/*

 * Copyright (c) 1997, 2014, 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/javaClasses.hpp"

#include "classfile/stringTable.hpp"

#include "classfile/systemDictionary.hpp"

#include "gc_interface/collectedHeap.inline.hpp"

#include "memory/allocation.inline.hpp"

#include "memory/filemap.hpp"

#include "memory/gcLocker.inline.hpp"

#include "oops/oop.inline.hpp"

#include "oops/oop.inline2.hpp"

#include "runtime/mutexLocker.hpp"

#include "utilities/hashtable.inline.hpp"

#if INCLUDE_ALL_GCS

#include "gc_implementation/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::_needs_rehashing = false;

volatile int StringTable::_parallel_claimed_idx = 0;

// Pick hashing algorithm

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

  return use_alternate_hashcode() ? AltHashing::murmur3_32(seed(), s, len) :

                                    java_lang_String::hash_code(s, len);

}

oop StringTable::lookup(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 >= BasicHashtable<mtSymbol>::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.

  No_Safepoint_Verifier 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 = 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.

  oop test = lookup(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);

}

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

  unsigned int hash = hash_string(name, len);

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

  return the_table()->lookup(index, name, len, hash);

}

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

                        int len, TRAPS) {

  unsigned int hashValue = hash_string(name, len);

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

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

  // Found

  if (found_string != NULL) 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");

  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.

  MutexLocker ml(StringTable_lock, THREAD);

  // Otherwise, add to symbol to table

  return the_table()->basic_add(index, string, name, len,

                                hashValue, CHECK_NULL);

}

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,

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

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

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

  assert(start_idx <= end_idx,

         err_msg("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,

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

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

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

  assert(start_idx <= end_idx,

         err_msg("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 = java_lang_String::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) {

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

}

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]",

                  (void *)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;

  }

  if (str->klass() != SystemDictionary::String_klass()) {

    if (mesg_mode == _verify_with_mesgs) {

      tty->print_cr("ERROR: oop is not a String in entry @ bucket[%d][%d]",

                    bkt, e_cnt);

    }

    // not a String means no more verifications are possible

    return _verify_fail_done;

  }

  unsigned int h = java_lang_String::hash_string(str);

  if (e_ptr->hash() != h) {

    if (mesg_mode == _verify_with_mesgs) {

      tty->print_cr("ERROR: broken hash value in entry @ bucket[%d][%d], "

                    "bkt_hash=%d, str_hash=%d", bkt, e_cnt, e_ptr->hash(), h);

    }

    ret = _verify_fail_continue;

  }

  if (the_table()->hash_to_index(h) != bkt) {

    if (mesg_mode == _verify_with_mesgs) {

      tty->print_cr("ERROR: wrong index value for entry @ bucket[%d][%d], "

                    "str_hash=%d, hash_to_index=%d", bkt, e_cnt, h,

                    the_table()->hash_to_index(h));

    }

    ret = _verify_fail_continue;

  }

  return ret;

}

// See StringTable::verify() above for the quick verification that is

// part of Universe::verify(). This verification is exhaustive and

// reports on every issue that is found. StringTable::verify() only

// reports on the first issue that is found.

//

// StringTable::verify_entry() checks:

// - oop value != NULL (same as verify())

// - oop value is a String

// - hash(String) == hash in entry (same as verify())

// - index for hash == index of entry (same as verify())

//

// StringTable::compare_entries() checks:

// - oops are unique across all entries

// - String values are unique across all entries

//

int StringTable::verify_and_compare_entries() {

  assert(StringTable_lock->is_locked(), "sanity check");

  int  fail_cnt = 0;

  // first, verify all the entries individually:

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

    HashtableEntry<oop, mtSymbol>* e_ptr = the_table()->bucket(bkt);

    for (int e_cnt = 0; e_ptr != NULL; e_ptr = e_ptr->next(), e_cnt++) {

      VerifyRetTypes ret = verify_entry(bkt, e_cnt, e_ptr, _verify_with_mesgs);

      if (ret != _verify_pass) {

        fail_cnt++;

      }

    }

  }

  // Optimization: if the above check did not find any failures, then

  // the comparison loop below does not need to call verify_entry()

  // before calling compare_entries(). If there were failures, then we

  // have to call verify_entry() to see if the entry can be passed to

  // compare_entries() safely. When we call verify_entry() in the loop

  // below, we do so quietly to void duplicate messages and we don't

  // increment fail_cnt because the failures have already been counted.

  bool need_entry_verify = (fail_cnt != 0);

  // second, verify all entries relative to each other:

  for (int bkt1 = 0; bkt1 < the_table()->table_size(); bkt1++) {

    HashtableEntry<oop, mtSymbol>* e_ptr1 = the_table()->bucket(bkt1);

    for (int e_cnt1 = 0; e_ptr1 != NULL; e_ptr1 = e_ptr1->next(), e_cnt1++) {

      if (need_entry_verify) {

        VerifyRetTypes ret = verify_entry(bkt1, e_cnt1, e_ptr1,

                                          _verify_quietly);

        if (ret == _verify_fail_done) {

          // cannot use the current entry to compare against other entries

          continue;

        }

      }

      for (int bkt2 = bkt1; bkt2 < the_table()->table_size(); bkt2++) {

        HashtableEntry<oop, mtSymbol>* e_ptr2 = the_table()->bucket(bkt2);

        int e_cnt2;

        for (e_cnt2 = 0; e_ptr2 != NULL; e_ptr2 = e_ptr2->next(), e_cnt2++) {

          if (bkt1 == bkt2 && e_cnt2 <= e_cnt1) {

            // skip the entries up to and including the one that

            // we're comparing against

            continue;

          }

          if (need_entry_verify) {

            VerifyRetTypes ret = verify_entry(bkt2, e_cnt2, e_ptr2,

                                              _verify_quietly);

            if (ret == _verify_fail_done) {

              // cannot compare against this entry

              continue;

            }

          }

          // compare two entries, report and count any failures:

          if (compare_entries(bkt1, e_cnt1, e_ptr1, bkt2, e_cnt2, e_ptr2)

              != _verify_pass) {

            fail_cnt++;

          }

        }

      }

    }

  }

  return fail_cnt;

}

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

// with the existing strings.   Set flag to use the alternate hash code afterwards.

void StringTable::rehash_table() {

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

  // This should never happen with -Xshare:dump but it might in testing mode.

  if (DumpSharedSpaces) return;

  StringTable* new_table = new StringTable();

  // Rehash the table

  the_table()->move_to(new_table);

  // Delete the table and buckets (entries are reused in new table).

  delete _the_table;