text: // Copyright (c) 2012 The Chromium Authors. All rights reserved.
  // Use of this source code is governed by a BSD-style license that can be
  // found in the LICENSE file.
  
  #include "base/files/file_util.h"
  
  #include <windows.h>
  #include <io.h>
  #include <psapi.h>
  #include <shellapi.h>
  #include <shlobj.h>
  #include <time.h>
  
  #include <algorithm>
  #include <limits>
  #include <string>
  
  #include "base/files/file_enumerator.h"
  #include "base/files/file_path.h"
  #include "base/logging.h"
  #include "base/metrics/histogram.h"
  #include "base/process/process_handle.h"
  #include "base/rand_util.h"
  #include "base/strings/string_number_conversions.h"
  #include "base/strings/string_util.h"
  #include "base/strings/utf_string_conversions.h"
  #include "base/threading/thread_restrictions.h"
  #include "base/time/time.h"
  #include "base/win/scoped_handle.h"
  #include "base/win/windows_version.h"
  
  namespace base {
  
  namespace {
  
  const DWORD kFileShareAll =
      FILE_SHARE_READ | FILE_SHARE_WRITE | FILE_SHARE_DELETE;
  
  }  // namespace
  
  FilePath MakeAbsoluteFilePath(const FilePath& input) {
    ThreadRestrictions::AssertIOAllowed();
    wchar_t file_path[MAX_PATH];
    if (!_wfullpath(file_path, input.value().c_str(), MAX_PATH))
      return FilePath();
    return FilePath(file_path);
  }
  
  bool DeleteFile(const FilePath& path, bool recursive) {
    ThreadRestrictions::AssertIOAllowed();
  
    if (path.value().length() >= MAX_PATH)
      return false;
  
    // On XP SHFileOperation will return ERROR_ACCESS_DENIED instead of
    // ERROR_FILE_NOT_FOUND, so just shortcut this here.
    if (path.empty())
      return true;
  
    if (!recursive) {
      // If not recursing, then first check to see if |path| is a directory.
      // If it is, then remove it with RemoveDirectory.
      File::Info file_info;
      if (GetFileInfo(path, &file_info) && file_info.is_directory)
        return RemoveDirectory(path.value().c_str()) != 0;
  
      // Otherwise, it's a file, wildcard or non-existant. Try DeleteFile first
      // because it should be faster. If DeleteFile fails, then we fall through
      // to SHFileOperation, which will do the right thing.
      if (::DeleteFile(path.value().c_str()) != 0)
        return true;
    }
  
    // SHFILEOPSTRUCT wants the path to be terminated with two NULLs,
    // so we have to use wcscpy because wcscpy_s writes non-NULLs
    // into the rest of the buffer.
    wchar_t double_terminated_path[MAX_PATH + 1] = {0};
  #pragma warning(suppress:4996)  // don't complain about wcscpy deprecation
    wcscpy(double_terminated_path, path.value().c_str());
  
    SHFILEOPSTRUCT file_operation = {0};
    file_operation.wFunc = FO_DELETE;
    file_operation.pFrom = double_terminated_path;
    file_operation.fFlags = FOF_NOERRORUI | FOF_SILENT | FOF_NOCONFIRMATION;
    if (!recursive)
      file_operation.fFlags |= FOF_NORECURSION | FOF_FILESONLY;
    int err = SHFileOperation(&file_operation);
  
    // Since we're passing flags to the operation telling it to be silent,
    // it's possible for the operation to be aborted/cancelled without err
    // being set (although MSDN doesn't give any scenarios for how this can
    // happen).  See MSDN for SHFileOperation and SHFILEOPTSTRUCT.
    if (file_operation.fAnyOperationsAborted)
      return false;
  
    // Some versions of Windows return ERROR_FILE_NOT_FOUND (0x2) when deleting
    // an empty directory and some return 0x402 when they should be returning
    // ERROR_FILE_NOT_FOUND. MSDN says Vista and up won't return 0x402.  Windows 7
    // can return DE_INVALIDFILES (0x7C) for nonexistent directories.
    return (err == 0 || err == ERROR_FILE_NOT_FOUND || err == 0x402 ||
            err == 0x7C);
  }
  
  bool DeleteFileAfterReboot(const FilePath& path) {
    ThreadRestrictions::AssertIOAllowed();
  
    if (path.value().length() >= MAX_PATH)
      return false;
  
