[PATCH] Suggestion: new module link

[Martin Lambers]

I'd like to suggest a new module 'link' that provides the link(2)
function for MinGW. The module is modelled after the existing fsync
module.

Martin

---
 lib/link.c      |   83 +++++++++++++++++++++++++++++++++++++++++++++++++++++++
 lib/unistd.in.h |   17 +++++++++++
 m4/link.m4      |   19 ++++++++++++
 m4/unistd_h.m4  |    2 +
 modules/link    |   24 ++++++++++++++++
 modules/unistd  |    4 ++
 6 files changed, 149 insertions(+), 0 deletions(-)
 create mode 100644 lib/link.c
 create mode 100644 m4/link.m4
 create mode 100644 modules/link

diff --git a/lib/link.c b/lib/link.c
new file mode 100644
index 0000000..f8ad49c
--- /dev/null
+++ b/lib/link.c
@@ -0,0 +1,83 @@
+/* Emulate link on platforms that lack it, primarily Windows and
+   cross-compilers like MinGW.
+
+   Copyright (C) 2009 Free Software Foundation, Inc.
+
+   This library is free software; you can redistribute it and/or
+   modify it under the terms of the GNU Lesser General Public
+   License as published by the Free Software Foundation; either
+   version 2.1 of the License, or (at your option) any later version.
+
+   This library is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+   Lesser General Public License for more details.
+
+   You should have received a copy of the GNU General Public License
+   along with this program.  If not, see <http://www.gnu.org/licenses/>.  */
+
+#include <config.h>
+
+#if (defined _WIN32 || defined __WIN32__) && ! defined __CYGWIN__
+
+#define WIN32_LEAN_AND_MEAN
+#define _WIN32_WINNT 0x0500
+#include <unistd.h>
+#include <windows.h>
+
+#include <errno.h>
+
+int
+link (const char *path1, const char *path2)
+{
+  if (CreateHardLink (path2, path1, NULL) == 0)
+    {
+      /* It is not documented which errors CreateHardLink() can produce.
+       * The following conversions are based on tests on a Windows XP SP2
+       * system. */
+      DWORD err = GetLastError ();
+      switch (err)
+       {
+       case ERROR_ACCESS_DENIED:
+         errno = EACCES;
+         break;
+
+       case ERROR_INVALID_FUNCTION:    /* fs does not support hard links */
+         errno = EPERM;
+         break;
+
+       case ERROR_NOT_SAME_DEVICE:
+         errno = EXDEV;
+         break;
+
+       case ERROR_PATH_NOT_FOUND:
+       case ERROR_FILE_NOT_FOUND:
+         errno = ENOENT;
+         break;
+
+       case ERROR_INVALID_PARAMETER:
+         errno = ENAMETOOLONG;
+         break;
+
+       case ERROR_TOO_MANY_LINKS:
+         errno = EMLINK;
+         break;
+
+       case ERROR_ALREADY_EXISTS:
+         errno = EEXIST;
+         break;
+
+       default:
+         errno = EIO;
+       }
+      return -1;
+    }
+
+  return 0;
+}
+
+#else /* !Windows */
+
+#error "This platform lacks a link function, and Gnulib doesn't provide a 
replacement. This is a bug in Gnulib."
+
+#endif /* !Windows */
diff --git a/lib/unistd.in.h b/lib/unistd.in.h
index 05778f9..8867d7b 100644
--- a/lib/unistd.in.h
+++ b/lib/unistd.in.h
@@ -475,6 +475,23 @@ extern int lchown (char const *file, uid_t owner, gid_t 
group);
 #endif
 
