base/platform_file.h

   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_PLATFORM_FILE_H_
   6 #define BASE_PLATFORM_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/time/time.h"
  19
  20 namespace base {
  21
  22 // ***************************************************************************
  23 // ***** Don't use anything from this file anymore. It is being removed!
  24 // ***** Use base/files/file.h instead
  25 // ***************************************************************************
  26
  27 // PLATFORM_FILE_(OPEN|CREATE).* are mutually exclusive. You should specify
  28 // exactly one of the five (possibly combining with other flags) when opening
  29 // or creating a file.
  30 // PLATFORM_FILE_(WRITE|APPEND) are mutually exclusive. This is so that APPEND
  31 // behavior will be consistent with O_APPEND on POSIX.
  32 // PLATFORM_FILE_EXCLUSIVE_(READ|WRITE) only grant exclusive access to the file
  33 // on creation on POSIX; for existing files, consider using LockPlatformFile().
  34 enum PlatformFileFlags {
  35   PLATFORM_FILE_OPEN = 1 << 0,             // Opens a file, only if it exists.
  36   PLATFORM_FILE_CREATE = 1 << 1,           // Creates a new file, only if it
  37                                            // does not already exist.
  38   PLATFORM_FILE_OPEN_ALWAYS = 1 << 2,      // May create a new file.
  39   PLATFORM_FILE_CREATE_ALWAYS = 1 << 3,    // May overwrite an old file.
  40   PLATFORM_FILE_OPEN_TRUNCATED = 1 << 4,   // Opens a file and truncates it,
  41                                            // only if it exists.
  42   PLATFORM_FILE_READ = 1 << 5,
  43   PLATFORM_FILE_WRITE = 1 << 6,
  44   PLATFORM_FILE_APPEND = 1 << 7,
  45   PLATFORM_FILE_EXCLUSIVE_READ = 1 << 8,   // EXCLUSIVE is opposite of Windows
  46                                            // SHARE
  47   PLATFORM_FILE_EXCLUSIVE_WRITE = 1 << 9,
  48   PLATFORM_FILE_ASYNC = 1 << 10,
  49   PLATFORM_FILE_TEMPORARY = 1 << 11,       // Used on Windows only
  50   PLATFORM_FILE_HIDDEN = 1 << 12,          // Used on Windows only
  51   PLATFORM_FILE_DELETE_ON_CLOSE = 1 << 13,
  52
  53   PLATFORM_FILE_WRITE_ATTRIBUTES = 1 << 14,  // Used on Windows only
  54
  55   PLATFORM_FILE_SHARE_DELETE = 1 << 15,      // Used on Windows only
  56
  57   PLATFORM_FILE_TERMINAL_DEVICE = 1 << 16,   // Serial port flags
  58   PLATFORM_FILE_BACKUP_SEMANTICS = 1 << 17,  // Used on Windows only
  59
  60   PLATFORM_FILE_EXECUTE = 1 << 18,           // Used on Windows only
  61 };
  62
  63 // This enum has been recorded in multiple histograms. If the order of the
  64 // fields needs to change, please ensure that those histograms are obsolete or
  65 // have been moved to a different enum.
  66 //
  67 // PLATFORM_FILE_ERROR_ACCESS_DENIED is returned when a call fails because of
  68 // a filesystem restriction. PLATFORM_FILE_ERROR_SECURITY is returned when a
  69 // browser policy doesn't allow the operation to be executed.
  70 enum PlatformFileError {
  71   PLATFORM_FILE_OK = 0,
  72   PLATFORM_FILE_ERROR_FAILED = -1,
  73   PLATFORM_FILE_ERROR_IN_USE = -2,
  74   PLATFORM_FILE_ERROR_EXISTS = -3,
  75   PLATFORM_FILE_ERROR_NOT_FOUND = -4,
  76   PLATFORM_FILE_ERROR_ACCESS_DENIED = -5,
  77   PLATFORM_FILE_ERROR_TOO_MANY_OPENED = -6,
  78   PLATFORM_FILE_ERROR_NO_MEMORY = -7,
  79   PLATFORM_FILE_ERROR_NO_SPACE = -8,
  80   PLATFORM_FILE_ERROR_NOT_A_DIRECTORY = -9,
  81   PLATFORM_FILE_ERROR_INVALID_OPERATION = -10,
  82   PLATFORM_FILE_ERROR_SECURITY = -11,
  83   PLATFORM_FILE_ERROR_ABORT = -12,
  84   PLATFORM_FILE_ERROR_NOT_A_FILE = -13,
  85   PLATFORM_FILE_ERROR_NOT_EMPTY = -14,
  86   PLATFORM_FILE_ERROR_INVALID_URL = -15,
  87   PLATFORM_FILE_ERROR_IO = -16,
  88   // Put new entries here and increment PLATFORM_FILE_ERROR_MAX.
