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_LIBARTBASE_BASE_UNIX_FILE_FD_FILE_H_ 18 #define ART_LIBARTBASE_BASE_UNIX_FILE_FD_FILE_H_ 19 20 #include <fcntl.h> 21 22 #include <string> 23 24 #include "base/macros.h" 25 #include "base/unix_file/random_access_file.h" 26 27 namespace unix_file { 28 29 // If true, check whether Flush and Close are called before destruction. 30 static constexpr bool kCheckSafeUsage = true; 31 32 // A RandomAccessFile implementation backed by a file descriptor. 33 // 34 // Not thread safe. 35 class FdFile : public RandomAccessFile { 36 public: 37 FdFile(); 38 // Creates an FdFile using the given file descriptor. Takes ownership of the 39 // file descriptor. (Use DisableAutoClose to retain ownership.) 40 FdFile(int fd, bool checkUsage); 41 FdFile(int fd, const std::string& path, bool checkUsage); 42 FdFile(int fd, const std::string& path, bool checkUsage, bool read_only_mode); 43 44 FdFile(const std::string& path, int flags, bool checkUsage) 45 : FdFile(path, flags, 0640, checkUsage) {} 46 FdFile(const std::string& path, int flags, mode_t mode, bool checkUsage); 47 48 // Move constructor. 49 FdFile(FdFile&& other) 50 : guard_state_(other.guard_state_), 51 fd_(other.fd_), 52 file_path_(std::move(other.file_path_)), 53 auto_close_(other.auto_close_), 54 read_only_mode_(other.read_only_mode_) { 55 other.Release(); // Release the src. 56 } 57 58 // Move assignment operator. 59 FdFile& operator=(FdFile&& other); 60 61 // Release the file descriptor. This will make further accesses to this FdFile invalid. Disables 62 // all further state checking. 63 int Release() { 64 int tmp_fd = fd_; 65 fd_ = -1; 66 guard_state_ = GuardState::kNoCheck; 67 auto_close_ = false; 68 return tmp_fd; 69 } 70 71 void Reset(int fd, bool check_usage) { 72 if (fd_ != -1 && fd_ != fd) { 73 Destroy(); 74 } 75 fd_ = fd; 76 if (check_usage) { 77 guard_state_ = fd == -1 ? GuardState::kNoCheck : GuardState::kBase; 78 } else { 79 guard_state_ = GuardState::kNoCheck; 80 } 81 // Keep the auto_close_ state. 82 } 83 84 // Destroys an FdFile, closing the file descriptor if Close hasn't already 85 // been called. (If you care about the return value of Close, call it 86 // yourself; this is meant to handle failure cases and read-only accesses. 87 // Note though that calling Close and checking its return value is still no 88 // guarantee that data actually made it to stable storage.) 89 virtual ~FdFile(); 90 91 // RandomAccessFile API. 92 int Close() OVERRIDE WARN_UNUSED; 93 int64_t Read(char* buf, int64_t byte_count, int64_t offset) const OVERRIDE WARN_UNUSED; 94 int SetLength(int64_t new_length) OVERRIDE WARN_UNUSED; 95 int64_t GetLength() const OVERRIDE; 96 int64_t Write(const char* buf, int64_t byte_count, int64_t offset) OVERRIDE WARN_UNUSED; 97 98 int Flush() OVERRIDE WARN_UNUSED; 99 100 // Short for SetLength(0); Flush(); Close(); 101 // If the file was opened with a path name and unlink = true, also calls Unlink() on the path. 102 // Note that it is the the caller's responsibility to avoid races. 103 bool Erase(bool unlink = false); 104 105 // Call unlink() if the file was opened with a path, and if open() with the name shows that 106 // the file descriptor of this file is still up-to-date. This is still racy, though, and it 107 // is up to the caller to ensure correctness in a multi-process setup. 108 bool Unlink(); 109 110 // Try to Flush(), then try to Close(); If either fails, call Erase(). 111 int FlushCloseOrErase() WARN_UNUSED; 112 113 // Try to Flush and Close(). Attempts both, but returns the first error. 114 int FlushClose() WARN_UNUSED; 115 116 // Bonus API. 117 int Fd() const; 118 bool ReadOnlyMode() const; 119 bool CheckUsage() const; 120 bool IsOpened() const; 121 const std::string& GetPath() const { 122 return file_path_; 123 } 124 void DisableAutoClose(); 125 bool ReadFully(void* buffer, size_t byte_count) WARN_UNUSED; 126 bool PreadFully(void* buffer, size_t byte_count, size_t offset) WARN_UNUSED; 127 bool WriteFully(const void* buffer, size_t byte_count) WARN_UNUSED; 128 bool PwriteFully(const void* buffer, size_t byte_count, size_t offset) WARN_UNUSED; 129 130 // Copy data from another file. 131 bool Copy(FdFile* input_file, int64_t offset, int64_t size); 132 // Clears the file content and resets the file offset to 0. 133 // Returns true upon success, false otherwise. 134 bool ClearContent(); 135 // Resets the file offset to the beginning of the file. 136 bool ResetOffset(); 137 138 // This enum is public so that we can define the << operator over it. 139 enum class GuardState { 140 kBase, // Base, file has not been flushed or closed. 141 kFlushed, // File has been flushed, but not closed. 142 kClosed, // File has been flushed and closed. 143 kNoCheck // Do not check for the current file instance. 144 }; 145 146 // WARNING: Only use this when you know what you're doing! 147 void MarkUnchecked(); 148 149 // Compare against another file. Returns 0 if the files are equivalent, otherwise returns -1 or 1 150 // depending on if the lenghts are different. If the lengths are the same, the function returns 151 // the difference of the first byte that differs. 152 int Compare(FdFile* other); 153 154 protected: 155 // If the guard state indicates checking (!=kNoCheck), go to the target state "target". Print the 156 // given warning if the current state is or exceeds warn_threshold. 157 void moveTo(GuardState target, GuardState warn_threshold, const char* warning); 158 159 // If the guard state indicates checking (<kNoCheck), and is below the target state "target", go 160 // to "target." If the current state is higher (excluding kNoCheck) than the trg state, print the 161 // warning. 162 void moveUp(GuardState target, const char* warning); 163 164 // Forcefully sets the state to the given one. This can overwrite kNoCheck. 165 void resetGuard(GuardState new_state) { 166 if (kCheckSafeUsage) { 167 guard_state_ = new_state; 168 } 169 } 170 171 GuardState guard_state_; 172 173 // Opens file 'file_path' using 'flags' and 'mode'. 174 bool Open(const std::string& file_path, int flags); 175 bool Open(const std::string& file_path, int flags, mode_t mode); 176 177 private: 178 template <bool kUseOffset> 179 bool WriteFullyGeneric(const void* buffer, size_t byte_count, size_t offset); 180 181 void Destroy(); // For ~FdFile and operator=(&&). 182 183 int fd_; 184 std::string file_path_; 185 bool auto_close_; 186 bool read_only_mode_; 187 188 DISALLOW_COPY_AND_ASSIGN(FdFile); 189 }; 190 191 std::ostream& operator<<(std::ostream& os, const FdFile::GuardState& kind); 192 193 } // namespace unix_file 194 195 #endif // ART_LIBARTBASE_BASE_UNIX_FILE_FD_FILE_H_ 196
