278 lines
13 KiB
C
278 lines
13 KiB
C
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//*********************************************************
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//
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// Copyright (c) Microsoft. All rights reserved.
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// This code is licensed under the MIT License.
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// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF
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// ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED
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// TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A
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// PARTICULAR PURPOSE AND NONINFRINGEMENT.
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//
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//*********************************************************
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#ifndef __WIL_REGISTRY_INCLUDED
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#define __WIL_REGISTRY_INCLUDED
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#ifdef _KERNEL_MODE
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#error This header is not supported in kernel-mode.
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#endif
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#include <winreg.h>
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#include <new.h> // new(std::nothrow)
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#include "resource.h" // unique_hkey
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namespace wil
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{
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//! The key name includes the absolute path of the key in the registry, always starting at a
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//! base key, for example, HKEY_LOCAL_MACHINE.
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size_t const max_registry_key_name_length = 255;
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//! The maximum number of characters allowed in a registry value's name.
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size_t const max_registry_value_name_length = 16383;
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// unique_registry_watcher/unique_registry_watcher_nothrow/unique_registry_watcher_failfast
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// These classes make it easy to execute a provided function when a
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// registry key changes (optionally recursively). Specify the key
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// either as a root key + path, or an open registry handle as wil::unique_hkey
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// or a raw HKEY value (that will be duplicated).
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//
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// Example use with exceptions base error handling:
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// auto watcher = wil::make_registry_watcher(HKEY_CURRENT_USER, L"Software\\MyApp", true, wil::RegistryChangeKind changeKind[]
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// {
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// if (changeKind == RegistryChangeKind::Delete)
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// {
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// watcher.reset();
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// }
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// // invalidate cached registry data here
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// });
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//
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// Example use with error code base error handling:
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// auto watcher = wil::make_registry_watcher_nothrow(HKEY_CURRENT_USER, L"Software\\MyApp", true, wil::RegistryChangeKind[]
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// {
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// // invalidate cached registry data here
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// });
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// RETURN_IF_NULL_ALLOC(watcher);
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enum class RegistryChangeKind
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{
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Modify = 0,
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Delete = 1,
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};
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/// @cond
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namespace details
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{
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struct registry_watcher_state
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{
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registry_watcher_state(unique_hkey &&keyToWatch, bool isRecursive, wistd::function<void(RegistryChangeKind)> &&callback)
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: m_callback(wistd::move(callback)), m_keyToWatch(wistd::move(keyToWatch)), m_isRecursive(isRecursive)
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{
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}
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wistd::function<void(RegistryChangeKind)> m_callback;
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unique_hkey m_keyToWatch;
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unique_event_nothrow m_eventHandle;
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// While not strictly needed since this is ref counted the thread pool wait
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// should be last to ensure that the other members are valid
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// when it is destructed as it will reference them.
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unique_threadpool_wait m_threadPoolWait;
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bool m_isRecursive;
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volatile long m_refCount = 1;
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srwlock m_lock;
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// Returns true if the refcount can be increased from a non zero value,
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// false it was zero impling that the object is in or on the way to the destructor.
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// In this case ReleaseFromCallback() should not be called.
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bool TryAddRef()
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{
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return ::InterlockedIncrement(&m_refCount) > 1;
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}
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void Release()
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{
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auto lock = m_lock.lock_exclusive();
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if (0 == ::InterlockedDecrement(&m_refCount))
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{
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lock.reset(); // leave the lock before deleting it.
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delete this;
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}
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}
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void ReleaseFromCallback(bool rearm)
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{
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auto lock = m_lock.lock_exclusive();
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if (0 == ::InterlockedDecrement(&m_refCount))
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{
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// Destroy the thread pool wait now to avoid the wait that would occur in the
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// destructor. That wait would cause a deadlock since we are doing this from the callback.
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::CloseThreadpoolWait(m_threadPoolWait.release());
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lock.reset(); // leave the lock before deleting it.
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delete this;
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// Sleep(1); // Enable for testing to find use after free bugs.
