storage/browser/fileapi/file_system_backend.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_BROWSER_FILEAPI_FILE_SYSTEM_BACKEND_H_
   6 #define STORAGE_BROWSER_FILEAPI_FILE_SYSTEM_BACKEND_H_
   7
   8 #include <limits>
   9 #include <string>
  10 #include <vector>
  11
  12 #include "base/callback_forward.h"
  13 #include "base/files/file.h"
  14 #include "base/files/file_path.h"
  15 #include "base/memory/scoped_ptr.h"
  16 #include "storage/browser/fileapi/file_permission_policy.h"
  17 #include "storage/browser/fileapi/open_file_system_mode.h"
  18 #include "storage/browser/fileapi/task_runner_bound_observer_list.h"
  19 #include "storage/browser/storage_browser_export.h"
  20 #include "storage/common/fileapi/file_system_types.h"
  21
  22 class GURL;
  23
  24 namespace storage {
  25
  26 class AsyncFileUtil;
  27 class CopyOrMoveFileValidatorFactory;
  28 class FileSystemURL;
  29 class FileStreamReader;
  30 class FileStreamWriter;
  31 class FileSystemContext;
  32 class FileSystemFileUtil;
  33 class FileSystemOperation;
  34 class FileSystemQuotaUtil;
  35 class WatcherManager;
  36
  37 // Callback to take GURL.
  38 typedef base::Callback<void(const GURL& url)> URLCallback;
  39
  40 // Maximum numer of bytes to be read by FileStreamReader classes. Used in
  41 // FileSystemBackend::CreateFileStreamReader(), when it's not known how many
  42 // bytes will be fetched in total.
  43 const int64 kMaximumLength = std::numeric_limits<int64>::max();
  44
  45 // An interface for defining a file system backend.
  46 //
  47 // NOTE: when you implement a new FileSystemBackend for your own
  48 // FileSystem module, please contact to kinuko@chromium.org.
  49 //
  50 class STORAGE_EXPORT FileSystemBackend {
  51  public:
  52   // Callback for InitializeFileSystem.
  53   typedef base::Callback<void(const GURL& root_url,
  54                               const std::string& name,
  55                               base::File::Error error)>
  56       OpenFileSystemCallback;
  57   virtual ~FileSystemBackend() {}
  58
  59   // Returns true if this filesystem backend can handle |type|.
  60   // One filesystem backend may be able to handle multiple filesystem types.
  61   virtual bool CanHandleType(FileSystemType type) const = 0;
  62
  63   // This method is called right after the backend is registered in the
  64   // FileSystemContext and before any other methods are called. Each backend can
  65   // do additional initialization which depends on FileSystemContext here.
  66   virtual void Initialize(FileSystemContext* context) = 0;
  67
  68   // Resolves the filesystem root URL and the name for the given |url|.
  69   // This verifies if it is allowed to request (or create) the filesystem and if
  70   // it can access (or create) the root directory.
  71   // If |mode| is CREATE_IF_NONEXISTENT calling this may also create the root
  72   // directory (and/or related database entries etc) for the filesystem if it
  73   // doesn't exist.
  74   virtual void ResolveURL(const FileSystemURL& url,
  75                           OpenFileSystemMode mode,
  76                           const OpenFileSystemCallback& callback) = 0;
  77
  78   // Returns the specialized AsyncFileUtil for this backend.
  79   virtual AsyncFileUtil* GetAsyncFileUtil(FileSystemType type) = 0;
  80
  81   // Returns the specialized WatcherManager for this backend.
  82   virtual WatcherManager* GetWatcherManager(FileSystemType type) = 0;
  83
  84   // Returns the specialized CopyOrMoveFileValidatorFactory for this backend
  85   // and |type|.  If |error_code| is File::FILE_OK and the result is NULL,
  86   // then no validator is required.
  87   virtual CopyOrMoveFileValidatorFactory* GetCopyOrMoveFileValidatorFactory(
  88       FileSystemType type, base::File::Error* error_code) = 0;
  89
  90   // Returns a new instance of the specialized FileSystemOperation for this
  91   // backend based on the given triplet of |origin_url|, |file_system_type|
  92   // and |virtual_path|. On failure to create a file system operation, set
  93   // |error_code| correspondingly.
  94   // This method is usually dispatched by
  95   // FileSystemContext::CreateFileSystemOperation.
  96   virtual FileSystemOperation* CreateFileSystemOperation(
  97       const FileSystemURL& url,
  98       FileSystemContext* context,
  99       base::File::Error* error_code) const = 0;
 100
 101   // Returns true if Blobs accessing |url| should use FileStreamReader.
