utils: Add fsbridge fstream function wrapper

1 files changed, 51 insertions, 0 deletions

diff --git a/src/fs.h b/src/fs.h
index a7074f446a..bdccb15232 100644
--- a/src/fs.h
+++ b/src/fs.h
@@ -7,6 +7,9 @@
 
 #include <stdio.h>
 #include <string>
+#if defined WIN32 && defined __GLIBCXX__
+#include <ext/stdio_filebuf.h>
+#endif
 
 #include <boost/filesystem.hpp>
 #include <boost/filesystem/fstream.hpp>
@@ -39,6 +42,54 @@ namespace fsbridge {
     };
 
     std::string get_filesystem_error_message(const fs::filesystem_error& e);
+
+    // GNU libstdc++ specific workaround for opening UTF-8 paths on Windows.
+    //
+    // On Windows, it is only possible to reliably access multibyte file paths through
+    // `wchar_t` APIs, not `char` APIs. But because the C++ standard doesn't
+    // require ifstream/ofstream `wchar_t` constructors, and the GNU library doesn't
+    // provide them (in contrast to the Microsoft C++ library, see
+    // https://stackoverflow.com/questions/821873/how-to-open-an-stdfstream-ofstream-or-ifstream-with-a-unicode-filename/822032#822032),
+    // Boost is forced to fall back to `char` constructors which may not work properly.
+    //
+    // Work around this issue by creating stream objects with `_wfopen` in
+    // combination with `__gnu_cxx::stdio_filebuf`. This workaround can be removed
+    // with an upgrade to C++17, where streams can be constructed directly from
+    // `std::filesystem::path` objects.
+
+#if defined WIN32 && defined __GLIBCXX__
+    class ifstream : public std::istream
+    {
+    public:
+        ifstream() = default;
+        explicit ifstream(const fs::path& p, std::ios_base::openmode mode = std::ios_base::in) { open(p, mode); }
+        ~ifstream() { close(); }
+        void open(const fs::path& p, std::ios_base::openmode mode = std::ios_base::in);
+        bool is_open() { return m_filebuf.is_open(); }
+        void close();
+
+    private:
+        __gnu_cxx::stdio_filebuf<char> m_filebuf;
+        FILE* m_file = nullptr;
+    };
+    class ofstream : public std::ostream
+    {
+    public:
+        ofstream() = default;
+        explicit ofstream(const fs::path& p, std::ios_base::openmode mode = std::ios_base::out) { open(p, mode); }
+        ~ofstream() { close(); }
+        void open(const fs::path& p, std::ios_base::openmode mode = std::ios_base::out);
+        bool is_open() { return m_filebuf.is_open(); }
+        void close();
+
+    private:
+        __gnu_cxx::stdio_filebuf<char> m_filebuf;
+        FILE* m_file = nullptr;
+    };
+#else  // !(WIN32 && __GLIBCXX__)
+    typedef fs::ifstream ifstream;
+    typedef fs::ofstream ofstream;
+#endif // WIN32 && __GLIBCXX__
 };
 
 #endif // BITCOIN_FS_H