/*

 * Copyright (c) 2003, 2017, 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/altHashing.hpp"

#include "classfile/dictionary.hpp"

#include "classfile/javaClasses.inline.hpp"

#include "classfile/moduleEntry.hpp"

#include "classfile/packageEntry.hpp"

#include "classfile/placeholders.hpp"

#include "classfile/protectionDomainCache.hpp"

#include "classfile/stringTable.hpp"

#include "memory/allocation.inline.hpp"

#include "memory/filemap.hpp"

#include "memory/resourceArea.hpp"

#include "oops/oop.inline.hpp"

#include "runtime/safepoint.hpp"

#include "utilities/dtrace.hpp"

#include "utilities/hashtable.hpp"

#include "utilities/hashtable.inline.hpp"

#include "utilities/numberSeq.hpp"

// This hashtable is implemented as an open hash table with a fixed number of buckets.

template <MEMFLAGS F> BasicHashtableEntry<F>* BasicHashtable<F>::new_entry_free_list() {

  BasicHashtableEntry<F>* entry = NULL;

  if (_free_list != NULL) {

    entry = _free_list;

    _free_list = _free_list->next();

  }

  return entry;

}

// HashtableEntrys are allocated in blocks to reduce the space overhead.

template <MEMFLAGS F> BasicHashtableEntry<F>* BasicHashtable<F>::new_entry(unsigned int hashValue) {

  BasicHashtableEntry<F>* entry = new_entry_free_list();

  if (entry == NULL) {

    if (_first_free_entry + _entry_size >= _end_block) {

      int block_size = MIN2(512, MAX2((int)_table_size / 2, (int)_number_of_entries));

      int len = _entry_size * block_size;

      len = 1 << log2_intptr(len); // round down to power of 2

      assert(len >= _entry_size, "");

      _first_free_entry = NEW_C_HEAP_ARRAY2(char, len, F, CURRENT_PC);

      _end_block = _first_free_entry + len;

    }

    entry = (BasicHashtableEntry<F>*)_first_free_entry;

    _first_free_entry += _entry_size;

  }

  assert(_entry_size % HeapWordSize == 0, "");

  entry->set_hash(hashValue);

  return entry;

}

template <class T, MEMFLAGS F> HashtableEntry<T, F>* Hashtable<T, F>::new_entry(unsigned int hashValue, T obj) {

  HashtableEntry<T, F>* entry;

  entry = (HashtableEntry<T, F>*)BasicHashtable<F>::new_entry(hashValue);

  entry->set_literal(obj);

  return entry;

}

// Version of hashtable entry allocation that allocates in the C heap directly.

// The allocator in blocks is preferable but doesn't have free semantics.

template <class T, MEMFLAGS F> HashtableEntry<T, F>* Hashtable<T, F>::allocate_new_entry(unsigned int hashValue, T obj) {

  HashtableEntry<T, F>* entry = (HashtableEntry<T, F>*) NEW_C_HEAP_ARRAY(char, this->entry_size(), F);

  entry->set_hash(hashValue);

  entry->set_literal(obj);

  entry->set_next(NULL);

  return entry;

}

// Check to see if the hashtable is unbalanced.  The caller set a flag to

// rehash at the next safepoint.  If this bucket is 60 times greater than the

// expected average bucket length, it's an unbalanced hashtable.

// This is somewhat an arbitrary heuristic but if one bucket gets to

// rehash_count which is currently 100, there's probably something wrong.

template <class T, MEMFLAGS F> bool RehashableHashtable<T, F>::check_rehash_table(int count) {

  assert(this->table_size() != 0, "underflow");

  if (count > (((double)this->number_of_entries()/(double)this->table_size())*rehash_multiple)) {

    // Set a flag for the next safepoint, which should be at some guaranteed

    // safepoint interval.

    return true;

  }

  return false;

}

// Create a new table and using alternate hash code, populate the new table

// with the existing elements.   This can be used to change the hash code

// and could in the future change the size of the table.

template <class T, MEMFLAGS F> void RehashableHashtable<T, F>::move_to(RehashableHashtable<T, F>* new_table) {

  // Initialize the global seed for hashing.

  _seed = AltHashing::compute_seed();

  assert(seed() != 0, "shouldn't be zero");

  int saved_entry_count = this->number_of_entries();

  // Iterate through the table and create a new entry for the new table

  for (int i = 0; i < new_table->table_size(); ++i) {

    for (HashtableEntry<T, F>* p = this->bucket(i); p != NULL; ) {

      HashtableEntry<T, F>* next = p->next();

      T string = p->literal();

      // Use alternate hashing algorithm on the symbol in the first table

      unsigned int hashValue = string->new_hash(seed());

      // Get a new index relative to the new table (can also change size)

      int index = new_table->hash_to_index(hashValue);

      p->set_hash(hashValue);

      // Keep the shared bit in the Hashtable entry to indicate that this entry

      // can't be deleted.   The shared bit is the LSB in the _next field so

      // walking the hashtable past these entries requires

      // BasicHashtableEntry::make_ptr() call.

      bool keep_shared = p->is_shared();

      this->unlink_entry(p);

      new_table->add_entry(index, p);

      if (keep_shared) {

        p->set_shared();

      }

      p = next;

    }

  }

  // give the new table the free list as well

  new_table->copy_freelist(this);

  assert(new_table->number_of_entries() == saved_entry_count, "lost entry on dictionary copy?");

  // Destroy memory used by the buckets in the hashtable.  The memory

  // for the elements has been used in a new table and is not

  // destroyed.  The memory reuse will benefit resizing the SystemDictionary

  // to avoid a memory allocation spike at safepoint.

