Disk cache: Reference CL for the implementation of file format version 3.

net/disk_cache/v3/entry_impl_v3.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 NET_DISK_CACHE_V3_ENTRY_IMPL_V3_H_
+#define NET_DISK_CACHE_V3_ENTRY_IMPL_V3_H_
+
+#include <queue>
+#include <string>
+
+#include "base/memory/scoped_ptr.h"
+#include "net/base/net_log.h"
+#include "net/disk_cache/disk_cache.h"
+#include "net/disk_cache/storage_block.h"
+#include "net/disk_cache/v3/disk_format_v3.h"
+
+namespace disk_cache {
+
+class BackendImplV3;
+class SparseControlV3;
+
+//typedef StorageBlock<EntryRecord> CacheEntryBlockV3;//?
+//typedef StorageBlock<ShortEntryRecord> CacheShortEntryBlock;
+
+// This class implements the Entry interface. An object of this
+// class represents a single entry on the cache.
+class NET_EXPORT_PRIVATE EntryImplV3
+    : public Entry,
+      public base::RefCounted<EntryImplV3> {
+  friend class base::RefCounted<EntryImplV3>;
+  friend class SparseControlV3;
+ public:
+  enum Operation {
+    kRead,
+    kWrite,
+    kSparseRead,
+    kSparseWrite,
+    kAsyncIO,
+    kReadAsync1,
+    kWriteAsync1
+  };
+
+  EntryImplV3(BackendImplV3* backend, Addr address, bool read_only);
+  EntryImplV3(BackendImplV3* backend, Addr address, const std::string& key,
+              scoped_ptr<EntryRecord> record);
+  EntryImplV3(BackendImplV3* backend, Addr address, const std::string& key,
+              scoped_ptr<ShortEntryRecord> record);
+
+  // Performs the initialization of a EntryImplV3 that will be added to the
+  // cache.
+  void CreateEntry(const std::string& key, uint32 hash,
+                   ShortEntryRecord* old_info);
+  void OnOpenEntry();
+
+  scoped_ptr<ShortEntryRecord> GetShortEntryRecord();
+
+  uint32 GetHash() const;
+  Addr GetAddress() const;
+  int GetReuseCounter() const;
+  void SetReuseCounter(int count);
+  int GetRefetchCounter() const;
+  void SetRefetchCounter(int count);
+  
+  // Returns true if this entry matches the lookup arguments.
+  bool IsSameEntry(const std::string& key, uint32 hash);
+
+  // Permamently destroys this entry.
+  void InternalDoom();
+
+  // Returns false if the entry is clearly invalid.
+  bool SanityCheck();
+  bool DataSanityCheck();
+  static bool BasicSanityCheck(const EntryRecord& record);
+  static bool DeletedSanityCheck(const ShortEntryRecord& record);
+
+  // Attempts to make this entry reachable though the key.
+  void FixForDelete();
+
+  // Set the access times for this entry. This method provides support for
+  // the upgrade tool.
+  void SetTimes(base::Time last_used, base::Time last_modified);
+
+  // Logs a begin event and enables logging for the EntryImplV3.  Will also cause
+  // an end event to be logged on destruction.  The EntryImplV3 must have its key
+  // initialized before this is called.  |created| is true if the Entry was
+  // created rather than opened.
+  void BeginLogging(net::NetLog* net_log, bool created);
+
+  const net::BoundNetLog& net_log() const;
+
+  void NotifyDestructionForTest(const CompletionCallback& callback);
+
+  // Entry interface.
+  virtual void Doom() OVERRIDE;
+  virtual void Close() OVERRIDE;
+  virtual std::string GetKey() const OVERRIDE;
+  virtual base::Time GetLastUsed() const OVERRIDE;
+  virtual base::Time GetLastModified() const OVERRIDE;
+  virtual int32 GetDataSize(int index) const OVERRIDE;
+  virtual int ReadData(int index, int offset, IOBuffer* buf, int buf_len,
+                       const CompletionCallback& callback) OVERRIDE;
+  virtual int WriteData(int index, int offset, IOBuffer* buf, int buf_len,
+                        const CompletionCallback& callback,
+                        bool truncate) OVERRIDE;
+  virtual int ReadSparseData(int64 offset, IOBuffer* buf, int buf_len,
+                             const CompletionCallback& callback) OVERRIDE;
+  virtual int WriteSparseData(int64 offset, IOBuffer* buf, int buf_len,
+                              const CompletionCallback& callback) OVERRIDE;
+  virtual int GetAvailableRange(int64 offset, int len, int64* start,
+                                const CompletionCallback& callback) OVERRIDE;
+  virtual bool CouldBeSparse() const OVERRIDE;
+  virtual void CancelSparseIO() OVERRIDE;
+  virtual int ReadyForSparseIO(const CompletionCallback& callback) OVERRIDE;
+
+ private:
+  enum {
+     kNumStreams = 3
+  };
+  class UserBuffer;
+
+  enum OperationAction {
+    PENDING_READ,
+    PENDING_WRITE,
+    PENDING_FLUSH,
+    PENDING_CLEANUP,
+    PENDING_DONE
+  };
+  struct PendingOperation {
+    OperationAction action;
+    int index;
+    int offset;
+    scoped_refptr<IOBuffer> buf;
+    int buf_len;
+    CompletionCallback callback;
+    bool truncate;
+  };
+  typedef std::queue<PendingOperation> PendingOperations;
+
+  virtual ~EntryImplV3();
+
+  void Cleanup();
+
+  void WriteKey();
+
+  // Do all the work for ReadDataImpl and WriteDataImpl.  Implemented as
+  // separate functions to make logging of results simpler.
