StringUtil: Add wide string<->utf8 conversion for Windows

src/common/string_util.cpp

@@ -1,7 +1,12 @@
 #include "string_util.h"
 #include <cctype>
+#include <codecvt>
 #include <cstdio>
 
+#ifdef WIN32
+#include "windows_headers.h"
+#endif
+
 namespace StringUtil {
 
 std::string StdStringFromFormat(const char* format, ...)
@@ -158,4 +163,37 @@ std::size_t Strlcpy(char* dst, const std::string_view& src, std::size_t size)
   return len;
 }
 
+#ifdef WIN32
+
+std::wstring UTF8StringToWideString(const std::string_view& str)
+{
+  int wlen = MultiByteToWideChar(CP_UTF8, 0, str.data(), static_cast<int>(str.length()), nullptr, 0);
+  if (wlen <= 0)
+    return {};
+
+  std::wstring ret;
+  ret.resize(wlen);
+  if (MultiByteToWideChar(CP_UTF8, 0, str.data(), static_cast<int>(str.length()), ret.data(), wlen) <= 0)
+    return {};
+
+  return ret;
+}
+
+std::string WideStringToUTF8String(const std::wstring_view& str)
+{
+  int mblen = WideCharToMultiByte(CP_UTF8, 0, str.data(), static_cast<int>(str.length()), nullptr, 0, nullptr, nullptr);
+  if (mblen <= 0)
+    return {};
+
+  std::string ret;
+  ret.resize(mblen);
+  if (WideCharToMultiByte(CP_UTF8, 0, str.data(), static_cast<int>(str.length()), ret.data(), mblen, nullptr, nullptr) <
+      0)
+    return {};
+
+  return ret;
+}
+
+#endif
+
 } // namespace StringUtil

src/common/string_util.h

@@ -53,7 +53,7 @@ static inline int Strncasecmp(const char* s1, const char* s2, std::size_t n)
 
 /// Wrapper arond std::from_chars
 template<typename T>
-inline std::optional<T> FromChars(std::string_view str)
+inline std::optional<T> FromChars(const std::string_view& str)
 {
   T value;
 
@@ -74,7 +74,7 @@ inline std::optional<T> FromChars(std::string_view str)
 
 /// Explicit override for booleans
 template<>
-inline std::optional<bool> FromChars(std::string_view str)
+inline std::optional<bool> FromChars(const std::string_view& str)
 {
   if (Strncasecmp("true", str.data(), str.length()) == 0 || Strncasecmp("yes", str.data(), str.length()) == 0 ||
       Strncasecmp("on", str.data(), str.length()) == 0 || Strncasecmp("1", str.data(), str.length()) == 0)
@@ -94,7 +94,7 @@ inline std::optional<bool> FromChars(std::string_view str)
 #ifndef _MSC_VER
 /// from_chars doesn't seem to work with floats on gcc
 template<>
-inline std::optional<float> FromChars(std::string_view str)
+inline std::optional<float> FromChars(const std::string_view& str)
 {
   float value;
   std::string temp(str);
@@ -108,9 +108,19 @@ inline std::optional<float> FromChars(std::string_view str)
 #endif
 
 /// starts_with from C++20
-ALWAYS_INLINE static bool StartsWith(std::string_view str, const char* prefix)
+ALWAYS_INLINE static bool StartsWith(const std::string_view& str, const char* prefix)
 {
   return (str.compare(0, std::strlen(prefix), prefix) == 0);
 }
 
+#ifdef WIN32
+
+/// Converts the specified UTF-8 string to a wide string.
+std::wstring UTF8StringToWideString(const std::string_view& str);
+
+/// Converts the specified wide string to a UTF-8 string.
+std::string WideStringToUTF8String(const std::wstring_view& str);
+
+#endif
+
 } // namespace StringUtil

src/frontend-common/common_host_interface.cpp

@@ -626,23 +626,12 @@ void CommonHostInterface::SetUserDirectory()
     PWSTR documents_directory;
     if (SUCCEEDED(SHGetKnownFolderPath(FOLDERID_Documents, 0, NULL, &documents_directory)))
     {
-      const size_t documents_directory_len = std::wcslen(documents_directory);
-      int documents_directory_u8len = WideCharToMultiByte(
-        CP_UTF8, 0, documents_directory, static_cast<int>(documents_directory_len), nullptr, 0, nullptr, nullptr);
-      if (documents_directory_u8len > 0)
+      const std::string documents_directory_str(StringUtil::WideStringToUTF8String(documents_directory));
+      if (!documents_directory_str.empty())
       {
-        std::string documents_directory_str;
-        documents_directory_str.resize(documents_directory_u8len);
-        documents_directory_u8len = WideCharToMultiByte(
-          CP_UTF8, 0, documents_directory, static_cast<int>(documents_directory_len), documents_directory_str.data(),
-          static_cast<int>(documents_directory_str.size()), 0, nullptr);
-        if (documents_directory_u8len > 0)
-        {
-          documents_directory_str.resize(documents_directory_u8len);
         m_user_directory = StringUtil::StdStringFromFormat("%s%c%s", documents_directory_str.c_str(),
                                                            FS_OSPATH_SEPERATOR_CHARACTER, "DuckStation");
       }
-      }
       CoTaskMemFree(documents_directory);
     }
 #elif __linux__