From 3cea6c6e9612ca2b04b4742c04721d24f4b316be Mon Sep 17 00:00:00 2001
From: Reuben Thomas <rrt@sc3d.org>
Date: Thu, 9 Jun 2011 19:49:29 +0100
Subject: [PATCH] Add lfs.link.

---
 doc/us/manual.html |  7 +++++++
 src/lfs.c          | 43 +++++++++++++++++++++++++++++++++++++++++++
 tests/test.lua     |  7 +++++--
 3 files changed, 55 insertions(+), 2 deletions(-)

diff --git a/doc/us/manual.html b/doc/us/manual.html
index a7e2efb..996dc1f 100644
--- a/doc/us/manual.html
+++ b/doc/us/manual.html
@@ -206,6 +206,13 @@ LuaFileSystem offers the following functions:
     Returns <code>true</code> if the operation was successful; in
     case of error, it returns <code>nil</code> plus an error string.
     </dd>
+
+    <dt><a name="link"></a><strong><code>lfs.link (old, new[, symlink])</code></strong></dt>
+    <dd>Creates a link. The first argument is the object to link to
+    and the second is the name of the link. If the optional third
+    argument is true, the link will by a symbolic link (by default, a
+    hard link is created).
+    </dd>
     
     <dt><a name="mkdir"></a><strong><code>lfs.mkdir (dirname)</code></strong></dt>
     <dd>Creates a new directory. The argument is the name of the new
diff --git a/src/lfs.c b/src/lfs.c
index dd41df8..f33b5ae 100644
--- a/src/lfs.c
+++ b/src/lfs.c
@@ -106,6 +106,29 @@ typedef struct dir_data {
 #define LSTAT_FUNC lstat
 #endif
 
+/*
+** Utility functions
+*/
+static int pusherror(lua_State *L, const char *info)
+{
+	lua_pushnil(L);
+	if (info==NULL)
+		lua_pushstring(L, strerror(errno));
+	else
+		lua_pushfstring(L, "%s: %s", info, strerror(errno));
+	lua_pushinteger(L, errno);
+	return 3;
+}
+
+static int pushresult(lua_State *L, int i, const char *info)
+{
+	if (i==-1)
+		return pusherror(L, info);
+	lua_pushinteger(L, i);
+	return 1;
+}
+
+
 /*
 ** This function changes the working (current) directory
 */
@@ -354,6 +377,25 @@ static int file_unlock (lua_State *L) {
 }
 
 
+/*
+** Creates a link.
+** @param #1 Object to link to.
+** @param #2 Name of link.
+** @param #3 True if link is symbolic (optional).
+*/
+static int make_link(lua_State *L)
+{
+#ifndef _WIN32
+	const char *oldpath = luaL_checkstring(L, 1);
+	const char *newpath = luaL_checkstring(L, 2);
+	return pushresult(L,
+		(lua_toboolean(L,3) ? symlink : link)(oldpath, newpath), NULL);
+#else
+        pusherror(L, "make_link is not supported on Windows");
+#endif
+}
+
+
 /*
 ** Creates a directory.
 ** @param #1 Directory path.
@@ -763,6 +805,7 @@ static const struct luaL_Reg fslib[] = {
 	{"chdir", change_dir},
 	{"currentdir", get_dir},
 	{"dir", dir_iter_factory},
+        {"link", make_link},
 	{"lock", file_lock},
 	{"mkdir", make_dir},
 	{"rmdir", remove_dir},
diff --git a/tests/test.lua b/tests/test.lua
index 81a0ab6..c4911c9 100644
--- a/tests/test.lua
+++ b/tests/test.lua
@@ -69,11 +69,14 @@ local new_att = assert (lfs.attributes (tmpfile))
 assert (new_att.access == testdate2, "could not set access time")
 assert (new_att.modification == testdate1, "could not set modification time")
 
--- Checking symbolic link information (does not work in Windows)
-if (os.execute ("ln -s "..tmpfile.." _a_link_for_test_")) then
+-- Checking link (does not work on Windows)
+if lfs.link (tmpfile, "_a_link_for_test_", true) then
   assert (lfs.attributes"_a_link_for_test_".mode == "file")
   assert (lfs.symlinkattributes"_a_link_for_test_".mode == "link")
+  assert (lfs.link (tmpfile, "_a_hard_link_for_test_"))
+  assert (lfs.attributes (tmpfile, "nlink") == 2)
   assert (os.remove"_a_link_for_test_")
+  assert (os.remove"_a_hard_link_for_test_")
 end
 
 -- Checking text/binary modes (only has an effect in Windows)