[fsp] First part of support for reading files.

chrome/browser/chromeos/file_system_provider/provided_file_system_interface.h

 // Copyright 2014 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_CHROMEOS_FILE_SYSTEM_PROVIDER_PROVIDED_FILE_SYSTEM_INTERFACE_H_
 #define CHROME_BROWSER_CHROMEOS_FILE_SYSTEM_PROVIDER_PROVIDED_FILE_SYSTEM_INTERFACE_H_
 
+#include "base/callback.h"
+#include "base/files/file.h"
+#include "base/files/file_path.h"
 #include "webkit/browser/fileapi/async_file_util.h"
 
 class EventRouter;
 
-namespace base {
-class FilePath;
-}  // namespace base
+namespace net {
+class IOBuffer;
+}  // namespace net
 
 namespace chromeos {
 namespace file_system_provider {
 
 class ProvidedFileSystemInfo;
 class RequestManager;
 
 // Interface for a provided file system. Acts as a proxy between providers
 // and clients.
 // TODO(mtomasz): Add more methods once implemented.
 class ProvidedFileSystemInterface {
  public:
   typedef base::Callback<void(int file_handle, base::File::Error result)>
       OpenFileCallback;
 
+  typedef base::Callback<
+      void(int chunk_length, bool has_next, base::File::Error result)>
+      ReadChunkReceivedCallback;
+
   // Mode of opening a file. Used by OpenFile().
   enum OpenFileMode { OPEN_FILE_MODE_READ, OPEN_FILE_MODE_WRITE };
 
   virtual ~ProvidedFileSystemInterface() {}
 
   // Requests unmounting of the file system. The callback is called when the
   // request is accepted or rejected, with an error code.
   virtual void RequestUnmount(
       const fileapi::AsyncFileUtil::StatusCallback& callback) = 0;
 
   // Requests metadata of the passed |entry_path|. It can be either a file
   // or a directory.
   virtual void GetMetadata(
       const base::FilePath& entry_path,
       const fileapi::AsyncFileUtil::GetFileInfoCallback& callback) = 0;
 
   // Requests enumerating entries from the passed |directory_path|. The callback
-  // can be called multiple times until either an error is returned or the
-  // has_more field is set to false.
+  // can be called multiple times until |has_more| is set to false.
   virtual void ReadDirectory(
       const base::FilePath& directory_path,
       const fileapi::AsyncFileUtil::ReadDirectoryCallback& callback) = 0;
 
   // Requests opening a file at |file_path|. If |create| is set to true, it will
   // create a file and return success in case it didn't exist.
   virtual void OpenFile(const base::FilePath& file_path,
                         OpenFileMode mode,
                         bool create,
                         const OpenFileCallback& callback) = 0;
 
   // Requests closing a file, previously opened with OpenFile() as a file with
   // |file_handle|. For either succes or error |callback| must be called.
   virtual void CloseFile(
       int file_handle,
       const fileapi::AsyncFileUtil::StatusCallback& callback) = 0;
 
+  // Requests reading a file previously opened with |file_handle|. The callback
+  // can be called multiple times until |has_more| is set to false. On success
+  // it should return |length| bytes starting from |offset| in total. It can
+  // return less only in case EOF is encountered.
+  virtual void ReadFile(int file_handle,
+                        net::IOBuffer* buffer,
+                        int64 offset,
+                        int length,
+                        const ReadChunkReceivedCallback& callback) = 0;
+
   // Returns a provided file system info for this file system.
   virtual const ProvidedFileSystemInfo& GetFileSystemInfo() const = 0;
 
   // Returns a request manager for the file system.
   virtual RequestManager* GetRequestManager() = 0;
 };
 
 }  // namespace file_system_provider
 }  // namespace chromeos
 
 #endif  // CHROME_BROWSER_CHROMEOS_FILE_SYSTEM_PROVIDER_PROVIDED_FILE_SYSTEM_INTERFACE_H_