = placeholders->compute_hash(name, loader);

          int p_index = placeholders->hash_to_index(p_hash);

          PlaceholderEntry* entry = placeholders->get_entry(p_index, p_hash,

                                                            name, loader);

          // The instanceKlass might not be on the entry, so the only

          // thing we can check here is whether we were successful in

          // finding the class in the placeholders table.

          guarantee(entry != NULL, "klass should be in the placeholders");

        }

      }

      for (int n = 0; n< probe->num_loaders(); n++) {

        guarantee(probe->loader(n)->is_oop_or_null(), "should be oop");

      }

    }

  }

}

#ifndef PRODUCT

// Called with the system dictionary lock held

void LoaderConstraintTable::print() {

  ResourceMark rm;

  assert_locked_or_safepoint(SystemDictionary_lock);

  tty->print_cr("Java loader constraints (entries=%d)", _loader_constraint_size);

  for (int cindex = 0; cindex < _loader_constraint_size; cindex++) {

    for (LoaderConstraintEntry* probe = bucket(cindex);

                                probe != NULL;

                                probe = probe->next()) {

      tty->print("%4d: ", cindex);

      probe->name()->print();

      tty->print(" , loaders:");

      for (int n = 0; n < probe->num_loaders(); n++) {

        probe->loader(n)->print_value();

        tty->print(", ");

      }

      tty->cr();

    }

  }

}

#endif