    return MoveFileEx(path.value().c_str(), NULL,
                      MOVEFILE_DELAY_UNTIL_REBOOT |
                          MOVEFILE_REPLACE_EXISTING) != FALSE;
  }
  
  bool ReplaceFile(const FilePath& from_path,
                   const FilePath& to_path,
                   File::Error* error) {
    ThreadRestrictions::AssertIOAllowed();
    // Try a simple move first.  It will only succeed when |to_path| doesn't
    // already exist.
    if (::MoveFile(from_path.value().c_str(), to_path.value().c_str()))
      return true;
    // Try the full-blown replace if the move fails, as ReplaceFile will only
    // succeed when |to_path| does exist. When writing to a network share, we may
    // not be able to change the ACLs. Ignore ACL errors then
    // (REPLACEFILE_IGNORE_MERGE_ERRORS).
    if (::ReplaceFile(to_path.value().c_str(), from_path.value().c_str(), NULL,
                      REPLACEFILE_IGNORE_MERGE_ERRORS, NULL, NULL)) {
      return true;
    }
    if (error)
      *error = File::OSErrorToFileError(GetLastError());
    return false;
  }
  
  bool CopyDirectory(const FilePath& from_path, const FilePath& to_path,
                     bool recursive) {
    // NOTE(maruel): Previous version of this function used to call
    // SHFileOperation().  This used to copy the file attributes and extended
    // attributes, OLE structured storage, NTFS file system alternate data
    // streams, SECURITY_DESCRIPTOR. In practice, this is not what we want, we
    // want the containing directory to propagate its SECURITY_DESCRIPTOR.
    ThreadRestrictions::AssertIOAllowed();
  
    // NOTE: I suspect we could support longer paths, but that would involve
    // analyzing all our usage of files.
    if (from_path.value().length() >= MAX_PATH ||
        to_path.value().length() >= MAX_PATH) {
      return false;
    }
  
    // This function does not properly handle destinations within the source.
    FilePath real_to_path = to_path;
    if (PathExists(real_to_path)) {
      real_to_path = MakeAbsoluteFilePath(real_to_path);
      if (real_to_path.empty())
        return false;
    } else {
      real_to_path = MakeAbsoluteFilePath(real_to_path.DirName());
      if (real_to_path.empty())
        return false;
    }
    FilePath real_from_path = MakeAbsoluteFilePath(from_path);
    if (real_from_path.empty())
      return false;
    if (real_to_path.value().size() >= real_from_path.value().size() &&
        real_to_path.value().compare(0, real_from_path.value().size(),
                                     real_from_path.value()) == 0) {
      return false;
    }
  
    int traverse_type = FileEnumerator::FILES;
    if (recursive)
      traverse_type |= FileEnumerator::DIRECTORIES;
    FileEnumerator traversal(from_path, recursive, traverse_type);
  
    if (!PathExists(from_path)) {
      DLOG(ERROR) << "CopyDirectory() couldn't stat source directory: "
                  << from_path.value().c_str();
      return false;
    }
    // TODO(maruel): This is not necessary anymore.
    DCHECK(recursive || DirectoryExists(from_path));
  
    FilePath current = from_path;
    bool from_is_dir = DirectoryExists(from_path);
    bool success = true;
    FilePath from_path_base = from_path;
    if (recursive && DirectoryExists(to_path)) {
      // If the destination already exists and is a directory, then the
      // top level of source needs to be copied.
      from_path_base = from_path.DirName();
    }
  
    while (success && !current.empty()) {
      // current is the source path, including from_path, so append
      // the suffix after from_path to to_path to create the target_path.
      FilePath target_path(to_path);
      if (from_path_base != current) {
        if (!from_path_base.AppendRelativePath(current, &target_path)) {
          success = false;
          break;
        }
      }
  
      if (from_is_dir) {
        if (!DirectoryExists(target_path) &&
            !::CreateDirectory(target_path.value().c_str(), NULL)) {
          DLOG(ERROR) << "CopyDirectory() couldn't create directory: "
                      << target_path.value().c_str();
          success = false;
        }
      } else if (!internal::CopyFileUnsafe(current, target_path)) {
        DLOG(ERROR) << "CopyDirectory() couldn't create file: "
                    << target_path.value().c_str();
        success = false;
      }
  
      current = traversal.Next();
      if (!current.empty())
        from_is_dir = traversal.GetInfo().IsDirectory();
    }
  
    return success;
  }
  
  bool PathExists(const FilePath& path) {
    ThreadRestrictions::AssertIOAllowed();
    return (GetFileAttributes(path.value().c_str()) != INVALID_FILE_ATTRIBUTES);
  }
  
  bool PathIsWritable(const FilePath& path) {
    ThreadRestrictions::AssertIOAllowed();
    HANDLE dir =
        CreateFile(path.value().c_str(), FILE_ADD_FILE, kFileShareAll,
                   NULL, OPEN_EXISTING, FILE_FLAG_BACKUP_SEMANTICS, NULL);
  
    if (dir == INVALID_HANDLE_VALUE)
      return false;
  
