/*

 * Copyright (c) 1997, 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 "classfile/altHashing.hpp"

#include "classfile/compactHashtable.hpp"

#include "classfile/javaClasses.inline.hpp"

#include "classfile/stringTable.hpp"

#include "classfile/systemDictionary.hpp"

#include "gc/shared/collectedHeap.hpp"

#include "gc/shared/oopStorage.inline.hpp"

#include "gc/shared/oopStorageSet.hpp"

#include "logging/log.hpp"

#include "logging/logStream.hpp"

#include "memory/allocation.inline.hpp"

#include "memory/filemap.hpp"

#include "memory/heapShared.inline.hpp"

#include "memory/resourceArea.hpp"

#include "memory/universe.hpp"

#include "oops/access.inline.hpp"

#include "oops/compressedOops.hpp"

#include "oops/oop.inline.hpp"

#include "oops/typeArrayOop.inline.hpp"

#include "oops/weakHandle.inline.hpp"

#include "runtime/atomic.hpp"

#include "runtime/handles.inline.hpp"

#include "runtime/mutexLocker.hpp"

#include "runtime/safepointVerifiers.hpp"

#include "runtime/timerTrace.hpp"

#include "runtime/interfaceSupport.inline.hpp"

#include "services/diagnosticCommand.hpp"

#include "utilities/concurrentHashTable.inline.hpp"

#include "utilities/concurrentHashTableTasks.inline.hpp"

#include "utilities/macros.hpp"

#include "utilities/utf8.hpp"

// We prefer short chains of avg 2

const double PREF_AVG_LIST_LEN = 2.0;

// 2^24 is max size

const size_t END_SIZE = 24;

// If a chain gets to 100 something might be wrong

const size_t REHASH_LEN = 100;

// If we have as many dead items as 50% of the number of bucket

const double CLEAN_DEAD_HIGH_WATER_MARK = 0.5;

#if INCLUDE_CDS_JAVA_HEAP

inline oop read_string_from_compact_hashtable(address base_address, u4 offset) {

  assert(sizeof(narrowOop) == sizeof(offset), "must be");

  narrowOop v = (narrowOop)offset;

  return HeapShared::decode_from_archive(v);

}

static CompactHashtable<

  const jchar*, oop,

  read_string_from_compact_hashtable,

  java_lang_String::equals

> _shared_table;

#endif

// --------------------------------------------------------------------------

typedef ConcurrentHashTable<StringTableConfig, mtSymbol> StringTableHash;

static StringTableHash* _local_table = NULL;

volatile bool StringTable::_has_work = false;

volatile bool StringTable::_needs_rehashing = false;

volatile size_t StringTable::_uncleaned_items_count = 0;

static size_t _current_size = 0;

static volatile size_t _items_count = 0;

volatile bool _alt_hash = false;

static juint murmur_seed = 0;

uintx hash_string(const jchar* s, int len, bool useAlt) {

  return  useAlt ?

    AltHashing::murmur3_32(murmur_seed, s, len) :

    java_lang_String::hash_code(s, len);

}

class StringTableConfig : public StackObj {

 private:

 public:

  typedef WeakHandle<vm_string_table_data> Value;

  static uintx get_hash(Value const& value, bool* is_dead) {

    EXCEPTION_MARK;

    oop val_oop = value.peek();

    if (val_oop == NULL) {

      *is_dead = true;

      return 0;

    }

    *is_dead = false;

    ResourceMark rm(THREAD);

    // All String oops are hashed as unicode

    int length;

    jchar* chars = java_lang_String::as_unicode_string(val_oop, length, THREAD);

    if (chars != NULL) {

      return hash_string(chars, length, _alt_hash);

    }

    vm_exit_out_of_memory(length, OOM_MALLOC_ERROR, "get hash from oop");

    return 0;

  }

  // We use default allocation/deallocation but counted

  static void* allocate_node(size_t size, Value const& value) {

    StringTable::item_added();

    return AllocateHeap(size, mtSymbol);