 
+#if @GNULIB_LINK@
+/* Create a new link for an existing file.
+   Return 0 if successful, otherwise -1 and errno set.
+   See POSIX:2001 specification
+   <http://www.opengroup.org/susv3xsh/link.html>.  */
+# if address@hidden@
+extern int link (const char *path1, const char *path2);
+# endif
+#elif defined GNULIB_POSIXCHECK
+# undef link
+# define link(path1, path2) \
+    (GL_LINK_WARNING ("link is unportable - " \
+                      "use gnulib module link for portability"), \
+     link (path1, path2))
+#endif
+
+
 #if @GNULIB_LSEEK@
 # if @REPLACE_LSEEK@
 /* Set the offset of FD relative to SEEK_SET, SEEK_CUR, or SEEK_END.
diff --git a/m4/link.m4 b/m4/link.m4
new file mode 100644
index 0000000..349d537
--- /dev/null
+++ b/m4/link.m4
@@ -0,0 +1,19 @@
+# link.m4 serial 1
+dnl Copyright (C) 2009 Free Software Foundation, Inc.
+dnl This file is free software; the Free Software Foundation
+dnl gives unlimited permission to copy and/or distribute it,
+dnl with or without modifications, as long as this notice is preserved.
+
+AC_DEFUN([gl_FUNC_LINK],
+[
+  AC_REQUIRE([gl_UNISTD_H_DEFAULTS])
+  AC_CHECK_FUNCS_ONCE([link])
+  if test $ac_cv_func_link = no; then
+    HAVE_LINK=0
+    AC_LIBOBJ([link])
+    gl_PREREQ_LINK
+  fi
+])
+
+# Prerequisites of lib/link.c.
+AC_DEFUN([gl_PREREQ_LINK], [:])
diff --git a/m4/unistd_h.m4 b/m4/unistd_h.m4
index 5685273..0878381 100644
--- a/m4/unistd_h.m4
+++ b/m4/unistd_h.m4
@@ -48,6 +48,7 @@ AC_DEFUN([gl_UNISTD_H_DEFAULTS],
   GNULIB_GETPAGESIZE=0;      AC_SUBST([GNULIB_GETPAGESIZE])
   GNULIB_GETUSERSHELL=0;     AC_SUBST([GNULIB_GETUSERSHELL])
   GNULIB_LCHOWN=0;           AC_SUBST([GNULIB_LCHOWN])
+  GNULIB_LINK=0;             AC_SUBST([GNULIB_LINK])
   GNULIB_LSEEK=0;            AC_SUBST([GNULIB_LSEEK])
   GNULIB_READLINK=0;         AC_SUBST([GNULIB_READLINK])
   GNULIB_SLEEP=0;            AC_SUBST([GNULIB_SLEEP])
@@ -63,6 +64,7 @@ AC_DEFUN([gl_UNISTD_H_DEFAULTS],
   HAVE_GETHOSTNAME=1;     AC_SUBST([HAVE_GETHOSTNAME])
   HAVE_GETPAGESIZE=1;     AC_SUBST([HAVE_GETPAGESIZE])
   HAVE_GETUSERSHELL=1;    AC_SUBST([HAVE_GETUSERSHELL])
+  HAVE_LINK=1;            AC_SUBST([HAVE_LINK])
   HAVE_READLINK=1;        AC_SUBST([HAVE_READLINK])
   HAVE_SLEEP=1;           AC_SUBST([HAVE_SLEEP])
   HAVE_DECL_ENVIRON=1;    AC_SUBST([HAVE_DECL_ENVIRON])
diff --git a/modules/link b/modules/link
new file mode 100644
index 0000000..22f7452
--- /dev/null
+++ b/modules/link
@@ -0,0 +1,24 @@
+Description:
+link(2) function: create a new link for an existing file
+
+Files:
+lib/link.c
+m4/link.m4
+
+Depends-on:
+unistd
+
+configure.ac:
+gl_FUNC_LINK
+gl_UNISTD_MODULE_INDICATOR([link])
+
+Makefile.am:
+
+Include:
+<unistd.h>
+
+License:
+LGPLv2+
+
+Maintainer:
+?
diff --git a/modules/unistd b/modules/unistd
index 225abf9..680ec47 100644
--- a/modules/unistd
+++ b/modules/unistd
@@ -40,10 +40,12 @@ unistd.h: unistd.in.h
              -e 's|@''GNULIB_GETPAGESIZE''@|$(GNULIB_GETPAGESIZE)|g' \
              -e 's|@''GNULIB_GETUSERSHELL''@|$(GNULIB_GETUSERSHELL)|g' \
              -e 's|@''GNULIB_LCHOWN''@|$(GNULIB_LCHOWN)|g' \
+             -e 's|@''GNULIB_LINK''@|$(GNULIB_LINK)|g' \
              -e 's|@''GNULIB_LSEEK''@|$(GNULIB_LSEEK)|g' \
              -e 's|@''GNULIB_READLINK''@|$(GNULIB_READLINK)|g' \
              -e 's|@''GNULIB_SLEEP''@|$(GNULIB_SLEEP)|g' \
              -e 's|@''GNULIB_UNISTD_H_SIGPIPE''@|$(GNULIB_UNISTD_H_SIGPIPE)|g' 
\
+             -e 's|@''GNULIB_UNLINK''@|$(GNULIB_UNLINK)|g' \
              -e 's|@''GNULIB_WRITE''@|$(GNULIB_WRITE)|g' \
              -e 's|@''HAVE_DUP2''@|$(HAVE_DUP2)|g' \
              -e 's|@''HAVE_EUIDACCESS''@|$(HAVE_EUIDACCESS)|g' \
@@ -54,8 +56,10 @@ unistd.h: unistd.in.h
              -e 's|@''HAVE_GETHOSTNAME''@|$(HAVE_GETHOSTNAME)|g' \
              -e 's|@''HAVE_GETPAGESIZE''@|$(HAVE_GETPAGESIZE)|g' \
              -e 's|@''HAVE_GETUSERSHELL''@|$(HAVE_GETUSERSHELL)|g' \
+             -e 's|@''HAVE_LINK''@|$(HAVE_LINK)|g' \
              -e 's|@''HAVE_READLINK''@|$(HAVE_READLINK)|g' \
              -e 's|@''HAVE_SLEEP''@|$(HAVE_SLEEP)|g' \
+             -e 's|@''HAVE_UNLINK''@|$(HAVE_UNLINK)|g' \
              -e 's|@''HAVE_DECL_ENVIRON''@|$(HAVE_DECL_ENVIRON)|g' \
              -e 's|@''HAVE_DECL_GETLOGIN_R''@|$(HAVE_DECL_GETLOGIN_R)|g' \
              -e 's|@''HAVE_OS_H''@|$(HAVE_OS_H)|g' \
-- 
1.5.6.5