fd_file.h revision 4303ba97313458491e038d78efa041d41cf7bb43 
1/*
2 * Copyright (C) 2009 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 ART_RUNTIME_BASE_UNIX_FILE_FD_FILE_H_
18#define ART_RUNTIME_BASE_UNIX_FILE_FD_FILE_H_
19
20#include <fcntl.h>
21#include <string>
22#include "base/unix_file/random_access_file.h"
23#include "base/macros.h"
24
25namespace unix_file {
26
27// If true, check whether Flush and Close are called before destruction.
28static constexpr bool kCheckSafeUsage = true;
29
30// A RandomAccessFile implementation backed by a file descriptor.
31//
32// Not thread safe.
33class FdFile : public RandomAccessFile {
34 public:
35  FdFile();
36  // Creates an FdFile using the given file descriptor. Takes ownership of the
37  // file descriptor. (Use DisableAutoClose to retain ownership.)
38  explicit FdFile(int fd, bool checkUsage);
39  explicit FdFile(int fd, const std::string& path, bool checkUsage);
40
41  // Destroys an FdFile, closing the file descriptor if Close hasn't already
42  // been called. (If you care about the return value of Close, call it
43  // yourself; this is meant to handle failure cases and read-only accesses.
44  // Note though that calling Close and checking its return value is still no
45  // guarantee that data actually made it to stable storage.)
46  virtual ~FdFile();
47
48  // Opens file 'file_path' using 'flags' and 'mode'.
49  bool Open(const std::string& file_path, int flags);
50  bool Open(const std::string& file_path, int flags, mode_t mode);
51
52  // RandomAccessFile API.
53  virtual int Close() WARN_UNUSED;
54  virtual int64_t Read(char* buf, int64_t byte_count, int64_t offset) const WARN_UNUSED;
55  virtual int SetLength(int64_t new_length) WARN_UNUSED;
56  virtual int64_t GetLength() const;
57  virtual int64_t Write(const char* buf, int64_t byte_count, int64_t offset) WARN_UNUSED;
58  virtual int Flush() WARN_UNUSED;
59
60  // Short for SetLength(0); Flush(); Close();
61  void Erase();
62
63  // Try to Flush(), then try to Close(); If either fails, call Erase().
64  int FlushCloseOrErase() WARN_UNUSED;
65
66  // Try to Flush and Close(). Attempts both, but returns the first error.
67  int FlushClose() WARN_UNUSED;
68
69  // Bonus API.
70  int Fd() const;
71  bool IsOpened() const;
72  const std::string& GetPath() const {
73    return file_path_;
74  }
75  void DisableAutoClose();
76  bool ReadFully(void* buffer, size_t byte_count) WARN_UNUSED;
77  bool WriteFully(const void* buffer, size_t byte_count) WARN_UNUSED;
78
79  // This enum is public so that we can define the << operator over it.
80  enum class GuardState {
81    kBase,           // Base, file has not been flushed or closed.
82    kFlushed,        // File has been flushed, but not closed.
83    kClosed,         // File has been flushed and closed.
84    kNoCheck         // Do not check for the current file instance.
85  };
86
87 protected:
88  // If the guard state indicates checking (!=kNoCheck), go to the target state "target". Print the
89  // given warning if the current state is or exceeds warn_threshold.
90  void moveTo(GuardState target, GuardState warn_threshold, const char* warning);
91
92  // If the guard state indicates checking (<kNoCheck), and is below the target state "target", go
93  // to "target." If the current state is higher (excluding kNoCheck) than the trg state, print the
94  // warning.
95  void moveUp(GuardState target, const char* warning);
96
97  // Forcefully sets the state to the given one. This can overwrite kNoCheck.
98  void resetGuard(GuardState new_state) {
99    if (kCheckSafeUsage) {
100      guard_state_ = new_state;
101    }
102  }
103
104  GuardState guard_state_;
105
106 private:
107  int fd_;
108  std::string file_path_;
109  bool auto_close_;
110
111  DISALLOW_COPY_AND_ASSIGN(FdFile);
112};
113
114std::ostream& operator<<(std::ostream& os, const FdFile::GuardState& kind);
115
116}  // namespace unix_file
117
118#endif  // ART_RUNTIME_BASE_UNIX_FILE_FD_FILE_H_
119