/*

 * Copyright (c) 1997, 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/compactHashtable.inline.hpp"

#include "classfile/javaClasses.inline.hpp"

#include "classfile/stringTable.hpp"

#include "classfile/systemDictionary.hpp"

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

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

#include "memory/allocation.inline.hpp"

#include "memory/filemap.hpp"

#include "memory/resourceArea.hpp"

#include "oops/oop.inline.hpp"

#include "runtime/atomic.hpp"

#include "runtime/mutexLocker.hpp"

#include "utilities/hashtable.inline.hpp"

#include "utilities/macros.hpp"

#if INCLUDE_ALL_GCS

#include "gc/g1/g1CollectedHeap.hpp"

#include "gc/g1/g1SATBCardTableModRefBS.hpp"

#include "gc/g1/g1StringDedup.hpp"

#endif

// the number of buckets a thread claims

const int ClaimChunkSize = 32;

#ifdef ASSERT

class StableMemoryChecker : public StackObj {

  enum { _bufsize = wordSize*4 };

  address _region;

  jint    _size;

  u1      _save_buf[_bufsize];

  int sample(u1* save_buf) {

    if (_size <= _bufsize) {

      memcpy(save_buf, _region, _size);

      return _size;

    } else {

      // copy head and tail

      memcpy(&save_buf[0],          _region,                      _bufsize/2);

      memcpy(&save_buf[_bufsize/2], _region + _size - _bufsize/2, _bufsize/2);

      return (_bufsize/2)*2;

    }

  }

 public:

  StableMemoryChecker(const void* region, jint size) {

    _region = (address) region;

    _size   = size;

    sample(_save_buf);

  }

  bool verify() {

    u1 check_buf[sizeof(_save_buf)];

    int check_size = sample(check_buf);

    return (0 == memcmp(_save_buf, check_buf, check_size));

  }

  void set_region(const void* region) { _region = (address) region; }

};

#endif

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

StringTable* StringTable::_the_table = NULL;

bool StringTable::_ignore_shared_strings = false;

bool StringTable::_needs_rehashing = false;

volatile int StringTable::_parallel_claimed_idx = 0;

CompactHashtable<oop, char> StringTable::_shared_table;

// Pick hashing algorithm

unsigned int StringTable::hash_string(const jchar* s, int len) {

  return use_alternate_hashcode() ? alt_hash_string(s, len) :

                                    java_lang_String::hash_code(s, len);

}

unsigned int StringTable::alt_hash_string(const jchar* s, int len) {

  return AltHashing::murmur3_32(seed(), s, len);

}

unsigned int StringTable::hash_string(oop string) {

  EXCEPTION_MARK;

  if (string == NULL) {

    return hash_string((jchar*)NULL, 0);

  }

  ResourceMark rm(THREAD);

  // All String oops are hashed as unicode

  int length;

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

  if (chars != NULL) {

    return hash_string(chars, length);

  } else {

    vm_exit_out_of_memory(length, OOM_MALLOC_ERROR, "unable to create Unicode string for verification");

    return 0;

  }

}

oop StringTable::lookup_shared(jchar* name, int len, unsigned int hash) {

  assert(hash == java_lang_String::hash_code(name, len),

         "hash must be computed using java_lang_String::hash_code");

  return _shared_table.lookup((const char*)name, hash, len);

}

oop StringTable::lookup_in_main_table(int index, jchar* name,

                                int len, unsigned int hash) {

  int count = 0;

  for (HashtableEntry<oop, mtSymbol>* l = bucket(index); l != NULL; l = l->next()) {

    count++;

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

      if (java_lang_String::equals(l->literal(), name, len)) {

        return l->literal();

      }

    }

  }

  // If the bucket size is too deep check if this hash code is insufficient.

  if (count >= rehash_count && !needs_rehashing()) {

    _needs_rehashing = check_rehash_table(count);

  }

  return NULL;

}

oop StringTable::basic_add(int index_arg, Handle string, jchar* name,

                           int len, unsigned int hashValue_arg, TRAPS) {

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

         "string must be properly initialized");

  // Cannot hit a safepoint in this function because the "this" pointer can move.

  NoSafepointVerifier nsv;

  // Check if the symbol table has been rehashed, if so, need to recalculate

  // the hash value and index before second lookup.

  unsigned int hashValue;

  int index;

  if (use_alternate_hashcode()) {

    hashValue = alt_hash_string(name, len);

    index = hash_to_index(hashValue);

  } else {

    hashValue = hashValue_arg;

    index = index_arg;

  }

  // Since look-up was done lock-free, we need to check if another

  // thread beat us in the race to insert the symbol.

