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 "chrome/browser/download/download_path_reservation_tracker.h"
6
7#include <map>
8
9#include "base/bind.h"
10#include "base/callback.h"
11#include "base/file_util.h"
12#include "base/logging.h"
13#include "base/path_service.h"
14#include "base/stl_util.h"
15#include "base/strings/string_util.h"
16#include "base/strings/stringprintf.h"
17#include "base/third_party/icu/icu_utf.h"
18#include "chrome/common/chrome_paths.h"
19#include "content/public/browser/browser_thread.h"
20#include "content/public/browser/download_item.h"
21
22using content::BrowserThread;
23using content::DownloadItem;
24
25namespace {
26
27typedef DownloadItem* ReservationKey;
28typedef std::map<ReservationKey, base::FilePath> ReservationMap;
29
30// The lower bound for file name truncation. If the truncation results in a name
31// shorter than this limit, we give up automatic truncation and prompt the user.
32static const size_t kTruncatedNameLengthLowerbound = 5;
33
34// The length of the suffix string we append for an intermediate file name.
35// In the file name truncation, we keep the margin to append the suffix.
36// TODO(kinaba): remove the margin. The user should be able to set maximum
37// possible filename.
38static const size_t kIntermediateNameSuffixLength = sizeof(".crdownload") - 1;
39
40// Map of download path reservations. Each reserved path is associated with a
41// ReservationKey=DownloadItem*. This object is destroyed in |Revoke()| when
42// there are no more reservations.
43//
44// It is not an error, although undesirable, to have multiple DownloadItem*s
45// that are mapped to the same path. This can happen if a reservation is created
46// that is supposed to overwrite an existing reservation.
47ReservationMap* g_reservation_map = NULL;
48
49// Observes a DownloadItem for changes to its target path and state. Updates or
50// revokes associated download path reservations as necessary. Created, invoked
51// and destroyed on the UI thread.
52class DownloadItemObserver : public DownloadItem::Observer {
53 public:
54  explicit DownloadItemObserver(DownloadItem* download_item);
55
56 private:
57  virtual ~DownloadItemObserver();
58
59  // DownloadItem::Observer
60  virtual void OnDownloadUpdated(DownloadItem* download) OVERRIDE;
61  virtual void OnDownloadDestroyed(DownloadItem* download) OVERRIDE;
62
63  DownloadItem* download_item_;
64
65  // Last known target path for the download.
66  base::FilePath last_target_path_;
67
68  DISALLOW_COPY_AND_ASSIGN(DownloadItemObserver);
69};
70
71// Returns true if the given path is in use by a path reservation.
72bool IsPathReserved(const base::FilePath& path) {
73  DCHECK(BrowserThread::CurrentlyOn(BrowserThread::FILE));
74  // No reservation map => no reservations.
75  if (g_reservation_map == NULL)
76    return false;
77  // Unfortunately path normalization doesn't work reliably for non-existant
78  // files. So given a FilePath, we can't derive a normalized key that we can
79  // use for lookups. We only expect a small number of concurrent downloads at
80  // any given time, so going through all of them shouldn't be too slow.
81  for (ReservationMap::const_iterator iter = g_reservation_map->begin();
82       iter != g_reservation_map->end(); ++iter) {
83    if (iter->second == path)
84      return true;
85  }
86  return false;
87}
88
89// Returns true if the given path is in use by any path reservation or the
90// file system. Called on the FILE thread.
91bool IsPathInUse(const base::FilePath& path) {
92  DCHECK(BrowserThread::CurrentlyOn(BrowserThread::FILE));
93  // If there is a reservation, then the path is in use.
94  if (IsPathReserved(path))
95    return true;
96
97  // If the path exists in the file system, then the path is in use.
98  if (base::PathExists(path))
99    return true;
100
101  return false;
102}
103
104// Truncates path->BaseName() to make path->BaseName().value().size() <= limit.
105// - It keeps the extension as is. Only truncates the body part.
106// - It secures the base filename length to be more than or equals to
107//   kTruncatedNameLengthLowerbound.
108// If it was unable to shorten the name, returns false.
109bool TruncateFileName(base::FilePath* path, size_t limit) {
110  base::FilePath basename(path->BaseName());
111  // It is already short enough.
112  if (basename.value().size() <= limit)
113    return true;
114
115  base::FilePath dir(path->DirName());
116  base::FilePath::StringType ext(basename.Extension());
117  base::FilePath::StringType name(basename.RemoveExtension().value());
118
119  // Impossible to satisfy the limit.
120  if (limit < kTruncatedNameLengthLowerbound + ext.size())
121    return false;
122  limit -= ext.size();
123
124  // Encoding specific truncation logic.
125  base::FilePath::StringType truncated;
126#if defined(OS_CHROMEOS) || defined(OS_MACOSX)
127  // UTF-8.
