Avoiding duplication of singular iterator

base/memory/mru_cache.h

 // Copyright (c) 2011 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.
 
 // This file contains a template for a Most Recently Used cache that allows
 // constant-time access to items using a key, but easy identification of the
 // least-recently-used items for removal.  Each key can only be associated with
 // one payload item at a time.
 //
 // The key object will be stored twice, so it should support efficient copying.
@@ skipping 73 matching lines @@
       // Erase the reference to it. This will call the deletor on the removed
       // element. The index reference will be replaced in the code below.
       Erase(index_iter->second);
     } else if (max_size_ != NO_AUTO_EVICT) {
       // New item is being inserted which might make it larger than the maximum
       // size: kick the oldest thing out if necessary.
       ShrinkToSize(max_size_ - 1);
     }
 
     ordering_.push_front(value_type(key, payload));
-    index_[key] = ordering_.begin();
+    index_.insert(std::make_pair(key, ordering_.begin()));

[tzik, 2011/06/16 08:55:19]

Previous 10 lines guarantee the absence of occupant.

     return ordering_.begin();
   }
 
   // Retrieves the contents of the given key, or end() if not found. This method
   // has the side effect of moving the requested item to the front of the
   // recency list.
   //
   // TODO(brettw) We may want a const version of this function in the future.
   iterator Get(const KeyType& key) {
     typename KeyIndex::iterator index_iter = index_.find(key);
@@ skipping 149 matching lines @@
   virtual ~OwningMRUCache() {
   }
 
  private:
   DISALLOW_COPY_AND_ASSIGN(OwningMRUCache);
 };
 
 }  // namespace base
 
 #endif  // BASE_MEMORY_MRU_CACHE_H_