diff --git a/src/libipc/platform/win/shm_win.cpp b/src/libipc/platform/win/shm_win.cpp
index 6361df2..73ca08c 100755
--- a/src/libipc/platform/win/shm_win.cpp
+++ b/src/libipc/platform/win/shm_win.cpp
@@ -1,144 +1,188 @@
-
-#if defined(__MINGW32__)
-#include <windows.h>
-#else
-#include <Windows.h>
-#endif
-
-#include <string>
-#include <utility>
-
-#include "libipc/shm.h"
-#include "libipc/def.h"
-#include "libipc/pool_alloc.h"
-
-#include "libipc/utility/log.h"
-#include "libipc/memory/resource.h"
-
-#include "to_tchar.h"
-#include "get_sa.h"
-
-namespace {
-
-struct id_info_t {
-    HANDLE      h_    = NULL;
-    void*       mem_  = nullptr;
-    std::size_t size_ = 0;
-};
-
-} // internal-linkage
-
-namespace ipc {
-namespace shm {
-
-id_t acquire(char const * name, std::size_t size, unsigned mode) {
-    if (!is_valid_string(name)) {
-        ipc::error("fail acquire: name is empty\n");
-        return nullptr;
-    }
-    HANDLE h;
-    auto fmt_name = ipc::detail::to_tchar(name);
-    // Opens a named file mapping object.
-    if (mode == open) {
-        h = ::OpenFileMapping(FILE_MAP_ALL_ACCESS, FALSE, fmt_name.c_str());
-        if (h == NULL) {
-          ipc::error("fail OpenFileMapping[%d]: %s\n", static_cast<int>(::GetLastError()), name);
-          return nullptr;
-        }
-    }
-    // Creates or opens a named file mapping object for a specified file.
-    else {
-        h = ::CreateFileMapping(INVALID_HANDLE_VALUE, detail::get_sa(), PAGE_READWRITE | SEC_COMMIT,
-                                0, static_cast<DWORD>(size), fmt_name.c_str());
-        DWORD err = ::GetLastError();
-        // If the object exists before the function call, the function returns a handle to the existing object 
-        // (with its current size, not the specified size), and GetLastError returns ERROR_ALREADY_EXISTS.
-        if ((mode == create) && (err == ERROR_ALREADY_EXISTS)) {
-            if (h != NULL) ::CloseHandle(h);
-            h = NULL;
-        }
-        if (h == NULL) {
-          ipc::error("fail CreateFileMapping[%d]: %s\n", static_cast<int>(err), name);
-          return nullptr;
-        }
-    }
-    auto ii = mem::alloc<id_info_t>();
-    ii->h_    = h;
-    ii->size_ = size;
-    return ii;
-}
-
-std::int32_t get_ref(id_t) {
-    return 0;
-}
-
-void sub_ref(id_t) {
-    // Do Nothing.
-}
-
-void * get_mem(id_t id, std::size_t * size) {
-    if (id == nullptr) {
-        ipc::error("fail get_mem: invalid id (null)\n");
-        return nullptr;
-    }
-    auto ii = static_cast<id_info_t*>(id);
-    if (ii->mem_ != nullptr) {
-        if (size != nullptr) *size = ii->size_;
-        return ii->mem_;
-    }
-    if (ii->h_ == NULL) {
-        ipc::error("fail to_mem: invalid id (h = null)\n");
-        return nullptr;
-    }
-    LPVOID mem = ::MapViewOfFile(ii->h_, FILE_MAP_ALL_ACCESS, 0, 0, 0);
-    if (mem == NULL) {
-        ipc::error("fail MapViewOfFile[%d]\n", static_cast<int>(::GetLastError()));
-        return nullptr;
-    }
-    MEMORY_BASIC_INFORMATION mem_info;
-    if (::VirtualQuery(mem, &mem_info, sizeof(mem_info)) == 0) {
-        ipc::error("fail VirtualQuery[%d]\n", static_cast<int>(::GetLastError()));
-        return nullptr;
-    }
-    ii->mem_  = mem;
-    ii->size_ = static_cast<std::size_t>(mem_info.RegionSize);
-    if (size != nullptr) *size = ii->size_;
-    return static_cast<void *>(mem);
-}
-
-std::int32_t release(id_t id) noexcept {
-    if (id == nullptr) {
-        ipc::error("fail release: invalid id (null)\n");
-        return -1;
-    }
-    auto ii = static_cast<id_info_t*>(id);
-    if (ii->mem_ == nullptr || ii->size_ == 0) {
-        ipc::error("fail release: invalid id (mem = %p, size = %zd)\n", ii->mem_, ii->size_);
-    }
-    else ::UnmapViewOfFile(static_cast<LPCVOID>(ii->mem_));
-    if (ii->h_ == NULL) {
-        ipc::error("fail release: invalid id (h = null)\n");
-    }
-    else ::CloseHandle(ii->h_);
-    mem::free(ii);
-    return 0;
-}
-
-void remove(id_t id) noexcept {
-    if (id == nullptr) {
-        ipc::error("fail release: invalid id (null)\n");
-        return;
-    }
-    release(id);
-}
-
-void remove(char const * name) noexcept {
-    if (!is_valid_string(name)) {
-        ipc::error("fail remove: name is empty\n");
-        return;
-    }
-    // Do Nothing.
