1 /* 2 * Copyright (c) 2011 The WebRTC project authors. All Rights Reserved. 3 * 4 * Use of this source code is governed by a BSD-style license 5 * that can be found in the LICENSE file in the root of the source 6 * tree. An additional intellectual property rights grant can be found 7 * in the file PATENTS. All contributing project authors may 8 * be found in the AUTHORS file in the root of the source tree. 9 */ 10 11 #ifndef RTC_BASE_SYSTEM_FILE_WRAPPER_H_ 12 #define RTC_BASE_SYSTEM_FILE_WRAPPER_H_ 13 14 #include <stddef.h> 15 #include <stdio.h> 16 17 #include <string> 18 19 // Implementation that can read (exclusive) or write from/to a file. 20 21 namespace webrtc { 22 23 // This class is a thin wrapper around FILE*. It's main features are that it 24 // owns the FILE*, calling fclose on destruction, and that on windows, file 25 // names passed to the open methods are always treated as utf-8, regardless of 26 // system code page. 27 28 // Most of the methods return only a success/fail indication. When needed, an 29 // optional argument |int* error| should be added to all methods, in the same 30 // way as for the OpenWriteOnly methods. 31 class FileWrapper final { 32 public: 33 // Opens a file, in read or write mode. Use the is_open() method on the 34 // returned object to check if the open operation was successful. On failure, 35 // and if |error| is non-null, the system errno value is stored at |*error|. 36 // The file is closed by the destructor. 37 static FileWrapper OpenReadOnly(const char* file_name_utf8); 38 static FileWrapper OpenReadOnly(const std::string& file_name_utf8); 39 static FileWrapper OpenWriteOnly(const char* file_name_utf8, 40 int* error = nullptr); 41 static FileWrapper OpenWriteOnly(const std::string& file_name_utf8, 42 int* error = nullptr); 43 44 FileWrapper() = default; 45 46 // Takes over ownership of |file|, closing it on destruction. Calling with 47 // null |file| is allowed, and results in a FileWrapper with is_open() false. FileWrapper(FILE * file)48 explicit FileWrapper(FILE* file) : file_(file) {} ~FileWrapper()49 ~FileWrapper() { Close(); } 50 51 // Copying is not supported. 52 FileWrapper(const FileWrapper&) = delete; 53 FileWrapper& operator=(const FileWrapper&) = delete; 54 55 // Support for move semantics. 56 FileWrapper(FileWrapper&&); 57 FileWrapper& operator=(FileWrapper&&); 58 59 // Returns true if a file has been opened. If the file is not open, no methods 60 // but is_open and Close may be called. is_open()61 bool is_open() const { return file_ != nullptr; } 62 63 // Closes the file, and implies Flush. Returns true on success, false if 64 // writing buffered data fails. On failure, the file is nevertheless closed. 65 // Calling Close on an already closed file does nothing and returns success. 66 bool Close(); 67 68 // Releases and returns the wrapped file without closing it. This call passes 69 // the ownership of the file to the caller, and the wrapper is no longer 70 // responsible for closing it. Similarly the previously wrapped file is no 71 // longer available for the wrapper to use in any aspect. 72 FILE* Release(); 73 74 // Write any buffered data to the underlying file. Returns true on success, 75 // false on write error. Note: Flushing when closing, is not required. 76 bool Flush(); 77 78 // Seeks to the beginning of file. Returns true on success, false on failure, 79 // e.g., if the underlying file isn't seekable. Rewind()80 bool Rewind() { return SeekTo(0); } 81 // TODO(nisse): The seek functions are used only by the WavReader. If that 82 // code is demoted to test code, seek functions can be deleted from this 83 // utility. 84 // Seek relative to current file position. 85 bool SeekRelative(int64_t offset); 86 // Seek to given position. 87 bool SeekTo(int64_t position); 88 89 // Returns the file size or -1 if a size could not be determined. 90 // (A file size might not exists for non-seekable files or file-like 91 // objects, for example /dev/tty on unix.) 92 long FileSize(); 93 94 // Returns number of bytes read. Short count indicates EOF or error. 95 size_t Read(void* buf, size_t length); 96 97 // If the most recent Read() returned a short count, this methods returns true 98 // if the short count was due to EOF, and false it it was due to some i/o 99 // error. 100 bool ReadEof() const; 101 102 // Returns true if all data was successfully written (or buffered), or false 103 // if there was an error. Writing buffered data can fail later, and is 104 // reported with return value from Flush or Close. 105 bool Write(const void* buf, size_t length); 106 107 private: 108 FILE* file_ = nullptr; 109 }; 110 111 } // namespace webrtc 112 113 #endif // RTC_BASE_SYSTEM_FILE_WRAPPER_H_ 114