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