Disk cache: Remove all non essential synchronization from the cache destructor.

net/disk_cache/disk_cache.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.
 
 // Defines the public interface of the disk cache. For more details see
 // http://dev.chromium.org/developers/design-documents/network-stack/disk-cache
 
 #ifndef NET_DISK_CACHE_DISK_CACHE_H_
 #define NET_DISK_CACHE_DISK_CACHE_H_
 #pragma once
@@ skipping 40 matching lines @@
 // completes (the callback is notified).
 NET_EXPORT int CreateCacheBackend(net::CacheType type, const FilePath& path,
                                   int max_bytes, bool force,
                                   base::MessageLoopProxy* thread,
                                   net::NetLog* net_log, Backend** backend,
                                   const net::CompletionCallback& callback);
 
 // The root interface for a disk cache instance.
 class NET_EXPORT Backend {
  public:
+  typedef net::CompletionCallback CompletionCallback;

[gavinp, 2012/03/16 17:31:35]

This is a great idea! Unfortunately, all of the namespace qualification changes
are making this CL too hard for me to read.

+
   // If the backend is destroyed when there are operations in progress (any
   // callback that has not been invoked yet), this method cancels said
   // operations so the callbacks are not invoked, possibly leaving the work
   // half way (for instance, dooming just a few entries). Note that pending IO
   // for a given Entry (as opposed to the Backend) will still generate a
   // callback from within this method.
   virtual ~Backend() {}
 
   // Returns the number of entries in the cache.
   virtual int32 GetEntryCount() const = 0;
 
   // Opens an existing entry. Upon success, |entry| holds a pointer to an Entry
   // object representing the specified disk cache entry. When the entry pointer
   // is no longer needed, its Close method should be called. The return value is
   // a net error code. If this method returns ERR_IO_PENDING, the |callback|
   // will be invoked when the entry is available. The pointer to receive the
   // |entry| must remain valid until the operation completes.
   virtual int OpenEntry(const std::string& key, Entry** entry,
-                        const net::CompletionCallback& callback) = 0;
+                        const CompletionCallback& callback) = 0;
 
   // Creates a new entry. Upon success, the out param holds a pointer to an
   // Entry object representing the newly created disk cache entry. When the
   // entry pointer is no longer needed, its Close method should be called. The
   // return value is a net error code. If this method returns ERR_IO_PENDING,
   // the |callback| will be invoked when the entry is available. The pointer to
   // receive the |entry| must remain valid until the operation completes.
   virtual int CreateEntry(const std::string& key, Entry** entry,
-                          const net::CompletionCallback& callback) = 0;
+                          const CompletionCallback& callback) = 0;
 
   // Marks the entry, specified by the given key, for deletion. The return value
   // is a net error code. If this method returns ERR_IO_PENDING, the |callback|
   // will be invoked after the entry is doomed.
   virtual int DoomEntry(const std::string& key,
-                        const net::CompletionCallback& callback) = 0;
+                        const CompletionCallback& callback) = 0;
 
   // Marks all entries for deletion. The return value is a net error code. If
   // this method returns ERR_IO_PENDING, the |callback| will be invoked when the
   // operation completes.
-  virtual int DoomAllEntries(const net::CompletionCallback& callback) = 0;
+  virtual int DoomAllEntries(const CompletionCallback& callback) = 0;
 
   // Marks a range of entries for deletion. This supports unbounded deletes in
   // either direction by using null Time values for either argument. The return
   // value is a net error code. If this method returns ERR_IO_PENDING, the
   // |callback| will be invoked when the operation completes.
   virtual int DoomEntriesBetween(const base::Time initial_time,
                                  const base::Time end_time,
-                                 const net::CompletionCallback& callback) = 0;
+                                 const CompletionCallback& callback) = 0;
 
   // Marks all entries accessed since |initial_time| for deletion. The return
   // value is a net error code. If this method returns ERR_IO_PENDING, the
   // |callback| will be invoked when the operation completes.
   virtual int DoomEntriesSince(const base::Time initial_time,
-                               const net::CompletionCallback& callback) = 0;
+                               const CompletionCallback& callback) = 0;
 
