root/content/browser/indexed_db/leveldb/leveldb_transaction.cc

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DEFINITIONS

This source file includes following definitions.
  1. finished_
  2. Clear
  3. Set
  4. Put
  5. Remove
  6. Get
  7. Commit
  8. Rollback
  9. CreateIterator
  10. Create
  11. IsValid
  12. SeekToLast
  13. Seek
  14. Next
  15. Prev
  16. Key
  17. Value
  18. IsDeleted
  19. iterator_
  20. Create
  21. data_changed_
  22. IsValid
  23. SeekToLast
  24. Seek
  25. Next
  26. Prev
  27. Key
  28. Value
  29. DataChanged
  30. RefreshDataIterator
  31. DataIteratorIsLower
  32. DataIteratorIsHigher
  33. HandleConflictsAndDeletes
  34. SetCurrentIteratorToSmallestKey
  35. SetCurrentIteratorToLargestKey
  36. RegisterIterator
  37. UnregisterIterator
  38. NotifyIterators
  39. Create
  40. finished_
  41. Put
  42. Get
  43. Remove
  44. Commit
// Copyright (c) 2013 The Chromium Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

#include "content/browser/indexed_db/leveldb/leveldb_transaction.h"

#include "base/logging.h"
#include "content/browser/indexed_db/leveldb/leveldb_database.h"
#include "content/browser/indexed_db/leveldb/leveldb_write_batch.h"
#include "third_party/leveldatabase/src/include/leveldb/db.h"

using base::StringPiece;

namespace content {

LevelDBTransaction::LevelDBTransaction(LevelDBDatabase* db)
    : db_(db),
      snapshot_(db),
      comparator_(db->Comparator()),
      data_comparator_(comparator_),
      data_(data_comparator_),
      finished_(false) {}

LevelDBTransaction::Record::Record() : deleted(false) {}
LevelDBTransaction::Record::~Record() {}

void LevelDBTransaction::Clear() {
  for (DataType::iterator it = data_.begin(); it != data_.end(); ++it) {
    delete it->second;
  }
  data_.clear();
}

LevelDBTransaction::~LevelDBTransaction() { Clear(); }

void LevelDBTransaction::Set(const StringPiece& key,
                             std::string* value,
                             bool deleted) {
  DCHECK(!finished_);
  DataType::iterator it = data_.find(key);

  if (it == data_.end()) {
    Record* record = new Record();
    record->key.assign(key.begin(), key.end() - key.begin());
    record->value.swap(*value);
    record->deleted = deleted;
    data_[record->key] = record;
    NotifyIterators();
    return;
  }

  it->second->value.swap(*value);
  it->second->deleted = deleted;
}

void LevelDBTransaction::Put(const StringPiece& key, std::string* value) {
  Set(key, value, false);
}

void LevelDBTransaction::Remove(const StringPiece& key) {
  std::string empty;
  Set(key, &empty, true);
}

leveldb::Status LevelDBTransaction::Get(const StringPiece& key,
                                        std::string* value,
                                        bool* found) {
  *found = false;
  DCHECK(!finished_);
  std::string string_key(key.begin(), key.end() - key.begin());
  DataType::const_iterator it = data_.find(string_key);

  if (it != data_.end()) {
    if (it->second->deleted)
      return leveldb::Status::OK();

    *value = it->second->value;
    *found = true;
    return leveldb::Status::OK();
  }

  leveldb::Status s = db_->Get(key, value, found, &snapshot_);
  if (!s.ok())
    DCHECK(!*found);
  return s;
}

leveldb::Status LevelDBTransaction::Commit() {
  DCHECK(!finished_);

  if (data_.empty()) {
    finished_ = true;
    return leveldb::Status::OK();
  }

  scoped_ptr<LevelDBWriteBatch> write_batch = LevelDBWriteBatch::Create();

  for (DataType::iterator iterator = data_.begin(); iterator != data_.end();
       ++iterator) {
    if (!iterator->second->deleted)
      write_batch->Put(iterator->first, iterator->second->value);
    else
      write_batch->Remove(iterator->first);
  }

  leveldb::Status s = db_->Write(*write_batch);
  if (s.ok()) {
    Clear();
    finished_ = true;
  }
  return s;
}

void LevelDBTransaction::Rollback() {
  DCHECK(!finished_);
  finished_ = true;
  Clear();
}

scoped_ptr<LevelDBIterator> LevelDBTransaction::CreateIterator() {
  return TransactionIterator::Create(this).PassAs<LevelDBIterator>();
}

scoped_ptr<LevelDBTransaction::DataIterator>
LevelDBTransaction::DataIterator::Create(LevelDBTransaction* transaction) {
  return make_scoped_ptr(new DataIterator(transaction));
}

bool LevelDBTransaction::DataIterator::IsValid() const {
  return iterator_ != data_->end();
}

void LevelDBTransaction::DataIterator::SeekToLast() {
  iterator_ = data_->end();
  if (iterator_ != data_->begin())
    --iterator_;
}

void LevelDBTransaction::DataIterator::Seek(const StringPiece& target) {
  iterator_ = data_->lower_bound(target);
}

void LevelDBTransaction::DataIterator::Next() {
  DCHECK(IsValid());
  ++iterator_;
}

void LevelDBTransaction::DataIterator::Prev() {
  DCHECK(IsValid());
  if (iterator_ != data_->begin())
    --iterator_;
  else
    iterator_ = data_->end();
}

