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