base/file_util_win.cc

   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 #include "base/file_util.h"
   6
   7 #include <windows.h>
   8 #include <psapi.h>
   9 #include <shellapi.h>
  10 #include <shlobj.h>
  11 #include <time.h>
  12
  13 #include <algorithm>
  14 #include <limits>
  15 #include <string>
  16
  17 #include "base/files/file_path.h"
  18 #include "base/logging.h"
  19 #include "base/metrics/histogram.h"
  20 #include "base/process/process_handle.h"
  21 #include "base/rand_util.h"
  22 #include "base/strings/string_number_conversions.h"
  23 #include "base/strings/string_util.h"
  24 #include "base/strings/utf_string_conversions.h"
  25 #include "base/threading/thread_restrictions.h"
  26 #include "base/time/time.h"
  27 #include "base/win/scoped_handle.h"
  28 #include "base/win/windows_version.h"
  29
  30 namespace base {
  31
  32 namespace {
  33
  34 const DWORD kFileShareAll =
  35     FILE_SHARE_READ | FILE_SHARE_WRITE | FILE_SHARE_DELETE;
  36
  37 bool ShellCopy(const FilePath& from_path,
  38                const FilePath& to_path,
  39                bool recursive) {
  40   // WinXP SHFileOperation doesn't like trailing separators.
  41   FilePath stripped_from = from_path.StripTrailingSeparators();
  42   FilePath stripped_to = to_path.StripTrailingSeparators();
  43
  44   ThreadRestrictions::AssertIOAllowed();
  45
  46   // NOTE: I suspect we could support longer paths, but that would involve
  47   // analyzing all our usage of files.
  48   if (stripped_from.value().length() >= MAX_PATH ||
  49       stripped_to.value().length() >= MAX_PATH) {
  50     return false;
  51   }
  52
  53   // SHFILEOPSTRUCT wants the path to be terminated with two NULLs,
  54   // so we have to use wcscpy because wcscpy_s writes non-NULLs
  55   // into the rest of the buffer.
  56   wchar_t double_terminated_path_from[MAX_PATH + 1] = {0};
  57   wchar_t double_terminated_path_to[MAX_PATH + 1] = {0};
  58 #pragma warning(suppress:4996)  // don't complain about wcscpy deprecation
  59   wcscpy(double_terminated_path_from, stripped_from.value().c_str());
  60 #pragma warning(suppress:4996)  // don't complain about wcscpy deprecation
  61   wcscpy(double_terminated_path_to, stripped_to.value().c_str());
  62
  63   SHFILEOPSTRUCT file_operation = {0};
  64   file_operation.wFunc = FO_COPY;
  65   file_operation.pFrom = double_terminated_path_from;
  66   file_operation.pTo = double_terminated_path_to;
  67   file_operation.fFlags = FOF_NOERRORUI | FOF_SILENT | FOF_NOCONFIRMATION |
  68                           FOF_NOCONFIRMMKDIR;
  69   if (!recursive)
  70     file_operation.fFlags |= FOF_NORECURSION | FOF_FILESONLY;
  71
  72   return (SHFileOperation(&file_operation) == 0);
  73 }
  74
  75 }  // namespace
  76
  77 FilePath MakeAbsoluteFilePath(const FilePath& input) {
  78   ThreadRestrictions::AssertIOAllowed();
  79   wchar_t file_path[MAX_PATH];
  80   if (!_wfullpath(file_path, input.value().c_str(), MAX_PATH))
  81     return FilePath();
  82   return FilePath(file_path);
  83 }
  84
  85 bool DeleteFile(const FilePath& path, bool recursive) {
  86   ThreadRestrictions::AssertIOAllowed();
  87
  88   if (path.value().length() >= MAX_PATH)
  89     return false;
  90
  91   if (!recursive) {
  92     // If not recursing, then first check to see if |path| is a directory.
  93     // If it is, then remove it with RemoveDirectory.
