Revert of Move prefix_set and parts of s_b_util into a new component safe_browsing_db.

chrome/browser/safe_browsing/prefix_set.h

Index: chrome/browser/safe_browsing/prefix_set.h
diff --git a/chrome/browser/safe_browsing/prefix_set.h b/chrome/browser/safe_browsing/prefix_set.h
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+// Copyright (c) 2012 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
+// be stored as:
+//  A pair {20, 0} in |index_|.
+//  5, 16, 65391 in |deltas_|.
+//  A pair {150000, 3} in |index_|.
+//  10000 in |deltas_|.
+// |index_.size()| will be 2, |deltas_.size()| will be 4.
+//
+// This structure is intended for storage of sparse uniform sets of
+// prefixes of a certain size.  As of this writing, my safe-browsing
+// database contains:
+//   653132 add prefixes
+//   6446 are duplicates (from different chunks)
+//   24301 w/in 2^8 of the prior prefix
+//   622337 w/in 2^16 of the prior prefix
+//   47 further than 2^16 from the prior prefix
+// For this input, the memory usage is approximately 2 bytes per
+// prefix, a bit over 1.2M.  The bloom filter used 25 bits per prefix,
+// a bit over 1.9M on this data.
+//
+// Experimenting with random selections of the above data, storage
+// size drops almost linearly as prefix count drops, until the index
+// overhead starts to become a problem a bit under 200k prefixes.  The
+// memory footprint gets worse than storing the raw prefix data around
+// 75k prefixes.  Fortunately, the actual memory footprint also falls.
+// If the prefix count increases the memory footprint should increase
+// approximately linearly.  The worst-case would be 2^16 items all
+// 2^16 apart, which would need 512k (versus 256k to store the raw
+// data).
+//
+// The on-disk format looks like:
+//         4 byte magic number
+//         4 byte version number
+//         4 byte |index_.size()|
+//         4 byte |deltas_.size()|
+//     n * 8 byte |&index_[0]..&index_[n]|
+//     m * 2 byte |&deltas_[0]..&deltas_[m]|
+//        16 byte digest
+
+#ifndef CHROME_BROWSER_SAFE_BROWSING_PREFIX_SET_H_
+#define CHROME_BROWSER_SAFE_BROWSING_PREFIX_SET_H_
+
+#include <utility>
+#include <vector>
+
+#include "base/gtest_prod_util.h"
+#include "base/memory/scoped_ptr.h"
+#include "chrome/browser/safe_browsing/safe_browsing_util.h"
+
+namespace base {
+class FilePath;
+}
+
+namespace safe_browsing {
+
+class PrefixSet {
+ public:
+  ~PrefixSet();
+
+  // |true| if |hash| is in the hashes passed to the set's builder, or if
+  // |hash.prefix| is one of the prefixes passed to the set's builder.
+  bool Exists(const SBFullHash& hash) const;
+
+  // Persist the set on disk.
+  static scoped_ptr<const PrefixSet> LoadFile(
+      const base::FilePath& filter_name);
+  bool WriteFile(const base::FilePath& filter_name) const;
+
+ private:
+  friend class PrefixSetBuilder;
+
+  friend class PrefixSetTest;
+  FRIEND_TEST_ALL_PREFIXES(PrefixSetTest, AllBig);
+  FRIEND_TEST_ALL_PREFIXES(PrefixSetTest, EdgeCases);
+  FRIEND_TEST_ALL_PREFIXES(PrefixSetTest, Empty);
+  FRIEND_TEST_ALL_PREFIXES(PrefixSetTest, FullHashBuild);
+  FRIEND_TEST_ALL_PREFIXES(PrefixSetTest, IntMinMax);
+  FRIEND_TEST_ALL_PREFIXES(PrefixSetTest, OneElement);
+  FRIEND_TEST_ALL_PREFIXES(PrefixSetTest, ReadWrite);
+  FRIEND_TEST_ALL_PREFIXES(PrefixSetTest, ReadWriteSigned);
+  FRIEND_TEST_ALL_PREFIXES(PrefixSetTest, Version3);
+
+  FRIEND_TEST_ALL_PREFIXES(SafeBrowsingStoreFileTest, BasicStore);
+  FRIEND_TEST_ALL_PREFIXES(SafeBrowsingStoreFileTest, DeleteChunks);
+  FRIEND_TEST_ALL_PREFIXES(SafeBrowsingStoreFileTest, DetectsCorruption);
+  FRIEND_TEST_ALL_PREFIXES(SafeBrowsingStoreFileTest, Empty);
+  FRIEND_TEST_ALL_PREFIXES(SafeBrowsingStoreFileTest, PrefixMinMax);
+  FRIEND_TEST_ALL_PREFIXES(SafeBrowsingStoreFileTest, SubKnockout);
+  FRIEND_TEST_ALL_PREFIXES(SafeBrowsingStoreFileTest, Version7);
+  FRIEND_TEST_ALL_PREFIXES(SafeBrowsingStoreFileTest, Version8);
+
+  // 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;
+
+  // Helpers to make |index_| easier to deal with.
