1/*	$NetBSD: luareadhappy.c,v 1.2 2020/01/30 07:58:33 kamil Exp $	*/
2
3/*-
4 * Copyright (c) 2015 The NetBSD Foundation, Inc.
5 * All rights reserved.
6 *
7 * Redistribution and use in source and binary forms, with or without
8 * modification, are permitted provided that the following conditions
9 * are met:
10 * 1. Redistributions of source code must retain the above copyright
11 *    notice, this list of conditions and the following disclaimer.
12 * 2. Redistributions in binary form must reproduce the above copyright
13 *    notice, this list of conditions and the following disclaimer in the
14 *    documentation and/or other materials provided with the distribution.
15 *
16 * THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. AND CONTRIBUTORS
17 * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
18 * TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
19 * PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE FOUNDATION OR CONTRIBUTORS
20 * BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
21 * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
22 * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
23 * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
24 * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
25 * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
26 * POSSIBILITY OF SUCH DAMAGE.
27 */
28
29#include <sys/cdefs.h>
30__KERNEL_RCSID(0, "$NetBSD: luareadhappy.c,v 1.2 2020/01/30 07:58:33 kamil Exp $");
31
32#include <sys/param.h>
33#include <sys/conf.h>
34#include <sys/device.h>
35#include <sys/kernel.h>
36#include <sys/lua.h>
37#include <sys/module.h>
38#include <lua.h>
39
40/*
41 * Create a device /dev/happy from which you can read sequential
42 * happy numbers.
43 *
44 * To use this device you need to do:
45 *     mknod /dev/happy c 351 0
46 *
47 * Commentary:
48 * A happy number is a number defined by the following process: Starting with
49 * any positive integer, replace the number by the sum of the squares of its
50 * digits, and repeat the process until the number equals 1 (where it will
51 * stay), or it loops endlessly in a cycle which does not include 1. Those
52 * numbers for which this process ends in 1 are happy numbers, while those that
53 * do not end in 1 are unhappy numbers (or sad numbers).
54 *
55 * For more information on happy numbers, and the algorithms, see
56 *	http://en.wikipedia.org/wiki/Happy_number
57 *
58 * The happy number generator is here only to have something that the user
59 * can read from our device.  Any other arbitrary data generator could
60 * have been used.  The algorithm is not critical to the implementation
61 * of the module.
62 */
63
64dev_type_open(happy_open);
65dev_type_close(happy_close);
66dev_type_read(happy_read);
67
68static struct cdevsw happy_cdevsw = {
69	.d_open = happy_open,
70	.d_close = happy_close,
71	.d_read = happy_read,
72	.d_write = nowrite,
73	.d_ioctl = noioctl,
74	.d_stop = nostop,
75	.d_tty = notty,
76	.d_poll = nopoll,
77	.d_mmap = nommap,
78	.d_kqfilter = nokqfilter,
79	.d_discard = nodiscard,
80	.d_flag = D_OTHER
81};
82
83
84struct happy_softc {
85	int		 refcnt;
86	unsigned	 last;
87	klua_State	*kL;
88};
89
90static struct happy_softc sc;
91
92/* Function that calls a Lua routine and returns whether a number is happy */
93static int
94check_happy(unsigned n)
95{
96	int rv;
97
98	klua_lock(sc.kL);
99	lua_getglobal(sc.kL->L, "is_happy");
100
101        if (!lua_isfunction(sc.kL->L, -1)) {
102		lua_pop(sc.kL->L, 1);
103		klua_unlock(sc.kL);
104		return -1;
105        }
106
107        lua_pushnumber(sc.kL->L, n);
108        if (lua_pcall(sc.kL->L, 1 /* args */, 1 /* res */, 0) != 0) {
109		lua_pop(sc.kL->L, 2);
110		klua_unlock(sc.kL);
111		return -1;
112        }
113
114        if (!lua_isnumber(sc.kL->L, -1)) {
115		lua_pop(sc.kL->L, 1);
116		klua_unlock(sc.kL);
117		return -1;
118        }
119
120        rv = lua_tointeger(sc.kL->L, -1);
121
122        lua_pop(sc.kL->L, 1);
123        klua_unlock(sc.kL);
124
125	/* Consistency check */
126	if (rv != 0 && rv != 1)
127		rv = -1;
128
129	return rv;
130}
131
132int
133happy_open(dev_t self __unused, int flag __unused, int mode __unused,
134           struct lwp *l __unused)
135{
136	if (sc.refcnt > 0)
137		return EBUSY;
138
139	sc.last = 0;
140	++sc.refcnt;
141
142	return 0;
143}
144
145int
146happy_close(dev_t self __unused, int flag __unused, int mode __unused,
147            struct lwp *l __unused)
148{
149	--sc.refcnt;
150
151	return 0;
152}
153
154int
155happy_read(dev_t self __unused, struct uio *uio, int flags __unused)
156{
157	int rv;
158	char line[80];
159
160	/* Get next happy number */
161	while ((rv = check_happy(++sc.last)) == 0)
162		continue;
163
164	/* Something went wrong */
165	if (rv == -1)
166		return ECANCELED;
167
168	/* Print it into line[] with trailing \n */
169	int len = snprintf(line, sizeof(line), "%u\n", sc.last);
170
171	/* Is there room? */
172	if (uio->uio_resid < len) {
173		--sc.last; /* Step back */
174		return EINVAL;
175	}
176
177	/* Send it to User-Space */
178	int e;
179	if ((e = uiomove(line, len, uio)))
180		return e;
181
182	return 0;
183}
184
185MODULE(MODULE_CLASS_MISC, happy, "lua");
186
187static int
188happy_modcmd(modcmd_t cmd, void *arg __unused)
189{
190	/* The major should be verified and changed if needed to avoid
191	 * conflicts with other devices. */
192	int cmajor = 351, bmajor = -1;
193
194	switch (cmd) {
195	case MODULE_CMD_INIT:
196		if (devsw_attach("happy", NULL, &bmajor, &happy_cdevsw,
197		                 &cmajor))
198			return ENXIO;
199		if ((sc.kL = kluaL_newstate("happy",
200		                            "Example Happy Number calculator",
201		                            IPL_NONE)) == NULL) {
202			devsw_detach(NULL, &happy_cdevsw);
203			return ENXIO;
204		}
205		return 0;
206	case MODULE_CMD_FINI:
207		if (sc.refcnt > 0)
208			return EBUSY;
209
210		klua_close(sc.kL);
211
212		devsw_detach(NULL, &happy_cdevsw);
213		return 0;
214	default:
215		return ENOTTY;
216	}
217}
218