pool.h

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// Copyright 2011 Google Inc.

#ifndef PAGESPEED_KERNEL_BASE_POOL_H_
#define PAGESPEED_KERNEL_BASE_POOL_H_
#include <cstddef>
#include <list>
#include "base/logging.h"  
#include "pagespeed/kernel/base/basictypes.h"
#include "pagespeed/kernel/base/pool_element.h"
#include "pagespeed/kernel/base/stl_util.h"

namespace net_instaweb {

template<class T>
class Pool {
 public:
  typedef typename PoolElement<T>::Position iterator;
  typedef typename std::list<T*>::const_iterator const_iterator;

  Pool() { }

  ~Pool() {
    DeleteAll();
  }

  bool empty() const {
    return contents_.empty();
  }

  size_t size() const {
    return contents_.size();
  }

  iterator begin() {
    return contents_.begin();
  }

  const_iterator begin() const {
    return contents_.begin();
  }

  iterator end() {
    return contents_.end();
  }

  const_iterator end() const {
    return contents_.end();
  }

  void Add(T* object) {
    iterator* position = object->pool_position();
    contents_.push_back(object);
    iterator back_iter = contents_.end();
    --back_iter;
    *position = back_iter;
  }

  T* Remove(T* object) {
    iterator* position = object->pool_position();
    DCHECK(**position == object);
    contents_.erase(*position);
    *position = contents_.end();
    return object;
  }

  T* oldest() const {
    T* result = NULL;
    if (!contents_.empty()) {
      result = contents_.front();
    }
    return result;
  }

  T* RemoveOldest() {
    T* result = NULL;
    if (!contents_.empty()) {
      result = contents_.front();
      iterator* position = result->pool_position();
      DCHECK(*position == contents_.begin());
      contents_.pop_front();
      *position = contents_.end();
    }
    return result;
  }

  void DeleteAll() {
    STLDeleteElements(&contents_);
  }

  void Clear() {
    contents_.clear();
  }

 private:
  std::list<T*> contents_;

  
};

}  

#endif