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}
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else if (rearm)
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{
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::SetThreadpoolWait(m_threadPoolWait.get(), m_eventHandle.get(), nullptr);
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}
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}
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};
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inline void delete_registry_watcher_state(_In_opt_ registry_watcher_state *watcherStorage) { watcherStorage->Release(); }
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typedef resource_policy<registry_watcher_state *, decltype(&details::delete_registry_watcher_state),
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details::delete_registry_watcher_state, details::pointer_access_none> registry_watcher_state_resource_policy;
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}
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/// @endcond
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template <typename storage_t, typename err_policy = err_exception_policy>
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class registry_watcher_t : public storage_t
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{
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public:
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// forward all base class constructors...
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template <typename... args_t>
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explicit registry_watcher_t(args_t&&... args) WI_NOEXCEPT : storage_t(wistd::forward<args_t>(args)...) {}
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// HRESULT or void error handling...
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typedef typename err_policy::result result;
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// Exception-based constructors
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registry_watcher_t(HKEY rootKey, _In_ PCWSTR subKey, bool isRecursive, wistd::function<void(RegistryChangeKind)> &&callback)
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{
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static_assert(wistd::is_same<void, result>::value, "this constructor requires exceptions; use the create method");
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create(rootKey, subKey, isRecursive, wistd::move(callback));
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}
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registry_watcher_t(unique_hkey &&keyToWatch, bool isRecursive, wistd::function<void(RegistryChangeKind)> &&callback)
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{
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static_assert(wistd::is_same<void, result>::value, "this constructor requires exceptions; use the create method");
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create(wistd::move(keyToWatch), isRecursive, wistd::move(callback));
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}
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// Pass a root key, sub key pair or use an empty string to use rootKey as the key to watch.
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result create(HKEY rootKey, _In_ PCWSTR subKey, bool isRecursive, wistd::function<void(RegistryChangeKind)> &&callback)
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{
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// Most use will want to create the key, consider adding an option for open as a future design change.
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unique_hkey keyToWatch;
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HRESULT hr = HRESULT_FROM_WIN32(RegCreateKeyExW(rootKey, subKey, 0, nullptr, 0, KEY_NOTIFY, nullptr, &keyToWatch, nullptr));
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if (FAILED(hr))
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{
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return err_policy::HResult(hr);
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}
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return err_policy::HResult(create_common(wistd::move(keyToWatch), isRecursive, wistd::move(callback)));
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}
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result create(unique_hkey &&keyToWatch, bool isRecursive, wistd::function<void(RegistryChangeKind)> &&callback)
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{
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return err_policy::HResult(create_common(wistd::move(keyToWatch), isRecursive, wistd::move(callback)));
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}
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private:
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// Factored into a standalone function to support Clang which does not support conversion of stateless lambdas
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// to __stdcall
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static void __stdcall callback(PTP_CALLBACK_INSTANCE, void *context, TP_WAIT *, TP_WAIT_RESULT)
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{
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#ifndef __WIL_REGISTRY_CHANGE_CALLBACK_TEST
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#define __WIL_REGISTRY_CHANGE_CALLBACK_TEST
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#endif
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__WIL_REGISTRY_CHANGE_CALLBACK_TEST
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auto watcherState = static_cast<details::registry_watcher_state *>(context);
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if (watcherState->TryAddRef())
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{
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// using auto reset event so don't need to manually reset.
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// failure here is a programming error.
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const LSTATUS error = RegNotifyChangeKeyValue(watcherState->m_keyToWatch.get(), watcherState->m_isRecursive,
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REG_NOTIFY_CHANGE_LAST_SET | REG_NOTIFY_CHANGE_NAME | REG_NOTIFY_THREAD_AGNOSTIC,
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watcherState->m_eventHandle.get(), TRUE);
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// Call the client before re-arming to ensure that multiple callbacks don't
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// run concurrently.
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switch (error)
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{
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case ERROR_SUCCESS:
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case ERROR_ACCESS_DENIED:
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// Normal modification: send RegistryChangeKind::Modify and re-arm.
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watcherState->m_callback(RegistryChangeKind::Modify);
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watcherState->ReleaseFromCallback(true);
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break;
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case ERROR_KEY_DELETED:
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// Key deleted, send RegistryChangeKind::Delete, do not re-arm.
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watcherState->m_callback(RegistryChangeKind::Delete);
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watcherState->ReleaseFromCallback(false);
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break;
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case ERROR_HANDLE_REVOKED:
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// Handle revoked. This can occur if the user session ends before
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// the watcher shuts-down. Disarm silently since there is generally no way to respond.
