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 
25 namespace unix_file {
26 
27 // If true, check whether Flush and Close are called before destruction.
28 static constexpr bool kCheckSafeUsage = true;
29 
30 // A RandomAccessFile implementation backed by a file descriptor.
31 //
32 // Not thread safe.
33 class 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;
GetPath()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   // WARNING: Only use this when you know what you're doing!
88   void MarkUnchecked();
89 
90  protected:
91   // If the guard state indicates checking (!=kNoCheck), go to the target state "target". Print the
92   // given warning if the current state is or exceeds warn_threshold.
93   void moveTo(GuardState target, GuardState warn_threshold, const char* warning);
94 
95   // If the guard state indicates checking (<kNoCheck), and is below the target state "target", go
96   // to "target." If the current state is higher (excluding kNoCheck) than the trg state, print the
97   // warning.
98   void moveUp(GuardState target, const char* warning);
99 
100   // Forcefully sets the state to the given one. This can overwrite kNoCheck.
resetGuard(GuardState new_state)101   void resetGuard(GuardState new_state) {
102     if (kCheckSafeUsage) {
103       guard_state_ = new_state;
104     }
105   }
106 
107   GuardState guard_state_;
108 
109  private:
110   int fd_;
111   std::string file_path_;
112   bool auto_close_;
113 
114   DISALLOW_COPY_AND_ASSIGN(FdFile);
115 };
116 
117 std::ostream& operator<<(std::ostream& os, const FdFile::GuardState& kind);
118 
119 }  // namespace unix_file
120 
121 #endif  // ART_RUNTIME_BASE_UNIX_FILE_FD_FILE_H_
122