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