Move Courgette...

third_party/courgette/difference_estimator.h

-// Copyright (c) 2009 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.
-
-// A DifferenceEstimator class provides a means for quickly estimating the
-// difference between two regions of memory.
-
-#ifndef COURGETTE_DIFFERENCE_ESTIMATOR_H_
-#define COURGETTE_DIFFERENCE_ESTIMATOR_H_
-
-#include <vector>
-
-#include "third_party/courgette/region.h"
-
-namespace courgette {
-
-// A DifferenceEstimator simplifies the task of determining which 'Subject' byte
-// strings (stored in regions of memory) are good matches to existing 'Base'
-// regions.  The ultimate measure would be to try full differential compression
-// and measure the output size, but an estimate that correlates well with the
-// full compression is more efficient.
-//
-// The measure is asymmetric, if the Subject is a small substring of the Base
-// then it should match very well.
-//
-// The comparison is staged: first make Base and Subject objects for the regions
-// and then call 'Measure' to get the estimate.  The staging allows multiple
-// comparisons to be more efficient by precomputing information used in the
-// comparison.
-//
-class DifferenceEstimator {
- public:
-  DifferenceEstimator();
-  ~DifferenceEstimator();
-
-  class Base;
-  class Subject;
-
-  // This DifferenceEstimator owns the objects returned by MakeBase and
-  // MakeSubject.  Caller continues to own memory at |region| and must not free
-  // it until ~DifferenceEstimator has been called.
-  Base* MakeBase(const Region& region);
-  Subject* MakeSubject(const Region& region);
-
-  // Returns a value correlated with the size of the bsdiff or xdelta difference
-  // from |base| to |subject|.  Returns zero iff the base and subject regions
-  // are bytewise identical.
-  size_t Measure(Base* base,  Subject* subject);
-
- private:
-  std::vector<Base*> owned_bases_;
-  std::vector<Subject*> owned_subjects_;
-  DISALLOW_COPY_AND_ASSIGN(DifferenceEstimator);
-};
-
-}  // namespace
-
-#endif  // COURGETTE_DIFFERENCE_ESTIMATOR_H_