  89   PLATFORM_FILE_ERROR_MAX = -17
  90 };
  91
  92 // This explicit mapping matches both FILE_ on Windows and SEEK_ on Linux.
  93 enum PlatformFileWhence {
  94   PLATFORM_FILE_FROM_BEGIN   = 0,
  95   PLATFORM_FILE_FROM_CURRENT = 1,
  96   PLATFORM_FILE_FROM_END     = 2
  97 };
  98
  99 // Used to hold information about a given file.
 100 // If you add more fields to this structure (platform-specific fields are OK),
 101 // make sure to update all functions that use it in file_util_{win|posix}.cc
 102 // too, and the ParamTraits<base::PlatformFileInfo> implementation in
 103 // chrome/common/common_param_traits.cc.
 104 struct BASE_EXPORT PlatformFileInfo {
 105   PlatformFileInfo();
 106   ~PlatformFileInfo();
 107
 108   // The size of the file in bytes.  Undefined when is_directory is true.
 109   int64 size;
 110
 111   // True if the file corresponds to a directory.
 112   bool is_directory;
 113
 114   // True if the file corresponds to a symbolic link.
 115   bool is_symbolic_link;
 116
 117   // The last modified time of a file.
 118   base::Time last_modified;
 119
 120   // The last accessed time of a file.
 121   base::Time last_accessed;
 122
 123   // The creation time of a file.
 124   base::Time creation_time;
 125 };
 126
 127 #if defined(OS_WIN)
 128 typedef HANDLE PlatformFile;
 129 const PlatformFile kInvalidPlatformFileValue = INVALID_HANDLE_VALUE;
 130 BASE_EXPORT PlatformFileError LastErrorToPlatformFileError(DWORD last_error);
 131 #elif defined(OS_POSIX)
 132 typedef int PlatformFile;
 133 const PlatformFile kInvalidPlatformFileValue = -1;
 134 BASE_EXPORT PlatformFileError ErrnoToPlatformFileError(int saved_errno);
 135 #endif
 136
 137 // Creates or opens the given file. If |created| is provided, it will be set to
 138 // true if a new file was created [or an old one truncated to zero length to
 139 // simulate a new file, which can happen with PLATFORM_FILE_CREATE_ALWAYS], and
 140 // false otherwise.  |error| can be NULL.
 141 //
 142 // This function fails with 'access denied' if the |name| contains path
 143 // traversal ('..') components.
 144 BASE_EXPORT PlatformFile CreatePlatformFile(const FilePath& name,
 145                                             int flags,
 146                                             bool* created,
 147                                             PlatformFileError* error);
 148
 149 // Same as CreatePlatformFile but allows paths with traversal (like \..\)
 150 // components. Use only with extreme care.
 151 BASE_EXPORT PlatformFile CreatePlatformFileUnsafe(const FilePath& name,
 152                                                   int flags,
 153                                                   bool* created,
 154                                                   PlatformFileError* error);
 155
 156 BASE_EXPORT FILE* FdopenPlatformFile(PlatformFile file, const char* mode);
 157
 158 // Closes a file handle. Returns |true| on success and |false| otherwise.
 159 BASE_EXPORT bool ClosePlatformFile(PlatformFile file);
 160
 161 // Changes current position in the file to an |offset| relative to an origin
 162 // defined by |whence|. Returns the resultant current position in the file
 163 // (relative to the start) or -1 in case of error.
 164 BASE_EXPORT int64 SeekPlatformFile(PlatformFile file,
 165                                    PlatformFileWhence whence,
 166                                    int64 offset);
 167
 168 // Reads the given number of bytes (or until EOF is reached) starting with the
 169 // given offset. Returns the number of bytes read, or -1 on error. Note that
 170 // this function makes a best effort to read all data on all platforms, so it is
 171 // not intended for stream oriented files but instead for cases when the normal
 172 // expectation is that actually |size| bytes are read unless there is an error.
 173 BASE_EXPORT int ReadPlatformFile(PlatformFile file, int64 offset,
 174                                  char* data, int size);
 175
 176 // Same as above but without seek.
 177 BASE_EXPORT int ReadPlatformFileAtCurrentPos(PlatformFile file,
 178                                              char* data, int size);
 179
 180 // Reads the given number of bytes (or until EOF is reached) starting with the
 181 // given offset, but does not make any effort to read all data on all platforms.
 182 // Returns the number of bytes read, or -1 on error.
 183 BASE_EXPORT int ReadPlatformFileNoBestEffort(PlatformFile file, int64 offset,
 184                                              char* data, int size);
 185
 186 // Same as above but without seek.