    CloseHandle(dir);
    return true;
  }
  
  bool DirectoryExists(const FilePath& path) {
    ThreadRestrictions::AssertIOAllowed();
    DWORD fileattr = GetFileAttributes(path.value().c_str());
    if (fileattr != INVALID_FILE_ATTRIBUTES)
      return (fileattr & FILE_ATTRIBUTE_DIRECTORY) != 0;
    return false;
  }
  
  bool GetTempDir(FilePath* path) {
    wchar_t temp_path[MAX_PATH + 1];
    DWORD path_len = ::GetTempPath(MAX_PATH, temp_path);
    if (path_len >= MAX_PATH || path_len <= 0)
      return false;
    // TODO(evanm): the old behavior of this function was to always strip the
    // trailing slash.  We duplicate this here, but it shouldn't be necessary
    // when everyone is using the appropriate FilePath APIs.
    *path = FilePath(temp_path).StripTrailingSeparators();
    return true;
  }
  
  FilePath GetHomeDir() {
    char16 result[MAX_PATH];
    if (SUCCEEDED(SHGetFolderPath(NULL, CSIDL_PROFILE, NULL, SHGFP_TYPE_CURRENT,
                                  result)) &&
        result[0]) {
      return FilePath(result);
    }
  
    // Fall back to the temporary directory on failure.
    FilePath temp;
    if (GetTempDir(&temp))
      return temp;
  
    // Last resort.
    return FilePath(L"C:\\");
  }
  
  bool CreateTemporaryFile(FilePath* path) {
    ThreadRestrictions::AssertIOAllowed();
  
    FilePath temp_file;
  
    if (!GetTempDir(path))
      return false;
  
    if (CreateTemporaryFileInDir(*path, &temp_file)) {
      *path = temp_file;
      return true;
    }
  
    return false;
  }
  
  // On POSIX we have semantics to create and open a temporary file
  // atomically.
  // TODO(jrg): is there equivalent call to use on Windows instead of
  // going 2-step?
  FILE* CreateAndOpenTemporaryFileInDir(const FilePath& dir, FilePath* path) {
    ThreadRestrictions::AssertIOAllowed();
    if (!CreateTemporaryFileInDir(dir, path)) {
      return NULL;
    }
    // Open file in binary mode, to avoid problems with fwrite. On Windows
    // it replaces \n's with \r\n's, which may surprise you.
    // Reference: http://msdn.microsoft.com/en-us/library/h9t88zwz(VS.71).aspx
    return OpenFile(*path, "wb+");
  }
  
  bool CreateTemporaryFileInDir(const FilePath& dir, FilePath* temp_file) {
    ThreadRestrictions::AssertIOAllowed();
  
    wchar_t temp_name[MAX_PATH + 1];
  
    if (!GetTempFileName(dir.value().c_str(), L"", 0, temp_name)) {
      DPLOG(WARNING) << "Failed to get temporary file name in "
                     << UTF16ToUTF8(dir.value());
      return false;
    }
  
    wchar_t long_temp_name[MAX_PATH + 1];
    DWORD long_name_len = GetLongPathName(temp_name, long_temp_name, MAX_PATH);
    if (long_name_len > MAX_PATH || long_name_len == 0) {
      // GetLongPathName() failed, but we still have a temporary file.
      *temp_file = FilePath(temp_name);
      return true;
    }
  
    FilePath::StringType long_temp_name_str;
    long_temp_name_str.assign(long_temp_name, long_name_len);
    *temp_file = FilePath(long_temp_name_str);
    return true;
  }
  
  bool CreateTemporaryDirInDir(const FilePath& base_dir,
                               const FilePath::StringType& prefix,
                               FilePath* new_dir) {
    ThreadRestrictions::AssertIOAllowed();
  
