FileStream: Fix opening long paths on Windows (taglib#1216)

To make sure paths longer than MAX_PATH (260) can be opened, prefix local
paths with `\\?\`, and UNC paths with `\\?\UNC\`.

I've tested on Windows 10 22H2 (Build 19045.3930), even when setting
LongPathsEnabled to 1 in the registry, it still won't open files with long
paths without prefixing them.

For more information see:
https://learn.microsoft.com/en-us/windows/win32/fileio/maximum-file-path-limitation?tabs=registry

taglib/toolkit/tfilestream.cpp

@@ -56,7 +56,21 @@ namespace
 #if defined (PLATFORM_WINRT)
  return CreateFile2(path.wstr().c_str(), access, FILE_SHARE_READ, OPEN_EXISTING, nullptr);
 #else
- return CreateFileW(path.wstr().c_str(), access, FILE_SHARE_READ, nullptr, OPEN_EXISTING, 0, nullptr);
+ constexpr wchar_t LongLocalPathPrefix[] = L"\\\\?\\";
+ constexpr wchar_t UNCPathPrefix[] = L"\\\\";
+ constexpr wchar_t LongUNCPathPrefix[] = L"\\\\?\\UNC\\";
+ std::wstring pathWStr = path.wstr();
+ if(pathWStr.length() > MAX_PATH &&
+ pathWStr.compare(0, std::size(LongLocalPathPrefix) - 1, LongLocalPathPrefix) != 0 &&
+ pathWStr.compare(0, std::size(LongUNCPathPrefix) - 1, LongUNCPathPrefix) != 0) {
+ if(pathWStr.compare(0, std::size(UNCPathPrefix) - 1, UNCPathPrefix) == 0) {
+ pathWStr = LongUNCPathPrefix + pathWStr.substr(2);
+ }
+ else {
+ pathWStr = LongLocalPathPrefix + pathWStr;
+ }
+ }
+ return CreateFileW(pathWStr.c_str(), access, FILE_SHARE_READ, nullptr, OPEN_EXISTING, 0, nullptr);
 #endif
  }