1 // Copyright (c) 2012 The Chromium Authors. All rights reserved. 2 // Use of this source code is governed by a BSD-style license that can be 3 // found in the LICENSE file. 4 5 #ifndef BASE_FILES_FILE_H_ 6 #define BASE_FILES_FILE_H_ 7 8 #include "build/build_config.h" 9 #if defined(OS_WIN) 10 #include <windows.h> 11 #endif 12 13 #include <string> 14 15 #include "base/base_export.h" 16 #include "base/basictypes.h" 17 #include "base/files/file_path.h" 18 #include "base/move.h" 19 #include "base/time/time.h" 20 21 #if defined(OS_WIN) 22 #include "base/win/scoped_handle.h" 23 #endif 24 25 namespace base { 26 27 #if defined(OS_WIN) 28 typedef HANDLE PlatformFile; 29 #elif defined(OS_POSIX) 30 typedef int PlatformFile; 31 #endif 32 33 34 // Thin wrapper around an OS-level file. 35 // Note that this class does not provide any support for asynchronous IO, other 36 // than the ability to create asynchronous handles on Windows. 37 // 38 // Note about const: this class does not attempt to determine if the underlying 39 // file system object is affected by a particular method in order to consider 40 // that method const or not. Only methods that deal with member variables in an 41 // obvious non-modifying way are marked as const. Any method that forward calls 42 // to the OS is not considered const, even if there is no apparent change to 43 // member variables. 44 class BASE_EXPORT File { 45 MOVE_ONLY_TYPE_FOR_CPP_03(File, RValue) 46 47 public: 48 // FLAG_(OPEN|CREATE).* are mutually exclusive. You should specify exactly one 49 // of the five (possibly combining with other flags) when opening or creating 50 // a file. 51 // FLAG_(WRITE|APPEND) are mutually exclusive. This is so that APPEND behavior 52 // will be consistent with O_APPEND on POSIX. 53 // FLAG_EXCLUSIVE_(READ|WRITE) only grant exclusive access to the file on 54 // creation on POSIX; for existing files, consider using Lock(). 55 enum Flags { 56 FLAG_OPEN = 1 << 0, // Opens a file, only if it exists. 57 FLAG_CREATE = 1 << 1, // Creates a new file, only if it does not 58 // already exist. 59 FLAG_OPEN_ALWAYS = 1 << 2, // May create a new file. 60 FLAG_CREATE_ALWAYS = 1 << 3, // May overwrite an old file. 61 FLAG_OPEN_TRUNCATED = 1 << 4, // Opens a file and truncates it, only if it 62 // exists. 63 FLAG_READ = 1 << 5, 64 FLAG_WRITE = 1 << 6, 65 FLAG_APPEND = 1 << 7, 66 FLAG_EXCLUSIVE_READ = 1 << 8, // EXCLUSIVE is opposite of Windows SHARE. 67 FLAG_EXCLUSIVE_WRITE = 1 << 9, 68 FLAG_ASYNC = 1 << 10, 69 FLAG_TEMPORARY = 1 << 11, // Used on Windows only. 70 FLAG_HIDDEN = 1 << 12, // Used on Windows only. 71 FLAG_DELETE_ON_CLOSE = 1 << 13, 72 FLAG_WRITE_ATTRIBUTES = 1 << 14, // Used on Windows only. 73 FLAG_SHARE_DELETE = 1 << 15, // Used on Windows only. 74 FLAG_TERMINAL_DEVICE = 1 << 16, // Serial port flags. 75 FLAG_BACKUP_SEMANTICS = 1 << 17, // Used on Windows only. 76 FLAG_EXECUTE = 1 << 18, // Used on Windows only. 77 }; 78 79 // This enum has been recorded in multiple histograms. If the order of the 80 // fields needs to change, please ensure that those histograms are obsolete or 81 // have been moved to a different enum. 82 // 83 // FILE_ERROR_ACCESS_DENIED is returned when a call fails because of a 84 // filesystem restriction. FILE_ERROR_SECURITY is returned when a browser 85 // policy doesn't allow the operation to be executed. 86 enum Error { 87 FILE_OK = 0, 88 FILE_ERROR_FAILED = -1, 89 FILE_ERROR_IN_USE = -2, 90 FILE_ERROR_EXISTS = -3, 91 FILE_ERROR_NOT_FOUND = -4, 92 FILE_ERROR_ACCESS_DENIED = -5, 93 FILE_ERROR_TOO_MANY_OPENED = -6, 94 FILE_ERROR_NO_MEMORY = -7, 95 FILE_ERROR_NO_SPACE = -8, 96 FILE_ERROR_NOT_A_DIRECTORY = -9, 97 FILE_ERROR_INVALID_OPERATION = -10, 98 FILE_ERROR_SECURITY = -11, 99 FILE_ERROR_ABORT = -12, 100 FILE_ERROR_NOT_A_FILE = -13, 101 FILE_ERROR_NOT_EMPTY = -14, 102 FILE_ERROR_INVALID_URL = -15, 103 FILE_ERROR_IO = -16, 104 // Put new entries here and increment FILE_ERROR_MAX. 105 FILE_ERROR_MAX = -17 106 }; 107 108 // This explicit mapping matches both FILE_ on Windows and SEEK_ on Linux. 109 enum Whence { 110 FROM_BEGIN = 0, 111 FROM_CURRENT = 1, 112 FROM_END = 2 113 }; 114 115 // Used to hold information about a given file. 116 // If you add more fields to this structure (platform-specific fields are OK), 117 // make sure to update all functions that use it in file_util_{win|posix}.cc 118 // too, and the ParamTraits<base::PlatformFileInfo> implementation in 119 // chrome/common/common_param_traits.cc. 120 struct BASE_EXPORT Info { 121 Info(); 122 ~Info(); 123 124 // The size of the file in bytes. Undefined when is_directory is true. 125 int64 size; 126 127 // True if the file corresponds to a directory. 128 bool is_directory; 129 130 // True if the file corresponds to a symbolic link. 131 bool is_symbolic_link; 132 133 // The last modified time of a file. 134 base::Time last_modified; 135 136 // The last accessed time of a file. 137 base::Time last_accessed; 138 139 // The creation time of a file. 140 base::Time creation_time; 141 }; 142 143 File(); 144 145 // Creates or opens the given file. This will fail with 'access denied' if the 146 // |name| contains path traversal ('..') components. 