From 1e322e6298ebed31e982bb4ad3a4132f8e7b2036 Mon Sep 17 00:00:00 2001
From: Maxime Devos <maximedevos@telenet.be>
Date: Fri, 12 Mar 2021 17:30:58 +0100
Subject: [PATCH 11/17] =?UTF-8?q?Define=20a=20Scheme=20binding=20to=20?=
 =?UTF-8?q?=E2=80=98fchownat=E2=80=99=20when=20available.?=
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* configure.ac: Detect whether ‘fchownat’ is available.
* libguile/filesys.c (scm_chownat): Define a Scheme binding to
  ‘fchownat’ when available.
* libguile/filesys.h (scm_chownat): Make it part of the API.
* doc/ref/posix.texi (File System): Document it.
---
 configure.ac       |  3 ++-
 doc/ref/posix.texi | 11 +++++++++++
 libguile/filesys.c | 35 +++++++++++++++++++++++++++++++++++
 libguile/filesys.h |  1 +
 4 files changed, 49 insertions(+), 1 deletion(-)

diff --git a/configure.ac b/configure.ac
index dea94a364..5f8389b82 100644
--- a/configure.ac
+++ b/configure.ac
@@ -482,7 +482,8 @@ AC_CHECK_HEADERS([assert.h crt_externs.h])
 #
 AC_CHECK_FUNCS([DINFINITY DQNAN cexp chsize clog clog10 ctermid         \
   fesetround ftime ftruncate fchown fchmod fchdir readlinkat		\
-  symlinkat mkdirat renameat fchmodat unlinkat getcwd geteuid getsid		\
+  symlinkat mkdirat renameat fchmodat unlinkat fchownat			\
+  getcwd geteuid getsid	     	      	       				\
   gettimeofday getuid getgid gmtime_r ioctl lstat mkdir mkdtemp mknod   \
   nice readlink rename rmdir setegid seteuid                            \
   setlocale setuid setgid setpgid setsid sigaction siginterrupt stat64  \
diff --git a/doc/ref/posix.texi b/doc/ref/posix.texi
index dcea0352a..077ba8c79 100644
--- a/doc/ref/posix.texi
+++ b/doc/ref/posix.texi
@@ -817,6 +817,17 @@ unsupported at present).  If @var{owner} or @var{group} is specified
 as @code{-1}, then that ID is not changed.
 @end deffn
 
+@findex fchownat
+@deffn {Scheme Procedure} chownat dir name owner group [flags]
+@deffnx {C Function} scm_chownat (dir, name, owner, group, flags)
+Like @code{chown}, but modify the owner and/or group of
+the file named @var{name} in the directory referred to
+by the file port @var{dir} instead.  The optional argument
+@var{flags} is a bitmask.  If @code{AT_SYMLINK_NOFOLLOW} is
+present, then @var{name} will not be dereferenced if it is a
+symbolic link.
+@end deffn
+
 @findex fchmod
 @deffn {Scheme Procedure} chmod object mode
 @deffnx {C Function} scm_chmod (object, mode)
diff --git a/libguile/filesys.c b/libguile/filesys.c
index baa149a33..a319d9794 100644
--- a/libguile/filesys.c
+++ b/libguile/filesys.c
@@ -193,6 +193,41 @@ SCM_DEFINE (scm_chown, "chown", 3, 0, 0,
 #undef FUNC_NAME
 #endif /* HAVE_CHOWN */
 
+#ifdef HAVE_FCHOWNAT
+SCM_DEFINE (scm_chownat, "chownat", 4, 1, 0,
+            (SCM dir, SCM name, SCM owner, SCM group, SCM flags),
+            "Like @code{chown}, but modify the owner and/or group of\n"
+            "the file named @var{name} in the directory referred to\n"
+            "by the file port @var{dir} instead.  The optional argument\n"
+            "@var{flags} is a bitmask.  If @code{AT_SYMLINK_NOFOLLOW} is\n"
+            "present, then @var{name} will not be dereferenced if it is a\n"
+            "symbolic link.")
+#define FUNC_NAME s_scm_chownat
+{
+  int rv;
+  int dir_fdes;
+  int c_flags;
+
+  if (SCM_UNBNDP (flags))
+    c_flags = 0;
+  else
+    c_flags = scm_to_int (flags);
+
+  SCM_VALIDATE_OPFPORT (SCM_ARG1, dir);
+  dir_fdes = SCM_FPORT_FDES (dir);
+
+  STRING_SYSCALL (name, c_name,
+                  rv = fchownat (dir_fdes, c_name,
+                                 scm_to_int (owner), scm_to_int (group),
+                                 c_flags));
+  scm_remember_upto_here_1 (dir);
+  if (rv == -1)
+    SCM_SYSERROR;
+  return SCM_UNSPECIFIED;
+}
+#undef FUNC_NAME
+#endif /* HAVE_FCHOWNAT */
+
 
 
 SCM_DEFINE (scm_open_fdes, "open-fdes", 2, 1, 0, 
diff --git a/libguile/filesys.h b/libguile/filesys.h
index 37d084cd5..7673c8051 100644
--- a/libguile/filesys.h
+++ b/libguile/filesys.h
@@ -39,6 +39,7 @@ SCM_API scm_t_bits scm_tc16_dir;
 
 
 SCM_API SCM scm_chown (SCM object, SCM owner, SCM group);
+SCM_API SCM scm_chownat (SCM dir, SCM object, SCM owner, SCM group, SCM flags);
 SCM_API SCM scm_chmod (SCM object, SCM mode);
 SCM_API SCM scm_chmodat (SCM dir, SCM pathname, SCM mode, SCM flags);
 SCM_API SCM scm_umask (SCM mode);
-- 
2.30.2