-}
-
-} // namespace shm
-} // namespace ipc
+
+#if defined(__MINGW32__)
+#include <windows.h>
+#else
+#include <Windows.h>
+#endif
+
+#include <atomic>
+#include <string>
+#include <utility>
+
+#include "libipc/shm.h"
+#include "libipc/def.h"
+#include "libipc/pool_alloc.h"
+
+#include "libipc/utility/log.h"
+#include "libipc/memory/resource.h"
+
+#include "to_tchar.h"
+#include "get_sa.h"
+
+namespace {
+
+struct info_t {
+    std::atomic<std::int32_t> acc_;
+};
+
+struct id_info_t {
+    HANDLE      h_    = NULL;
+    void*       mem_  = nullptr;
+    std::size_t size_ = 0;
+};
+
+constexpr std::size_t calc_size(std::size_t size) {
+    return ((((size - 1) / alignof(info_t)) + 1) * alignof(info_t)) + sizeof(info_t);
+}
+
+inline auto& acc_of(void* mem, std::size_t size) {
+    return reinterpret_cast<info_t*>(static_cast<ipc::byte_t*>(mem) + size - sizeof(info_t))->acc_;
+}
+
+} // internal-linkage
+
+namespace ipc {
+namespace shm {
+
+id_t acquire(char const * name, std::size_t size, unsigned mode) {
+    if (!is_valid_string(name)) {
+        ipc::error("fail acquire: name is empty\n");
+        return nullptr;
+    }
+    HANDLE h;
+    auto fmt_name = ipc::detail::to_tchar(name);
+    // Opens a named file mapping object.
+    if (mode == open) {
+        h = ::OpenFileMapping(FILE_MAP_ALL_ACCESS, FALSE, fmt_name.c_str());
+        if (h == NULL) {
+          ipc::error("fail OpenFileMapping[%d]: %s\n", static_cast<int>(::GetLastError()), name);
+          return nullptr;
+        }
+    }
+    // Creates or opens a named file mapping object for a specified file.
+    else {
+        std::size_t alloc_size = calc_size(size);
+        h = ::CreateFileMapping(INVALID_HANDLE_VALUE, detail::get_sa(), PAGE_READWRITE | SEC_COMMIT,
+                                0, static_cast<DWORD>(alloc_size), fmt_name.c_str());
+        DWORD err = ::GetLastError();
+        // If the object exists before the function call, the function returns a handle to the existing object 
+        // (with its current size, not the specified size), and GetLastError returns ERROR_ALREADY_EXISTS.
