Add helper to make native path from internal representaton

conversion/stringconversion.cpp

@@ -193,7 +193,30 @@ StringData convertUtf8ToLatin1(const char *inputBuffer, std::size_t inputBufferS
 
 #ifdef PLATFORM_WINDOWS
 /*!
- * \brief Converts the specified multi-byte string to a wide string using the WinAPI.
+ * \brief Converts the specified multi-byte string (assumed to be UTF-8) to a wide string using the WinAPI.
+ * \remarks Only available under Windows.
+ */
+std::wstring convertMultiByteToWide(std::error_code &ec, std::string_view inputBuffer)
+{
+    // calculate required size
+    auto widePath = std::wstring();
+    auto size = MultiByteToWideChar(CP_UTF8, 0, inputBuffer.data(), inputBuffer.size(), nullptr, 0);
+    if (size <= 0) {
+        ec = std::error_code(GetLastError(), std::system_category());
+        return widePath;
+    }
+    // do the actual conversion
+    widePath.resize(static_cast<std::wstring::size_type>(size));
+    size = MultiByteToWideChar(CP_UTF8, 0, inputBuffer.data(), inputBuffer.size(), widePath.data(), size);
+    if (size <= 0) {
+        ec = std::error_code(GetLastError(), std::system_category());
+        widePath.clear();
+    }
+    return widePath;
+}
+
+/*!
+ * \brief Converts the specified multi-byte string (assumed to be UTF-8) to a wide string using the WinAPI.
  * \remarks
  * - Only available under Windows.
  * - If \a inputBufferSize is -1, \a inputBuffer is considered null-terminated.
@@ -218,7 +241,7 @@ WideStringData convertMultiByteToWide(std::error_code &ec, const char *inputBuff
 }
 
 /*!
- * \brief Converts the specified multi-byte string to a wide string using the WinAPI.
+ * \brief Converts the specified multi-byte string (assumed to be UTF-8) to a wide string using the WinAPI.
  * \remarks Only available under Windows.
  */
 WideStringData convertMultiByteToWide(std::error_code &ec, const std::string &inputBuffer)
@@ -228,7 +251,7 @@ WideStringData convertMultiByteToWide(std::error_code &ec, const std::string &in
 }
 
 /*!
- * \brief Converts the specified multi-byte string to a wide string using the WinAPI.
+ * \brief Converts the specified multi-byte string (assumed to be UTF-8) to a wide string using the WinAPI.
  * \remarks
  * - Only available under Windows.
  * - If \a inputBufferSize is -1, \a inputBuffer is considered null-terminated.
@@ -240,7 +263,7 @@ WideStringData convertMultiByteToWide(const char *inputBuffer, int inputBufferSi
 }
 
 /*!
- * \brief Converts the specified multi-byte string to a wide string using the WinAPI.
+ * \brief Converts the specified multi-byte string (assumed to be UTF-8) to a wide string using the WinAPI.
  * \remarks Only available under Windows.
  */
 WideStringData convertMultiByteToWide(const std::string &inputBuffer)

conversion/stringconversion.h

@@ -58,6 +58,7 @@ CPP_UTILITIES_EXPORT StringData convertUtf8ToLatin1(const char *inputBuffer, std
 
 #ifdef PLATFORM_WINDOWS
 using WideStringData = std::pair<std::unique_ptr<wchar_t[]>, int>;
+CPP_UTILITIES_EXPORT std::wstring convertMultiByteToWide(std::error_code &ec, std::string_view inputBuffer);
 CPP_UTILITIES_EXPORT WideStringData convertMultiByteToWide(std::error_code &ec, const char *inputBuffer, int inputBufferSize = -1);
 CPP_UTILITIES_EXPORT WideStringData convertMultiByteToWide(std::error_code &ec, const std::string &inputBuffer);
 CPP_UTILITIES_EXPORT WideStringData convertMultiByteToWide(const char *inputBuffer, int inputBufferSize = -1);

io/path.h

@@ -3,8 +3,13 @@
 
 #include "../global.h"
 
+#ifdef PLATFORM_WINDOWS
+#include "../conversion/stringconversion.h"
+#endif
+
 #include <list>
 #include <string>
+#include <string_view>
 
 #ifdef PLATFORM_WINDOWS
 #define PATH_SEP_CHAR '\\'
@@ -27,6 +32,34 @@ CPP_UTILITIES_EXPORT std::string_view fileName(std::string_view path);
 CPP_UTILITIES_EXPORT std::string_view directory(std::string_view path);
 #endif
 CPP_UTILITIES_EXPORT void removeInvalidChars(std::string &fileName);
+
+/*!
+ * \brief Returns \a path in the platform's native encoding.
+ * \remarks
+ * - On Windows we store paths internally as UTF-8 strings. So it is assumed that \a path is UTF-8 and a UTF-16
+ *   std::wstring is returned.
+ * - On any other platforms we store paths internally using the native format (usually UTF-8). So it is assumed
+ *   that \a path is already encoded as intended and passed as-is.
+ * - This function does basically the same as libstdc++'s `std::filesystem::u8path` implementation. However, the
+ *   C++ standard actually imposes a conversion to UTF-8 when a non-UTF-8 narrow encoding is used. That's not
+ *   wanted here. Besides, that function is deprecated in C++ 20.
+ */
+inline
+#ifdef PLATFORM_WINDOWS
+    std::wstring
+#else
+    std::string_view
+#endif
+    makeNativePath(std::string_view path)
+{
+#ifdef PLATFORM_WINDOWS
+    auto ec = std::error_code();
+    return convertMultiByteToWide(ec, path);
+#else
+    return path;
+#endif
+}
+
 } // namespace CppUtilities
 
 #endif // IOUTILITIES_PATHHELPER_H

tests/iotests.cpp

@@ -1,5 +1,23 @@
 #include "./testutils.h"
 
+#include "../conversion/stringconversion.h"
+
+/*!
+ * \brief Allows printing std::wstring using CPPUNIT_ASSERT_EQUAL.
+ */
+std::ostream &operator<<(std::ostream &out, const std::wstring &s)
+{
+    const auto utf8 = CppUtilities::
+#ifdef CONVERSION_UTILITIES_IS_BYTE_ORDER_LITTLE_ENDIAN
+        convertUtf16LEToUtf8
+#else
+        convertUtf16BEToUtf8
+#endif
+        (reinterpret_cast<const char *>(s.data()), s.size() * (sizeof(std::wstring::value_type) / sizeof(char)));
+    out.write(utf8.first.get(), utf8.second);
+    return out;
+}
+
 #include "../conversion/conversionexception.h"
 #include "../conversion/stringbuilder.h"
 
@@ -312,6 +330,15 @@ void IoTests::testPathUtilities()
     string invalidPath("lib/c++uti*lities.so?");
     removeInvalidChars(invalidPath);
     CPPUNIT_ASSERT(invalidPath == "libc++utilities.so");
+
+    const auto input = std::string_view("some/path/täst");
+#ifdef PLATFORM_WINDOWS
+    const auto expected = std::wstring(L"some/path/täst");
+#else
+    const auto expected = input;
+#endif
+    const auto output = makeNativePath(input);
+    CPPUNIT_ASSERT_EQUAL_MESSAGE("makeNativePath()", expected, output);
 }
 
 /*!