  // No need to lookup the shared table from here since the caller (intern()) already did

  oop test = lookup_in_main_table(index, name, len, hashValue); // calls lookup(u1*, int)

  if (test != NULL) {

    // Entry already added

    return test;

  }

  HashtableEntry<oop, mtSymbol>* entry = new_entry(hashValue, string());

  add_entry(index, entry);

  return string();

}

oop StringTable::lookup(Symbol* symbol) {

  ResourceMark rm;

  int length;

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

  return lookup(chars, length);

}

// Tell the GC that this string was looked up in the StringTable.

static void ensure_string_alive(oop string) {

  // A lookup in the StringTable could return an object that was previously

  // considered dead. The SATB part of G1 needs to get notified about this

  // potential resurrection, otherwise the marking might not find the object.

#if INCLUDE_ALL_GCS

  if (UseG1GC && string != NULL) {

    G1SATBCardTableModRefBS::enqueue(string);

  }

#endif

}

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

  // shared table always uses java_lang_String::hash_code

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

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

  if (string != NULL) {

    return string;

  }

  if (use_alternate_hashcode()) {

    hash = alt_hash_string(name, len);

  }

  int index = the_table()->hash_to_index(hash);

  string = the_table()->lookup_in_main_table(index, name, len, hash);

  ensure_string_alive(string);

  return string;

}

oop StringTable::intern(Handle string_or_null, jchar* name,

                        int len, TRAPS) {

  // shared table always uses java_lang_String::hash_code

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

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

  if (found_string != NULL) {

    return found_string;

  }

  if (use_alternate_hashcode()) {

    hashValue = alt_hash_string(name, len);

  }

  int index = the_table()->hash_to_index(hashValue);

  found_string = the_table()->lookup_in_main_table(index, name, len, hashValue);

  // Found

  if (found_string != NULL) {

    if (found_string != string_or_null()) {

      ensure_string_alive(found_string);

    }

    return found_string;

  }

  debug_only(StableMemoryChecker smc(name, len * sizeof(name[0])));

  assert(!Universe::heap()->is_in_reserved(name),

         "proposed name of symbol must be stable");

  HandleMark hm(THREAD);  // cleanup strings created

  Handle string;

  // try to reuse the string if possible

  if (!string_or_null.is_null()) {

    string = string_or_null;

  } else {

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

  }

#if INCLUDE_ALL_GCS

  if (G1StringDedup::is_enabled()) {

    // 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.

    G1StringDedup::deduplicate(string());

  }

#endif

  // Grab the StringTable_lock before getting the_table() because it could

  // change at safepoint.

  oop added_or_found;

  {

    MutexLocker ml(StringTable_lock, THREAD);

    // Otherwise, add to symbol to table

    added_or_found = the_table()->basic_add(index, string, name, len,

                                  hashValue, CHECK_NULL);

  }

  if (added_or_found != string()) {

    ensure_string_alive(added_or_found);

  }

  return added_or_found;

}

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;

}

void StringTable::unlink_or_oops_do(BoolObjectClosure* is_alive, OopClosure* f, int* processed, int* removed) {

  buckets_unlink_or_oops_do(is_alive, f, 0, the_table()->table_size(), processed, removed);

}

void StringTable::possibly_parallel_unlink_or_oops_do(BoolObjectClosure* is_alive, OopClosure* f, int* processed, int* removed) {

  // Readers of the table are unlocked, so we should only be removing

  // entries at a safepoint.

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

  const int limit = the_table()->table_size();

  for (;;) {

    // Grab next set of buckets to scan

    int start_idx = Atomic::add(ClaimChunkSize, &_parallel_claimed_idx) - ClaimChunkSize;

    if (start_idx >= limit) {

      // End of table

      break;

    }

    int end_idx = MIN2(limit, start_idx + ClaimChunkSize);

    buckets_unlink_or_oops_do(is_alive, f, start_idx, end_idx, processed, removed);

  }

}

void StringTable::buckets_oops_do(OopClosure* f, int start_idx, int end_idx) {

  const int limit = the_table()->table_size();

  assert(0 <= start_idx && start_idx <= limit,

         "start_idx (%d) is out of bounds", start_idx);

  assert(0 <= end_idx && end_idx <= limit,

         "end_idx (%d) is out of bounds", end_idx);

  assert(start_idx <= end_idx,

         "Index ordering: start_idx=%d, end_idx=%d",

         start_idx, end_idx);

  for (int i = start_idx; i < end_idx; i += 1) {

    HashtableEntry<oop, mtSymbol>* entry = the_table()->bucket(i);

    while (entry != NULL) {

      assert(!entry->is_shared(), "CDS not used for the StringTable");

      f->do_oop((oop*)entry->literal_addr());

      entry = entry->next();

    }

  }

}

void StringTable::buckets_unlink_or_oops_do(BoolObjectClosure* is_alive, OopClosure* f, int start_idx, int end_idx, int* processed, int* removed) {

  const int limit = the_table()->table_size();

  assert(0 <= start_idx && start_idx <= limit,

         "start_idx (%d) is out of bounds", start_idx);

  assert(0 <= end_idx && end_idx <= limit,

         "end_idx (%d) is out of bounds", end_idx);

  assert(start_idx <= end_idx,

         "Index ordering: start_idx=%d, end_idx=%d",

         start_idx, end_idx);

  for (int i = start_idx; i < end_idx; ++i) {

    HashtableEntry<oop, mtSymbol>** p = the_table()->bucket_addr(i);