128  base::TruncateUTF8ToByteSize(name, limit, &truncated);
129#elif defined(OS_WIN)
130  // UTF-16.
131  DCHECK(name.size() > limit);
132  truncated = name.substr(0, CBU16_IS_TRAIL(name[limit]) ? limit - 1 : limit);
133#else
134  // We cannot generally assume that the file name encoding is in UTF-8 (see
135  // the comment for FilePath::AsUTF8Unsafe), hence no safe way to truncate.
136#endif
137
138  if (truncated.size() < kTruncatedNameLengthLowerbound)
139    return false;
140  *path = dir.Append(truncated + ext);
141  return true;
142}
143
144// Called on the FILE thread to reserve a download path. This method:
145// - Creates directory |default_download_path| if it doesn't exist.
146// - Verifies that the parent directory of |suggested_path| exists and is
147//   writeable.
148// - Truncates the suggested name if it exceeds the filesystem's limit.
149// - Uniquifies |suggested_path| if |should_uniquify_path| is true.
150// - Schedules |callback| on the UI thread with the reserved path and a flag
151//   indicating whether the returned path has been successfully verified.
152void CreateReservation(
153    ReservationKey key,
154    const base::FilePath& suggested_path,
155    const base::FilePath& default_download_path,
156    bool create_directory,
157    DownloadPathReservationTracker::FilenameConflictAction conflict_action,
158    const DownloadPathReservationTracker::ReservedPathCallback& callback) {
159  DCHECK(BrowserThread::CurrentlyOn(BrowserThread::FILE));
160  DCHECK(suggested_path.IsAbsolute());
161
162  // Create a reservation map if one doesn't exist. It will be automatically
163  // deleted when all the reservations are revoked.
164  if (g_reservation_map == NULL)
165    g_reservation_map = new ReservationMap;
166
167  ReservationMap& reservations = *g_reservation_map;
168  DCHECK(!ContainsKey(reservations, key));
169
170  base::FilePath target_path(suggested_path.NormalizePathSeparators());
171  base::FilePath target_dir = target_path.DirName();
172  base::FilePath filename = target_path.BaseName();
173  bool is_path_writeable = true;
174  bool has_conflicts = false;
175  bool name_too_long = false;
176
177  // Create target_dir if necessary and appropriate. target_dir may be the last
178  // directory that the user selected in a FilePicker; if that directory has
179  // since been removed, do NOT automatically re-create it. Only automatically
180  // create the directory if it is the default Downloads directory or if the
181  // caller explicitly requested automatic directory creation.
182  if (!base::DirectoryExists(target_dir) &&
183      (create_directory ||
184       (!default_download_path.empty() &&
185        (default_download_path == target_dir)))) {
186    base::CreateDirectory(target_dir);
187  }
188
189  // Check writability of the suggested path. If we can't write to it, default
190  // to the user's "My Documents" directory. We'll prompt them in this case.
191  if (!base::PathIsWritable(target_dir)) {
192    DVLOG(1) << "Unable to write to directory \"" << target_dir.value() << "\"";
193    is_path_writeable = false;
194    PathService::Get(chrome::DIR_USER_DOCUMENTS, &target_dir);
195    target_path = target_dir.Append(filename);
196  }
197
198  if (is_path_writeable) {
199    // Check the limit of file name length if it could be obtained. When the
200    // suggested name exceeds the limit, truncate or prompt the user.
201    int max_length = file_util::GetMaximumPathComponentLength(target_dir);
202    if (max_length != -1) {
203      int limit = max_length - kIntermediateNameSuffixLength;
204      if (limit <= 0 || !TruncateFileName(&target_path, limit))
205        name_too_long = true;
206    }
207
208    // Uniquify the name, if it already exists.
209    if (!name_too_long && IsPathInUse(target_path)) {
210      has_conflicts = true;
211      if (conflict_action == DownloadPathReservationTracker::OVERWRITE) {
212        has_conflicts = false;
213      }
214      // If ...PROMPT, then |has_conflicts| will remain true, |verified| will be
215      // false, and CDMD will prompt.
216      if (conflict_action == DownloadPathReservationTracker::UNIQUIFY) {
217        for (int uniquifier = 1;
218            uniquifier <= DownloadPathReservationTracker::kMaxUniqueFiles;
219            ++uniquifier) {
220          // Append uniquifier.
221          std::string suffix(base::StringPrintf(" (%d)", uniquifier));
222          base::FilePath path_to_check(target_path);
223          // If the name length limit is available (max_length != -1), and the
224          // the current name exceeds the limit, truncate.
225          if (max_length != -1) {
226            int limit =
227                max_length - kIntermediateNameSuffixLength - suffix.size();
228            // If truncation failed, give up uniquification.
