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