  94     PlatformFileInfo file_info;
  95     if (file_util::GetFileInfo(path, &file_info) && file_info.is_directory)
  96       return RemoveDirectory(path.value().c_str()) != 0;
  97
  98     // Otherwise, it's a file, wildcard or non-existant. Try DeleteFile first
  99     // because it should be faster. If DeleteFile fails, then we fall through
 100     // to SHFileOperation, which will do the right thing.
 101     if (::DeleteFile(path.value().c_str()) != 0)
 102       return true;
 103   }
 104
 105   // SHFILEOPSTRUCT wants the path to be terminated with two NULLs,
 106   // so we have to use wcscpy because wcscpy_s writes non-NULLs
 107   // into the rest of the buffer.
 108   wchar_t double_terminated_path[MAX_PATH + 1] = {0};
 109 #pragma warning(suppress:4996)  // don't complain about wcscpy deprecation
 110   wcscpy(double_terminated_path, path.value().c_str());
 111
 112   SHFILEOPSTRUCT file_operation = {0};
 113   file_operation.wFunc = FO_DELETE;
 114   file_operation.pFrom = double_terminated_path;
 115   file_operation.fFlags = FOF_NOERRORUI | FOF_SILENT | FOF_NOCONFIRMATION;
 116   if (!recursive)
 117     file_operation.fFlags |= FOF_NORECURSION | FOF_FILESONLY;
 118   int err = SHFileOperation(&file_operation);
 119
 120   // Since we're passing flags to the operation telling it to be silent,
 121   // it's possible for the operation to be aborted/cancelled without err
 122   // being set (although MSDN doesn't give any scenarios for how this can
 123   // happen).  See MSDN for SHFileOperation and SHFILEOPTSTRUCT.
 124   if (file_operation.fAnyOperationsAborted)
 125     return false;
 126
 127   // Some versions of Windows return ERROR_FILE_NOT_FOUND (0x2) when deleting
 128   // an empty directory and some return 0x402 when they should be returning
 129   // ERROR_FILE_NOT_FOUND. MSDN says Vista and up won't return 0x402.
 130   return (err == 0 || err == ERROR_FILE_NOT_FOUND || err == 0x402);
 131 }
 132
 133 bool DeleteFileAfterReboot(const FilePath& path) {
 134   ThreadRestrictions::AssertIOAllowed();
 135
 136   if (path.value().length() >= MAX_PATH)
 137     return false;
 138
 139   return MoveFileEx(path.value().c_str(), NULL,
 140                     MOVEFILE_DELAY_UNTIL_REBOOT |
 141                         MOVEFILE_REPLACE_EXISTING) != FALSE;
 142 }
 143
 144 bool ReplaceFile(const FilePath& from_path,
 145                  const FilePath& to_path,
 146                  PlatformFileError* error) {
 147   ThreadRestrictions::AssertIOAllowed();
 148   // Try a simple move first.  It will only succeed when |to_path| doesn't
 149   // already exist.
 150   if (::MoveFile(from_path.value().c_str(), to_path.value().c_str()))
 151     return true;
 152   // Try the full-blown replace if the move fails, as ReplaceFile will only
 153   // succeed when |to_path| does exist. When writing to a network share, we may
 154   // not be able to change the ACLs. Ignore ACL errors then
 155   // (REPLACEFILE_IGNORE_MERGE_ERRORS).
 156   if (::ReplaceFile(to_path.value().c_str(), from_path.value().c_str(), NULL,
 157                     REPLACEFILE_IGNORE_MERGE_ERRORS, NULL, NULL)) {
 158     return true;
 159   }
 160   if (error)
 161     *error = LastErrorToPlatformFileError(GetLastError());
 162   return false;
 163 }
 164
 165 bool CopyDirectory(const FilePath& from_path, const FilePath& to_path,
 166                    bool recursive) {
 167   ThreadRestrictions::AssertIOAllowed();
 168
 169   if (recursive)
 170     return ShellCopy(from_path, to_path, true);
 171
 172   // The following code assumes that from path is a directory.
 173   DCHECK(DirectoryExists(from_path));
 174
 175   // Instead of creating a new directory, we copy the old one to include the
 176   // security information of the folder as part of the copy.