StringPiece LevelDBTransaction::DataIterator::Key() const {
  DCHECK(IsValid());
  return iterator_->first;
}

StringPiece LevelDBTransaction::DataIterator::Value() const {
  DCHECK(IsValid());
  DCHECK(!IsDeleted());
  return iterator_->second->value;
}

bool LevelDBTransaction::DataIterator::IsDeleted() const {
  DCHECK(IsValid());
  return iterator_->second->deleted;
}

LevelDBTransaction::DataIterator::~DataIterator() {}

LevelDBTransaction::DataIterator::DataIterator(LevelDBTransaction* transaction)
    : data_(&transaction->data_),
      iterator_(data_->end()) {}

scoped_ptr<LevelDBTransaction::TransactionIterator>
LevelDBTransaction::TransactionIterator::Create(
    scoped_refptr<LevelDBTransaction> transaction) {
  return make_scoped_ptr(new TransactionIterator(transaction));
}

LevelDBTransaction::TransactionIterator::TransactionIterator(
    scoped_refptr<LevelDBTransaction> transaction)
    : transaction_(transaction),
      comparator_(transaction_->comparator_),
      data_iterator_(DataIterator::Create(transaction_.get())),
      db_iterator_(transaction_->db_->CreateIterator(&transaction_->snapshot_)),
      current_(0),
      direction_(FORWARD),
      data_changed_(false) {
  transaction_->RegisterIterator(this);
}

LevelDBTransaction::TransactionIterator::~TransactionIterator() {
  transaction_->UnregisterIterator(this);
}

bool LevelDBTransaction::TransactionIterator::IsValid() const {
  return !!current_;
}

void LevelDBTransaction::TransactionIterator::SeekToLast() {
  data_iterator_->SeekToLast();
  db_iterator_->SeekToLast();
  direction_ = REVERSE;

  HandleConflictsAndDeletes();
  SetCurrentIteratorToLargestKey();
}

void LevelDBTransaction::TransactionIterator::Seek(const StringPiece& target) {
  data_iterator_->Seek(target);
  db_iterator_->Seek(target);
  direction_ = FORWARD;

  HandleConflictsAndDeletes();
  SetCurrentIteratorToSmallestKey();
}

void LevelDBTransaction::TransactionIterator::Next() {
  DCHECK(IsValid());
  if (data_changed_)
    RefreshDataIterator();

  if (direction_ != FORWARD) {
    // Ensure the non-current iterator is positioned after Key().

    LevelDBIterator* non_current = (current_ == db_iterator_.get())
                                       ? data_iterator_.get()
                                       : db_iterator_.get();

    non_current->Seek(Key());
    if (non_current->IsValid() &&
        !comparator_->Compare(non_current->Key(), Key())) {
      // Take an extra step so the non-current key is
      // strictly greater than Key().
      non_current->Next();
    }
    DCHECK(!non_current->IsValid() ||
           comparator_->Compare(non_current->Key(), Key()) > 0);

    direction_ = FORWARD;
  }

  current_->Next();
  HandleConflictsAndDeletes();
  SetCurrentIteratorToSmallestKey();
}

void LevelDBTransaction::TransactionIterator::Prev() {
  DCHECK(IsValid());
  if (data_changed_)
    RefreshDataIterator();

  if (direction_ != REVERSE) {
    // Ensure the non-current iterator is positioned before Key().

    LevelDBIterator* non_current = (current_ == db_iterator_.get())
                                       ? data_iterator_.get()
                                       : db_iterator_.get();

    non_current->Seek(Key());
    if (non_current->IsValid()) {
      // Iterator is at first entry >= Key().
      // Step back once to entry < key.
      // This is why we don't check for the keys being the same before
      // stepping, like we do in Next() above.
      non_current->Prev();
    } else {
      // Iterator has no entries >= Key(). Position at last entry.
      non_current->SeekToLast();
    }
    DCHECK(!non_current->IsValid() ||
           comparator_->Compare(non_current->Key(), Key()) < 0);

    direction_ = REVERSE;
  }

  current_->Prev();
  HandleConflictsAndDeletes();
  SetCurrentIteratorToLargestKey();
}

StringPiece LevelDBTransaction::TransactionIterator::Key() const {
  DCHECK(IsValid());
  if (data_changed_)
    RefreshDataIterator();
  return current_->Key();
}

StringPiece LevelDBTransaction::TransactionIterator::Value() const {
  DCHECK(IsValid());
  if (data_changed_)
    RefreshDataIterator();
  return current_->Value();
}

void LevelDBTransaction::TransactionIterator::DataChanged() {
  data_changed_ = true;
}

void LevelDBTransaction::TransactionIterator::RefreshDataIterator() const {
  DCHECK(data_changed_);

  data_changed_ = false;

  if (data_iterator_->IsValid() && data_iterator_.get() == current_) {
    return;
  }

  if (db_iterator_->IsValid()) {
    // There could be new records in data that we should iterate over.

