Componentize visitedlinks to src/components/visitedlink

chrome/browser/visitedlink/visitedlink_master.h

-// 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.
-
-#ifndef CHROME_BROWSER_VISITEDLINK_VISITEDLINK_MASTER_H_
-#define CHROME_BROWSER_VISITEDLINK_VISITEDLINK_MASTER_H_
-
-#if defined(OS_WIN)
-#include <windows.h>
-#endif
-#include <set>
-#include <vector>
-
-#include "base/callback.h"
-#include "base/callback_forward.h"
-#include "base/file_path.h"
-#include "base/gtest_prod_util.h"
-#include "base/shared_memory.h"
-#include "base/threading/sequenced_worker_pool.h"
-#include "chrome/common/visitedlink_common.h"
-
-#if defined(UNIT_TEST) || defined(PERF_TEST) || !defined(NDEBUG)
-#include "base/logging.h"
-#endif
-
-class GURL;
-class VisitedLinkDelegate;
-
-namespace content {
-class BrowserContext;
-}  // namespace content
-
-
-// Controls the link coloring database. The master controls all writing to the
-// database as well as disk I/O. There should be only one master.
-//
-// This class will defer writing operations to the file thread. This means that
-// class destruction, the file may still be open since operations are pending on
-// another thread.
-class VisitedLinkMaster : public VisitedLinkCommon {
- public:
-  // Listens to the link coloring database events. The master is given this
-  // event as a constructor argument and dispatches events using it.
-  class Listener {
-   public:
-    virtual ~Listener() {}
-
-    // Called when link coloring database has been created or replaced. The
-    // argument is the new table handle.
-    virtual void NewTable(base::SharedMemory*) = 0;
-
-    // Called when new link has been added. The argument is the fingerprint
-    // (hash) of the link.
-    virtual void Add(Fingerprint fingerprint) = 0;
-
-    // Called when link coloring state has been reset. This may occur when
-    // entire or parts of history were deleted.
-    virtual void Reset() = 0;
-  };
-
-  VisitedLinkMaster(content::BrowserContext* browser_context,
-                    VisitedLinkDelegate* delegate);
-
-  // In unit test mode, we allow the caller to optionally specify the database
-  // filename so that it can be run from a unit test. The directory where this
-  // file resides must exist in this mode. You can also specify the default
-  // table size to test table resizing. If this parameter is 0, we will use the
-  // defaults.
-  //
-  // In the unit test mode, we also allow the caller to provide a history
-  // service pointer (the history service can't be fetched from the browser
-  // process when we're in unit test mode). This can be NULL to try to access
-  // the main version, which will probably fail (which can be good for testing
-  // this failure mode).
-  //
-  // When |suppress_rebuild| is set, we'll not attempt to load data from
-  // history if the file can't be loaded. This should generally be set for
-  // testing except when you want to test the rebuild process explicitly.
-  VisitedLinkMaster(Listener* listener,
-                    VisitedLinkDelegate* delegate,
-                    bool suppress_rebuild,
-                    const FilePath& filename,
-                    int32 default_table_size);
-  virtual ~VisitedLinkMaster();
-
-  // Must be called immediately after object creation. Nothing else will work
-  // until this is called. Returns true on success, false means that this
-  // object won't work.
-  bool Init();
-
-  base::SharedMemory* shared_memory() { return shared_memory_; }
-
-  // Adds a URL to the table.
-  void AddURL(const GURL& url);
-
-  // Adds a set of URLs to the table.
-  void AddURLs(const std::vector<GURL>& url);
-
-  // See DeleteURLs.
-  class URLIterator {
-   public:
-    // HasNextURL must return true when this is called. Returns the next URL
-    // then advances the iterator. Note that the returned reference is only
-    // valid until the next call of NextURL.
-    virtual const GURL& NextURL() = 0;
-
-    // Returns true if still has URLs to be iterated.
-    virtual bool HasNextURL() const = 0;
-
-   protected:
-    virtual ~URLIterator() {}
-  };
-
-  // Deletes the specified URLs from |rows| from the table.
-  void DeleteURLs(URLIterator* iterator);
-
-  // Clears the visited links table by deleting the file from disk. Used as
-  // part of history clearing.
-  void DeleteAllURLs();
-
-  // Returns the Delegate of this Master.