 177   if (!PathExists(to_path)) {
 178     // Except that Vista fails to do that, and instead do a recursive copy if
 179     // the target directory doesn't exist.
 180     if (base::win::GetVersion() >= base::win::VERSION_VISTA)
 181       file_util::CreateDirectory(to_path);
 182     else
 183       ShellCopy(from_path, to_path, false);
 184   }
 185
 186   FilePath directory = from_path.Append(L"*.*");
 187   return ShellCopy(directory, to_path, false);
 188 }
 189
 190 bool PathExists(const FilePath& path) {
 191   ThreadRestrictions::AssertIOAllowed();
 192   return (GetFileAttributes(path.value().c_str()) != INVALID_FILE_ATTRIBUTES);
 193 }
 194
 195 bool PathIsWritable(const FilePath& path) {
 196   ThreadRestrictions::AssertIOAllowed();
 197   HANDLE dir =
 198       CreateFile(path.value().c_str(), FILE_ADD_FILE, kFileShareAll,
 199                  NULL, OPEN_EXISTING, FILE_FLAG_BACKUP_SEMANTICS, NULL);
 200
 201   if (dir == INVALID_HANDLE_VALUE)
 202     return false;
 203
 204   CloseHandle(dir);
 205   return true;
 206 }
 207
 208 bool DirectoryExists(const FilePath& path) {
 209   ThreadRestrictions::AssertIOAllowed();
 210   DWORD fileattr = GetFileAttributes(path.value().c_str());
 211   if (fileattr != INVALID_FILE_ATTRIBUTES)
 212     return (fileattr & FILE_ATTRIBUTE_DIRECTORY) != 0;
 213   return false;
 214 }
 215
 216 }  // namespace base
 217
 218 // -----------------------------------------------------------------------------
 219
 220 namespace file_util {
 221
 222 using base::DirectoryExists;
 223 using base::FilePath;
 224 using base::kFileShareAll;
 225
 226 bool GetTempDir(FilePath* path) {
 227   base::ThreadRestrictions::AssertIOAllowed();
 228
 229   wchar_t temp_path[MAX_PATH + 1];
 230   DWORD path_len = ::GetTempPath(MAX_PATH, temp_path);
 231   if (path_len >= MAX_PATH || path_len <= 0)
 232     return false;
 233   // TODO(evanm): the old behavior of this function was to always strip the
 234   // trailing slash.  We duplicate this here, but it shouldn't be necessary
 235   // when everyone is using the appropriate FilePath APIs.
 236   *path = FilePath(temp_path).StripTrailingSeparators();
 237   return true;
 238 }
 239
 240 bool GetShmemTempDir(FilePath* path, bool executable) {
 241   return GetTempDir(path);
 242 }
 243
 244 bool CreateTemporaryFile(FilePath* path) {
 245   base::ThreadRestrictions::AssertIOAllowed();
 246
 247   FilePath temp_file;
 248
 249   if (!GetTempDir(path))
 250     return false;
 251
 252   if (CreateTemporaryFileInDir(*path, &temp_file)) {
 253     *path = temp_file;
 254     return true;
 255   }
 256
 257   return false;
 258 }
 259
 260 FILE* CreateAndOpenTemporaryShmemFile(FilePath* path, bool executable) {
 261   base::ThreadRestrictions::AssertIOAllowed();
 262   return CreateAndOpenTemporaryFile(path);
 263 }
 264
 265 // On POSIX we have semantics to create and open a temporary file
 266 // atomically.
 267 // TODO(jrg): is there equivalent call to use on Windows instead of
 268 // going 2-step?
 269 FILE* CreateAndOpenTemporaryFileInDir(const FilePath& dir, FilePath* path) {
 270   base::ThreadRestrictions::AssertIOAllowed();
 271   if (!CreateTemporaryFileInDir(dir, path)) {
 272     return NULL;
 273   }
 274   // Open file in binary mode, to avoid problems with fwrite. On Windows
 275   // it replaces \n's with \r\n's, which may surprise you.