 102   // If false, Blobs are accessed using a snapshot file by calling
 103   // AsyncFileUtil::CreateSnapshotFile.
 104   virtual bool SupportsStreaming(const FileSystemURL& url) const = 0;
 105
 106   // Returns true if specified |type| of filesystem can handle Copy()
 107   // of the files in the same file system instead of streaming
 108   // read/write implementation.
 109   virtual bool HasInplaceCopyImplementation(FileSystemType type) const = 0;
 110
 111   // Creates a new file stream reader for a given filesystem URL |url| with an
 112   // offset |offset|. |expected_modification_time| specifies the expected last
 113   // modification if the value is non-null, the reader will check the underlying
 114   // file's actual modification time to see if the file has been modified, and
 115   // if it does any succeeding read operations should fail with
 116   // ERR_UPLOAD_FILE_CHANGED error.
 117   // This method itself does *not* check if the given path exists and is a
 118   // regular file. At most |max_bytes_to_read| can be fetched from the file
 119   // stream reader.
 120   virtual scoped_ptr<storage::FileStreamReader> CreateFileStreamReader(
 121       const FileSystemURL& url,
 122       int64 offset,
 123       int64 max_bytes_to_read,
 124       const base::Time& expected_modification_time,
 125       FileSystemContext* context) const = 0;
 126
 127   // Creates a new file stream writer for a given filesystem URL |url| with an
 128   // offset |offset|.
 129   // This method itself does *not* check if the given path exists and is a
 130   // regular file.
 131   virtual scoped_ptr<FileStreamWriter> CreateFileStreamWriter(
 132       const FileSystemURL& url,
 133       int64 offset,
 134       FileSystemContext* context) const = 0;
 135
 136   // Returns the specialized FileSystemQuotaUtil for this backend.
 137   // This could return NULL if this backend does not support quota.
 138   virtual FileSystemQuotaUtil* GetQuotaUtil() = 0;
 139
 140   // Returns the update observer list for |type|. It may return NULL when no
 141   // observers are added.
 142   virtual const UpdateObserverList* GetUpdateObservers(
 143       FileSystemType type) const = 0;
 144
 145   // Returns the change observer list for |type|. It may return NULL when no
 146   // observers are added.
 147   virtual const ChangeObserverList* GetChangeObservers(
 148       FileSystemType type) const = 0;
 149
 150   // Returns the access observer list for |type|. It may return NULL when no
 151   // observers are added.
 152   virtual const AccessObserverList* GetAccessObservers(
 153       FileSystemType type) const = 0;
 154 };
 155
 156 // An interface to control external file system access permissions.
 157 // TODO(satorux): Move this out of 'storage/browser/fileapi'. crbug.com/257279
 158 class ExternalFileSystemBackend : public FileSystemBackend {
 159  public:
 160   // Returns true if |url| is allowed to be accessed.
 161   // This is supposed to perform ExternalFileSystem-specific security
 162   // checks.
 163   virtual bool IsAccessAllowed(const storage::FileSystemURL& url) const = 0;
 164   // Returns the list of top level directories that are exposed by this
 165   // provider. This list is used to set appropriate child process file access
 166   // permissions.
 167   virtual std::vector<base::FilePath> GetRootDirectories() const = 0;
 168   // Grants access to all external file system from extension identified with
 169   // |extension_id|.
 170   virtual void GrantFullAccessToExtension(const std::string& extension_id) = 0;
 171   // Grants access to |virtual_path| from |origin_url|.
 172   virtual void GrantFileAccessToExtension(
 173       const std::string& extension_id,
 174       const base::FilePath& virtual_path) = 0;
 175   // Revokes file access from extension identified with |extension_id|.
 176   virtual void RevokeAccessForExtension(
 177         const std::string& extension_id) = 0;
 178   // Gets virtual path by known filesystem path. Returns false when filesystem
 179   // path is not exposed by this provider.
 180   virtual bool GetVirtualPath(const base::FilePath& file_system_path,
 181                               base::FilePath* virtual_path) = 0;
 182   // Gets a redirect URL for contents. e.g. Google Drive URL for hosted
 183   // documents. Returns empty URL if the entry does not have the redirect URL.
 184   virtual void GetRedirectURLForContents(
 185       const storage::FileSystemURL& url,
 186       const storage::URLCallback& callback) = 0;
 187 };
 188
 189 }  // namespace storage
 190
 191 #endif  // STORAGE_BROWSER_FILEAPI_FILE_SYSTEM_BACKEND_H_