  }

  static void free_node(void* memory, Value const& value) {

    value.release();

    FreeHeap(memory);

    StringTable::item_removed();

  }

};

class StringTableLookupJchar : StackObj {

 private:

  Thread* _thread;

  uintx _hash;

  int _len;

  const jchar* _str;

  Handle _found;

 public:

  StringTableLookupJchar(Thread* thread, uintx hash, const jchar* key, int len)

    : _thread(thread), _hash(hash), _len(len), _str(key) {

  }

  uintx get_hash() const {

    return _hash;

  }

  bool equals(WeakHandle<vm_string_table_data>* value, bool* is_dead) {

    oop val_oop = value->peek();

    if (val_oop == NULL) {

      // dead oop, mark this hash dead for cleaning

      *is_dead = true;

      return false;

    }

    bool equals = java_lang_String::equals(val_oop, _str, _len);

    if (!equals) {

      return false;

    }

    // Need to resolve weak handle and Handleize through possible safepoint.

     _found = Handle(_thread, value->resolve());

    return true;

  }

};

class StringTableLookupOop : public StackObj {

 private:

  Thread* _thread;

  uintx _hash;

  Handle _find;

  Handle _found;  // Might be a different oop with the same value that's already

                  // in the table, which is the point.

 public:

  StringTableLookupOop(Thread* thread, uintx hash, Handle handle)

    : _thread(thread), _hash(hash), _find(handle) { }

  uintx get_hash() const {

    return _hash;

  }

  bool equals(WeakHandle<vm_string_table_data>* value, bool* is_dead) {

    oop val_oop = value->peek();

    if (val_oop == NULL) {

      // dead oop, mark this hash dead for cleaning

      *is_dead = true;

      return false;

    }

    bool equals = java_lang_String::equals(_find(), val_oop);

    if (!equals) {

      return false;

    }

    // Need to resolve weak handle and Handleize through possible safepoint.

    _found = Handle(_thread, value->resolve());

    return true;

  }

};

static size_t ceil_log2(size_t val) {

  size_t ret;

  for (ret = 1; ((size_t)1 << ret) < val; ++ret);

  return ret;

}

void StringTable::create_table() {

  size_t start_size_log_2 = ceil_log2(StringTableSize);

  _current_size = ((size_t)1) << start_size_log_2;

  log_trace(stringtable)("Start size: " SIZE_FORMAT " (" SIZE_FORMAT ")",

                         _current_size, start_size_log_2);

  _local_table = new StringTableHash(start_size_log_2, END_SIZE, REHASH_LEN);

}

size_t StringTable::item_added() {

  return Atomic::add((size_t)1, &_items_count);

}

size_t StringTable::add_items_to_clean(size_t ndead) {

  size_t total = Atomic::add((size_t)ndead, &_uncleaned_items_count);

  log_trace(stringtable)(

     "Uncleaned items:" SIZE_FORMAT " added: " SIZE_FORMAT " total:" SIZE_FORMAT,

     _uncleaned_items_count, ndead, total);

  return total;

}

void StringTable::item_removed() {

  Atomic::add((size_t)-1, &_items_count);

}

double StringTable::get_load_factor() {

  return (double)_items_count/_current_size;

}

double StringTable::get_dead_factor() {

  return (double)_uncleaned_items_count/_current_size;

}

size_t StringTable::table_size() {

  return ((size_t)1) << _local_table->get_size_log2(Thread::current());

}

void StringTable::trigger_concurrent_work() {

  MutexLocker ml(Service_lock, Mutex::_no_safepoint_check_flag);

  _has_work = true;

  Service_lock->notify_all();

}

// Probing

oop StringTable::lookup(Symbol* symbol) {

  ResourceMark rm;

  int length;

  jchar* chars = symbol->as_unicode(length);

  return lookup(chars, length);