 276   // Reference: http://msdn.microsoft.com/en-us/library/h9t88zwz(VS.71).aspx
 277   return OpenFile(*path, "wb+");
 278 }
 279
 280 bool CreateTemporaryFileInDir(const FilePath& dir,
 281                               FilePath* temp_file) {
 282   base::ThreadRestrictions::AssertIOAllowed();
 283
 284   wchar_t temp_name[MAX_PATH + 1];
 285
 286   if (!GetTempFileName(dir.value().c_str(), L"", 0, temp_name)) {
 287     DPLOG(WARNING) << "Failed to get temporary file name in " << dir.value();
 288     return false;
 289   }
 290
 291   wchar_t long_temp_name[MAX_PATH + 1];
 292   DWORD long_name_len = GetLongPathName(temp_name, long_temp_name, MAX_PATH);
 293   if (long_name_len > MAX_PATH || long_name_len == 0) {
 294     // GetLongPathName() failed, but we still have a temporary file.
 295     *temp_file = FilePath(temp_name);
 296     return true;
 297   }
 298
 299   FilePath::StringType long_temp_name_str;
 300   long_temp_name_str.assign(long_temp_name, long_name_len);
 301   *temp_file = FilePath(long_temp_name_str);
 302   return true;
 303 }
 304
 305 bool CreateTemporaryDirInDir(const FilePath& base_dir,
 306                              const FilePath::StringType& prefix,
 307                              FilePath* new_dir) {
 308   base::ThreadRestrictions::AssertIOAllowed();
 309
 310   FilePath path_to_create;
 311
 312   for (int count = 0; count < 50; ++count) {
 313     // Try create a new temporary directory with random generated name. If
 314     // the one exists, keep trying another path name until we reach some limit.
 315     string16 new_dir_name;
 316     new_dir_name.assign(prefix);
 317     new_dir_name.append(base::IntToString16(::base::GetCurrentProcId()));
 318     new_dir_name.push_back('_');
 319     new_dir_name.append(base::IntToString16(base::RandInt(0, kint16max)));
 320
 321     path_to_create = base_dir.Append(new_dir_name);
 322     if (::CreateDirectory(path_to_create.value().c_str(), NULL)) {
 323       *new_dir = path_to_create;
 324       return true;
 325     }
 326   }
 327
 328   return false;
 329 }
 330
 331 bool CreateNewTempDirectory(const FilePath::StringType& prefix,
 332                             FilePath* new_temp_path) {
 333   base::ThreadRestrictions::AssertIOAllowed();
 334
 335   FilePath system_temp_dir;
 336   if (!GetTempDir(&system_temp_dir))
 337     return false;
 338
 339   return CreateTemporaryDirInDir(system_temp_dir, prefix, new_temp_path);
 340 }
 341
 342 bool CreateDirectoryAndGetError(const FilePath& full_path,
 343                                 base::PlatformFileError* error) {
 344   base::ThreadRestrictions::AssertIOAllowed();
 345
 346   // If the path exists, we've succeeded if it's a directory, failed otherwise.
 347   const wchar_t* full_path_str = full_path.value().c_str();
 348   DWORD fileattr = ::GetFileAttributes(full_path_str);
 349   if (fileattr != INVALID_FILE_ATTRIBUTES) {
 350     if ((fileattr & FILE_ATTRIBUTE_DIRECTORY) != 0) {
 351       DVLOG(1) << "CreateDirectory(" << full_path_str << "), "
 352                << "directory already exists.";
 353       return true;
 354     }
 355     DLOG(WARNING) << "CreateDirectory(" << full_path_str << "), "
 356                   << "conflicts with existing file.";
 357     if (error) {
 358       *error = base::PLATFORM_FILE_ERROR_NOT_A_DIRECTORY;
 359     }
 360     return false;
 361   }
 362
 363   // Invariant:  Path does not exist as file or directory.
 364
 365   // Attempt to create the parent recursively.  This will immediately return
 366   // true if it already exists, otherwise will create all required parent
 367   // directories starting with the highest-level missing parent.