+        if ((mode == create) && (err == ERROR_ALREADY_EXISTS)) {
+            if (h != NULL) ::CloseHandle(h);
+            h = NULL;
+        }
+        if (h == NULL) {
+          ipc::error("fail CreateFileMapping[%d]: %s\n", static_cast<int>(err), name);
+          return nullptr;
+        }
+    }
+    auto ii = mem::alloc<id_info_t>();
+    ii->h_    = h;
+    ii->size_ = size;
+    return ii;
+}
+
+std::int32_t get_ref(id_t id) {
+    if (id == nullptr) {
+        return 0;
+    }
+    auto ii = static_cast<id_info_t*>(id);
+    if (ii->mem_ == nullptr || ii->size_ == 0) {
+        return 0;
+    }
+    return acc_of(ii->mem_, calc_size(ii->size_)).load(std::memory_order_acquire);
+}
+
+void sub_ref(id_t id) {
+    if (id == nullptr) {
+        ipc::error("fail sub_ref: invalid id (null)\n");
+        return;
+    }
+    auto ii = static_cast<id_info_t*>(id);
+    if (ii->mem_ == nullptr || ii->size_ == 0) {
+        ipc::error("fail sub_ref: invalid id (mem = %p, size = %zd)\n", ii->mem_, ii->size_);
+        return;
+    }
+    acc_of(ii->mem_, calc_size(ii->size_)).fetch_sub(1, std::memory_order_acq_rel);
+}
+
+void * get_mem(id_t id, std::size_t * size) {
+    if (id == nullptr) {
+        ipc::error("fail get_mem: invalid id (null)\n");
+        return nullptr;
+    }
+    auto ii = static_cast<id_info_t*>(id);
+    if (ii->mem_ != nullptr) {
+        if (size != nullptr) *size = ii->size_;
+        return ii->mem_;
+    }
+    if (ii->h_ == NULL) {
+        ipc::error("fail to_mem: invalid id (h = null)\n");
+        return nullptr;
+    }
+    LPVOID mem = ::MapViewOfFile(ii->h_, FILE_MAP_ALL_ACCESS, 0, 0, 0);
+    if (mem == NULL) {
+        ipc::error("fail MapViewOfFile[%d]\n", static_cast<int>(::GetLastError()));
+        return nullptr;
+    }
+    MEMORY_BASIC_INFORMATION mem_info;
+    if (::VirtualQuery(mem, &mem_info, sizeof(mem_info)) == 0) {
+        ipc::error("fail VirtualQuery[%d]\n", static_cast<int>(::GetLastError()));
+        return nullptr;
+    }
+    std::size_t actual_size = static_cast<std::size_t>(mem_info.RegionSize);
+    if (ii->size_ == 0) {
+        // Opening existing shared memory
+        ii->size_ = actual_size - sizeof(info_t);
+    }
+    else {
+        // Should match the size we allocated in acquire
+        ii->size_ = ii->size_;  // Keep user-requested size
+    }
+    ii->mem_ = mem;
+    if (size != nullptr) *size = ii->size_;
+    // Initialize or increment reference counter
+    acc_of(mem, calc_size(ii->size_)).fetch_add(1, std::memory_order_release);
+    return static_cast<void *>(mem);
+}
+
+std::int32_t release(id_t id) noexcept {
+    if (id == nullptr) {
+        ipc::error("fail release: invalid id (null)\n");
+        return -1;
+    }
+    std::int32_t ret = -1;
+    auto ii = static_cast<id_info_t*>(id);
+    if (ii->mem_ == nullptr || ii->size_ == 0) {
+        ipc::error("fail release: invalid id (mem = %p, size = %zd)\n", ii->mem_, ii->size_);
+    }
+    else {
+        ret = acc_of(ii->mem_, calc_size(ii->size_)).fetch_sub(1, std::memory_order_acq_rel);
+        ::UnmapViewOfFile(static_cast<LPCVOID>(ii->mem_));
+    }
+    if (ii->h_ == NULL) {
+        ipc::error("fail release: invalid id (h = null)\n");
+    }
+    else ::CloseHandle(ii->h_);
+    mem::free(ii);
+    return ret;
+}
+
+void remove(id_t id) noexcept {
+    if (id == nullptr) {
+        ipc::error("fail release: invalid id (null)\n");
+        return;
+    }
+    release(id);
+}
+
+void remove(char const * name) noexcept {
+    if (!is_valid_string(name)) {
+        ipc::error("fail remove: name is empty\n");
+        return;
+    }
+    // Do Nothing.
+}
+
+} // namespace shm
+} // namespace ipc