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