diff --git a/include/libimp/result.h b/include/libimp/result.h
index 6b9d374..d9f2a9a 100644
--- a/include/libimp/result.h
+++ b/include/libimp/result.h
@@ -92,7 +92,8 @@ struct default_traits<void, ___> {
 };
 
 template <typename T>
-struct default_traits<T, std::enable_if_t<std::is_integral<T>::value>> : generic_traits<T> {
+struct default_traits<T, std::enable_if_t<std::is_integral<T>::value || std::is_enum<T>::value>>
+     : generic_traits<T> {
   /// \brief Custom initialization.
   static constexpr void init_code(typename generic_traits<T>::storage_t &code, 
                                   T value, bool ok) noexcept {
@@ -192,7 +193,7 @@ std::string default_traits<void, ___>::format(result<void> const &r) {
 }
 
 template <typename T>
-std::string default_traits<T, std::enable_if_t<std::is_integral<T>::value>>
+std::string default_traits<T, std::enable_if_t<std::is_integral<T>::value || std::is_enum<T>::value>>
           ::format(result<T> const &r) noexcept {
   return fmt(*r);
 }
diff --git a/src/libipc/platform/win/api.h b/src/libipc/platform/win/api.h
index 45f94e3..455df0d 100644
--- a/src/libipc/platform/win/api.h
+++ b/src/libipc/platform/win/api.h
@@ -14,10 +14,12 @@
 #include "libimp/log.h"
 #include "libimp/system.h"
 #include "libimp/codecvt.h"
+#include "libimp/span.h"
 
 #include "libipc/def.h"
 
 LIBIPC_NAMESPACE_BEG_
+
 using namespace ::LIBIMP;
 
 namespace winapi {
@@ -94,7 +96,7 @@ inline result<void> close_handle(HANDLE h) noexcept {
  * 
  * \return File mapping object HANDLE, NULL on error.
  */
-result<HANDLE> mmap_open(std::string const &file, std::size_t size, mode::type type) noexcept {
+inline result<HANDLE> mmap_open(std::string const &file, std::size_t size, mode::type type) noexcept {
   LIBIMP_LOG_();
   if (file.empty()) {
     log.error("file name is empty.");
@@ -157,7 +159,7 @@ result<HANDLE> mmap_open(std::string const &file, std::size_t size, mode::type t
  * \brief Maps a view of a file mapping into the address space of a calling process.
  * \see https://docs.microsoft.com/en-us/windows/win32/api/memoryapi/nf-memoryapi-mapviewoffile
  */
-result<LPVOID> mmap_memof(HANDLE h) {
+inline result<LPVOID> mmap_memof(HANDLE h) {
   LIBIMP_LOG_();
   if (h == NULL) {
     log.error("handle is null.");
@@ -176,7 +178,7 @@ result<LPVOID> mmap_memof(HANDLE h) {
  * \brief Retrieves the size about a range of pages in the virtual address space of the calling process.
  * \see https://docs.microsoft.com/en-us/windows/win32/api/memoryapi/nf-memoryapi-virtualquery
  */
-result<SIZE_T> mmap_sizeof(LPCVOID mem) {
+inline result<SIZE_T> mmap_sizeof(LPCVOID mem) {
   LIBIMP_LOG_();
   if (mem == NULL) {
     log.error("memory pointer is null.");
@@ -195,7 +197,7 @@ result<SIZE_T> mmap_sizeof(LPCVOID mem) {
  * \brief Unmaps a mapped view of a file from the calling process's address space.
  * \see https://docs.microsoft.com/en-us/windows/win32/api/memoryapi/nf-memoryapi-unmapviewoffile
  */
-result<void> mmap_release(HANDLE h, LPCVOID mem) {
+inline result<void> mmap_release(HANDLE h, LPCVOID mem) {
   LIBIMP_LOG_();
   if (h == NULL) {
     log.error("handle is null.");
@@ -211,5 +213,55 @@ result<void> mmap_release(HANDLE h, LPCVOID mem) {
   return winapi::close_handle(h);
 }
 
