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