  BasicHashtable<F>::free_buckets();

}

template <MEMFLAGS F> void BasicHashtable<F>::free_buckets() {

  if (NULL != _buckets) {

    // Don't delete the buckets in the shared space.  They aren't

    // allocated by os::malloc

    if (!UseSharedSpaces ||

        !FileMapInfo::current_info()->is_in_shared_space(_buckets)) {

       FREE_C_HEAP_ARRAY(HashtableBucket, _buckets);

    }

    _buckets = NULL;

  }

}

template <MEMFLAGS F> void BasicHashtable<F>::BucketUnlinkContext::free_entry(BasicHashtableEntry<F>* entry) {

  entry->set_next(_removed_head);

  _removed_head = entry;

  if (_removed_tail == NULL) {

    _removed_tail = entry;

  }

  _num_removed++;

}

template <MEMFLAGS F> void BasicHashtable<F>::bulk_free_entries(BucketUnlinkContext* context) {

  if (context->_num_removed == 0) {

    assert(context->_removed_head == NULL && context->_removed_tail == NULL,

           "Zero entries in the unlink context, but elements linked from " PTR_FORMAT " to " PTR_FORMAT,

           p2i(context->_removed_head), p2i(context->_removed_tail));

    return;

  }

  // MT-safe add of the list of BasicHashTableEntrys from the context to the free list.

  BasicHashtableEntry<F>* current = _free_list;

  while (true) {

    context->_removed_tail->set_next(current);

    BasicHashtableEntry<F>* old = (BasicHashtableEntry<F>*)Atomic::cmpxchg_ptr(context->_removed_head, &_free_list, current);

    if (old == current) {

      break;

    }

    current = old;

  }

  Atomic::add(-context->_num_removed, &_number_of_entries);

}

// Copy the table to the shared space.

  int i;

  for (i = 0; i < _table_size; ++i) {

    for (BasicHashtableEntry<F>** p = _buckets[i].entry_addr();

    }

  }

  // Set the shared bit.

  for (i = 0; i < _table_size; ++i) {

    for (BasicHashtableEntry<F>* p = bucket(i); p != NULL; p = p->next()) {

      p->set_shared();

    }

  }

}

// For oops and Strings the size of the literal is interesting. For other types, nobody cares.

static int literal_size(ConstantPool*) { return 0; }

static int literal_size(Klass*)        { return 0; }

#if INCLUDE_ALL_GCS

static int literal_size(nmethod*)      { return 0; }

#endif

static int literal_size(Symbol *symbol) {

  return symbol->size() * HeapWordSize;

}

static int literal_size(oop obj) {

  // NOTE: this would over-count if (pre-JDK8) java_lang_Class::has_offset_field() is true,

  // and the String.value array is shared by several Strings. However, starting from JDK8,

  // the String.value array is not shared anymore.

  if (obj == NULL) {

    return 0;

  } else if (obj->klass() == SystemDictionary::String_klass()) {

    return (obj->size() + java_lang_String::value(obj)->size()) * HeapWordSize;

  } else {

    return obj->size();

  }

}

// Dump footprint and bucket length statistics

//

// Note: if you create a new subclass of Hashtable<MyNewType, F>, you will need to

// add a new function static int literal_size(MyNewType lit)

// because I can't get template <class T> int literal_size(T) to pick the specializations for Symbol and oop.

//

// The StringTable and SymbolTable dumping print how much footprint is used by the String and Symbol

// literals.

template <class T, MEMFLAGS F> void Hashtable<T, F>::print_table_statistics(outputStream* st,

                                                                            const char *table_name) {

  NumberSeq summary;

  int literal_bytes = 0;

  for (int i = 0; i < this->table_size(); ++i) {

    int count = 0;

    for (HashtableEntry<T, F>* e = this->bucket(i);

      count++;

      literal_bytes += literal_size(e->literal());

    }

    summary.add((double)count);

  }

  double num_buckets = summary.num();

  double num_entries = summary.sum();

  int bucket_bytes = (int)num_buckets * sizeof(HashtableBucket<F>);

  int entry_bytes  = (int)num_entries * sizeof(HashtableEntry<T, F>);

  int total_bytes = literal_bytes +  bucket_bytes + entry_bytes;

  int bucket_size  = (num_buckets <= 0) ? 0 : (bucket_bytes  / num_buckets);

  int entry_size   = (num_entries <= 0) ? 0 : (entry_bytes   / num_entries);

  st->print_cr("%s statistics:", table_name);

  st->print_cr("Number of buckets       : %9d = %9d bytes, each %d", (int)num_buckets, bucket_bytes,  bucket_size);

  st->print_cr("Number of entries       : %9d = %9d bytes, each %d", (int)num_entries, entry_bytes,   entry_size);

  if (literal_bytes != 0) {

    double literal_avg = (num_entries <= 0) ? 0 : (literal_bytes / num_entries);

    st->print_cr("Number of literals      : %9d = %9d bytes, avg %7.3f", (int)num_entries, literal_bytes, literal_avg);