 187 BASE_EXPORT int ReadPlatformFileCurPosNoBestEffort(PlatformFile file,
 188                                                    char* data, int size);
 189
 190 // Writes the given buffer into the file at the given offset, overwritting any
 191 // data that was previously there. Returns the number of bytes written, or -1
 192 // on error. Note that this function makes a best effort to write all data on
 193 // all platforms.
 194 // Ignores the offset and writes to the end of the file if the file was opened
 195 // with PLATFORM_FILE_APPEND.
 196 BASE_EXPORT int WritePlatformFile(PlatformFile file, int64 offset,
 197                                   const char* data, int size);
 198
 199 // Save as above but without seek.
 200 BASE_EXPORT int WritePlatformFileAtCurrentPos(PlatformFile file,
 201                                               const char* data, int size);
 202
 203 // Save as above but does not make any effort to write all data on all
 204 // platforms. Returns the number of bytes written, or -1 on error.
 205 BASE_EXPORT int WritePlatformFileCurPosNoBestEffort(PlatformFile file,
 206                                                     const char* data, int size);
 207
 208 // Truncates the given file to the given length. If |length| is greater than
 209 // the current size of the file, the file is extended with zeros. If the file
 210 // doesn't exist, |false| is returned.
 211 BASE_EXPORT bool TruncatePlatformFile(PlatformFile file, int64 length);
 212
 213 // Flushes the buffers of the given file.
 214 BASE_EXPORT bool FlushPlatformFile(PlatformFile file);
 215
 216 // Touches the given file.
 217 BASE_EXPORT bool TouchPlatformFile(PlatformFile file,
 218                                    const Time& last_access_time,
 219                                    const Time& last_modified_time);
 220
 221 // Returns some information for the given file.
 222 BASE_EXPORT bool GetPlatformFileInfo(PlatformFile file, PlatformFileInfo* info);
 223
 224 // Attempts to take an exclusive write lock on the file. Returns immediately
 225 // (i.e. does not wait for another process to unlock the file). If the lock
 226 // was obtained, the result will be PLATFORM_FILE_OK. A lock only guarantees
 227 // that other processes may not also take a lock on the same file with the
 228 // same API - it may still be opened, renamed, unlinked, etc.
 229 //
 230 // Common semantics:
 231 //  * Locks are held by processes, but not inherited by child processes.
 232 //  * Locks are released by the OS on file handle close or process termination.
 233 //  * Locks are reliable only on local filesystems.
 234 //  * Duplicated file handles may also write to locked files.
 235 // Windows-specific semantics:
 236 //  * Locks are mandatory for read/write APIs, advisory for mapping APIs.
 237 //  * Within a process, locking the same file (by the same or new handle)
 238 //    will fail.
 239 // POSIX-specific semantics:
 240 //  * Locks are advisory only.
 241 //  * Within a process, locking the same file (by the same or new handle)
 242 //    will succeed.
 243 //  * Closing any descriptor on a given file releases the lock.
 244 BASE_EXPORT PlatformFileError LockPlatformFile(PlatformFile file);
 245
 246 // Unlock a file previously locked with LockPlatformFile.
 247 BASE_EXPORT PlatformFileError UnlockPlatformFile(PlatformFile file);
 248
 249 // Use this class to pass ownership of a PlatformFile to a receiver that may or
 250 // may not want to accept it.  This class does not own the storage for the
 251 // PlatformFile.
 252 //
 253 // EXAMPLE:
 254 //
 255 //  void MaybeProcessFile(PassPlatformFile pass_file) {
 256 //    if (...) {
 257 //      PlatformFile file = pass_file.ReleaseValue();
 258 //      // Now, we are responsible for closing |file|.
 259 //    }
 260 //  }
 261 //
 262 //  void OpenAndMaybeProcessFile(const FilePath& path) {
 263 //    PlatformFile file = CreatePlatformFile(path, ...);
 264 //    MaybeProcessFile(PassPlatformFile(&file));
 265 //    if (file != kInvalidPlatformFileValue)
 266 //      ClosePlatformFile(file);
 267 //  }
 268 //
 269 class BASE_EXPORT PassPlatformFile {
 270  public:
 271   explicit PassPlatformFile(PlatformFile* value) : value_(value) {
 272   }
 273
 274   // Called to retrieve the PlatformFile stored in this object.  The caller
 275   // gains ownership of the PlatformFile and is now responsible for closing it.
 276   // Any subsequent calls to this method will return an invalid PlatformFile.
 277   PlatformFile ReleaseValue() {
 278     PlatformFile temp = *value_;
 279     *value_ = kInvalidPlatformFileValue;
 280     return temp;
 281   }
 282
 283  private:
 284   PlatformFile* value_;
 285 };
 286
 287 }  // namespace base
 288
 289 #endif  // BASE_PLATFORM_FILE_H_