229            if (limit <= 0 || !TruncateFileName(&path_to_check, limit))
230              break;
231          }
232          path_to_check = path_to_check.InsertBeforeExtensionASCII(suffix);
233
234          if (!IsPathInUse(path_to_check)) {
235            target_path = path_to_check;
236            has_conflicts = false;
237            break;
238          }
239        }
240      }
241    }
242  }
243
244  reservations[key] = target_path;
245  bool verified = (is_path_writeable && !has_conflicts && !name_too_long);
246  BrowserThread::PostTask(BrowserThread::UI, FROM_HERE,
247                          base::Bind(callback, target_path, verified));
248}
249
250// Called on the FILE thread to update the path of the reservation associated
251// with |key| to |new_path|.
252void UpdateReservation(ReservationKey key, const base::FilePath& new_path) {
253  DCHECK(BrowserThread::CurrentlyOn(BrowserThread::FILE));
254  DCHECK(g_reservation_map != NULL);
255  ReservationMap::iterator iter = g_reservation_map->find(key);
256  if (iter != g_reservation_map->end()) {
257    iter->second = new_path;
258  } else {
259    // This would happen if an UpdateReservation() notification was scheduled on
260    // the FILE thread before ReserveInternal(), or after a Revoke()
261    // call. Neither should happen.
262    NOTREACHED();
263  }
264}
265
266// Called on the FILE thread to remove the path reservation associated with
267// |key|.
268void RevokeReservation(ReservationKey key) {
269  DCHECK(BrowserThread::CurrentlyOn(BrowserThread::FILE));
270  DCHECK(g_reservation_map != NULL);
271  DCHECK(ContainsKey(*g_reservation_map, key));
272  g_reservation_map->erase(key);
273  if (g_reservation_map->size() == 0) {
274    // No more reservations. Delete map.
275    delete g_reservation_map;
276    g_reservation_map = NULL;
277  }
278}
279
280DownloadItemObserver::DownloadItemObserver(DownloadItem* download_item)
281    : download_item_(download_item),
282      last_target_path_(download_item->GetTargetFilePath()) {
283  DCHECK(BrowserThread::CurrentlyOn(BrowserThread::UI));
284  download_item_->AddObserver(this);
285}
286
287DownloadItemObserver::~DownloadItemObserver() {
288  download_item_->RemoveObserver(this);
289}
290
291void DownloadItemObserver::OnDownloadUpdated(DownloadItem* download) {
292  switch (download->GetState()) {
293    case DownloadItem::IN_PROGRESS: {
294      // Update the reservation.
295      base::FilePath new_target_path = download->GetTargetFilePath();
296      if (new_target_path != last_target_path_) {
297        BrowserThread::PostTask(BrowserThread::FILE, FROM_HERE, base::Bind(
298            &UpdateReservation, download, new_target_path));
299        last_target_path_ = new_target_path;
300      }
301      break;
302    }
303
304    case DownloadItem::COMPLETE:
305      // If the download is complete, then it has already been renamed to the
306      // final name. The existence of the file on disk is sufficient to prevent
307      // conflicts from now on.
308
309    case DownloadItem::CANCELLED:
310      // We no longer need the reservation if the download is being removed.
311
312    case DownloadItem::INTERRUPTED:
313      // The download filename will need to be re-generated when the download is
314      // restarted. Holding on to the reservation now would prevent the name
315      // from being used for a subsequent retry attempt.
316
317      BrowserThread::PostTask(BrowserThread::FILE, FROM_HERE, base::Bind(
318          &RevokeReservation, download));
319      delete this;
320      break;
321
322    case DownloadItem::MAX_DOWNLOAD_STATE:
323      // Compiler appeasement.
324      NOTREACHED();
325  }
326}
327
328void DownloadItemObserver::OnDownloadDestroyed(DownloadItem* download) {
329  // Items should be COMPLETE/INTERRUPTED/CANCELLED before being destroyed.
330  NOTREACHED();
331  BrowserThread::PostTask(BrowserThread::FILE, FROM_HERE, base::Bind(
332      &RevokeReservation, download));
333  delete this;
334}
335
336}  // namespace
337
338// static
339void DownloadPathReservationTracker::GetReservedPath(
340    DownloadItem* download_item,
341    const base::FilePath& target_path,
342    const base::FilePath& default_path,
343    bool create_directory,
344    FilenameConflictAction conflict_action,
345    const ReservedPathCallback& callback) {
346  DCHECK(BrowserThread::CurrentlyOn(BrowserThread::UI));
347  // Attach an observer to the download item so that we know when the target
348  // path changes and/or the download is no longer active.
349  new DownloadItemObserver(download_item);
350  // DownloadItemObserver deletes itself.
351
352  BrowserThread::PostTask(BrowserThread::FILE, FROM_HERE, base::Bind(
353      &CreateReservation,
354      download_item,
355      target_path,
356      default_path,
357      create_directory,
358      conflict_action,
359      callback));
360}
361
362// static
363bool DownloadPathReservationTracker::IsPathInUseForTesting(
364    const base::FilePath& path) {
365  return IsPathInUse(path);
366}
367