diff --git a/include/stdex/unicode.hpp b/include/stdex/unicode.hpp
new file mode 100644
index 000000000..57228ecbe
--- /dev/null
+++ b/include/stdex/unicode.hpp
@@ -0,0 +1,196 @@
+/*
+	SPDX-License-Identifier: MIT
+	Copyright © 2023 Amebis
+*/
+
+#pragma once
+
+#include "sal.hpp"
+#include <assert.h>
+#ifdef _WIN32
+#include <windows.h>
+#endif
+#include <memory>
+#include <string>
+
+namespace stdex
+{
+	enum class charset_id {
+		default = 0,
+	};
+
+	///
+	/// Convert string to Unicode (UTF-16 on Windows) and append to string
+	///
+	/// \param[inout]  dst        String to append Unicode to
+	/// \param[in]     src        String
+	/// \param[in]     count_src  String character count limit
+	/// \param[in]     charset    Charset (stdex::charset_id::default - system default)
+	///
+	/// \return Unicode string
+	///
+	inline void str2wstr(
+		_Inout_ std::wstring& dst,
+		_In_reads_or_z_opt_(count_src) const char* src, _In_ size_t count_src,
+		_In_ charset_id charset = charset_id::default)
+	{
+		assert(src || !count_src);
+#ifdef _WIN32
+		assert(count_src < INT_MAX || count_src == SIZE_MAX);
+		constexpr DWORD dwFlags = MB_PRECOMPOSED;
+
+		// Try to convert to stack buffer first.
+		WCHAR szStackBuffer[1024/sizeof(WCHAR)];
+		int cch = MultiByteToWideChar(static_cast<UINT>(charset), dwFlags, src, static_cast<int>(count_src), szStackBuffer, _countof(szStackBuffer));
+		if (cch) {
+			// Append from stack.
+			dst.append(szStackBuffer, count_src != SIZE_MAX ? wcsnlen(szStackBuffer, cch) : (size_t)cch - 1);
+		} else if (::GetLastError() == ERROR_INSUFFICIENT_BUFFER) {
+			// Query the required output size. Allocate buffer. Then convert again.
+			cch = MultiByteToWideChar(static_cast<UINT>(charset), dwFlags, src, static_cast<int>(count_src), NULL, 0);
+			std::unique_ptr<WCHAR[]> szBuffer(new WCHAR[cch]);
+			cch = MultiByteToWideChar(static_cast<UINT>(charset), dwFlags, src, static_cast<int>(count_src), szBuffer.get(), cch);
+			dst.append(szBuffer.get(), count_src != SIZE_MAX ? wcsnlen(szBuffer.get(), cch) : (size_t)cch - 1);
+		}
+#else
+		throw std::exception("not implemented");
+#endif
+	}
+
+	///
+	/// Convert string to Unicode (UTF-16 on Windows) and append to string
+	///
+	/// \param[inout]  dst        String to append Unicode to
+	/// \param[in]     src        String
+	/// \param[in]     charset    Charset (stdex::charset_id::default - system default)
+	///
+	/// \return Unicode string
+	///
+	inline void str2wstr(
+		_Inout_ std::wstring& dst,
+		_In_ const std::string& src,
+		_In_ charset_id charset = charset_id::default)
+	{
+		str2wstr(dst, src.data(), src.size(), charset);
+	}
+
+	///
+	/// Convert string to Unicode string (UTF-16 on Windows)
+	///
+	/// \param[in]  src        String
+	/// \param[in]  count_src  String character count limit
+	/// \param[in]  charset    Charset (stdex::charset_id::default - system default)
+	///
+	/// \return Unicode string
+	///
+	inline std::wstring str2wstr(
+		_In_reads_or_z_opt_(count_src) const char* src, _In_ size_t count_src,
+		_In_ charset_id charset = charset_id::default)
+	{
+		std::wstring dst;
+		str2wstr(dst, src, count_src, charset);
+		return dst;
+	}
+
+	///
+	/// Convert string to Unicode string (UTF-16 on Windows)
+	///
+	/// \param[in]  src        String
+	/// \param[in]  charset    Charset (stdex::charset_id::default - system default)
+	///
+	/// \return Unicode string
+	///
+	inline std::wstring str2wstr(
+		_In_ const std::string& src,
+		_In_ charset_id charset = charset_id::default)
+	{
+		return str2wstr(src.c_str(), src.size(), charset);
+	}
+
+	///
+	/// Convert Unicode string (UTF-16 on Windows) to SGML and append to string
+	///
+	/// \param[inout]  dst        String to append SGML to
+	/// \param[in]     src        Unicode string
+	/// \param[in]     count_src  Unicode string character count limit
+	/// \param[in]     charset    Charset (stdex::charset_id::default - system default)
+	///
+	inline void wstr2str(
+		_Inout_ std::string& dst,
+		_In_reads_or_z_opt_(count_src) const wchar_t* src,
+		_In_ size_t count_src,
+		_In_ charset_id charset = charset_id::default)
+	{
+		assert(src || !count_src);
+#ifdef _WIN32
+		assert(count_src < INT_MAX || count_src == SIZE_MAX);
+		constexpr DWORD dwFlags = 0;
+		constexpr LPCCH lpDefaultChar = NULL;
+
+		// Try to convert to stack buffer first.
