lib/io: Add a replacement for fopen() which works on Windows

fopen() does not correctly handle non-ASCII paths on Windows.

src/lib/io/fstream.cpp

@@ -54,4 +54,16 @@ void open_utf8_path(std::fstream& stream, const std::string& path, std::ios_base
     open_utf8_path_impl(stream, path, mode);
 }
 
+std::FILE* fopen_utf8_path(const std::string& path, const std::string& mode)
+{
+#if SYSAPI_WIN32
+    auto wchar_path = utf8_to_win_char(path);
+    auto wchar_mode = utf8_to_win_char(mode);
+    return _wfopen(reinterpret_cast<wchar_t*>(wchar_path.data()),
+                   reinterpret_cast<wchar_t*>(wchar_mode.data()));
+#else
+    return std::fopen(path.c_str(), mode.c_str());
+#endif
+}
+
 } // namespace barrier

src/lib/io/fstream.h

@@ -18,6 +18,7 @@
 #ifndef BARRIER_LIB_IO_FSTREAM_H
 #define BARRIER_LIB_IO_FSTREAM_H
 
+#include <cstdio>
 #include <iosfwd>
 #include <ios>
 
@@ -30,6 +31,8 @@ void open_utf8_path(std::ofstream& stream, const std::string& path,
 void open_utf8_path(std::fstream& stream, const std::string& path,
                     std::ios_base::openmode mode = std::ios_base::in | std::ios_base::out);
 
+std::FILE* fopen_utf8_path(const std::string& path, const std::string& mode);
+
 } // namespace barrier
 
 #endif