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