    if (direction_ == FORWARD) {
      // Try to seek data iterator to something greater than the db iterator.
      data_iterator_->Seek(db_iterator_->Key());
      if (data_iterator_->IsValid() &&
          !comparator_->Compare(data_iterator_->Key(), db_iterator_->Key())) {
        // If equal, take another step so the data iterator is strictly greater.
        data_iterator_->Next();
      }
    } else {
      // If going backward, seek to a key less than the db iterator.
      DCHECK_EQ(REVERSE, direction_);
      data_iterator_->Seek(db_iterator_->Key());
      if (data_iterator_->IsValid())
        data_iterator_->Prev();
    }
  }
}

bool LevelDBTransaction::TransactionIterator::DataIteratorIsLower() const {
  return comparator_->Compare(data_iterator_->Key(), db_iterator_->Key()) < 0;
}

bool LevelDBTransaction::TransactionIterator::DataIteratorIsHigher() const {
  return comparator_->Compare(data_iterator_->Key(), db_iterator_->Key()) > 0;
}

void LevelDBTransaction::TransactionIterator::HandleConflictsAndDeletes() {
  bool loop = true;

  while (loop) {
    loop = false;

    if (data_iterator_->IsValid() && db_iterator_->IsValid() &&
        !comparator_->Compare(data_iterator_->Key(), db_iterator_->Key())) {
      // For equal keys, the data iterator takes precedence, so move the
      // database iterator another step.
      if (direction_ == FORWARD)
        db_iterator_->Next();
      else
        db_iterator_->Prev();
    }

    // Skip over delete markers in the data iterator until it catches up with
    // the db iterator.
    if (data_iterator_->IsValid() && data_iterator_->IsDeleted()) {
      if (direction_ == FORWARD &&
          (!db_iterator_->IsValid() || DataIteratorIsLower())) {
        data_iterator_->Next();
        loop = true;
      } else if (direction_ == REVERSE &&
                 (!db_iterator_->IsValid() || DataIteratorIsHigher())) {
        data_iterator_->Prev();
        loop = true;
      }
    }
  }
}

void
LevelDBTransaction::TransactionIterator::SetCurrentIteratorToSmallestKey() {
  LevelDBIterator* smallest = 0;

  if (data_iterator_->IsValid())
    smallest = data_iterator_.get();

  if (db_iterator_->IsValid()) {
    if (!smallest ||
        comparator_->Compare(db_iterator_->Key(), smallest->Key()) < 0)
      smallest = db_iterator_.get();
  }

  current_ = smallest;
}

void LevelDBTransaction::TransactionIterator::SetCurrentIteratorToLargestKey() {
  LevelDBIterator* largest = 0;

  if (data_iterator_->IsValid())
    largest = data_iterator_.get();

  if (db_iterator_->IsValid()) {
    if (!largest ||
        comparator_->Compare(db_iterator_->Key(), largest->Key()) > 0)
      largest = db_iterator_.get();
  }

  current_ = largest;
}

void LevelDBTransaction::RegisterIterator(TransactionIterator* iterator) {
  DCHECK(iterators_.find(iterator) == iterators_.end());
  iterators_.insert(iterator);
}

void LevelDBTransaction::UnregisterIterator(TransactionIterator* iterator) {
  DCHECK(iterators_.find(iterator) != iterators_.end());
  iterators_.erase(iterator);
}

void LevelDBTransaction::NotifyIterators() {
  for (std::set<TransactionIterator*>::iterator i = iterators_.begin();
       i != iterators_.end();
       ++i) {
    TransactionIterator* transaction_iterator = *i;
    transaction_iterator->DataChanged();
  }
}

scoped_ptr<LevelDBDirectTransaction> LevelDBDirectTransaction::Create(
    LevelDBDatabase* db) {
  return make_scoped_ptr(new LevelDBDirectTransaction(db));
}

LevelDBDirectTransaction::LevelDBDirectTransaction(LevelDBDatabase* db)
    : db_(db), write_batch_(LevelDBWriteBatch::Create()), finished_(false) {}

LevelDBDirectTransaction::~LevelDBDirectTransaction() {
  write_batch_->Clear();
}

void LevelDBDirectTransaction::Put(const StringPiece& key,
                                   const std::string* value) {
  DCHECK(!finished_);
  write_batch_->Put(key, *value);
}

leveldb::Status LevelDBDirectTransaction::Get(const StringPiece& key,
                                              std::string* value,
                                              bool* found) {
  *found = false;
  DCHECK(!finished_);

  leveldb::Status s = db_->Get(key, value, found);
  DCHECK(s.ok() || !*found);
  return s;
}

void LevelDBDirectTransaction::Remove(const StringPiece& key) {
  DCHECK(!finished_);
  write_batch_->Remove(key);
}

leveldb::Status LevelDBDirectTransaction::Commit() {
  DCHECK(!finished_);

  leveldb::Status s = db_->Write(*write_batch_);
  if (s.ok()) {
    finished_ = true;
    write_batch_->Clear();
  }
  return s;
}

}  // namespace content
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