 368   FilePath parent_path(full_path.DirName());
 369   if (parent_path.value() == full_path.value()) {
 370     if (error) {
 371       *error = base::PLATFORM_FILE_ERROR_NOT_FOUND;
 372     }
 373     return false;
 374   }
 375   if (!CreateDirectoryAndGetError(parent_path, error)) {
 376     DLOG(WARNING) << "Failed to create one of the parent directories.";
 377     if (error) {
 378       DCHECK(*error != base::PLATFORM_FILE_OK);
 379     }
 380     return false;
 381   }
 382
 383   if (!::CreateDirectory(full_path_str, NULL)) {
 384     DWORD error_code = ::GetLastError();
 385     if (error_code == ERROR_ALREADY_EXISTS && DirectoryExists(full_path)) {
 386       // This error code ERROR_ALREADY_EXISTS doesn't indicate whether we
 387       // were racing with someone creating the same directory, or a file
 388       // with the same path.  If DirectoryExists() returns true, we lost the
 389       // race to create the same directory.
 390       return true;
 391     } else {
 392       if (error)
 393         *error = base::LastErrorToPlatformFileError(error_code);
 394       DLOG(WARNING) << "Failed to create directory " << full_path_str
 395                     << ", last error is " << error_code << ".";
 396       return false;
 397     }
 398   } else {
 399     return true;
 400   }
 401 }
 402
 403 // TODO(rkc): Work out if we want to handle NTFS junctions here or not, handle
 404 // them if we do decide to.
 405 bool IsLink(const FilePath& file_path) {
 406   return false;
 407 }
 408
 409 bool GetFileInfo(const FilePath& file_path, base::PlatformFileInfo* results) {
 410   base::ThreadRestrictions::AssertIOAllowed();
 411
 412   WIN32_FILE_ATTRIBUTE_DATA attr;
 413   if (!GetFileAttributesEx(file_path.value().c_str(),
 414                            GetFileExInfoStandard, &attr)) {
 415     return false;
 416   }
 417
 418   ULARGE_INTEGER size;
 419   size.HighPart = attr.nFileSizeHigh;
 420   size.LowPart = attr.nFileSizeLow;
 421   results->size = size.QuadPart;
 422
 423   results->is_directory =
 424       (attr.dwFileAttributes & FILE_ATTRIBUTE_DIRECTORY) != 0;
 425   results->last_modified = base::Time::FromFileTime(attr.ftLastWriteTime);
 426   results->last_accessed = base::Time::FromFileTime(attr.ftLastAccessTime);
 427   results->creation_time = base::Time::FromFileTime(attr.ftCreationTime);
 428
 429   return true;
 430 }
 431
 432 FILE* OpenFile(const FilePath& filename, const char* mode) {
 433   base::ThreadRestrictions::AssertIOAllowed();
 434   std::wstring w_mode = ASCIIToWide(std::string(mode));
 435   return _wfsopen(filename.value().c_str(), w_mode.c_str(), _SH_DENYNO);
 436 }
 437
 438 FILE* OpenFile(const std::string& filename, const char* mode) {
 439   base::ThreadRestrictions::AssertIOAllowed();
 440   return _fsopen(filename.c_str(), mode, _SH_DENYNO);
 441 }
 442
 443 int ReadFile(const FilePath& filename, char* data, int size) {
 444   base::ThreadRestrictions::AssertIOAllowed();
 445   base::win::ScopedHandle file(CreateFile(filename.value().c_str(),
 446                                           GENERIC_READ,
 447                                           FILE_SHARE_READ | FILE_SHARE_WRITE,
 448                                           NULL,
 449                                           OPEN_EXISTING,
 450                                           FILE_FLAG_SEQUENTIAL_SCAN,
 451                                           NULL));
 452   if (!file)
 453     return -1;
 454
 455   DWORD read;
 456   if (::ReadFile(file, data, size, &read, NULL) &&
 457       static_cast<int>(read) == size)
 458     return read;
 459   return -1;
 460 }
 461
 462 int WriteFile(const FilePath& filename, const char* data, int size) {
 463   base::ThreadRestrictions::AssertIOAllowed();
 464   base::win::ScopedHandle file(CreateFile(filename.value().c_str(),
 465                                           GENERIC_WRITE,
 466                                           0,
 467                                           NULL,
 468                                           CREATE_ALWAYS,
 469                                           0,
 470                                           NULL));
 471   if (!file) {
 472     DLOG_GETLASTERROR(WARNING) << "CreateFile failed for path "
 473                                << filename.value();
 474     return -1;
 475   }
 476
 477   DWORD written;
 478   BOOL result = ::WriteFile(file, data, size, &written, NULL);
 479   if (result && static_cast<int>(written) == size)
 480     return written;
 481
 482   if (!result) {
 483     // WriteFile failed.