    FilePath path_to_create;
  
    for (int count = 0; count < 50; ++count) {
      // Try create a new temporary directory with random generated name. If
      // the one exists, keep trying another path name until we reach some limit.
      string16 new_dir_name;
      new_dir_name.assign(prefix);
      new_dir_name.append(IntToString16(GetCurrentProcId()));
      new_dir_name.push_back('_');
      new_dir_name.append(IntToString16(RandInt(0, kint16max)));
  
      path_to_create = base_dir.Append(new_dir_name);
      if (::CreateDirectory(path_to_create.value().c_str(), NULL)) {
        *new_dir = path_to_create;
        return true;
      }
    }
  
    return false;
  }
  
  bool CreateNewTempDirectory(const FilePath::StringType& prefix,
                              FilePath* new_temp_path) {
    ThreadRestrictions::AssertIOAllowed();
  
    FilePath system_temp_dir;
    if (!GetTempDir(&system_temp_dir))
      return false;
  
    return CreateTemporaryDirInDir(system_temp_dir, prefix, new_temp_path);
  }
  
  bool CreateDirectoryAndGetError(const FilePath& full_path,
                                  File::Error* error) {
    ThreadRestrictions::AssertIOAllowed();
  
    // If the path exists, we've succeeded if it's a directory, failed otherwise.
    const wchar_t* full_path_str = full_path.value().c_str();
    DWORD fileattr = ::GetFileAttributes(full_path_str);
    if (fileattr != INVALID_FILE_ATTRIBUTES) {
      if ((fileattr & FILE_ATTRIBUTE_DIRECTORY) != 0) {
        DVLOG(1) << "CreateDirectory(" << full_path_str << "), "
                 << "directory already exists.";
        return true;
      }
      DLOG(WARNING) << "CreateDirectory(" << full_path_str << "), "
                    << "conflicts with existing file.";
      if (error) {
        *error = File::FILE_ERROR_NOT_A_DIRECTORY;
      }
      return false;
    }
  
    // Invariant:  Path does not exist as file or directory.
  
    // Attempt to create the parent recursively.  This will immediately return
    // true if it already exists, otherwise will create all required parent
    // directories starting with the highest-level missing parent.
    FilePath parent_path(full_path.DirName());
    if (parent_path.value() == full_path.value()) {
      if (error) {
        *error = File::FILE_ERROR_NOT_FOUND;
      }
      return false;
    }
    if (!CreateDirectoryAndGetError(parent_path, error)) {
      DLOG(WARNING) << "Failed to create one of the parent directories.";
      if (error) {
        DCHECK(*error != File::FILE_OK);
      }
      return false;
    }
  
    if (!::CreateDirectory(full_path_str, NULL)) {
      DWORD error_code = ::GetLastError();
      if (error_code == ERROR_ALREADY_EXISTS && DirectoryExists(full_path)) {
        // This error code ERROR_ALREADY_EXISTS doesn't indicate whether we
        // were racing with someone creating the same directory, or a file
        // with the same path.  If DirectoryExists() returns true, we lost the
        // race to create the same directory.
        return true;
      } else {
        if (error)
          *error = File::OSErrorToFileError(error_code);
        DLOG(WARNING) << "Failed to create directory " << full_path_str
                      << ", last error is " << error_code << ".";
        return false;
      }
    } else {
      return true;
    }
  }
  
  bool NormalizeFilePath(const FilePath& path, FilePath* real_path) {
    ThreadRestrictions::AssertIOAllowed();
    FilePath mapped_file;
    if (!NormalizeToNativeFilePath(path, &mapped_file))
      return false;
    // NormalizeToNativeFilePath() will return a path that starts with
    // "\Device\Harddisk...".  Helper DevicePathToDriveLetterPath()
    // will find a drive letter which maps to the path's device, so
    // that we return a path starting with a drive letter.
    return DevicePathToDriveLetterPath(mapped_file, real_path);
  }
  
  bool DevicePathToDriveLetterPath(const FilePath& nt_device_path,
                                   FilePath* out_drive_letter_path) {
    ThreadRestrictions::AssertIOAllowed();
  
    // Get the mapping of drive letters to device paths.
    const int kDriveMappingSize = 1024;
    wchar_t drive_mapping[kDriveMappingSize] = {'\0'};
    if (!::GetLogicalDriveStrings(kDriveMappingSize - 1, drive_mapping)) {
      DLOG(ERROR) << "Failed to get drive mapping.";
      return false;
    }
  
