Instrument to catch corruption constructing safe-browsing filters.

chrome/browser/safe_browsing/prefix_set.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.
 //
 // A read-only set implementation for |SBPrefix| items.  Prefixes are
 // sorted and stored as 16-bit deltas from the previous prefix.  An
 // index structure provides quick random access, and also handles
 // cases where 16 bits cannot encode a delta.
 //
 // For example, the sequence {20, 25, 41, 65432, 150000, 160000} would
@@ skipping 71 matching lines @@
   size_t GetSize() const;
 
   // Returns |true| if the element at |target_index| is between items in the
   // |index_| array.
   bool IsDeltaAt(size_t target_index) const;
 
   // Returns the delta used to calculate the element at
   // |target_index|.  Only call if |IsDeltaAt()| returned |true|.
   uint16 DeltaAt(size_t target_index) const;
 
-  // Check whether |index_| and |deltas_| still match the CRC
+  // Check whether |index_| and |deltas_| still match the checksum
   // generated during construction.
   bool CheckChecksum() const;
 
+  // Accumulates xor checksum over what GetPrefixes() would return,
+  // without requiring a large temporary structure.
+  SBPrefix GetPrefixesChecksum() const;
+
  private:
   // Maximum number of consecutive deltas to encode before generating
   // a new index entry.  This helps keep the worst-case performance
   // for |Exists()| under control.
   static const size_t kMaxRun = 100;
 
   // Helper for |LoadFile()|.  Steals the contents of |index| and
   // |deltas| using |swap()|.
   PrefixSet(std::vector<std::pair<SBPrefix,size_t> > *index,
             std::vector<uint16> *deltas);
@@ skipping 13 matching lines @@
   // changed after generation during construction.  |checksum_| is
   // calculated from the data used to construct those vectors.
   uint32 checksum_;
 
   DISALLOW_COPY_AND_ASSIGN(PrefixSet);
 };
 
 }  // namespace safe_browsing
 
 #endif  // CHROME_BROWSER_SAFE_BROWSING_PREFIX_SET_H_