 484     DLOG_GETLASTERROR(WARNING) << "writing file " << filename.value()
 485                                << " failed";
 486   } else {
 487     // Didn't write all the bytes.
 488     DLOG(WARNING) << "wrote" << written << " bytes to "
 489                   << filename.value() << " expected " << size;
 490   }
 491   return -1;
 492 }
 493
 494 int AppendToFile(const FilePath& filename, const char* data, int size) {
 495   base::ThreadRestrictions::AssertIOAllowed();
 496   base::win::ScopedHandle file(CreateFile(filename.value().c_str(),
 497                                           FILE_APPEND_DATA,
 498                                           0,
 499                                           NULL,
 500                                           OPEN_EXISTING,
 501                                           0,
 502                                           NULL));
 503   if (!file) {
 504     DLOG_GETLASTERROR(WARNING) << "CreateFile failed for path "
 505                                << filename.value();
 506     return -1;
 507   }
 508
 509   DWORD written;
 510   BOOL result = ::WriteFile(file, data, size, &written, NULL);
 511   if (result && static_cast<int>(written) == size)
 512     return written;
 513
 514   if (!result) {
 515     // WriteFile failed.
 516     DLOG_GETLASTERROR(WARNING) << "writing file " << filename.value()
 517                                << " failed";
 518   } else {
 519     // Didn't write all the bytes.
 520     DLOG(WARNING) << "wrote" << written << " bytes to "
 521                   << filename.value() << " expected " << size;
 522   }
 523   return -1;
 524 }
 525
 526 // Gets the current working directory for the process.
 527 bool GetCurrentDirectory(FilePath* dir) {
 528   base::ThreadRestrictions::AssertIOAllowed();
 529
 530   wchar_t system_buffer[MAX_PATH];
 531   system_buffer[0] = 0;
 532   DWORD len = ::GetCurrentDirectory(MAX_PATH, system_buffer);
 533   if (len == 0 || len > MAX_PATH)
 534     return false;
 535   // TODO(evanm): the old behavior of this function was to always strip the
 536   // trailing slash.  We duplicate this here, but it shouldn't be necessary
 537   // when everyone is using the appropriate FilePath APIs.
 538   std::wstring dir_str(system_buffer);
 539   *dir = FilePath(dir_str).StripTrailingSeparators();
 540   return true;
 541 }
 542
 543 // Sets the current working directory for the process.
 544 bool SetCurrentDirectory(const FilePath& directory) {
 545   base::ThreadRestrictions::AssertIOAllowed();
 546   BOOL ret = ::SetCurrentDirectory(directory.value().c_str());
 547   return ret != 0;
 548 }
 549
 550 bool NormalizeFilePath(const FilePath& path, FilePath* real_path) {
 551   base::ThreadRestrictions::AssertIOAllowed();
 552   FilePath mapped_file;
 553   if (!NormalizeToNativeFilePath(path, &mapped_file))
 554     return false;
 555   // NormalizeToNativeFilePath() will return a path that starts with
 556   // "\Device\Harddisk...".  Helper DevicePathToDriveLetterPath()
 557   // will find a drive letter which maps to the path's device, so
 558   // that we return a path starting with a drive letter.
 559   return DevicePathToDriveLetterPath(mapped_file, real_path);
 560 }
 561
 562 bool DevicePathToDriveLetterPath(const FilePath& nt_device_path,
 563                                  FilePath* out_drive_letter_path) {
 564   base::ThreadRestrictions::AssertIOAllowed();
 565
 566   // Get the mapping of drive letters to device paths.