    // The drive mapping is a sequence of null terminated strings.
    // The last string is empty.
    wchar_t* drive_map_ptr = drive_mapping;
    wchar_t device_path_as_string[MAX_PATH];
    wchar_t drive[] = L" :";
  
    // For each string in the drive mapping, get the junction that links
    // to it.  If that junction is a prefix of |device_path|, then we
    // know that |drive| is the real path prefix.
    while (*drive_map_ptr) {
      drive[0] = drive_map_ptr[0];  // Copy the drive letter.
  
      if (QueryDosDevice(drive, device_path_as_string, MAX_PATH)) {
        FilePath device_path(device_path_as_string);
        if (device_path == nt_device_path ||
            device_path.IsParent(nt_device_path)) {
          *out_drive_letter_path = FilePath(drive +
              nt_device_path.value().substr(wcslen(device_path_as_string)));
          return true;
        }
      }
      // Move to the next drive letter string, which starts one
      // increment after the '\0' that terminates the current string.
      while (*drive_map_ptr++);
    }
  
    // No drive matched.  The path does not start with a device junction
    // that is mounted as a drive letter.  This means there is no drive
    // letter path to the volume that holds |device_path|, so fail.
    return false;
  }
  
  bool NormalizeToNativeFilePath(const FilePath& path, FilePath* nt_path) {
    ThreadRestrictions::AssertIOAllowed();
    // In Vista, GetFinalPathNameByHandle() would give us the real path
    // from a file handle.  If we ever deprecate XP, consider changing the
    // code below to a call to GetFinalPathNameByHandle().  The method this
    // function uses is explained in the following msdn article:
    // http://msdn.microsoft.com/en-us/library/aa366789(VS.85).aspx
    base::win::ScopedHandle file_handle(
        ::CreateFile(path.value().c_str(),
                     GENERIC_READ,
                     kFileShareAll,
                     NULL,
                     OPEN_EXISTING,
                     FILE_ATTRIBUTE_NORMAL,
                     NULL));
    if (!file_handle)
      return false;
  
    // Create a file mapping object.  Can't easily use MemoryMappedFile, because
    // we only map the first byte, and need direct access to the handle. You can
    // not map an empty file, this call fails in that case.
    base::win::ScopedHandle file_map_handle(
        ::CreateFileMapping(file_handle.Get(),
                            NULL,
                            PAGE_READONLY,
                            0,
                            1,  // Just one byte.  No need to look at the data.
                            NULL));
    if (!file_map_handle)
      return false;
  
    // Use a view of the file to get the path to the file.
    void* file_view = MapViewOfFile(file_map_handle.Get(),
                                    FILE_MAP_READ, 0, 0, 1);
    if (!file_view)
      return false;
  
    // The expansion of |path| into a full path may make it longer.
    // GetMappedFileName() will fail if the result is longer than MAX_PATH.
    // Pad a bit to be safe.  If kMaxPathLength is ever changed to be less
    // than MAX_PATH, it would be nessisary to test that GetMappedFileName()
    // not return kMaxPathLength.  This would mean that only part of the
    // path fit in |mapped_file_path|.
    const int kMaxPathLength = MAX_PATH + 10;
    wchar_t mapped_file_path[kMaxPathLength];
    bool success = false;
    HANDLE cp = GetCurrentProcess();
    if (::GetMappedFileNameW(cp, file_view, mapped_file_path, kMaxPathLength)) {
      *nt_path = FilePath(mapped_file_path);
      success = true;
    }
    ::UnmapViewOfFile(file_view);
    return success;
  }
  
  // TODO(rkc): Work out if we want to handle NTFS junctions here or not, handle
  // them if we do decide to.
  bool IsLink(const FilePath& file_path) {
    return false;
  }
  
  bool GetFileInfo(const FilePath& file_path, File::Info* results) {
    ThreadRestrictions::AssertIOAllowed();
  
    WIN32_FILE_ATTRIBUTE_DATA attr;
    if (!GetFileAttributesEx(file_path.value().c_str(),
                             GetFileExInfoStandard, &attr)) {
      return false;
    }
  
