DSK-658 - Support non ascii

[OleksiiShvachenko]

DSK-658: mailcore paths are UTF-8 (fileSystemRepresentation), but the Windows layer used narrow CRT calls (fopen_s, _unlink, _mkdir, stat) that resolve paths through the ANSI codepage. Any path with characters outside the codepage — e.g. a temp dir under a non-ASCII user profile — failed to open, breaking RFC822 temp files (MCOErrorFile) and stalling Outbox.

Convert UTF-8 to UTF-16 and call _wfopen_s/_wunlink/_wmkdir/_wstat64i32, falling back to the narrow call when the input is not valid UTF-8. Also route MCDataStreamDecoder and MCCertificateUtils through MCWin32.h so their fopen calls hit the wrapper.

---

Note

Medium Risk
Changes core Win32 path handling for fopen, unlink, mkdir, and stat across the library via header macros; incorrect UTF-8 handling or stat layout assumptions could cause subtle file failures on Windows.

Overview
Fixes Windows file I/O when mailcore paths are UTF-8 (fileSystemRepresentation) but narrow CRT calls (fopen_s, _unlink, _mkdir, stat) interpret them via the ANSI codepage, which broke temp RFC822 files and Outbox on non-ASCII profile paths.

win32_fopen now converts paths with MultiByteToWideChar(CP_UTF8, …) and opens via _wfopen_s, with fallback to the existing narrow fopen_s when conversion fails or the mode string is too long. New win32_unlink, win32_mkdir, and win32_stat follow the same pattern using _wunlink, _wmkdir, and _wstat64i32.

MCWin32.h (source and public include) redefines unlink, mkdir, and stat to those wrappers (alongside the existing fopen macro), adds io.h/wchar.h, and declares the new helpers. MCDataStreamDecoder.cpp and MCCertificateUtils.cpp include MCWin32.h first so their fopen calls use the wrapper.

^{Reviewed by Cursor Bugbot for commit 72c919b. Bugbot is set up for automated code reviews on this repo. Configure here.}

[lxbndr]

Testing is problematic and comes ugly. It would become legacy very fast.

UPD. see tests were reverted

[cursor]

Cursor Bugbot has reviewed your changes and found 1 potential issue.

^{❌ Bugbot Autofix is OFF. To automatically fix reported issues with cloud agents, enable autofix in the Cursor dashboard.}

^{Reviewed by Cursor Bugbot for commit 4cc613c. Configure here.}