}

oop StringTable::lookup(const jchar* name, int len) {

  unsigned int hash = java_lang_String::hash_code(name, len);

  oop string = lookup_shared(name, len, hash);

  if (string != NULL) {

    return string;

  }

  if (_alt_hash) {

    hash = hash_string(name, len, true);

  }

  return do_lookup(name, len, hash);

}

class StringTableGet : public StackObj {

  Thread* _thread;

  Handle  _return;

 public:

  StringTableGet(Thread* thread) : _thread(thread) {}

  void operator()(WeakHandle<vm_string_table_data>* val) {

    oop result = val->resolve();

    assert(result != NULL, "Result should be reachable");

    _return = Handle(_thread, result);

  }

  oop get_res_oop() {

    return _return();

  }

};

oop StringTable::do_lookup(const jchar* name, int len, uintx hash) {

  Thread* thread = Thread::current();

  StringTableLookupJchar lookup(thread, hash, name, len);

  StringTableGet stg(thread);

  bool rehash_warning;

  _local_table->get(thread, lookup, stg, &rehash_warning);

  update_needs_rehash(rehash_warning);

  return stg.get_res_oop();

}

// Interning

oop StringTable::intern(Symbol* symbol, TRAPS) {

  if (symbol == NULL) return NULL;

  ResourceMark rm(THREAD);

  int length;

  jchar* chars = symbol->as_unicode(length);

  Handle string;

  oop result = intern(string, chars, length, CHECK_NULL);

  return result;

}

oop StringTable::intern(oop string, TRAPS) {

  if (string == NULL) return NULL;

  ResourceMark rm(THREAD);

  int length;

  Handle h_string (THREAD, string);

  jchar* chars = java_lang_String::as_unicode_string(string, length,

                                                     CHECK_NULL);

  oop result = intern(h_string, chars, length, CHECK_NULL);

  return result;

}

oop StringTable::intern(const char* utf8_string, TRAPS) {

  if (utf8_string == NULL) return NULL;

  ResourceMark rm(THREAD);

  int length = UTF8::unicode_length(utf8_string);

  jchar* chars = NEW_RESOURCE_ARRAY(jchar, length);

  UTF8::convert_to_unicode(utf8_string, chars, length);

  Handle string;

  oop result = intern(string, chars, length, CHECK_NULL);

  return result;

}

oop StringTable::intern(Handle string_or_null_h, const jchar* name, int len, TRAPS) {

  // shared table always uses java_lang_String::hash_code

  unsigned int hash = java_lang_String::hash_code(name, len);

  oop found_string = lookup_shared(name, len, hash);

  if (found_string != NULL) {

    return found_string;

  }

  if (_alt_hash) {

    hash = hash_string(name, len, true);

  }

  found_string = do_lookup(name, len, hash);

  if (found_string != NULL) {

    return found_string;

  }

  return do_intern(string_or_null_h, name, len, hash, THREAD);

}

oop StringTable::do_intern(Handle string_or_null_h, const jchar* name,

                           int len, uintx hash, TRAPS) {

  HandleMark hm(THREAD);  // cleanup strings created

  Handle string_h;

  if (!string_or_null_h.is_null()) {

    string_h = string_or_null_h;

  } else {

    string_h = java_lang_String::create_from_unicode(name, len, CHECK_NULL);

  }

  // Deduplicate the string before it is interned. Note that we should never

  // deduplicate a string after it has been interned. Doing so will counteract

  // compiler optimizations done on e.g. interned string literals.

  Universe::heap()->deduplicate_string(string_h());

  assert(java_lang_String::equals(string_h(), name, len),

         "string must be properly initialized");

  assert(len == java_lang_String::length(string_h()), "Must be same length");

  StringTableLookupOop lookup(THREAD, hash, string_h);

  StringTableGet stg(THREAD);

  bool rehash_warning;

  do {

    // Callers have already looked up the String using the jchar* name, so just go to add.