+  int ReadDataImpl(int index, int offset, IOBuffer* buf,
+                       int buf_len, PendingOperation* operation,
+                       const CompletionCallback& callback);
+  int WriteDataImpl(int index, int offset, IOBuffer* buf, int buf_len,
+                        PendingOperation* operation,
+                        const CompletionCallback& callback, bool truncate);
+
+  // Initializes the storage for an internal or external data block.
+  bool CreateDataBlock(int index, int size);
+
+  // Initializes the storage for an internal or external generic block.
+  bool CreateBlock(int size, Addr* address);
+
+  // Deletes the data pointed by address.
+  // Note that most likely the caller should delete (and store) the reference to
+  // |address| *before* calling this method because we don't want to have an
+  // entry using an address that is already free.
+  void DeleteData(Addr address);
+
+  // Updates ranking information.
+  void UpdateRank(bool modified);
+
+  // Deletes this entry from disk.
+  bool DeleteEntryData();
+
+  // Prepares the target file or buffer for a write of buf_len bytes at the
+  // given offset.
+  int PrepareTarget(int index, int offset, int buf_len, bool truncate);
+
+  // Adjusts the internal buffer and file handle for a write that truncates this
+  // stream.
+  int HandleTruncation(int index, int offset, int buf_len);
+
+  bool IsSimpleWrite(int index, int offset, int buf_len);
+  int HandleOldData(int index, int offset, int buf_len);
+
+  // Makes sure that the internal buffer can handle the a write of |buf_len|
+  // bytes to |offset|.
+  int PrepareBuffer(int index, int offset, int buf_len);
+
+  // Flushes the in-memory data to the backing storage. The data destination
+  // is determined based on the current data length and |min_len|.
+  int Flush(int index, int min_len);
+
+  // Updates the size of a given data stream.
+  void UpdateSize(int index, int old_size, int new_size);
+
+  void WriteEntryData();
+
+  // Adds the provided |flags| to the current EntryFlags for this entry.
+  void SetEntryFlags(uint32 flags);
+
+  // Returns the current EntryFlags for this entry.
+  uint32 GetEntryFlags();
+
+  void OnEntryModified();
+
+  int GetAdjustedSize(int index, int real_size) const;
+
+  // Gets the data stored at the given index. If the information is in memory,
+  // a buffer will be allocated and the data will be copied to it (the caller
+  // can find out the size of the buffer before making this call). Otherwise,
+  // the cache address of the data will be returned, and that address will be
+  // removed from the regular book keeping of this entry so the caller is
+  // responsible for deleting the block (or file) from the backing store at some
+  // point; there is no need to report any storage-size change, only to do the
+  // actual cleanup.
+  void GetData(int index, scoped_refptr<IOBuffer>* buffer, Addr* address);
+
+  // Generates a histogram for the time spent working on this operation.
+  void ReportIOTime(Operation op, const base::TimeTicks& start);
+
+  // Logs this entry to the internal trace buffer.
+  void Log(const char* msg);
+
+  void OnIOComplete(int result);
+
+  scoped_ptr<EntryRecord> entry_;  // Basic record for this entry.
+  scoped_ptr<ShortEntryRecord> short_entry_;  // Valid for evicted entries.
+  base::WeakPtr<BackendImplV3> backend_;  // Back pointer to the cache.
+  scoped_ptr<UserBuffer> user_buffers_[kNumStreams];  // Stores user data.
+  // Files to store external user data and key.
+  //scoped_refptr<File> files_[kNumStreams + 1];
+  mutable std::string key_;           // Copy of the key.
+  Addr address_;
+  int unreported_size_[kNumStreams];  // Bytes not reported yet to the backend.
+  int num_handles_;           // References held by "real" users.
+  bool doomed_;               // True if this entry was removed from the cache.
+  bool read_only_;
+  bool dirty_;                // True if there is something to write.
+  bool modified_;
+  scoped_ptr<SparseControlV3> sparse_;  // Support for sparse entries.
+  PendingOperations pending_operations_;
+  CompletionCallback callback_;
+  CompletionCallback destruction_callback_;
+
+  net::BoundNetLog net_log_;
+
+  DISALLOW_COPY_AND_ASSIGN(EntryImplV3);
+};
+
+}  // namespace disk_cache
+
+#endif  // NET_DISK_CACHE_V3_ENTRY_IMPL_V3_H_