 567   const int kDriveMappingSize = 1024;
 568   wchar_t drive_mapping[kDriveMappingSize] = {'\0'};
 569   if (!::GetLogicalDriveStrings(kDriveMappingSize - 1, drive_mapping)) {
 570     DLOG(ERROR) << "Failed to get drive mapping.";
 571     return false;
 572   }
 573
 574   // The drive mapping is a sequence of null terminated strings.
 575   // The last string is empty.
 576   wchar_t* drive_map_ptr = drive_mapping;
 577   wchar_t device_path_as_string[MAX_PATH];
 578   wchar_t drive[] = L" :";
 579
 580   // For each string in the drive mapping, get the junction that links
 581   // to it.  If that junction is a prefix of |device_path|, then we
 582   // know that |drive| is the real path prefix.
 583   while (*drive_map_ptr) {
 584     drive[0] = drive_map_ptr[0];  // Copy the drive letter.
 585
 586     if (QueryDosDevice(drive, device_path_as_string, MAX_PATH)) {
 587       FilePath device_path(device_path_as_string);
 588       if (device_path == nt_device_path ||
 589           device_path.IsParent(nt_device_path)) {
 590         *out_drive_letter_path = FilePath(drive +
 591             nt_device_path.value().substr(wcslen(device_path_as_string)));
 592         return true;
 593       }
 594     }
 595     // Move to the next drive letter string, which starts one
 596     // increment after the '\0' that terminates the current string.
 597     while (*drive_map_ptr++);
 598   }
 599
 600   // No drive matched.  The path does not start with a device junction
 601   // that is mounted as a drive letter.  This means there is no drive
 602   // letter path to the volume that holds |device_path|, so fail.
 603   return false;
 604 }
 605
 606 bool NormalizeToNativeFilePath(const FilePath& path, FilePath* nt_path) {
 607   base::ThreadRestrictions::AssertIOAllowed();
 608   // In Vista, GetFinalPathNameByHandle() would give us the real path
 609   // from a file handle.  If we ever deprecate XP, consider changing the
 610   // code below to a call to GetFinalPathNameByHandle().  The method this
 611   // function uses is explained in the following msdn article:
 612   // http://msdn.microsoft.com/en-us/library/aa366789(VS.85).aspx
 613   base::win::ScopedHandle file_handle(
 614       ::CreateFile(path.value().c_str(),
 615                    GENERIC_READ,
 616                    kFileShareAll,
 617                    NULL,
 618                    OPEN_EXISTING,
 619                    FILE_ATTRIBUTE_NORMAL,
 620                    NULL));
 621   if (!file_handle)
 622     return false;
 623
 624   // Create a file mapping object.  Can't easily use MemoryMappedFile, because
 625   // we only map the first byte, and need direct access to the handle. You can
 626   // not map an empty file, this call fails in that case.
 627   base::win::ScopedHandle file_map_handle(
 628       ::CreateFileMapping(file_handle.Get(),
 629                           NULL,
 630                           PAGE_READONLY,
 631                           0,
 632                           1,  // Just one byte.  No need to look at the data.
 633                           NULL));
 634   if (!file_map_handle)
 635     return false;
 636
 637   // Use a view of the file to get the path to the file.
 638   void* file_view = MapViewOfFile(file_map_handle.Get(),
 639                                   FILE_MAP_READ, 0, 0, 1);
 640   if (!file_view)
 641     return false;
 642
 643   // The expansion of |path| into a full path may make it longer.
 644   // GetMappedFileName() will fail if the result is longer than MAX_PATH.
 645   // Pad a bit to be safe.  If kMaxPathLength is ever changed to be less
 646   // than MAX_PATH, it would be nessisary to test that GetMappedFileName()
 647   // not return kMaxPathLength.  This would mean that only part of the
 648   // path fit in |mapped_file_path|.
