storage/browser/fileapi/file_stream_reader.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 #ifndef STORAGE_BLOB_FILE_STREAM_READER_H_
   6 #define STORAGE_BLOB_FILE_STREAM_READER_H_
   7
   8 #include "base/basictypes.h"
   9 #include "base/compiler_specific.h"
  10 #include "base/files/file.h"
  11 #include "net/base/completion_callback.h"
  12 #include "storage/browser/storage_browser_export.h"
  13
  14 namespace base {
  15 class FilePath;
  16 class TaskRunner;
  17 class Time;
  18 }
  19
  20 namespace net {
  21 class IOBuffer;
  22 }
  23
  24 namespace storage {
  25 class FileSystemContext;
  26 class FileSystemURL;
  27 }
  28
  29 namespace storage {
  30
  31 // A generic interface for reading a file-like object.
  32 class FileStreamReader {
  33  public:
  34   // Creates a new FileReader for a local file |file_path|.
  35   // |initial_offset| specifies the offset in the file where the first read
  36   // should start.  If the given offset is out of the file range any
  37   // read operation may error out with net::ERR_REQUEST_RANGE_NOT_SATISFIABLE.
  38   // |expected_modification_time| specifies the expected last modification
  39   // If the value is non-null, the reader will check the underlying file's
  40   // actual modification time to see if the file has been modified, and if
  41   // it does any succeeding read operations should fail with
  42   // ERR_UPLOAD_FILE_CHANGED error.
  43   STORAGE_EXPORT static FileStreamReader*
  44       CreateForLocalFile(base::TaskRunner* task_runner,
  45                          const base::FilePath& file_path,
  46                          int64 initial_offset,
  47                          const base::Time& expected_modification_time);
  48
  49   // Creates a new reader for a filesystem URL |url| form |initial_offset|.
  50   // |expected_modification_time| specifies the expected last modification if
  51   // the value is non-null, the reader will check the underlying file's actual
  52   // modification time to see if the file has been modified, and if it does any
  53   // succeeding read operations should fail with ERR_UPLOAD_FILE_CHANGED error.
  54   STORAGE_EXPORT static FileStreamReader*
  55       CreateForFileSystemFile(storage::FileSystemContext* context,
  56                               const storage::FileSystemURL& url,
  57                               int64 initial_offset,
  58                               const base::Time& expected_modification_time);
  59
  60   // Verify if the underlying file has not been modified.
  61   STORAGE_EXPORT static bool VerifySnapshotTime(
  62       const base::Time& expected_modification_time,
  63       const base::File::Info& file_info);
  64
  65   // It is valid to delete the reader at any time.  If the stream is deleted
  66   // while it has a pending read, its callback will not be called.
  67   virtual ~FileStreamReader() {}
  68
  69   // Reads from the current cursor position asynchronously.
  70   //
  71   // Up to buf_len bytes will be copied into buf.  (In other words, partial
  72   // reads are allowed.)  Returns the number of bytes copied, 0 if at
  73   // end-of-file, or an error code if the operation could not be performed.
  74   // If the read could not complete synchronously, then ERR_IO_PENDING is
  75   // returned, and the callback will be run on the thread where Read()
  76   // was called, when the read has completed.
  77   //
  78   // It is invalid to call Read while there is an in-flight Read operation.
  79   //
  80   // If the stream is deleted while it has an in-flight Read operation
  81   // |callback| will not be called.
  82   virtual int Read(net::IOBuffer* buf, int buf_len,
  83                    const net::CompletionCallback& callback) = 0;
  84
  85   // Returns the length of the file if it could successfully retrieve the
  86   // file info *and* its last modification time equals to
  87   // expected modification time (rv >= 0 cases).
  88   // Otherwise, a negative error code is returned (rv < 0 cases).
  89   // If the stream is deleted while it has an in-flight GetLength operation
  90   // |callback| will not be called.
  91   // Note that the return type is int64 to return a larger file's size (a file
  92   // larger than 2G) but an error code should fit in the int range (may be
  93   // smaller than int64 range).
  94   virtual int64 GetLength(const net::Int64CompletionCallback& callback) = 0;
  95 };
  96
  97 }  // namespace storage
  98
  99 #endif  // STORAGE_BLOB_FILE_STREAM_READER_H_