auto_reset.h 1.18 KB
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// 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.

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#ifndef BUTIL_AUTO_RESET_H_
#define BUTIL_AUTO_RESET_H_
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#include "butil/basictypes.h"
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// butil::AutoReset<> is useful for setting a variable to a new value only within
// a particular scope. An butil::AutoReset<> object resets a variable to its
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// original value upon destruction, making it an alternative to writing
// "var = false;" or "var = old_val;" at all of a block's exit points.
//
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// This should be obvious, but note that an butil::AutoReset<> instance should
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// have a shorter lifetime than its scoped_variable, to prevent invalid memory
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// writes when the butil::AutoReset<> object is destroyed.
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namespace butil {
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template<typename T>
class AutoReset {
 public:
  AutoReset(T* scoped_variable, T new_value)
      : scoped_variable_(scoped_variable),
        original_value_(*scoped_variable) {
    *scoped_variable_ = new_value;
  }

  ~AutoReset() { *scoped_variable_ = original_value_; }

 private:
  T* scoped_variable_;
  T original_value_;

  DISALLOW_COPY_AND_ASSIGN(AutoReset);
};

}

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#endif  // BUTIL_AUTO_RESET_H_