[UCRT] Import Microsoft.Windows.SDK.CRTSource version 10.0.22621.3

Imported from https://www.nuget.org/packages/Microsoft.Windows.SDK.CRTSource/10.0.22621.3
License: MIT

sdk/lib/ucrt/stdio/fdopen.cpp

@@ -0,0 +1,70 @@
+//
+// fdopen.cpp
+//
+//      Copyright (c) Microsoft Corporation.  All rights reserved.
+//
+// Defines functions that open a stdio stream over an existing lowio file handle.
+//
+#include <corecrt_internal_stdio.h>
+
+
+
+// Opens a lowio file handle as a stdio stream.  This associates a stream with
+// the specified file handle, thus allowing buffering and use with the stdio
+// functions.  The mode must be specified and must be compatible with the mode
+// with which the file was opened in lowio.
+//
+// Returns the new FILE* associated with the file handle on success; returns
+// nullptr on failure.
+template <typename Character>
+static FILE* __cdecl common_fdopen(
+    int              const fh,
+    Character const* const mode
+    ) throw()
+{
+    _VALIDATE_RETURN(mode != nullptr, EINVAL, nullptr);
+
+    _CHECK_FH_RETURN(fh, EBADF, nullptr);
+    _VALIDATE_RETURN(fh >= 0 && (unsigned)fh < (unsigned)_nhandle, EBADF, nullptr);
+    _VALIDATE_RETURN(_osfile(fh) & FOPEN, EBADF, nullptr);
+
+    __acrt_stdio_stream_mode const parsed_mode = __acrt_stdio_parse_mode(mode);
+    if (!parsed_mode._success)
+        return nullptr;
+
+    __crt_stdio_stream stream = __acrt_stdio_allocate_stream();
+    if (!stream.valid())
+    {
+        errno = EMFILE;
+        return nullptr;
+    }
+
+    __try
+    {
+        // Ensure that streams get flushed during pre-termination:
+        #ifndef CRTDLL
+        ++_cflush;
+        #endif
+
+        stream.set_flags(parsed_mode._stdio_mode);
+        stream->_file = fh;
+    }
+    __finally
+    {
+        stream.unlock();
+    }
+
+    return stream.public_stream();
+}
+
+
+
+extern "C" FILE* __cdecl _fdopen(int const fh, char const* const mode)
+{
+    return common_fdopen(fh, mode);
+}
+
+extern "C" FILE* __cdecl _wfdopen(int const fh, wchar_t const* const mode)
+{
+    return common_fdopen(fh, mode);
+}