From cb1e39f0a35cc2b36fb748c26f69cd27e0ed5332 Mon Sep 17 00:00:00 2001
From: Pieter Wuille <sipa@ulyssis.org>
Date: Tue, 20 Aug 2013 14:17:45 +0200
Subject: Squashed 'src/leveldb/' content from commit a02ddf9

git-subtree-dir: src/leveldb
git-subtree-split: a02ddf9b14d145e88185ee209ab8b01d8826663a
---
 table/iterator_wrapper.h | 63 ++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 63 insertions(+)
 create mode 100644 table/iterator_wrapper.h

(limited to 'table/iterator_wrapper.h')

diff --git a/table/iterator_wrapper.h b/table/iterator_wrapper.h
new file mode 100644
index 0000000000..9e16b3dbed
--- /dev/null
+++ b/table/iterator_wrapper.h
@@ -0,0 +1,63 @@
+// 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_
-- 
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