chrome/browser/android/thumbnail/scoped_ptr_expiring_cache.h

   1 // Copyright 2014 The Chromium 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.
   4
   5 #ifndef CHROME_BROWSER_ANDROID_THUMBNAIL_SCOPED_PTR_EXPIRING_CACHE_H_
   6 #define CHROME_BROWSER_ANDROID_THUMBNAIL_SCOPED_PTR_EXPIRING_CACHE_H_
   7
   8 #include "base/memory/scoped_ptr.h"
   9 #include "net/base/linked_hash_map.h"
  10
  11 template <class Key, class Value>
  12 class ScopedPtrExpiringCache {
  13  private:
  14   typedef linked_hash_map<Key, Value*> LinkedHashMap;
  15
  16  public:
  17   typedef typename LinkedHashMap::iterator iterator;
  18
  19   explicit ScopedPtrExpiringCache(size_t max_cache_size)
  20       : max_cache_size_(max_cache_size) {}
  21
  22   ~ScopedPtrExpiringCache() {}
  23
  24   void Put(const Key& key, scoped_ptr<Value> value) {
  25     Remove(key);
  26     map_[key] = value.release();
  27     EvictIfFull();
  28   }
  29
  30   Value* Get(const Key& key) {
  31     iterator iter = map_.find(key);
  32     if (iter != map_.end())
  33       return iter->second;
  34     return NULL;
  35   }
  36
  37   void Remove(const Key& key) {
  38     iterator iter = map_.find(key);
  39     if (iter != map_.end()) {
  40       delete iter->second;
  41       map_.erase(key);
  42     }
  43   }
  44
  45   void Clear() {
  46     for (iterator iter = map_.begin(); iter != map_.end(); iter++) {
  47       delete iter->second;
  48     }
  49     map_.clear();
  50   }
  51
  52   iterator begin() { return map_.begin(); }
  53   iterator end() { return map_.end(); }
  54   size_t MaximumCacheSize() const { return max_cache_size_; }
  55   size_t size() const { return map_.size(); }
  56
  57  private:
  58   void EvictIfFull() {
  59     while (map_.size() > max_cache_size_) {
  60       iterator it = map_.begin();
  61       delete it->second;
  62       map_.erase(it);
  63     }
  64   }
  65
  66   size_t max_cache_size_;
  67   LinkedHashMap map_;
  68
  69   DISALLOW_COPY_AND_ASSIGN(ScopedPtrExpiringCache);
  70 };
  71
  72 #endif  // CHROME_BROWSER_ANDROID_THUMBNAIL_SCOPED_PTR_EXPIRING_CACHE_H_