+		CHAR szStackBuffer[1024/sizeof(CHAR)];
+		int cch = WideCharToMultiByte(static_cast<UINT>(charset), dwFlags, src, static_cast<int>(count_src), szStackBuffer, _countof(szStackBuffer), lpDefaultChar, NULL);
+		if (cch) {
+			// Copy from stack. Be careful not to include zero terminator.
+			dst.append(szStackBuffer, count_src != SIZE_MAX ? strnlen(szStackBuffer, cch) : (size_t)cch - 1);
+		} else if (::GetLastError() == ERROR_INSUFFICIENT_BUFFER) {
+			// Query the required output size. Allocate buffer. Then convert again.
+			cch = WideCharToMultiByte(static_cast<UINT>(charset), dwFlags, src, static_cast<int>(count_src), NULL, 0, lpDefaultChar, NULL);
+			std::unique_ptr<CHAR[]> szBuffer(new CHAR[cch]);
+			cch = WideCharToMultiByte(static_cast<UINT>(charset), dwFlags, src, static_cast<int>(count_src), szBuffer.get(), cch, lpDefaultChar, NULL);
+			dst.append(szBuffer.get(), count_src != SIZE_MAX ? strnlen(szBuffer.get(), cch) : (size_t)cch - 1);
+		}
+#else
+		throw std::exception("not implemented");
+#endif
+	}
+
+	///
+	/// Convert Unicode string (UTF-16 on Windows) to SGML and append to string
+	///
+	/// \param[inout]  dst        String to append SGML to
+	/// \param[in]     src        Unicode string
+	/// \param[in]     charset    Charset (stdex::charset_id::default - system default)
+	///
+	inline void wstr2str(
+		_Inout_ std::string& dst,
+		_In_ const std::wstring& src,
+		_In_ charset_id charset = charset_id::default)
+	{
+		wstr2str(dst, src.c_str(), src.size(), charset);
+	}
+
+	///
+	/// Convert Unicode string (UTF-16 on Windows) to string
+	///
+	/// \param[in]  src        Unicode string
+	/// \param[in]  count_src  Unicode string character count limit
+	/// \param[in]  charset    Charset (stdex::charset_id::default - system default)
+	///
+	/// \return String
+	///
+	inline std::string wstr2str(
+		_In_reads_or_z_opt_(count_src) const wchar_t* src,
+		_In_ size_t count_src,
+		_In_ charset_id charset = charset_id::default)
+	{
+		std::string dst;
+		wstr2str(dst, src, count_src, charset);
+		return dst;
+	}
+
+	///
+	/// Convert Unicode string (UTF-16 on Windows) to string
+	///
+	/// \param[in]  src        Unicode string
+	/// \param[in]  charset    Charset (stdex::charset_id::default - system default)
+	///
+	/// \return String
+	///
+	inline std::string wstr2str(
+		_In_ const std::wstring& src,
+		_In_ charset_id charset = charset_id::default)
+	{
+		return wstr2str(src.c_str(), src.size(), charset);
+	}
+}
\ No newline at end of file