    WeakHandle<vm_string_table_data> wh = WeakHandle<vm_string_table_data>::create(string_h);

    // The hash table takes ownership of the WeakHandle, even if it's not inserted.

    if (_local_table->insert(THREAD, lookup, wh, &rehash_warning)) {

      update_needs_rehash(rehash_warning);

      return wh.resolve();

    }

    // In case another thread did a concurrent add, return value already in the table.

    // This could fail if the String got gc'ed concurrently, so loop back until success.

    if (_local_table->get(THREAD, lookup, stg, &rehash_warning)) {

      update_needs_rehash(rehash_warning);

      return stg.get_res_oop();

    }

  } while(true);

}

void StringTable::oops_do(OopClosure* f) {

  assert(f != NULL, "No closure");

  OopStorageSet::string_table_weak()->oops_do(f);

}

// Concurrent work

void StringTable::grow(JavaThread* jt) {

  StringTableHash::GrowTask gt(_local_table);

  if (!gt.prepare(jt)) {

    return;

  }

  log_trace(stringtable)("Started to grow");

  {

    TraceTime timer("Grow", TRACETIME_LOG(Debug, stringtable, perf));

    while (gt.do_task(jt)) {

      gt.pause(jt);

      {

        ThreadBlockInVM tbivm(jt);

      }

      gt.cont(jt);

    }

  }

  gt.done(jt);

  _current_size = table_size();

  log_debug(stringtable)("Grown to size:" SIZE_FORMAT, _current_size);

}

struct StringTableDoDelete : StackObj {

  void operator()(WeakHandle<vm_string_table_data>* val) {

    /* do nothing */

  }

};

struct StringTableDeleteCheck : StackObj {

  long _count;

  long _item;

  StringTableDeleteCheck() : _count(0), _item(0) {}

  bool operator()(WeakHandle<vm_string_table_data>* val) {

    ++_item;

    oop tmp = val->peek();

    if (tmp == NULL) {

      ++_count;

      return true;

    } else {

      return false;

    }

  }

};

void StringTable::clean_dead_entries(JavaThread* jt) {

  StringTableHash::BulkDeleteTask bdt(_local_table);

  if (!bdt.prepare(jt)) {

    return;

  }

  StringTableDeleteCheck stdc;

  StringTableDoDelete stdd;

  {

    TraceTime timer("Clean", TRACETIME_LOG(Debug, stringtable, perf));

    while(bdt.do_task(jt, stdc, stdd)) {

      bdt.pause(jt);

      {

        ThreadBlockInVM tbivm(jt);

      }

      bdt.cont(jt);

    }

    bdt.done(jt);

  }

  log_debug(stringtable)("Cleaned %ld of %ld", stdc._count, stdc._item);

}

void StringTable::check_concurrent_work() {

  if (_has_work) {

    return;

  }

  double load_factor = StringTable::get_load_factor();

  double dead_factor = StringTable::get_dead_factor();

  // We should clean/resize if we have more dead than alive,

  // more items than preferred load factor or

  // more dead items than water mark.

  if ((dead_factor > load_factor) ||

      (load_factor > PREF_AVG_LIST_LEN) ||

      (dead_factor > CLEAN_DEAD_HIGH_WATER_MARK)) {

    log_debug(stringtable)("Concurrent work triggered, live factor: %g dead factor: %g",

                           load_factor, dead_factor);

    trigger_concurrent_work();

  }

}

void StringTable::do_concurrent_work(JavaThread* jt) {

  _has_work = false;

  double load_factor = get_load_factor();

  log_debug(stringtable, perf)("Concurrent work, live factor: %g", load_factor);

  // We prefer growing, since that also removes dead items

  if (load_factor > PREF_AVG_LIST_LEN && !_local_table->is_max_size_reached()) {

    grow(jt);

  } else {

    clean_dead_entries(jt);

  }

}

// Rehash

bool StringTable::do_rehash() {

  if (!_local_table->is_safepoint_safe()) {