+enum class wait_result {
+  object_0,
+  abandoned,
+  timeout
+};
+
+/**
+ * \brief Waits until the specified object is in the signaled state or the time-out interval elapses.
+ * \see https://learn.microsoft.com/en-us/windows/win32/api/synchapi/nf-synchapi-waitforsingleobject
+ */
+inline result<wait_result> wait_for_single_object(HANDLE h, std::int64_t ms) noexcept {
+  LIBIMP_LOG_();
+  DWORD dwMilliseconds = (ms < 0) ? INFINITE : static_cast<DWORD>(ms);
+  DWORD r = ::WaitForSingleObject(h, dwMilliseconds);
+  if (r == WAIT_FAILED) {
+    auto err = sys::error();
+    log.error("failed: WaitForSingleObject(", h, ", ", dwMilliseconds, "). error = ", err);
+    return err;
+  }
+  if (r == WAIT_OBJECT_0) {
+    return wait_result::object_0;
+  }
+  if (r == WAIT_ABANDONED) {
+    return wait_result::abandoned;
+  }
+  return wait_result::timeout;
+}
+
+/**
+ * \brief Waits until one or all of the specified objects are in the signaled state or the time-out interval elapses.
+ * \see https://learn.microsoft.com/en-us/windows/win32/api/synchapi/nf-synchapi-waitformultipleobjects
+ */
+inline result<wait_result> wait_for_multiple_objects(span<HANDLE const> handles, std::int64_t ms) noexcept {
+  LIBIMP_LOG_();
+  DWORD dwMilliseconds = (ms < 0) ? INFINITE : static_cast<DWORD>(ms);
+  DWORD r = ::WaitForMultipleObjects(static_cast<DWORD>(handles.size()), handles.data(), FALSE, dwMilliseconds);
+  if (r == WAIT_FAILED) {
+    auto err = sys::error();
+    log.error("failed: WaitForMultipleObjects(", handles.size(), ", ", dwMilliseconds, "). error = ", err);
+    return err;
+  }
+  if ((r >= WAIT_OBJECT_0) && (r < WAIT_OBJECT_0 + handles.size())) {
+    return wait_result::object_0;
+  }
+  if ((r >= WAIT_ABANDONED_0) && (r < WAIT_ABANDONED_0 + handles.size())) {
+    return wait_result::abandoned;
+  }
+  return wait_result::timeout;
+}
+
 } // namespace winapi
 LIBIPC_NAMESPACE_END_
diff --git a/src/libipc/platform/win/event_impl.h b/src/libipc/platform/win/event_impl.h
index ada9d56..54038e8 100644
--- a/src/libipc/platform/win/event_impl.h
+++ b/src/libipc/platform/win/event_impl.h
@@ -95,21 +95,18 @@ result<bool> evt_wait(evt_t evt, std::int64_t ms) noexcept {
     log.error("handle is null.");
     return std::make_error_code(std::errc::invalid_argument);
   }
-  DWORD dwMilliseconds = (ms < 0) ? INFINITE : static_cast<DWORD>(ms);
-  auto r = ::WaitForSingleObject(evt->h_event, dwMilliseconds);
-  if (r == WAIT_TIMEOUT) {
-    return false;
+  auto r = winapi::wait_for_single_object(evt->h_event, ms);
+  if (!r) {
+    return r.error();
   }
-  if (r == WAIT_ABANDONED_0) {
-    log.error("failed: WaitForSingleObject(", evt->h_event, ", ", dwMilliseconds, "). error = WAIT_ABANDONED_0");
-    return {};
-  }
-  if (r == WAIT_OBJECT_0) {
+  if (*r == winapi::wait_result::object_0) {
     return true;
   }
-  auto err = sys::error();
-  log.error("failed: WaitForSingleObject(", evt->h_event, ", ", dwMilliseconds, "). error = ", err);
-  return err;
+  if (*r == winapi::wait_result::abandoned) {
+    log.error("failed: WaitForSingleObject(", evt->h_event, ", ", ms, "). error = WAIT_ABANDONED");
+    return false;
+  }
+  return false;
 }
 
 /**
@@ -132,21 +129,18 @@ result<bool> evt_wait(::LIBIMP::span<evt_t const> evts, std::int64_t ms) noexcep
     handles[i] = evts[i]->h_event;
   }
   // Wait for the events.
-  DWORD dwMilliseconds = (ms < 0) ? INFINITE : static_cast<DWORD>(ms);
-  auto r = ::WaitForMultipleObjects(static_cast<DWORD>(handles.size()), handles.data(), FALSE, dwMilliseconds);
-  if (r == WAIT_TIMEOUT) {
-    return false;
+  auto r = winapi::wait_for_multiple_objects(handles, ms);
+  if (!r) {
+    return r.error();
   }
-  if ((r >= WAIT_ABANDONED_0) && (r < WAIT_ABANDONED_0 + handles.size())) {
-    log.error("failed: WaitForMultipleObjects(", handles.size(), ", ", dwMilliseconds, "). error = WAIT_ABANDONED_0 + ", r - WAIT_ABANDONED_0);
-    return {};
-  }
-  if ((r >= WAIT_OBJECT_0) && (r < WAIT_OBJECT_0 + handles.size())) {
+  if (*r == winapi::wait_result::object_0) {
     return true;
   }
-  auto err = sys::error();
-  log.error("failed: WaitForMultipleObjects(", handles.size(), ", ", dwMilliseconds, "). error = ", err);
-  return err;
+  if (*r == winapi::wait_result::abandoned) {
+    log.error("failed: WaitForMultipleObjects(", handles.size(), ", ", ms, "). error = WAIT_ABANDONED");
+    return false;
+  }
+  return false;
 }
 
 LIBIPC_NAMESPACE_END_