-  VisitedLinkDelegate* GetDelegate();
-
-#if defined(UNIT_TEST) || !defined(NDEBUG) || defined(PERF_TEST)
-  // This is a debugging function that can be called to double-check internal
-  // data structures. It will assert if the check fails.
-  void DebugValidate();
-
-  // Sets a task to execute when the next rebuild from history is complete.
-  // This is used by unit tests to wait for the rebuild to complete before
-  // they continue. The pointer will be owned by this object after the call.
-  void set_rebuild_complete_task(const base::Closure& task) {
-    DCHECK(rebuild_complete_task_.is_null());
-    rebuild_complete_task_ = task;
-  }
-
-  // returns the number of items in the table for testing verification
-  int32 GetUsedCount() const {
-    return used_items_;
-  }
-
-  // Returns the listener.
-  VisitedLinkMaster::Listener* GetListener() const {
-    return listener_.get();
-  }
-
-  // Call to cause the entire database file to be re-written from scratch
-  // to disk. Used by the performance tester.
-  void RewriteFile() {
-    WriteFullTable();
-  }
-#endif
-
- private:
-  FRIEND_TEST_ALL_PREFIXES(VisitedLinkTest, Delete);
-  FRIEND_TEST_ALL_PREFIXES(VisitedLinkTest, BigDelete);
-  FRIEND_TEST_ALL_PREFIXES(VisitedLinkTest, BigImport);
-
-  // Object to rebuild the table on the history thread (see the .cc file).
-  class TableBuilder;
-
-  // Byte offsets of values in the header.
-  static const int32 kFileHeaderSignatureOffset;
-  static const int32 kFileHeaderVersionOffset;
-  static const int32 kFileHeaderLengthOffset;
-  static const int32 kFileHeaderUsedOffset;
-  static const int32 kFileHeaderSaltOffset;
-
-  // The signature at the beginning of a file.
-  static const int32 kFileSignature;
-
-  // version of the file format this module currently uses
-  static const int32 kFileCurrentVersion;
-
-  // Bytes in the file header, including the salt.
-  static const size_t kFileHeaderSize;
-
-  // When creating a fresh new table, we use this many entries.
-  static const unsigned kDefaultTableSize;
-
-  // When the user is deleting a boatload of URLs, we don't really want to do
-  // individual writes for each of them. When the count exceeds this threshold,
-  // we will write the whole table to disk at once instead of individual items.
-  static const size_t kBigDeleteThreshold;
-
-  // Backend for the constructors initializing the members.
-  void InitMembers();
-
-  // If a rebuild is in progress, we save the URL in the temporary list.
-  // Otherwise, we add this to the table. Returns the index of the
-  // inserted fingerprint or null_hash_ on failure.
-  Hash TryToAddURL(const GURL& url);
-
-  // File I/O functions
-  // ------------------
-
-  // Posts the given task to the blocking worker pool with our options.
-  void PostIOTask(const tracked_objects::Location& from_here,
-                  const base::Closure& task);
-
-  // Writes the entire table to disk. It will leave the table file open and
-  // the handle to it will be stored in file_.
-  void WriteFullTable();
-
-  // Try to load the table from the database file. If the file doesn't exist or
-  // is corrupt, this will return failure.
-  bool InitFromFile();
-
-  // Reads the header of the link coloring database from disk. Assumes the
-  // file pointer is at the beginning of the file and that there are no pending
-  // asynchronous I/O operations.
-  //
-  // Returns true on success and places the size of the table in num_entries
-  // and the number of nonzero fingerprints in used_count. This will fail if
-  // the version of the file is not the current version of the database.
-  bool ReadFileHeader(FILE* hfile, int32* num_entries, int32* used_count,
-                      uint8 salt[LINK_SALT_LENGTH]);
-
-  // Fills *filename with the name of the link database filename
-  bool GetDatabaseFileName(FilePath* filename);
-
-  // Wrapper around Window's WriteFile using asynchronous I/O. This will proxy
-  // the write to a background thread.
-  void WriteToFile(FILE** hfile, off_t offset, void* data, int32 data_size);
-
-  // Helper function to schedule and asynchronous write of the used count to
-  // disk (this is a common operation).
-  void WriteUsedItemCountToFile();
-
-  // Helper function to schedule an asynchronous write of the given range of
-  // hash functions to disk. The range is inclusive on both ends. The range can
-  // wrap around at 0 and this function will handle it.
