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// Copyright (c) 2011 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.
//
// A utility class that makes it easy to register for registry change
// notifications.
//
#include "chrome_frame/registry_watcher.h"
#include "chrome_frame/chrome_frame_helper_util.h"
namespace {
const wchar_t kRegistryWatcherEventName[] = L"chrome_registry_watcher_event";
} // namespace
RegistryWatcher::RegistryWatcher(HKEY hive,
const wchar_t* path,
NotifyFunc callback)
: callback_(callback),
wait_event_(NULL),
wait_handle_(NULL),
stopping_(false) {
// Enforce that we can open the given registry path with the KEY_NOTIFY
// permission.
LONG result = RegOpenKeyEx(hive, path, 0, KEY_NOTIFY, ®istry_key_);
if (result != ERROR_SUCCESS) {
registry_key_ = NULL;
}
}
RegistryWatcher::~RegistryWatcher() {
StopWatching();
if (registry_key_) {
RegCloseKey(registry_key_);
registry_key_ = NULL;
}
}
bool RegistryWatcher::StartWatching() {
if (!registry_key_ || wait_event_ || !callback_) {
return false;
}
bool result = false;
wait_event_ = CreateEvent(NULL,
FALSE, // Auto-resets
FALSE, // Initially non-signalled
kRegistryWatcherEventName);
if (wait_event_ != NULL) {
LONG notify_result = RegNotifyChangeKeyValue(
registry_key_,
TRUE, // Watch subtree
REG_NOTIFY_CHANGE_NAME, // Notifies if a subkey is added.
wait_event_,
TRUE); // Asynchronous, signal the event when a change occurs.
if (notify_result == ERROR_SUCCESS) {
if (RegisterWaitForSingleObject(&wait_handle_,
wait_event_,
&RegistryWatcher::WaitCallback,
reinterpret_cast<void*>(this),
INFINITE,
WT_EXECUTEDEFAULT)) {
stopping_ = false;
result = true;
}
}
}
// If we're not good to go we don't need to hold onto the event.
if (!result && wait_event_) {
CloseHandle(wait_event_);
wait_event_ = NULL;
}
return result;
}
void RegistryWatcher::StopWatching() {
stopping_ = true;
if (wait_handle_) {
// Unregister the wait and block until any current handlers have returned.
UnregisterWaitEx(wait_handle_, INVALID_HANDLE_VALUE);
wait_handle_ = NULL;
}
if (wait_event_) {
CloseHandle(wait_event_);
wait_event_ = NULL;
}
}
void CALLBACK RegistryWatcher::WaitCallback(void* param, BOOLEAN wait_fired) {
RegistryWatcher* watcher = reinterpret_cast<RegistryWatcher*>(param);
if (watcher->stopping_)
return;
if (watcher->callback_) {
watcher->callback_();
}
}
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