1 // Copyright (c) 2011 The LevelDB Authors. All rights reserved. 2 // Use of this source code is governed by a BSD-style license that can be 3 // found in the LICENSE file. See the AUTHORS file for names of contributors. 4 5 #ifndef STORAGE_LEVELDB_TABLE_ITERATOR_WRAPPER_H_ 6 #define STORAGE_LEVELDB_TABLE_ITERATOR_WRAPPER_H_ 7 8 namespace leveldb { 9 10 // A internal wrapper class with an interface similar to Iterator that 11 // caches the valid() and key() results for an underlying iterator. 12 // This can help avoid virtual function calls and also gives better 13 // cache locality. 14 class IteratorWrapper { 15 public: 16 IteratorWrapper(): iter_(NULL), valid_(false) { } 17 explicit IteratorWrapper(Iterator* iter): iter_(NULL) { 18 Set(iter); 19 } 20 ~IteratorWrapper() { delete iter_; } 21 Iterator* iter() const { return iter_; } 22 23 // Takes ownership of "iter" and will delete it when destroyed, or 24 // when Set() is invoked again. 25 void Set(Iterator* iter) { 26 delete iter_; 27 iter_ = iter; 28 if (iter_ == NULL) { 29 valid_ = false; 30 } else { 31 Update(); 32 } 33 } 34 35 36 // Iterator interface methods 37 bool Valid() const { return valid_; } 38 Slice key() const { assert(Valid()); return key_; } 39 Slice value() const { assert(Valid()); return iter_->value(); } 40 // Methods below require iter() != NULL 41 Status status() const { assert(iter_); return iter_->status(); } 42 void Next() { assert(iter_); iter_->Next(); Update(); } 43 void Prev() { assert(iter_); iter_->Prev(); Update(); } 44 void Seek(const Slice& k) { assert(iter_); iter_->Seek(k); Update(); } 45 void SeekToFirst() { assert(iter_); iter_->SeekToFirst(); Update(); } 46 void SeekToLast() { assert(iter_); iter_->SeekToLast(); Update(); } 47 48 private: 49 void Update() { 50 valid_ = iter_->Valid(); 51 if (valid_) { 52 key_ = iter_->key(); 53 } 54 } 55 56 Iterator* iter_; 57 bool valid_; 58 Slice key_; 59 }; 60 61 } // namespace leveldb 62 63 #endif // STORAGE_LEVELDB_TABLE_ITERATOR_WRAPPER_H_ 64
