stand: liblua: add a pager module

This is nearly a 1:1 mapping of the pager API from libsa.  The only real
difference is that pager.output() will accept any number of arguments and
coerce all of them to strings for output using luaL_tolstring (i.e. the
__tostring metamethod will be used).

The only consumer planned at this time is the upcoming "show-module-options"
implementation.

MFC after:	1 week

stand/common/interp_lua.c

@@ -95,6 +95,7 @@ static const luaL_Reg loadedlibs[] = {
   {"io", luaopen_io},
   {"lfs", luaopen_lfs},
   {"loader", luaopen_loader},
+  {"pager", luaopen_pager},
   {NULL, NULL}
 };
 

stand/liblua/Makefile

@@ -23,7 +23,7 @@ SRCS+=	lauxlib.c lbaselib.c lstrlib.c loadlib.c
 #SRCS+=	lbitlib.c liolib.c lmathlib.c loslib.c ltablib.c
 
 # Our utilities.
-SRCS+=	lerrno.c lstd.c lutils.c
+SRCS+=	lerrno.c lpager.c lstd.c lutils.c
 
 .PATH:	${FLUASRC}/modules
 SRCS+=	lfs.c

stand/liblua/lpager.c

@@ -0,0 +1,89 @@
+/*-
+ * Copyright (c) 2020 Kyle Evans <kevans@FreeBSD.org>
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in the
+ *    documentation and/or other materials provided with the distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
+ * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+ * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
+ * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+ * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
+ * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
+ * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
+ * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
+ * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
+ * SUCH DAMAGE.
+ */
+
+#include <sys/cdefs.h>
+__FBSDID("$FreeBSD$");
+
+#include <lua.h>
+#include "lauxlib.h"
+
+/* Open the pager.  No arguments, no return value. */
+static int
+lpager_open(lua_State *L)
+{
+
+	pager_open();
+	return (0);
+}
+
+/*
+ * Output to the pager.  All arguments are interpreted as strings and passed to
+ * pager_output().  No return value.
+ */
+static int
+lpager_output(lua_State *L)
+{
+	const char *outstr;
+	int i;
+
+	for (i = 1; i <= lua_gettop(L); i++) {
+		outstr = luaL_tolstring(L,  i, NULL);
+		pager_output(outstr);
+		lua_pop(L, -1);
+	}
+
+	return (0);
+}
+
+/* Output to the pager from a file.  Takes a filename, no return value. */
+static int
+lpager_file(lua_State *L)
+{
+
+	return (pager_file(luaL_checkstring(L, 1)));
+}
+
+static int
+lpager_close(lua_State *L)
+{
+
+	pager_close();
+	return (0);
+}
+
+static const struct luaL_Reg pagerlib[] = {
+	{ "open", lpager_open },
+	{ "output", lpager_output },
+	{ "file", lpager_file },
+	{ "close", lpager_close },
+	{ NULL, NULL },
+};
+
+int
+luaopen_pager(lua_State *L)
+{
+	luaL_newlib(L, pagerlib);
+	return 1;
+}

stand/liblua/lutils.h

@@ -30,3 +30,4 @@
 
 int	luaopen_loader(lua_State *);
 int	luaopen_io(lua_State *);
+int	luaopen_pager(lua_State *);