    HashtableEntry<oop, mtSymbol>* entry = the_table()->bucket(i);

    while (entry != NULL) {

      assert(!entry->is_shared(), "CDS not used for the StringTable");

      if (is_alive->do_object_b(entry->literal())) {

        if (f != NULL) {

          f->do_oop((oop*)entry->literal_addr());

        }

        p = entry->next_addr();

      } else {

        *p = entry->next();

        the_table()->free_entry(entry);

        (*removed)++;

      }

      (*processed)++;

      entry = *p;

    }

  }

}

void StringTable::oops_do(OopClosure* f) {

  buckets_oops_do(f, 0, the_table()->table_size());

}

void StringTable::possibly_parallel_oops_do(OopClosure* f) {

  const int limit = the_table()->table_size();

  for (;;) {

    // Grab next set of buckets to scan

    int start_idx = Atomic::add(ClaimChunkSize, &_parallel_claimed_idx) - ClaimChunkSize;

    if (start_idx >= limit) {

      // End of table

      break;

    }

    int end_idx = MIN2(limit, start_idx + ClaimChunkSize);

    buckets_oops_do(f, start_idx, end_idx);

  }

}

// This verification is part of Universe::verify() and needs to be quick.

// See StringTable::verify_and_compare() below for exhaustive verification.

void StringTable::verify() {

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

    HashtableEntry<oop, mtSymbol>* p = the_table()->bucket(i);

    for ( ; p != NULL; p = p->next()) {

      oop s = p->literal();

      guarantee(s != NULL, "interned string is NULL");

      unsigned int h = hash_string(s);

      guarantee(p->hash() == h, "broken hash in string table entry");

      guarantee(the_table()->hash_to_index(h) == i,

                "wrong index in string table");

    }

  }

}

void StringTable::dump(outputStream* st, bool verbose) {

  if (!verbose) {

    the_table()->dump_table(st, "StringTable");

  } else {

    Thread* THREAD = Thread::current();

    st->print_cr("VERSION: 1.1");

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

      HashtableEntry<oop, mtSymbol>* p = the_table()->bucket(i);

      for ( ; p != NULL; p = p->next()) {

        oop s = p->literal();

        typeArrayOop value  = java_lang_String::value(s);

        int          length = java_lang_String::length(s);

        bool      is_latin1 = java_lang_String::is_latin1(s);

        if (length <= 0) {

          st->print("%d: ", length);

        } else {

          ResourceMark rm(THREAD);

          int utf8_length = length;

          char* utf8_string;

          if (!is_latin1) {

            jchar* chars = value->char_at_addr(0);

            utf8_string = UNICODE::as_utf8(chars, utf8_length);

          } else {

            jbyte* bytes = value->byte_at_addr(0);

            utf8_string = UNICODE::as_utf8(bytes, utf8_length);

          }

          st->print("%d: ", utf8_length);

          HashtableTextDump::put_utf8(st, utf8_string, utf8_length);

        }

        st->cr();

      }

    }

  }

}

StringTable::VerifyRetTypes StringTable::compare_entries(

                                      int bkt1, int e_cnt1,

                                      HashtableEntry<oop, mtSymbol>* e_ptr1,

                                      int bkt2, int e_cnt2,

                                      HashtableEntry<oop, mtSymbol>* e_ptr2) {

  // These entries are sanity checked by verify_and_compare_entries()

  // before this function is called.

  oop str1 = e_ptr1->literal();

  oop str2 = e_ptr2->literal();

  if (str1 == str2) {

    tty->print_cr("ERROR: identical oop values (0x" PTR_FORMAT ") "

                  "in entry @ bucket[%d][%d] and entry @ bucket[%d][%d]",

                  p2i(str1), bkt1, e_cnt1, bkt2, e_cnt2);

    return _verify_fail_continue;

  }

  if (java_lang_String::equals(str1, str2)) {

    tty->print_cr("ERROR: identical String values in entry @ "

                  "bucket[%d][%d] and entry @ bucket[%d][%d]",

                  bkt1, e_cnt1, bkt2, e_cnt2);

    return _verify_fail_continue;

  }

  return _verify_pass;

}

StringTable::VerifyRetTypes StringTable::verify_entry(int bkt, int e_cnt,

                                      HashtableEntry<oop, mtSymbol>* e_ptr,

                                      StringTable::VerifyMesgModes mesg_mode) {

  VerifyRetTypes ret = _verify_pass;  // be optimistic

  oop str = e_ptr->literal();

  if (str == NULL) {

    if (mesg_mode == _verify_with_mesgs) {

      tty->print_cr("ERROR: NULL oop value in entry @ bucket[%d][%d]", bkt,

                    e_cnt);

    }

    // NULL oop means no more verifications are possible

    return _verify_fail_done;

  }