Add a FileWatcher to base/.

This is like Directory Watcher, but only for a single file.

Review URL: http://codereview.chromium.org/661359

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@40980 0039d316-1c4b-4281-b951-d872f2087c98

1 files changed, 134 insertions, 0 deletions

diff --git a/base/file_watcher_mac.cc b/base/file_watcher_mac.cc
new file mode 100644
index 0000000..2d85133
--- /dev/null
+++ b/base/file_watcher_mac.cc
@@ -0,0 +1,134 @@
+// Copyright (c) 2009 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/file_watcher.h"
+
+#include <CoreServices/CoreServices.h>
+
+#include "base/file_path.h"
+#include "base/file_util.h"
+#include "base/logging.h"
+#include "base/message_loop.h"
+#include "base/scoped_cftyperef.h"
+#include "base/time.h"
+
+namespace {
+
+const CFAbsoluteTime kEventLatencySeconds = 0.3;
+
+class FileWatcherImpl : public FileWatcher::PlatformDelegate {
+ public:
+  FileWatcherImpl() {}
+  ~FileWatcherImpl() {
+    if (!path_.value().empty()) {
+      FSEventStreamStop(fsevent_stream_);
+      FSEventStreamInvalidate(fsevent_stream_);
+      FSEventStreamRelease(fsevent_stream_);
+    }
+  }
+
+  virtual bool Watch(const FilePath& path, FileWatcher::Delegate* delegate,
+                     MessageLoop* backend_loop);
+
+  void OnFSEventsCallback(const FilePath& event_path) {
+    DCHECK(!path_.value().empty());
+    FilePath absolute_event_path = event_path;
+    if (!file_util::AbsolutePath(&absolute_event_path))
+      return;
+
+    file_util::FileInfo file_info;
+    bool file_exists = file_util::GetFileInfo(path_, &file_info);
+    if (file_exists && (last_modified_.is_null() ||
+        last_modified_ != file_info.last_modified)) {
+      last_modified_ = file_info.last_modified;
+      delegate_->OnFileChanged(path_);
+    } else if (file_exists && (base::Time::Now() - last_modified_ <
+               base::TimeDelta::FromSeconds(2))) {
+      // Since we only have a resolution of 1s, if we get a callback within
+      // 2s of the file having changed, go ahead and notify our observer.  This
+      // might be from a different file change, but it's better to notify too
+      // much rather than miss a notification.
+      delegate_->OnFileChanged(path_);
+    } else if (!file_exists && !last_modified_.is_null()) {
+      last_modified_ = base::Time();
+      delegate_->OnFileChanged(path_);
+    }
+  }
+
+ private:
+  // Delegate to notify upon changes.
+  FileWatcher::Delegate* delegate_;
+
+  // Path we're watching (passed to delegate).
+  FilePath path_;
+
+  // Backend stream we receive event callbacks from (strong reference).
+  FSEventStreamRef fsevent_stream_;
+
+  // Keep track of the last modified time of the file.  We use nulltime
+  // to represent the file not existing.
+  base::Time last_modified_;
+
+  DISALLOW_COPY_AND_ASSIGN(FileWatcherImpl);
+};
+
+void FSEventsCallback(ConstFSEventStreamRef stream,
+                      void* event_watcher, size_t num_events,
+                      void* event_paths, const FSEventStreamEventFlags flags[],
+                      const FSEventStreamEventId event_ids[]) {
+  char** paths = reinterpret_cast<char**>(event_paths);
+  FileWatcherImpl* watcher =
+      reinterpret_cast<FileWatcherImpl*>(event_watcher);
+  for (size_t i = 0; i < num_events; i++)
+    watcher->OnFSEventsCallback(FilePath(paths[i]));
+}
+
+bool FileWatcherImpl::Watch(const FilePath& path,
+                            FileWatcher::Delegate* delegate,
+                            MessageLoop* backend_loop) {
+  DCHECK(path_.value().empty());  // Can only watch one path.
+  DCHECK(MessageLoop::current()->type() == MessageLoop::TYPE_UI);
+
+  FilePath parent_dir = path.DirName();
+  if (!file_util::AbsolutePath(&parent_dir))
+    return false;
+
+  file_util::FileInfo file_info;
+  if (file_util::GetFileInfo(path, &file_info))
+    last_modified_ = file_info.last_modified;
+
+  path_ = path;
+  delegate_ = delegate;
+
+  scoped_cftyperef<CFStringRef> cf_path(CFStringCreateWithCString(
+      NULL, path.DirName().value().c_str(), kCFStringEncodingMacHFS));
+  CFStringRef path_for_array = cf_path.get();
+  scoped_cftyperef<CFArrayRef> watched_paths(CFArrayCreate(
+      NULL, reinterpret_cast<const void**>(&path_for_array), 1,
+      &kCFTypeArrayCallBacks));
+
+  FSEventStreamContext context;
+  context.version = 0;
+  context.info = this;
+  context.retain = NULL;
+  context.release = NULL;
+  context.copyDescription = NULL;
+
+  fsevent_stream_ = FSEventStreamCreate(NULL, &FSEventsCallback, &context,
+                                        watched_paths,
+                                        kFSEventStreamEventIdSinceNow,
+                                        kEventLatencySeconds,
+                                        kFSEventStreamCreateFlagNone);
+  FSEventStreamScheduleWithRunLoop(fsevent_stream_, CFRunLoopGetCurrent(),
+                                   kCFRunLoopDefaultMode);
+  FSEventStreamStart(fsevent_stream_);
+
+  return true;
+}
+
+}  // namespace
+
+FileWatcher::FileWatcher() {
+  impl_ = new FileWatcherImpl();
+}