147 File(const FilePath& name, uint32 flags); 148 149 // Takes ownership of |platform_file|. 150 explicit File(PlatformFile platform_file); 151 152 // Move constructor for C++03 move emulation of this type. 153 File(RValue other); 154 155 ~File(); 156 157 // Move operator= for C++03 move emulation of this type. 158 File& operator=(RValue other); 159 160 // Creates or opens the given file, allowing paths with traversal ('..') 161 // components. Use only with extreme care. 162 void CreateBaseFileUnsafe(const FilePath& name, uint32 flags); 163 164 bool IsValid() const; 165 166 // Returns true if a new file was created (or an old one truncated to zero 167 // length to simulate a new file, which can happen with 168 // FLAG_CREATE_ALWAYS), and false otherwise. 169 bool created() const { return created_; } 170 171 // Returns the OS result of opening this file. 172 Error error() const { return error_; } 173 174 PlatformFile GetPlatformFile() const { return file_; } 175 PlatformFile TakePlatformFile(); 176 177 // Destroying this object closes the file automatically. 178 void Close(); 179 180 // Changes current position in the file to an |offset| relative to an origin 181 // defined by |whence|. Returns the resultant current position in the file 182 // (relative to the start) or -1 in case of error. 183 int64 Seek(Whence whence, int64 offset); 184 185 // Reads the given number of bytes (or until EOF is reached) starting with the 186 // given offset. Returns the number of bytes read, or -1 on error. Note that 187 // this function makes a best effort to read all data on all platforms, so it 188 // is not intended for stream oriented files but instead for cases when the 189 // normal expectation is that actually |size| bytes are read unless there is 190 // an error. 191 int Read(int64 offset, char* data, int size); 192 193 // Same as above but without seek. 194 int ReadAtCurrentPos(char* data, int size); 195 196 // Reads the given number of bytes (or until EOF is reached) starting with the 197 // given offset, but does not make any effort to read all data on all 198 // platforms. Returns the number of bytes read, or -1 on error. 199 int ReadNoBestEffort(int64 offset, char* data, int size); 200 201 // Same as above but without seek. 202 int ReadAtCurrentPosNoBestEffort(char* data, int size); 203 204 // Writes the given buffer into the file at the given offset, overwritting any 205 // data that was previously there. Returns the number of bytes written, or -1 206 // on error. Note that this function makes a best effort to write all data on 207 // all platforms. 208 // Ignores the offset and writes to the end of the file if the file was opened 209 // with FLAG_APPEND. 210 int Write(int64 offset, const char* data, int size); 211 212 // Save as above but without seek. 213 int WriteAtCurrentPos(const char* data, int size); 214 215 // Save as above but does not make any effort to write all data on all 216 // platforms. Returns the number of bytes written, or -1 on error. 217 int WriteAtCurrentPosNoBestEffort(const char* data, int size); 218 219 // Truncates the file to the given length. If |length| is greater than the 220 // current size of the file, the file is extended with zeros. If the file 221 // doesn't exist, |false| is returned. 222 bool Truncate(int64 length); 223 224 // Flushes the buffers. 225 bool Flush(); 226 227 // Updates the file times. 228 bool SetTimes(Time last_access_time, Time last_modified_time); 229 230 // Returns some basic information for the given file. 231 bool GetInfo(Info* info); 232 233 // Attempts to take an exclusive write lock on the file. Returns immediately 234 // (i.e. does not wait for another process to unlock the file). If the lock 235 // was obtained, the result will be FILE_OK. A lock only guarantees 236 // that other processes may not also take a lock on the same file with the 237 // same API - it may still be opened, renamed, unlinked, etc. 238 // 239 // Common semantics: 240 // * Locks are held by processes, but not inherited by child processes. 241 // * Locks are released by the OS on file close or process termination. 242 // * Locks are reliable only on local filesystems. 243 // * Duplicated file handles may also write to locked files. 244 // Windows-specific semantics: 245 // * Locks are mandatory for read/write APIs, advisory for mapping APIs. 246 // * Within a process, locking the same file (by the same or new handle) 247 // will fail. 248 // POSIX-specific semantics: 249 // * Locks are advisory only. 250 // * Within a process, locking the same file (by the same or new handle) 251 // will succeed. 252 // * Closing any descriptor on a given file releases the lock. 253 Error Lock(); 254 255 // Unlock a file previously locked. 256 Error Unlock(); 257 258 #if defined(OS_WIN) 259 static Error OSErrorToFileError(DWORD last_error); 260 #elif defined(OS_POSIX) 261 static Error OSErrorToFileError(int saved_errno); 262 #endif 263 264 private: 265 void SetPlatformFile(PlatformFile file); 266 267 #if defined(OS_WIN) 268 win::ScopedHandle file_; 269 #elif defined(OS_POSIX) 270 PlatformFile file_; 271 #endif 272 273 Error error_; 274 bool created_; 275 bool async_; 276 }; 277 278 } // namespace base 279 280 #endif // BASE_FILES_FILE_H_ 281
