filesystem_interface.h revision aea4c1cea20dda7ae7e85fc8924a2d784f70d806 
1//
2// Copyright (C) 2015 The Android Open Source Project
3//
4// Licensed under the Apache License, Version 2.0 (the "License");
5// you may not use this file except in compliance with the License.
6// You may obtain a copy of the License at
7//
8//      http://www.apache.org/licenses/LICENSE-2.0
9//
10// Unless required by applicable law or agreed to in writing, software
11// distributed under the License is distributed on an "AS IS" BASIS,
12// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
13// See the License for the specific language governing permissions and
14// limitations under the License.
15//
16
17#ifndef UPDATE_ENGINE_PAYLOAD_GENERATOR_FILESYSTEM_INTERFACE_H_
18#define UPDATE_ENGINE_PAYLOAD_GENERATOR_FILESYSTEM_INTERFACE_H_
19
20// This class is used to abstract a filesystem and iterate the blocks
21// associated with the files and filesystem structures.
22// For the purposes of the update payload generation, a filesystem is a formated
23// partition composed by fixed-size blocks, since that's the interface used in
24// the update payload.
25
26#include <sys/stat.h>
27#include <sys/types.h>
28#include <unistd.h>
29
30#include <memory>
31#include <string>
32#include <vector>
33
34#include <base/macros.h>
35#include <chromeos/key_value_store.h>
36
37#include "update_engine/update_metadata.pb.h"
38
39namespace chromeos_update_engine {
40
41class FilesystemInterface {
42 public:
43  // This represents a file or pseudo-file in the filesystem. It can include
44  // all sort of files, like symlinks, hardlinks, directories and even a file
45  // entry representing the metadata, free space, journaling data, etc.
46  struct File {
47    File() {
48      memset(&file_stat, 0, sizeof(file_stat));
49    }
50
51    // The stat struct for the file. This is invalid (inode 0) for some
52    // pseudo-files.
53    struct stat file_stat;
54
55    // The absolute path to the file inside the filesystem, for example,
56    // "/usr/bin/bash". For pseudo-files, like blocks associated to internal
57    // filesystem tables or free space, the path doesn't start with a /.
58    std::string name;
59
60    // The list of all physical blocks holding the data of this file in
61    // the same order as the logical data. All the block numbers shall be
62    // between 0 and GetBlockCount() - 1. The blocks are encoded in extents,
63    // indicating the starting block, and the number of consecutive blocks.
64    std::vector<Extent> extents;
65  };
66
67  virtual ~FilesystemInterface() = default;
68
69  // Returns the size of a block in the filesystem.
70  virtual size_t GetBlockSize() const = 0;
71
72  // Returns the number of blocks in the filesystem.
73  virtual size_t GetBlockCount() const = 0;
74
75  // Stores in |files| the list of files and pseudo-files in the filesystem. See
76  // FileInterface for details. The paths returned by this method shall not
77  // be repeated; but the same block could be present in more than one file as
78  // happens for example with hard-linked files, but not limited to those cases.
79  // Returns whether the function succeeded.
80  virtual bool GetFiles(std::vector<File>* files) const = 0;
81
82  // Load the image settings stored in the filesystem in the
83  // /etc/update_engine.conf file. Returns whether the settings were found.
84  virtual bool LoadSettings(chromeos::KeyValueStore* store) const = 0;
85
86 protected:
87  FilesystemInterface() = default;
88
89 private:
90  DISALLOW_COPY_AND_ASSIGN(FilesystemInterface);
91};
92
93}  // namespace chromeos_update_engine
94
95#endif  // UPDATE_ENGINE_PAYLOAD_GENERATOR_FILESYSTEM_INTERFACE_H_
96