    ULARGE_INTEGER size;
    size.HighPart = attr.nFileSizeHigh;
    size.LowPart = attr.nFileSizeLow;
    results->size = size.QuadPart;
  
    results->is_directory =
        (attr.dwFileAttributes & FILE_ATTRIBUTE_DIRECTORY) != 0;
    results->last_modified = Time::FromFileTime(attr.ftLastWriteTime);
    results->last_accessed = Time::FromFileTime(attr.ftLastAccessTime);
    results->creation_time = Time::FromFileTime(attr.ftCreationTime);
  
    return true;
  }
  
  FILE* OpenFile(const FilePath& filename, const char* mode) {
    ThreadRestrictions::AssertIOAllowed();
    std::wstring w_mode = ASCIIToWide(std::string(mode));
    return _wfsopen(filename.value().c_str(), w_mode.c_str(), _SH_DENYNO);
  }
  
  FILE* FileToFILE(File file, const char* mode) {
    if (!file.IsValid())
      return NULL;
    int fd =
        _open_osfhandle(reinterpret_cast<intptr_t>(file.GetPlatformFile()), 0);
    if (fd < 0)
      return NULL;
    file.TakePlatformFile();
    FILE* stream = _fdopen(fd, mode);
    if (!stream)
      _close(fd);
    return stream;
  }
  
  int ReadFile(const FilePath& filename, char* data, int max_size) {
    ThreadRestrictions::AssertIOAllowed();
    base::win::ScopedHandle file(CreateFile(filename.value().c_str(),
                                            GENERIC_READ,
                                            FILE_SHARE_READ | FILE_SHARE_WRITE,
                                            NULL,
                                            OPEN_EXISTING,
                                            FILE_FLAG_SEQUENTIAL_SCAN,
                                            NULL));
    if (!file)
      return -1;
  
    DWORD read;
    if (::ReadFile(file, data, max_size, &read, NULL))
      return read;
  
    return -1;
  }
  
  int WriteFile(const FilePath& filename, const char* data, int size) {
    ThreadRestrictions::AssertIOAllowed();
    base::win::ScopedHandle file(CreateFile(filename.value().c_str(),
                                            GENERIC_WRITE,
                                            0,
                                            NULL,
                                            CREATE_ALWAYS,
                                            0,
                                            NULL));
    if (!file) {
      DPLOG(WARNING) << "CreateFile failed for path "
                     << UTF16ToUTF8(filename.value());
      return -1;
    }
  
    DWORD written;
    BOOL result = ::WriteFile(file, data, size, &written, NULL);
    if (result && static_cast<int>(written) == size)
      return written;
  
    if (!result) {
      // WriteFile failed.
      DPLOG(WARNING) << "writing file " << UTF16ToUTF8(filename.value())
                     << " failed";
    } else {
      // Didn't write all the bytes.
      DLOG(WARNING) << "wrote" << written << " bytes to "
                    << UTF16ToUTF8(filename.value()) << " expected " << size;
    }
    return -1;
  }
  
  int AppendToFile(const FilePath& filename, const char* data, int size) {
    ThreadRestrictions::AssertIOAllowed();
    base::win::ScopedHandle file(CreateFile(filename.value().c_str(),
                                            FILE_APPEND_DATA,
                                            0,
                                            NULL,
                                            OPEN_EXISTING,
                                            0,
                                            NULL));
    if (!file) {
      DPLOG(WARNING) << "CreateFile failed for path "
                     << UTF16ToUTF8(filename.value());
      return -1;
    }
  
    DWORD written;
    BOOL result = ::WriteFile(file, data, size, &written, NULL);
    if (result && static_cast<int>(written) == size)
      return written;
  
    if (!result) {
      // WriteFile failed.
      DPLOG(WARNING) << "writing file " << UTF16ToUTF8(filename.value())
                     << " failed";
    } else {
      // Didn't write all the bytes.
      DLOG(WARNING) << "wrote" << written << " bytes to "
                    << UTF16ToUTF8(filename.value()) << " expected " << size;
    }
    return -1;
  }
  
  // Gets the current working directory for the process.
  bool GetCurrentDirectory(FilePath* dir) {
    ThreadRestrictions::AssertIOAllowed();
  
    wchar_t system_buffer[MAX_PATH];
    system_buffer[0] = 0;
    DWORD len = ::GetCurrentDirectory(MAX_PATH, system_buffer);
    if (len == 0 || len > MAX_PATH)
      return false;
    // TODO(evanm): the old behavior of this function was to always strip the
    // trailing slash.  We duplicate this here, but it shouldn't be necessary
    // when everyone is using the appropriate FilePath APIs.
    std::wstring dir_str(system_buffer);
    *dir = FilePath(dir_str).StripTrailingSeparators();
    return true;
  }
  