-  void WriteHashRangeToFile(Hash first_hash, Hash last_hash);
-
-  // Synchronous read from the file. Assumes there are no pending asynchronous
-  // I/O functions. Returns true if the entire buffer was successfully filled.
-  bool ReadFromFile(FILE* hfile, off_t offset, void* data, size_t data_size);
-
-  // General table handling
-  // ----------------------
-
-  // Called to add a fingerprint to the table. If |send_notifications| is true
-  // and the item is added successfully, Listener::Add will be invoked.
-  // Returns the index of the inserted fingerprint or null_hash_ if there was a
-  // duplicate and this item was skippped.
-  Hash AddFingerprint(Fingerprint fingerprint, bool send_notifications);
-
-  // Deletes all fingerprints from the given vector from the current hash table
-  // and syncs it to disk if there are changes. This does not update the
-  // deleted_since_rebuild_ list, the caller must update this itself if there
-  // is an update pending.
-  void DeleteFingerprintsFromCurrentTable(
-      const std::set<Fingerprint>& fingerprints);
-
-  // Removes the indicated fingerprint from the table. If the update_file flag
-  // is set, the changes will also be written to disk. Returns true if the
-  // fingerprint was deleted, false if it was not in the table to delete.
-  bool DeleteFingerprint(Fingerprint fingerprint, bool update_file);
-
-  // Creates a new empty table, call if InitFromFile() fails. Normally, when
-  // |suppress_rebuild| is false, the table will be rebuilt from history,
-  // keeping us in sync. When |suppress_rebuild| is true, the new table will be
-  // empty and we will not consult history. This is used when clearing the
-  // database and for unit tests.
-  bool InitFromScratch(bool suppress_rebuild);
-
-  // Allocates the Fingerprint structure and length. When init_to_empty is set,
-  // the table will be filled with 0s and used_items_ will be set to 0 as well.
-  // If the flag is not set, these things are untouched and it is the
-  // responsibility of the caller to fill them (like when we are reading from
-  // a file).
-  bool CreateURLTable(int32 num_entries, bool init_to_empty);
-
-  // A wrapper for CreateURLTable, this will allocate a new table, initialized
-  // to empty. The caller is responsible for saving the shared memory pointer
-  // and handles before this call (they will be replaced with new ones) and
-  // releasing them later. This is designed for callers that make a new table
-  // and then copy values from the old table to the new one, then release the
-  // old table.
-  //
-  // Returns true on success. On failure, the old table will be restored. The
-  // caller should not attemp to release the pointer/handle in this case.
-  bool BeginReplaceURLTable(int32 num_entries);
-
-  // unallocates the Fingerprint table
-  void FreeURLTable();
-
-  // For growing the table. ResizeTableIfNecessary will check to see if the
-  // table should be resized and calls ResizeTable if needed. Returns true if
-  // we decided to resize the table.
-  bool ResizeTableIfNecessary();
-
-  // Resizes the table (growing or shrinking) as necessary to accomodate the
-  // current count.
-  void ResizeTable(int32 new_size);
-
-  // Returns the desired table size for |item_count| URLs.
-  uint32 NewTableSizeForCount(int32 item_count) const;
-
-  // Computes the table load as fraction. For example, if 1/4 of the entries are
-  // full, this value will be 0.25
-  float ComputeTableLoad() const {
-    return static_cast<float>(used_items_) / static_cast<float>(table_length_);
-  }
-
-  // Initializes a rebuild of the visited link database based on the browser
-  // history. This will set table_builder_ while working, and there should not
-  // already be a rebuild in place when called. See the definition for more
-  // details on how this works.
-  //
-  // Returns true on success. Failure means we're not attempting to rebuild
-  // the database because something failed.
-  bool RebuildTableFromDelegate();
-
-  // Callback that the table rebuilder uses when the rebuild is complete.
-  // |success| is true if the fingerprint generation succeeded, in which case
-  // |fingerprints| will contain the computed fingerprints. On failure, there
-  // will be no fingerprints.
-  void OnTableRebuildComplete(bool success,
-                              const std::vector<Fingerprint>& fingerprints);
-
-  // Increases or decreases the given hash value by one, wrapping around as
-  // necessary. Used for probing.
-  inline Hash IncrementHash(Hash hash) {
-    if (hash >= table_length_ - 1)
-      return 0;  // Wrap around.