+  typedef std::pair<SBPrefix, uint32> IndexPair;
+  typedef std::vector<IndexPair> IndexVector;
+  static bool PrefixLess(const IndexPair& a, const IndexPair& b);
+
+  // Helper to let |PrefixSetBuilder| add a run of data.  |index_prefix| is
+  // added to |index_|, with the other elements added into |deltas_|.
+  void AddRun(SBPrefix index_prefix,
+              const uint16* run_begin, const uint16* run_end);
+
+  // |true| if |prefix| is one of the prefixes passed to the set's builder.
+  // Provided for testing purposes.
+  bool PrefixExists(SBPrefix prefix) const;
+
+  // Regenerate the vector of prefixes passed to the constructor into
+  // |prefixes|.  Prefixes will be added in sorted order.  Useful for testing.
+  void GetPrefixes(std::vector<SBPrefix>* prefixes) const;
+
+  // Used by |PrefixSetBuilder|.
+  PrefixSet();
+
+  // Helper for |LoadFile()|.  Steals vector contents using |swap()|.
+  PrefixSet(IndexVector* index,
+            std::vector<uint16>* deltas,
+            std::vector<SBFullHash>* full_hashes);
+
+  // Top-level index of prefix to offset in |deltas_|.  Each pair
+  // indicates a base prefix and where the deltas from that prefix
+  // begin in |deltas_|.  The deltas for a pair end at the next pair's
+  // index into |deltas_|.
+  IndexVector index_;
+
+  // Deltas which are added to the prefix in |index_| to generate
+  // prefixes.  Deltas are only valid between consecutive items from
+  // |index_|, or the end of |deltas_| for the last |index_| pair.
+  std::vector<uint16> deltas_;
+
+  // Full hashes ordered by SBFullHashLess.
+  std::vector<SBFullHash> full_hashes_;
+
+  DISALLOW_COPY_AND_ASSIGN(PrefixSet);
+};
+
+// Helper to incrementally build a PrefixSet from a stream of sorted prefixes.
+class PrefixSetBuilder {
+ public:
+  PrefixSetBuilder();
+  ~PrefixSetBuilder();
+
+  // Helper for unit tests and format conversion.
+  explicit PrefixSetBuilder(const std::vector<SBPrefix>& prefixes);
+
+  // Add a prefix to the set.  Prefixes must arrive in ascending order.
+  // Duplicate prefixes are dropped.
+  void AddPrefix(SBPrefix prefix);
+
+  // Flush any buffered prefixes, and return the final PrefixSet instance.
+  // |hashes| are sorted and stored in |full_hashes_|.  Any call other than the
+  // destructor is illegal after this call.
+  scoped_ptr<const PrefixSet> GetPrefixSet(
+      const std::vector<SBFullHash>& hashes);
+
+  // Helper for clients which only track prefixes.  Calls GetPrefixSet() with
+  // empty hash vector.
+  scoped_ptr<const PrefixSet> GetPrefixSetNoHashes();
+
+ private:
+  // Encode a run of deltas for |AddRun()|.  The run is broken by a too-large
+  // delta, or kMaxRun, whichever comes first.
+  void EmitRun();
+
+  // Buffers prefixes until enough are avaliable to emit a run.
+  std::vector<SBPrefix> buffer_;
+
+  // The PrefixSet being built.
+  scoped_ptr<PrefixSet> prefix_set_;
+};
+
+}  // namespace safe_browsing
+
+#endif  // CHROME_BROWSER_SAFE_BROWSING_PREFIX_SET_H_