  }

  st->print_cr("Total footprint         : %9s = %9d bytes", "", total_bytes);

  st->print_cr("Average bucket size     : %9.3f", summary.avg());

  st->print_cr("Variance of bucket size : %9.3f", summary.variance());

  st->print_cr("Std. dev. of bucket size: %9.3f", summary.sd());

  st->print_cr("Maximum bucket size     : %9d", (int)summary.maximum());

}

// Dump the hash table buckets.

}

#ifndef PRODUCT

template <class T, MEMFLAGS F> void Hashtable<T, F>::print() {

  ResourceMark rm;

  for (int i = 0; i < BasicHashtable<F>::table_size(); i++) {

    HashtableEntry<T, F>* entry = bucket(i);

    while(entry != NULL) {

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

      entry->literal()->print();

      tty->cr();

      entry = entry->next();

    }

  }

}

template <MEMFLAGS F>

template <class T> void BasicHashtable<F>::verify_table(const char* table_name) {

  int element_count = 0;

  int max_bucket_count = 0;

  int max_bucket_number = 0;

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

    int bucket_count = 0;

    for (T* probe = (T*)bucket(index); probe != NULL; probe = probe->next()) {

      probe->verify();

      bucket_count++;

    }

    element_count += bucket_count;

    if (bucket_count > max_bucket_count) {

      max_bucket_count = bucket_count;

      max_bucket_number = index;

    }

  }

  guarantee(number_of_entries() == element_count,

            "Verify of %s failed", table_name);

  // Log some statistics about the hashtable

  log_info(hashtables)("%s max bucket size %d bucket %d element count %d table size %d", table_name,

                       max_bucket_count, max_bucket_number, _number_of_entries, _table_size);

  if (_number_of_entries > 0 && log_is_enabled(Debug, hashtables)) {

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

      int bucket_count = 0;

      for (T* probe = (T*)bucket(index); probe != NULL; probe = probe->next()) {

        log_debug(hashtables)("bucket %d hash " INTPTR_FORMAT, index, (intptr_t)probe->hash());

        bucket_count++;

      }

      if (bucket_count > 0) {

        log_debug(hashtables)("bucket %d count %d", index, bucket_count);

      }

    }

  }

}

#endif // PRODUCT

// Explicitly instantiate these types

#if INCLUDE_ALL_GCS

template class Hashtable<nmethod*, mtGC>;

template class HashtableEntry<nmethod*, mtGC>;

template class BasicHashtable<mtGC>;

#endif

template class Hashtable<ConstantPool*, mtClass>;

template class RehashableHashtable<Symbol*, mtSymbol>;

template class RehashableHashtable<oopDesc*, mtSymbol>;

template class Hashtable<Symbol*, mtSymbol>;

template class Hashtable<Klass*, mtClass>;

template class Hashtable<InstanceKlass*, mtClass>;

template class Hashtable<oop, mtClass>;

template class Hashtable<Symbol*, mtModule>;

#if defined(SOLARIS) || defined(CHECK_UNHANDLED_OOPS)

template class Hashtable<oop, mtSymbol>;

template class RehashableHashtable<oop, mtSymbol>;

#endif // SOLARIS || CHECK_UNHANDLED_OOPS

template class Hashtable<oopDesc*, mtSymbol>;

template class Hashtable<Symbol*, mtClass>;

template class HashtableEntry<Symbol*, mtSymbol>;

template class HashtableEntry<Symbol*, mtClass>;

template class HashtableEntry<oop, mtSymbol>;

template class BasicHashtableEntry<mtSymbol>;

template class BasicHashtableEntry<mtCode>;

template class BasicHashtable<mtClass>;

template class BasicHashtable<mtClassShared>;

template class BasicHashtable<mtSymbol>;

template class BasicHashtable<mtCode>;

template class BasicHashtable<mtInternal>;

template class BasicHashtable<mtModule>;

#if INCLUDE_TRACE

template class Hashtable<Symbol*, mtTracing>;

template class HashtableEntry<Symbol*, mtTracing>;

template class BasicHashtable<mtTracing>;

#endif

template class BasicHashtable<mtCompiler>;

template void BasicHashtable<mtClass>::verify_table<DictionaryEntry>(char const*);

template void BasicHashtable<mtModule>::verify_table<ModuleEntry>(char const*);

template void BasicHashtable<mtModule>::verify_table<PackageEntry>(char const*);

template void BasicHashtable<mtClass>::verify_table<ProtectionDomainCacheEntry>(char const*);

template void BasicHashtable<mtClass>::verify_table<PlaceholderEntry>(char const*);