-    return hash + 1;
-  }
-  inline Hash DecrementHash(Hash hash) {
-    if (hash <= 0)
-      return table_length_ - 1;  // Wrap around.
-    return hash - 1;
-  }
-
-#ifndef NDEBUG
-  // Indicates whether any asynchronous operation has ever been completed.
-  // We do some synchronous reads that require that no asynchronous operations
-  // are pending, yet we don't track whether they have been completed. This
-  // flag is a sanity check that these reads only happen before any
-  // asynchronous writes have been fired.
-  bool posted_asynchronous_operation_;
-#endif
-
-  // Reference to the browser context that this object belongs to
-  // (it knows the path to where the data is stored)
-  content::BrowserContext* browser_context_;
-
-  // Client owns the delegate and is responsible for it being valid through
-  // the life time this VisitedLinkMaster.
-  VisitedLinkDelegate* delegate_;
-
-  // VisitedLinkEventListener to handle incoming events.
-  scoped_ptr<Listener> listener_;
-
-  // Lazily initialized sequence token for posting file tasks.
-  base::SequencedWorkerPool::SequenceToken sequence_token_;
-
-  // When non-NULL, indicates we are in database rebuild mode and points to
-  // the class collecting fingerprint information from the history system.
-  // The pointer is owned by this class, but it must remain valid while the
-  // history query is running. We must only delete it when the query is done.
-  scoped_refptr<TableBuilder> table_builder_;
-
-  // Indicates URLs added and deleted since we started rebuilding the table.
-  std::set<Fingerprint> added_since_rebuild_;
-  std::set<Fingerprint> deleted_since_rebuild_;
-
-  // TODO(brettw) Support deletion, we need to track whether anything was
-  // deleted during the rebuild here. Then we should delete any of these
-  // entries from the complete table later.
-  // std::vector<Fingerprint> removed_since_rebuild_;
-
-  // The currently open file with the table in it. This may be NULL if we're
-  // rebuilding and haven't written a new version yet. Writing to the file may
-  // be safely ignored in this case. Also |file_| may be non-NULL but point to
-  // a NULL pointer. That would mean that opening of the file is already
-  // scheduled in a background thread and any writing to the file can also be
-  // scheduled to the background thread as it's guaranteed to be executed after
-  // the opening.
-  // The class owns both the |file_| pointer and the pointer pointed
-  // by |*file_|.
-  FILE** file_;
-
-  // Shared memory consists of a SharedHeader followed by the table.
-  base::SharedMemory *shared_memory_;
-
-  // When we generate new tables, we increment the serial number of the
-  // shared memory object.
-  int32 shared_memory_serial_;
-
-  // Number of non-empty items in the table, used to compute fullness.
-  int32 used_items_;
-
-  // Testing values -----------------------------------------------------------
-  //
-  // The following fields exist for testing purposes. They are not used in
-  // release builds. It'd be nice to eliminate them in release builds, but we
-  // don't want to change the signature of the object between the unit test and
-  // regular builds. Instead, we just have "default" values that these take
-  // in release builds that give "regular" behavior.
-
-  // Overridden database file name for testing
-  FilePath database_name_override_;
-
-  // When nonzero, overrides the table size for new databases for testing
-  int32 table_size_override_;
-
-  // When set, indicates the task that should be run after the next rebuild from
-  // history is complete.
-  base::Closure rebuild_complete_task_;
-
-  // Set to prevent us from attempting to rebuild the database from global
-  // history if we have an error opening the file. This is used for testing,
-  // will be false in production.
-  bool suppress_rebuild_;
-
-  DISALLOW_COPY_AND_ASSIGN(VisitedLinkMaster);
-};
-
-// NOTE: These methods are defined inline here, so we can share the compilation
-//       of visitedlink_master.cc between the browser and the unit/perf tests.
-
-#if defined(UNIT_TEST) || defined(PERF_TEST) || !defined(NDEBUG)
-inline void VisitedLinkMaster::DebugValidate() {
-  int32 used_count = 0;
-  for (int32 i = 0; i < table_length_; i++) {
-    if (hash_table_[i])
-      used_count++;
-  }
-  DCHECK_EQ(used_count, used_items_);
-}
-#endif
-
-#endif  // CHROME_BROWSER_VISITEDLINK_VISITEDLINK_MASTER_H_