Index: trunk/src/lib/nt/ntopenat.c
===================================================================
--- trunk/src/lib/nt/ntopenat.c	(revision 3533)
+++ trunk/src/lib/nt/ntopenat.c	(revision 3533)
@@ -0,0 +1,161 @@
+/* $Id: ntdir.c 3007 2016-11-06 16:46:43Z bird $ */
+/** @file
+ * MSC + NT openat API.
+ */
+
+/*
+ * Copyright (c) 2005-2021 knut st. osmundsen <bird-kBuild-spamx@anduin.net>
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a
+ * copy of this software and associated documentation files (the "Software"),
+ * to deal in the Software without restriction, including without limitation
+ * the rights to use, copy, modify, merge, publish, distribute, sublicense,
+ * and/or sell copies of the Software, and to permit persons to whom the
+ * Software is furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included
+ * in all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
+ * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS
+ * IN THE SOFTWARE.
+ *
+ * Alternatively, the content of this file may be used under the terms of the
+ * GPL version 2 or later, or LGPL version 2.1 or later.
+ */
+
+
+/*******************************************************************************
+*   Header Files                                                               *
+*******************************************************************************/
+#include <errno.h>
+#include <assert.h>
+#include <fcntl.h>
+#include <io.h>
+
+#include "ntstuff.h"
+#include "nthlp.h"
+#include "ntopenat.h"
+#include "ntstat.h"
+
+
+#define IS_ALPHA(ch) ( ((ch) >= 'A' && (ch) <= 'Z') || ((ch) >= 'a' && (ch) <= 'z') )
+#define IS_SLASH(ch) ((ch) == '\\' || (ch) == '/')
+
+
+
+static int birdOpenInt(const char *pszPath, int fFlags, unsigned __int16 fMode)
+{
+    /*
+     * Try open it using the CRT's open function, but deal with opening
+     * directories as the CRT doesn't allow doing that.
+     */
+    int const iErrnoSaved = errno;
+    int fd = open(pszPath, fFlags, fMode);
+    if (   fd < 0
+        && (errno == EACCES || errno == ENOENT || errno == EISDIR)
+        && (fFlags & (_O_WRONLY | _O_RDWR | _O_RDONLY)) == _O_RDONLY
+        && (fFlags & (_O_CREAT | _O_TRUNC | _O_EXCL)) == 0 )
+    {
+        BirdStat_T Stat;
+        if (!birdStatFollowLink(pszPath, &Stat))
+        {
+            if (S_ISDIR(Stat.st_mode))
+            {
+                HANDLE hDir;
+                errno = iErrnoSaved;
+                hDir = birdOpenFile(pszPath,
+                                    FILE_READ_DATA | FILE_READ_ATTRIBUTES | SYNCHRONIZE,
+                                    FILE_ATTRIBUTE_NORMAL,
+                                    FILE_SHARE_READ | FILE_SHARE_WRITE | FILE_SHARE_DELETE,
+                                    FILE_OPEN,
+                                    FILE_DIRECTORY_FILE | FILE_OPEN_FOR_BACKUP_INTENT | FILE_SYNCHRONOUS_IO_NONALERT,
+                                    OBJ_CASE_INSENSITIVE);
+                if (hDir != INVALID_HANDLE_VALUE)
+                {
+                    fd = _open_osfhandle((intptr_t)hDir, fFlags);
+                    if (fd >= 0)
+                        return fd;
+                    birdCloseFile(hDir);
+                }
+            }
+            else
+                errno = EACCES;
+        }
+        else
+            errno = EACCES;
+    }
+    return fd;
+}
+
+
+int birdOpen(const char *pszPath, int fFlags, ...)
+{
+    unsigned __int16 fMode;
+    va_list va;
+    va_start(va, fFlags);
+    fMode = va_arg(va, unsigned __int16);
+    va_end(va);
+    return birdOpenInt(pszPath, fFlags, fMode);
+}
+
+
+
+/**
+ * Implements opendir.
+ */
+int birdOpenAt(int fdDir, const char *pszPath, int fFlags, ...)
+{
+    HANDLE hDir;
+
+    /*
+     * Retrieve the mode mask.
+     */
+    unsigned __int16 fMode;
+    va_list va;
+    va_start(va, fFlags);
+    fMode = va_arg(va, unsigned __int16);
+    va_end(va);
+
+    /*
+     * Just call 'open' directly if we can get away with it:
+     */
+    if (fdDir == AT_FDCWD)
+        return birdOpenInt(pszPath, fFlags, fMode);
+
+    if (IS_SLASH(pszPath[0]))
+    {
+        if (IS_SLASH(pszPath[1]) && !IS_SLASH(pszPath[2]) && pszPath[2] != '\0')
+            return birdOpenInt(pszPath, fFlags, fMode);
+    }
+    else if (IS_ALPHA(pszPath[0]) && pszPath[1] == ':')
+    {
+        if (IS_SLASH(pszPath[2]))
+            return birdOpenInt(pszPath, fFlags, fMode);
+        /*
+         * Drive letter relative path like "C:kernel32.dll".
+         * We could try use fdDir as the CWD here if it refers to the same drive,
+         * however that's can be implemented later...
+         */
+        return birdOpenInt(pszPath, fFlags, fMode);
+    }
+
+    /*
+     * Otherwise query the path of fdDir and construct an absolute path from all that.
+     * This isn't atomic and safe and stuff, but it gets the work done for now.
+     */
+    hDir = (HANDLE)_get_osfhandle(fdDir);
+    if (hDir != INVALID_HANDLE_VALUE)
+    {
+        /** @todo implement me.   */
+        __debugbreak();
+        errno = EBADF;
+    }
+    return -1;
+}
+
+
Index: trunk/src/lib/nt/ntopenat.h
===================================================================
--- trunk/src/lib/nt/ntopenat.h	(revision 3533)
+++ trunk/src/lib/nt/ntopenat.h	(revision 3533)
@@ -0,0 +1,43 @@
+/* $Id: ntdir.h 3005 2016-11-06 00:07:37Z bird $ */
+/** @file
+ * MSC + NT openat.
+ */
+
+/*
+ * Copyright (c) 2005-2021 knut st. osmundsen <bird-kBuild-spamx@anduin.net>
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a
+ * copy of this software and associated documentation files (the "Software"),
+ * to deal in the Software without restriction, including without limitation
+ * the rights to use, copy, modify, merge, publish, distribute, sublicense,
+ * and/or sell copies of the Software, and to permit persons to whom the
+ * Software is furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included
+ * in all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
+ * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS
+ * IN THE SOFTWARE.
+ *
+ * Alternatively, the content of this file may be used under the terms of the
+ * GPL version 2 or later, or LGPL version 2.1 or later.
+ */
+
+#ifndef ___nt_ntopenat_h
+#define ___nt_ntopenat_h
+
+#include "nttypes.h"
+
+extern int birdOpenAt(int fdDir, const char *pszPath, int fFlags, ...);
+
+#define openat                      birdOpenAt
+
+#define AT_FDCWD        (-987654321)
+
+#endif
+
