file_win32 supports UTF-8 paths:

fix #793, close #1791, close #1793

This brings file_win32 in sync with the documentation.
Previously, the path passed to open worked if encoded in the system
codepage (which is almost never UTF-8).
Now, the path must be encoded as UTF-8, as stated in the
documentation.

Adapt file tests so that for file_win32 all paths include a unicorn
character.

CHANGELOG.md

@@ -2,6 +2,7 @@ Version 282:
 
 * Use superproject docca
 * Fix release build of docs
+* file_win32 supports UTF-8 paths
 
 --------------------------------------------------------------------------------
 

include/boost/beast/core/detail/win32_unicode_path.hpp

@@ -0,0 +1,82 @@
+//
+// Copyright (c) 2019 Mika Fischer (mika.fischer@zoopnet.de)
+//
+// Distributed under the Boost Software License, Version 1.0. (See accompanying
+// file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
+//
+// Official repository: https://github.com/boostorg/beast
+//
+
+#ifndef BOOST_BEAST_CORE_DETAIL_WIN32_UNICODE_PATH_HPP
+#define BOOST_BEAST_CORE_DETAIL_WIN32_UNICODE_PATH_HPP
+
+#ifdef _WIN32
+#include <boost/config.hpp>
+#include <boost/beast/core/error.hpp>
+#include <boost/winapi/character_code_conversion.hpp>
+#include <boost/winapi/file_management.hpp>
+#include <boost/winapi/get_last_error.hpp>
+#include <array>
+#include <vector>
+
+namespace boost {
+namespace beast {
+namespace detail {
+
+class win32_unicode_path
+{
+    using WCHAR_ = boost::winapi::WCHAR_;
+
+public:
+    win32_unicode_path(const char* utf8_path, error_code& ec) {
+        int ret = mb2wide(utf8_path, static_buf_.data(),
+            static_buf_.size());
+        if (ret == 0)
+        {
+            int sz = mb2wide(utf8_path, nullptr, 0);
+            if (sz == 0)
+            {
+                ec.assign(boost::winapi::GetLastError(),
+                    system_category());
+                return;
+            }
+            dynamic_buf_.resize(sz);
+            int ret2 = mb2wide(utf8_path,
+                dynamic_buf_.data(),
+                dynamic_buf_.size());
+            if (ret2 == 0)
+            {
+                ec.assign(boost::winapi::GetLastError(),
+                    system_category());
+                return;
+            }
+        }
+    }
+
+    WCHAR_ const* c_str() const noexcept
+    {
+        return dynamic_buf_.empty()
+            ? static_buf_.data()
+            : dynamic_buf_.data();
+    }
+
+private:
+    int mb2wide(const char* utf8_path, WCHAR_* buf, size_t sz)
+    {
+        return boost::winapi::MultiByteToWideChar(
+            boost::winapi::CP_UTF8_,
+            boost::winapi::MB_ERR_INVALID_CHARS_,
+            utf8_path, -1,
+            buf, static_cast<int>(sz));
+    }
+
+    std::array<WCHAR_, boost::winapi::MAX_PATH_> static_buf_;
+    std::vector<WCHAR_> dynamic_buf_;
+};
+
+} // detail
+} // beast
+} // boost
+#endif
+
+#endif

include/boost/beast/core/impl/file_win32.ipp

@@ -14,10 +14,10 @@
 
 #if BOOST_BEAST_USE_WIN32_FILE
 
+#include <boost/beast/core/detail/win32_unicode_path.hpp>
 #include <boost/core/exchange.hpp>
 #include <boost/winapi/access_rights.hpp>
 #include <boost/winapi/error_codes.hpp>
-#include <boost/winapi/file_management.hpp>
 #include <boost/winapi/get_last_error.hpp>
 #include <limits>
 #include <utility>
@@ -186,8 +186,12 @@ open(char const* path, file_mode mode, error_code& ec)
         flags_and_attributes = 0x08000000; // FILE_FLAG_SEQUENTIAL_SCAN
         break;
     }
-    h_ = ::CreateFileA(
-        path,
+    
+    detail::win32_unicode_path unicode_path(path, ec);
+    if (ec)
+        return;
+    h_ = ::CreateFileW(
+        unicode_path.c_str(),
         desired_access,
         share_mode,
         NULL,

test/beast/core/file_test.hpp

@@ -15,6 +15,7 @@
 #include <boost/beast/core/file_base.hpp>
 #include <boost/filesystem/path.hpp>
 #include <boost/filesystem/operations.hpp>
+#include <boost/filesystem/fstream.hpp>
 #include <cstdio>
 #include <string>
 #include <type_traits>
@@ -22,7 +23,7 @@
 namespace boost {
 namespace beast {
 
-template<class File>
+template<class File, bool append_unicode_suffix = false>
 void
 test_file()
 {
@@ -35,16 +36,38 @@ test_file()
 
     namespace fs = boost::filesystem;
 
+    static constexpr
+#ifdef _WIN32
+    boost::winapi::WCHAR_ unicode_suffix[] = { 0xd83e, 0xdd84, 0x0000 }; // UTF-16-LE unicorn
+#else
+    char                  unicode_suffix[] = { 0xf0, 0x9f, 0xa6, 0x84, 0x00 }; // UTF-8 unicorn
+#endif
+
     class temp_path
     {
         fs::path path_;
-        std::string str_;
+        std::vector<char> utf8_str_;
 
     public:
         temp_path()
             : path_(fs::unique_path())
-            , str_(path_.string<std::string>())
         {
+            if (append_unicode_suffix)
+                path_ += unicode_suffix;
+#ifdef _WIN32
+            constexpr auto cp = boost::winapi::CP_UTF8_;
+            constexpr auto flags = boost::winapi::WC_ERR_INVALID_CHARS_;
+            auto sz = boost::winapi::WideCharToMultiByte(
+                cp, flags, path_.c_str(), -1, nullptr, 0,
+                nullptr, nullptr);
+            BEAST_EXPECT(sz != 0);
+            utf8_str_.resize(sz);
+            auto ret = boost::winapi::WideCharToMultiByte(
+                cp, flags, path_.c_str(), -1,
+                utf8_str_.data(), sz,
+                nullptr, nullptr);
+            BEAST_EXPECT(ret == sz);
+#endif
         }
 
         operator fs::path const&()
@@ -54,25 +77,27 @@ test_file()
 
         operator char const*()
         {
-            return str_.c_str();
+#ifdef _WIN32
+            return utf8_str_.data();
+#else
+            return path_.c_str();
+#endif
         }
     };
 
     auto const create =
         [](fs::path const& path)
         {
-            auto const s =
-                path.string<std::string>();
             BEAST_EXPECT(! fs::exists(path));
-            FILE* f = ::fopen(s.c_str(), "w");
-            if( BEAST_EXPECT(f != nullptr))
-                ::fclose(f);
+            fs::ofstream out(path);
+            BEAST_EXPECT(out.is_open());
         };
 
     auto const remove =
         [](fs::path const& path)
         {
             fs::remove(path);
+            BEAST_EXPECT(! fs::exists(path));
         };
 
     temp_path path;

test/beast/core/file_win32.cpp

@@ -26,7 +26,7 @@ public:
     void
     run()
     {
-        test_file<file_win32>();
+        test_file<file_win32, true>();
     }
 };