 649   const int kMaxPathLength = MAX_PATH + 10;
 650   wchar_t mapped_file_path[kMaxPathLength];
 651   bool success = false;
 652   HANDLE cp = GetCurrentProcess();
 653   if (::GetMappedFileNameW(cp, file_view, mapped_file_path, kMaxPathLength)) {
 654     *nt_path = FilePath(mapped_file_path);
 655     success = true;
 656   }
 657   ::UnmapViewOfFile(file_view);
 658   return success;
 659 }
 660
 661 int GetMaximumPathComponentLength(const FilePath& path) {
 662   base::ThreadRestrictions::AssertIOAllowed();
 663
 664   wchar_t volume_path[MAX_PATH];
 665   if (!GetVolumePathNameW(path.NormalizePathSeparators().value().c_str(),
 666                           volume_path,
 667                           arraysize(volume_path))) {
 668     return -1;
 669   }
 670
 671   DWORD max_length = 0;
 672   if (!GetVolumeInformationW(volume_path, NULL, 0, NULL, &max_length, NULL,
 673                              NULL, 0)) {
 674     return -1;
 675   }
 676
 677   // Length of |path| with path separator appended.
 678   size_t prefix = path.StripTrailingSeparators().value().size() + 1;
 679   // The whole path string must be shorter than MAX_PATH. That is, it must be
 680   // prefix + component_length < MAX_PATH (or equivalently, <= MAX_PATH - 1).
 681   int whole_path_limit = std::max(0, MAX_PATH - 1 - static_cast<int>(prefix));
 682   return std::min(whole_path_limit, static_cast<int>(max_length));
 683 }
 684
 685 }  // namespace file_util
 686
 687 namespace base {
 688 namespace internal {
 689
 690 bool MoveUnsafe(const FilePath& from_path, const FilePath& to_path) {
 691   ThreadRestrictions::AssertIOAllowed();
 692
 693   // NOTE: I suspect we could support longer paths, but that would involve
 694   // analyzing all our usage of files.
 695   if (from_path.value().length() >= MAX_PATH ||
 696       to_path.value().length() >= MAX_PATH) {
 697     return false;
 698   }
 699   if (MoveFileEx(from_path.value().c_str(), to_path.value().c_str(),
 700                  MOVEFILE_COPY_ALLOWED | MOVEFILE_REPLACE_EXISTING) != 0)
 701     return true;
 702
 703   // Keep the last error value from MoveFileEx around in case the below
 704   // fails.
 705   bool ret = false;
 706   DWORD last_error = ::GetLastError();
 707
 708   if (DirectoryExists(from_path)) {
 709     // MoveFileEx fails if moving directory across volumes. We will simulate
 710     // the move by using Copy and Delete. Ideally we could check whether
 711     // from_path and to_path are indeed in different volumes.
 712     ret = internal::CopyAndDeleteDirectory(from_path, to_path);
 713   }
 714
 715   if (!ret) {
 716     // Leave a clue about what went wrong so that it can be (at least) picked
 717     // up by a PLOG entry.
 718     ::SetLastError(last_error);
 719   }
 720
 721   return ret;
 722 }
 723
 724 bool CopyFileUnsafe(const FilePath& from_path, const FilePath& to_path) {
 725   ThreadRestrictions::AssertIOAllowed();
 726
 727   // NOTE: I suspect we could support longer paths, but that would involve
 728   // analyzing all our usage of files.
 729   if (from_path.value().length() >= MAX_PATH ||
 730       to_path.value().length() >= MAX_PATH) {
 731     return false;
 732   }
 733   return (::CopyFile(from_path.value().c_str(), to_path.value().c_str(),
 734                      false) != 0);
 735 }
 736
 737 bool CopyAndDeleteDirectory(const FilePath& from_path,
 738                             const FilePath& to_path) {
 739   ThreadRestrictions::AssertIOAllowed();
 740   if (CopyDirectory(from_path, to_path, true)) {
 741     if (DeleteFile(from_path, true))
 742       return true;
 743
 744     // Like Move, this function is not transactional, so we just
 745     // leave the copied bits behind if deleting from_path fails.
 746     // If to_path exists previously then we have already overwritten
 747     // it by now, we don't get better off by deleting the new bits.
 748   }
 749   return false;
 750 }
 751
 752 }  // namespace internal
 753 }  // namespace base