   // Enumerates the cache. Initialize |iter| to NULL before calling this method
   // the first time. That will cause the enumeration to start at the head of
   // the cache. For subsequent calls, pass the same |iter| pointer again without
   // changing its value. This method returns ERR_FAILED when there are no more
   // entries to enumerate. When the entry pointer is no longer needed, its
   // Close method should be called. The return value is a net error code. If
   // this method returns ERR_IO_PENDING, the |callback| will be invoked when the
   // |next_entry| is available. The pointer to receive the |next_entry| must
   // remain valid until the operation completes.
   //
   // NOTE: This method does not modify the last_used field of the entry, and
   // therefore it does not impact the eviction ranking of the entry.
   virtual int OpenNextEntry(void** iter, Entry** next_entry,
-                            const net::CompletionCallback& callback) = 0;
+                            const CompletionCallback& callback) = 0;
 
   // Releases iter without returning the next entry. Whenever OpenNextEntry()
   // returns true, but the caller is not interested in continuing the
   // enumeration by calling OpenNextEntry() again, the enumeration must be
   // ended by calling this method with iter returned by OpenNextEntry().
   virtual void EndEnumeration(void** iter) = 0;
 
   // Return a list of cache statistics.
   virtual void GetStats(
       std::vector<std::pair<std::string, std::string> >* stats) = 0;
 
   // Called whenever an external cache in the system reuses the resource
   // referred to by |key|.
   virtual void OnExternalCacheHit(const std::string& key) = 0;
 };
 
 // This interface represents an entry in the disk cache.
 class NET_EXPORT Entry {
  public:
+  typedef net::CompletionCallback CompletionCallback;
+  typedef net::IOBuffer IOBuffer;
+
   // Marks this cache entry for deletion.
   virtual void Doom() = 0;
 
   // Releases this entry. Calling this method does not cancel pending IO
   // operations on this entry. Even after the last reference to this object has
   // been released, pending completion callbacks may be invoked.
   virtual void Close() = 0;
 
   // Returns the key associated with this cache entry.
   virtual std::string GetKey() const = 0;
@@ skipping 11 matching lines @@
   // completion_callback is null, then this call blocks until the read
   // operation is complete.  Otherwise, completion_callback will be
   // called on the current thread once the read completes.  Returns the
   // number of bytes read or a network error code. If a completion callback is
   // provided then it will be called if this function returns ERR_IO_PENDING,
   // and a reference to |buf| will be retained until the callback is called.
   // Note that the callback will be invoked in any case, even after Close has
   // been called; in other words, the caller may close this entry without
   // having to wait for all the callbacks, and still rely on the cleanup
   // performed from the callback code.
-  virtual int ReadData(int index, int offset, net::IOBuffer* buf, int buf_len,
-                       const net::CompletionCallback& callback) = 0;
+  virtual int ReadData(int index, int offset, IOBuffer* buf, int buf_len,
+                       const CompletionCallback& callback) = 0;
 
   // Copies cache data from the given buffer of length |buf_len|.  If
   // completion_callback is null, then this call blocks until the write
   // operation is complete.  Otherwise, completion_callback will be
   // called on the current thread once the write completes.  Returns the
   // number of bytes written or a network error code. If a completion callback
   // is provided then it will be called if this function returns ERR_IO_PENDING,
   // and a reference to |buf| will be retained until the callback is called.
   // Note that the callback will be invoked in any case, even after Close has
   // been called; in other words, the caller may close this entry without
   // having to wait for all the callbacks, and still rely on the cleanup
   // performed from the callback code.
   // If truncate is true, this call will truncate the stored data at the end of
   // what we are writing here.
-  virtual int WriteData(int index, int offset, net::IOBuffer* buf, int buf_len,
-                        const net::CompletionCallback& callback,
+  virtual int WriteData(int index, int offset, IOBuffer* buf, int buf_len,
+                        const CompletionCallback& callback,
                         bool truncate) = 0;
 
   // Sparse entries support:
   //
   // A Backend implementation can support sparse entries, so the cache keeps
   // track of which parts of the entry have been written before. The backend
   // will never return data that was not written previously, so reading from
   // such region will return 0 bytes read (or actually the number of bytes read
   // before reaching that region).
   //
@@ skipping 26 matching lines @@
   // requirement includes the case when an entry is closed while some operation
   // is in progress and another object is instantiated; any IO operation will
   // fail while the previous operation is still in-flight. In order to deal with
   // this requirement, the caller could either wait until the operation
   // completes before closing the entry, or call CancelSparseIO() before closing
   // the entry, and call ReadyForSparseIO() on the new entry and wait for the
   // callback before issuing new operations.
 