  // Sets the current working directory for the process.
  bool SetCurrentDirectory(const FilePath& directory) {
    ThreadRestrictions::AssertIOAllowed();
    BOOL ret = ::SetCurrentDirectory(directory.value().c_str());
    return ret != 0;
  }
  
  int GetMaximumPathComponentLength(const FilePath& path) {
    ThreadRestrictions::AssertIOAllowed();
  
    wchar_t volume_path[MAX_PATH];
    if (!GetVolumePathNameW(path.NormalizePathSeparators().value().c_str(),
                            volume_path,
                            arraysize(volume_path))) {
      return -1;
    }
  
    DWORD max_length = 0;
    if (!GetVolumeInformationW(volume_path, NULL, 0, NULL, &max_length, NULL,
                               NULL, 0)) {
      return -1;
    }
  
    // Length of |path| with path separator appended.
    size_t prefix = path.StripTrailingSeparators().value().size() + 1;
    // The whole path string must be shorter than MAX_PATH. That is, it must be
    // prefix + component_length < MAX_PATH (or equivalently, <= MAX_PATH - 1).
    int whole_path_limit = std::max(0, MAX_PATH - 1 - static_cast<int>(prefix));
    return std::min(whole_path_limit, static_cast<int>(max_length));
  }
  
  // -----------------------------------------------------------------------------
  
  namespace internal {
  
  bool MoveUnsafe(const FilePath& from_path, const FilePath& to_path) {
    ThreadRestrictions::AssertIOAllowed();
  
    // NOTE: I suspect we could support longer paths, but that would involve
    // analyzing all our usage of files.
    if (from_path.value().length() >= MAX_PATH ||
        to_path.value().length() >= MAX_PATH) {
      return false;
    }
    if (MoveFileEx(from_path.value().c_str(), to_path.value().c_str(),
                   MOVEFILE_COPY_ALLOWED | MOVEFILE_REPLACE_EXISTING) != 0)
      return true;
  
    // Keep the last error value from MoveFileEx around in case the below
    // fails.
    bool ret = false;
    DWORD last_error = ::GetLastError();
  
    if (DirectoryExists(from_path)) {
      // MoveFileEx fails if moving directory across volumes. We will simulate
      // the move by using Copy and Delete. Ideally we could check whether
      // from_path and to_path are indeed in different volumes.
      ret = internal::CopyAndDeleteDirectory(from_path, to_path);
    }
  
    if (!ret) {
      // Leave a clue about what went wrong so that it can be (at least) picked
      // up by a PLOG entry.
      ::SetLastError(last_error);
    }
  
    return ret;
  }
  
  bool CopyFileUnsafe(const FilePath& from_path, const FilePath& to_path) {
    ThreadRestrictions::AssertIOAllowed();
  
    // NOTE: I suspect we could support longer paths, but that would involve
    // analyzing all our usage of files.
    if (from_path.value().length() >= MAX_PATH ||
        to_path.value().length() >= MAX_PATH) {
      return false;
    }
  
    // Unlike the posix implementation that copies the file manually and discards
    // the ACL bits, CopyFile() copies the complete SECURITY_DESCRIPTOR and access
    // bits, which is usually not what we want. We can't do much about the
    // SECURITY_DESCRIPTOR but at least remove the read only bit.
    const wchar_t* dest = to_path.value().c_str();
    if (!::CopyFile(from_path.value().c_str(), dest, false)) {
      // Copy failed.
      return false;
    }
    DWORD attrs = GetFileAttributes(dest);
    if (attrs == INVALID_FILE_ATTRIBUTES) {
      return false;
    }
    if (attrs & FILE_ATTRIBUTE_READONLY) {
      SetFileAttributes(dest, attrs & ~FILE_ATTRIBUTE_READONLY);
    }
    return true;
  }
  
  bool CopyAndDeleteDirectory(const FilePath& from_path,
                              const FilePath& to_path) {
    ThreadRestrictions::AssertIOAllowed();
    if (CopyDirectory(from_path, to_path, true)) {
      if (DeleteFile(from_path, true))
        return true;
  
      // Like Move, this function is not transactional, so we just
      // leave the copied bits behind if deleting from_path fails.
      // If to_path exists previously then we have already overwritten
      // it by now, we don't get better off by deleting the new bits.
    }
    return false;
  }
  
  }  // namespace internal
  }  // namespace base
  