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watcherState->ReleaseFromCallback(false);
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break;
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default:
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FAIL_FAST_HR(HRESULT_FROM_WIN32(error));
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}
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}
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}
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// This function exists to avoid template expansion of this code based on err_policy.
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HRESULT create_common(unique_hkey &&keyToWatch, bool isRecursive, wistd::function<void(RegistryChangeKind)> &&callback)
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{
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wistd::unique_ptr<details::registry_watcher_state> watcherState(new(std::nothrow) details::registry_watcher_state(
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wistd::move(keyToWatch), isRecursive, wistd::move(callback)));
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RETURN_IF_NULL_ALLOC(watcherState);
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RETURN_IF_FAILED(watcherState->m_eventHandle.create());
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RETURN_IF_WIN32_ERROR(RegNotifyChangeKeyValue(watcherState->m_keyToWatch.get(),
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watcherState->m_isRecursive, REG_NOTIFY_CHANGE_LAST_SET | REG_NOTIFY_CHANGE_NAME | REG_NOTIFY_THREAD_AGNOSTIC,
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watcherState->m_eventHandle.get(), TRUE));
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watcherState->m_threadPoolWait.reset(CreateThreadpoolWait(®istry_watcher_t::callback, watcherState.get(), nullptr));
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RETURN_LAST_ERROR_IF(!watcherState->m_threadPoolWait);
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storage_t::reset(watcherState.release()); // no more failures after this, pass ownership
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SetThreadpoolWait(storage_t::get()->m_threadPoolWait.get(), storage_t::get()->m_eventHandle.get(), nullptr);
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return S_OK;
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}
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};
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typedef unique_any_t<registry_watcher_t<details::unique_storage<details::registry_watcher_state_resource_policy>, err_returncode_policy>> unique_registry_watcher_nothrow;
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typedef unique_any_t<registry_watcher_t<details::unique_storage<details::registry_watcher_state_resource_policy>, err_failfast_policy>> unique_registry_watcher_failfast;
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inline unique_registry_watcher_nothrow make_registry_watcher_nothrow(HKEY rootKey, _In_ PCWSTR subKey, bool isRecursive, wistd::function<void(RegistryChangeKind)> &&callback) WI_NOEXCEPT
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{
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unique_registry_watcher_nothrow watcher;
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watcher.create(rootKey, subKey, isRecursive, wistd::move(callback));
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return watcher; // caller must test for success using if (watcher)
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}
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inline unique_registry_watcher_nothrow make_registry_watcher_nothrow(unique_hkey &&keyToWatch, bool isRecursive, wistd::function<void(RegistryChangeKind)> &&callback) WI_NOEXCEPT
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{
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unique_registry_watcher_nothrow watcher;
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watcher.create(wistd::move(keyToWatch), isRecursive, wistd::move(callback));
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return watcher; // caller must test for success using if (watcher)
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}
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inline unique_registry_watcher_failfast make_registry_watcher_failfast(HKEY rootKey, _In_ PCWSTR subKey, bool isRecursive, wistd::function<void(RegistryChangeKind)> &&callback)
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{
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return unique_registry_watcher_failfast(rootKey, subKey, isRecursive, wistd::move(callback));
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}
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inline unique_registry_watcher_failfast make_registry_watcher_failfast(unique_hkey &&keyToWatch, bool isRecursive, wistd::function<void(RegistryChangeKind)> &&callback)
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{
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return unique_registry_watcher_failfast(wistd::move(keyToWatch), isRecursive, wistd::move(callback));
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}
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#ifdef WIL_ENABLE_EXCEPTIONS
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typedef unique_any_t<registry_watcher_t<details::unique_storage<details::registry_watcher_state_resource_policy>, err_exception_policy >> unique_registry_watcher;
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inline unique_registry_watcher make_registry_watcher(HKEY rootKey, _In_ PCWSTR subKey, bool isRecursive, wistd::function<void(RegistryChangeKind)> &&callback)
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{
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return unique_registry_watcher(rootKey, subKey, isRecursive, wistd::move(callback));
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}
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inline unique_registry_watcher make_registry_watcher(unique_hkey &&keyToWatch, bool isRecursive, wistd::function<void(RegistryChangeKind)> &&callback)
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{
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return unique_registry_watcher(wistd::move(keyToWatch), isRecursive, wistd::move(callback));
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}
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#endif // WIL_ENABLE_EXCEPTIONS
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} // namespace wil
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#endif
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