   // Behaves like ReadData() except that this method is used to access sparse
   // entries.
-  virtual int ReadSparseData(int64 offset, net::IOBuffer* buf, int buf_len,
-                             const net::CompletionCallback& callback) = 0;
+  virtual int ReadSparseData(int64 offset, IOBuffer* buf, int buf_len,
+                             const CompletionCallback& callback) = 0;
 
   // Behaves like WriteData() except that this method is used to access sparse
   // entries. |truncate| is not part of this interface because a sparse entry
   // is not expected to be reused with new data. To delete the old data and
   // start again, or to reduce the total size of the stream data (which implies
   // that the content has changed), the whole entry should be doomed and
   // re-created.
-  virtual int WriteSparseData(int64 offset, net::IOBuffer* buf, int buf_len,
-                              const net::CompletionCallback& callback) = 0;
+  virtual int WriteSparseData(int64 offset, IOBuffer* buf, int buf_len,
+                              const CompletionCallback& callback) = 0;
 
   // Returns information about the currently stored portion of a sparse entry.
   // |offset| and |len| describe a particular range that should be scanned to
   // find out if it is stored or not. |start| will contain the offset of the
   // first byte that is stored within this range, and the return value is the
   // minimum number of consecutive stored bytes. Note that it is possible that
   // this entry has stored more than the returned value. This method returns a
   // net error code whenever the request cannot be completed successfully. If
   // this method returns ERR_IO_PENDING, the |callback| will be invoked when the
   // operation completes, and |start| must remain valid until that point.
   virtual int GetAvailableRange(int64 offset, int len, int64* start,
-                                const net::CompletionCallback& callback) = 0;
+                                const CompletionCallback& callback) = 0;
 
   // Returns true if this entry could be a sparse entry or false otherwise. This
   // is a quick test that may return true even if the entry is not really
   // sparse. This method doesn't modify the state of this entry (it will not
   // create sparse tracking data). GetAvailableRange or ReadSparseData can be
   // used to perform a definitive test of whether an existing entry is sparse or
   // not, but that method may modify the current state of the entry (making it
   // sparse, for instance). The purpose of this method is to test an existing
   // entry, but without generating actual IO to perform a thorough check.
   virtual bool CouldBeSparse() const = 0;
 
   // Cancels any pending sparse IO operation (if any). The completion callback
   // of the operation in question will still be called when the operation
   // finishes, but the operation will finish sooner when this method is used.
   virtual void CancelSparseIO() = 0;
 
   // Returns OK if this entry can be used immediately. If that is not the
   // case, returns ERR_IO_PENDING and invokes the provided callback when this
   // entry is ready to use. This method always returns OK for non-sparse
   // entries, and returns ERR_IO_PENDING when a previous operation was cancelled
   // (by calling CancelSparseIO), but the cache is still busy with it. If there
   // is a pending operation that has not been cancelled, this method will return
   // OK although another IO operation cannot be issued at this time; in this
   // case the caller should just wait for the regular callback to be invoked
   // instead of using this method to provide another callback.
   //
   // Note that CancelSparseIO may have been called on another instance of this
   // object that refers to the same physical disk entry.
   // Note: This method is deprecated.
-  virtual int ReadyForSparseIO(
-      const net::CompletionCallback& completion_callback) = 0;
+  virtual int ReadyForSparseIO(const CompletionCallback& callback) = 0;
 
  protected:
   virtual ~Entry() {}
 };
 
 }  // namespace disk_cache
 
 #endif  // NET_DISK_CACHE_DISK_CACHE_H_