net/disk_cache/file.h

   1 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
   2 // Use of this source code is governed by a BSD-style license that can be
   3 // found in the LICENSE file.
   4
   5 // See net/disk_cache/disk_cache.h for the public interface of the cache.
   6
   7 #ifndef NET_DISK_CACHE_FILE_H_
   8 #define NET_DISK_CACHE_FILE_H_
   9
  10 #include "base/memory/ref_counted.h"
  11 #include "base/platform_file.h"
  12 #include "net/base/net_export.h"
  13
  14 namespace base {
  15 class FilePath;
  16 }
  17
  18 namespace disk_cache {
  19
  20 // This interface is used to support asynchronous ReadData and WriteData calls.
  21 class FileIOCallback {
  22  public:
  23   // Notified of the actual number of bytes read or written. This value is
  24   // negative if an error occurred.
  25   virtual void OnFileIOComplete(int bytes_copied) = 0;
  26
  27  protected:
  28   virtual ~FileIOCallback() {}
  29 };
  30
  31 // Simple wrapper around a file that allows asynchronous operations.
  32 class NET_EXPORT_PRIVATE File : public base::RefCounted<File> {
  33   friend class base::RefCounted<File>;
  34  public:
  35   File();
  36   // mixed_mode set to true enables regular synchronous operations for the file.
  37   explicit File(bool mixed_mode);
  38
  39   // Initializes the object to use the passed in file instead of opening it with
  40   // the Init() call. No asynchronous operations can be performed with this
  41   // object.
  42   explicit File(base::PlatformFile file);
  43
  44   // Initializes the object to point to a given file. The file must aready exist
  45   // on disk, and allow shared read and write.
  46   bool Init(const base::FilePath& name);
  47
  48   // Returns the handle or file descriptor.
  49   base::PlatformFile platform_file() const;
  50
  51   // Returns true if the file was opened properly.
  52   bool IsValid() const;
  53
  54   // Performs synchronous IO.
  55   bool Read(void* buffer, size_t buffer_len, size_t offset);
  56   bool Write(const void* buffer, size_t buffer_len, size_t offset);
  57
  58   // Performs asynchronous IO. callback will be called when the IO completes,
  59   // as an APC on the thread that queued the operation.
  60   bool Read(void* buffer, size_t buffer_len, size_t offset,
  61             FileIOCallback* callback, bool* completed);
  62   bool Write(const void* buffer, size_t buffer_len, size_t offset,
  63              FileIOCallback* callback, bool* completed);
  64
  65   // Sets the file's length. The file is truncated or extended with zeros to
  66   // the new length.
  67   bool SetLength(size_t length);
  68   size_t GetLength();
  69
  70   // Blocks until |num_pending_io| IO operations complete.
  71   static void WaitForPendingIO(int* num_pending_io);
  72
  73   // Drops current pending operations without waiting for them to complete.
  74   static void DropPendingIO();
  75
  76  protected:
  77   virtual ~File();
  78
  79   // Performs the actual asynchronous write. If notify is set and there is no
  80   // callback, the call will be re-synchronized.
  81   bool AsyncWrite(const void* buffer, size_t buffer_len, size_t offset,
  82                   FileIOCallback* callback, bool* completed);
  83
  84  private:
  85   bool init_;
  86   bool mixed_;
  87   base::PlatformFile platform_file_;  // Regular, asynchronous IO handle.
  88   base::PlatformFile sync_platform_file_;  // Synchronous IO handle.
  89
  90   DISALLOW_COPY_AND_ASSIGN(File);
  91 };
  92
  93 }  // namespace disk_cache
  94
  95 #endif  // NET_DISK_CACHE_FILE_H_