[libdazzle/wip/albfan/msys2] include realpath POSIX function in windows OS

[Alberto Fanjul <albfan src gnome org>]

commit 88626bad0301d861d3df428b7e9ec9c0ca769517
Author: albfan <albertofanjul gmail com>
Date:   Fri Jul 26 08:56:21 2019 +0200

    include realpath POSIX function in windows OS

 src/files/dzl-recursive-file-monitor.c | 93 ++++++++++++++++++++++++++++++++++
 1 file changed, 93 insertions(+)
---
diff --git a/src/files/dzl-recursive-file-monitor.c b/src/files/dzl-recursive-file-monitor.c
index 824fd83..6530fae 100644
--- a/src/files/dzl-recursive-file-monitor.c
+++ b/src/files/dzl-recursive-file-monitor.c
@@ -26,6 +26,99 @@
 #include "files/dzl-recursive-file-monitor.h"
 #include "util/dzl-macros.h"
 
+#include <io.h>
+#include <stdlib.h>
+#include <errno.h>
+
+
+/* realpath.c
+ * $Id$
+ *
+ * Provides an implementation of the "realpath" function, conforming
+ * approximately to SUSv3, and adapted for use on native Microsoft(R)
+ * Win32 platforms.
+ *
+ * Written by Keith Marshall <keithmarshall users sourceforge net>
+ *
+ * This is free software.  You may redistribute and/or modify it as you
+ * see fit, without restriction of copyright.
+ *
+ * This software is provided "as is", in the hope that it may be useful,
+ * but WITHOUT WARRANTY OF ANY KIND, not even any implied warranty of
+ * MERCHANTABILITY, nor of FITNESS FOR ANY PARTICULAR PURPOSE.  At no
+ * time will the author accept any form of liability for any damages,
+ * however caused, resulting from the use of this software.
+ *
+ */
+
+_CRTIMP char __cdecl
+*realpath( const char *__restrict__ name, char *__restrict__ resolved )
+{
+  char *retname = NULL;  /* we will return this, if we fail */
+
+  /* SUSv3 says we must set `errno = EINVAL', and return NULL,
+   * if `name' is passed as a NULL pointer.
+   */
+
+  if( name == NULL )
+    errno = EINVAL;
+
+  /* Otherwise, `name' must refer to a readable filesystem object,
+   * if we are going to resolve its absolute path name.
+   */
+
+  else if( access( name, 4 ) == 0 )
+  {
+    /* If `name' didn't point to an existing entity,
+     * then we don't get to here; we simply fall past this block,
+     * returning NULL, with `errno' appropriately set by `access'.
+     *
+     * When we _do_ get to here, then we can use `_fullpath' to
+     * resolve the full path for `name' into `resolved', but first,
+     * check that we have a suitable buffer, in which to return it.
+     */
+
+    if( (retname = resolved) == NULL )
+    {
+      /* Caller didn't give us a buffer, so we'll exercise the
+       * option granted by SUSv3, and allocate one.
+       *
+       * `_fullpath' would do this for us, but it uses `malloc', and
+       * Microsoft's implementation doesn't set `errno' on failure.
+       * If we don't do this explicitly ourselves, then we will not
+       * know if `_fullpath' fails on `malloc' failure, or for some
+       * other reason, and we want to set `errno = ENOMEM' for the
+       * `malloc' failure case.
+       */
+
+      retname = malloc( _MAX_PATH );
+    }
+
+    /* By now, we should have a valid buffer.
+     * If we don't, then we know that `malloc' failed,
+     * so we can set `errno = ENOMEM' appropriately.
+     */
+
+    if( retname == NULL )
+      errno = ENOMEM;
+
+    /* Otherwise, when we do have a valid buffer,
+     * `_fullpath' should only fail if the path name is too long.
+     */
+
+    else if( (retname = _fullpath( retname, name, _MAX_PATH )) == NULL )
+      errno = ENAMETOOLONG;
+  }
+
+  /* By the time we get to here,
+   * `retname' either points to the required resolved path name,
+   * or it is NULL, with `errno' set appropriately, either of which
+   * is our required return condition.
+   */
+  
+  return retname;
+}
+
 #define MONITOR_FLAGS 0
 
 /**