| // Copyright (c) 2011 The LevelDB Authors. All rights reserved. |
| // Use of this source code is governed by a BSD-style license that can be |
| // found in the LICENSE file. See the AUTHORS file for names of contributors. |
| |
| #ifndef STORAGE_LEVELDB_TABLE_ITERATOR_WRAPPER_H_ |
| #define STORAGE_LEVELDB_TABLE_ITERATOR_WRAPPER_H_ |
| |
| namespace leveldb { |
| |
| // A internal wrapper class with an interface similar to Iterator that |
| // caches the valid() and key() results for an underlying iterator. |
| // This can help avoid virtual function calls and also gives better |
| // cache locality. |
| class IteratorWrapper { |
| public: |
| IteratorWrapper(): iter_(NULL), valid_(false) { } |
| explicit IteratorWrapper(Iterator* iter): iter_(NULL) { |
| Set(iter); |
| } |
| ~IteratorWrapper() { delete iter_; } |
| Iterator* iter() const { return iter_; } |
| |
| // Takes ownership of "iter" and will delete it when destroyed, or |
| // when Set() is invoked again. |
| void Set(Iterator* iter) { |
| delete iter_; |
| iter_ = iter; |
| if (iter_ == NULL) { |
| valid_ = false; |
| } else { |
| Update(); |
| } |
| } |
| |
| |
| // Iterator interface methods |
| bool Valid() const { return valid_; } |
| Slice key() const { assert(Valid()); return key_; } |
| Slice value() const { assert(Valid()); return iter_->value(); } |
| // Methods below require iter() != NULL |
| Status status() const { assert(iter_); return iter_->status(); } |
| void Next() { assert(iter_); iter_->Next(); Update(); } |
| void Prev() { assert(iter_); iter_->Prev(); Update(); } |
| void Seek(const Slice& k) { assert(iter_); iter_->Seek(k); Update(); } |
| void SeekToFirst() { assert(iter_); iter_->SeekToFirst(); Update(); } |
| void SeekToLast() { assert(iter_); iter_->SeekToLast(); Update(); } |
| |
| private: |
| void Update() { |
| valid_ = iter_->Valid(); |
| if (valid_) { |
| key_ = iter_->key(); |
| } |
| } |
| |
| Iterator* iter_; |
| bool valid_; |
| Slice key_; |
| }; |
| |
| } // namespace leveldb |
| |
| #endif // STORAGE_LEVELDB_TABLE_ITERATOR_WRAPPER_H_ |