remove codecvt

Deprecated in C++17

Signed-off-by: Rosen Penev <rosenp@gmail.com>

src/helper_functions.cpp

@@ -3,9 +3,7 @@
 #include "helper_functions.hpp"
 
 #include <cmath>
-#include <codecvt>
 #include <cstring>
-#include <locale>
 #include <numeric>
 #include "enforce.hpp"
 
@@ -17,17 +15,22 @@ std::string string_from_unterminated(const char* data, size_t data_length) {
   return {data, StringLength};
 }
 
-namespace Exiv2 {
-
-std::string utf16ToUtf8(const std::wstring& wstr) {
-  using convert_typeX = std::codecvt_utf8<wchar_t>;
-  std::wstring_convert<convert_typeX, wchar_t> converterX;
-
-  std::string str = converterX.to_bytes(wstr);
+namespace {
+std::string utf16ToUtf8(const std::u16string& wstr) {
+#ifdef _MSC_VER
+#pragma warning(push)
+#pragma warning(disable : 4244)
+  auto str = std::string(wstr.begin(), wstr.end());
+#pragma warning(pop)
+#else
+  auto str = std::string(wstr.begin(), wstr.end());
+#endif
   str.erase(std::remove(str.begin(), str.end(), '\0'), str.end());
   return str;
 }
+}  // namespace
 
+namespace Exiv2 {
 uint64_t readQWORDTag(const BasicIo::UniquePtr& io) {
   Internal::enforce(QWORD <= io->size() - io->tell(), Exiv2::ErrorCode::kerCorruptedMetadata);
   DataBuf FieldBuf = io->read(QWORD);
@@ -50,7 +53,7 @@ std::string readStringWcharTag(const BasicIo::UniquePtr& io, size_t length) {
   Internal::enforce(length <= io->size() - io->tell(), Exiv2::ErrorCode::kerCorruptedMetadata);
   DataBuf FieldBuf(length + 1);
   io->readOrThrow(FieldBuf.data(), length, ErrorCode::kerFailedToReadImageData);
-  std::wstring wst(FieldBuf.begin(), FieldBuf.end());
+  std::u16string wst(FieldBuf.begin(), FieldBuf.end());
   return utf16ToUtf8(wst);
 }
 

src/helper_functions.hpp

@@ -32,17 +32,6 @@ static constexpr size_t DWORD = 0x4;
 static constexpr size_t QWORD = 0x8;
 static constexpr size_t GUID = 0x10;
 
-// @brief
-
-/*!
-    @brief The function utf16ToUtf8 takes a wide string wstr as input and converts it to a narrow string
-    The conversion is performed using the std::wstring_convert class template and a std::codecvt_utf8 facet, which
-    implements conversion between UTF-8 and wide characters.
-    @param wstr : wide string
-    @return Returns std::string object
-*/
-std::string utf16ToUtf8(const std::wstring& wstr);
-
 [[nodiscard]] uint64_t readQWORDTag(const Exiv2::BasicIo::UniquePtr& io);
 
 [[nodiscard]] uint32_t readDWORDTag(const Exiv2::BasicIo::UniquePtr& io);