chiark / gitweb /
New disorder-choose program for performing random selection.
[disorder] / server / choose.c
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bea6f6d5
RK
1/*
2 * This file is part of DisOrder
3 * Copyright (C) 2008 Richard Kettlewell
4 *
5 * This program is free software; you can redistribute it and/or modify
6 * it under the terms of the GNU General Public License as published by
7 * the Free Software Foundation; either version 2 of the License, or
8 * (at your option) any later version.
9 *
10 * This program is distributed in the hope that it will be useful, but
11 * WITHOUT ANY WARRANTY; without even the implied warranty of
12 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
13 * General Public License for more details.
14 *
15 * You should have received a copy of the GNU General Public License
16 * along with this program; if not, write to the Free Software
17 * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307
18 * USA
19 */
20/** @file choose.c
21 * @brief Random track chooser
22 *
23 * Picks a track at random and writes it to standard output. If for
24 * any reason no track can be picked - even a trivial reason like a
25 * deadlock - it just exits and expects the server to try again.
26 */
27
28#include <config.h>
29#include "types.h"
30
31#include <getopt.h>
32#include <stdio.h>
33#include <stdlib.h>
34#include <db.h>
35#include <locale.h>
36#include <errno.h>
37#include <sys/types.h>
38#include <unistd.h>
39#include <pcre.h>
40#include <string.h>
41#include <fcntl.h>
42#include <syslog.h>
43
44#include "configuration.h"
45#include "log.h"
46#include "defs.h"
47#include "mem.h"
48#include "kvp.h"
49#include "syscalls.h"
50#include "printf.h"
51#include "trackdb.h"
52#include "trackdb-int.h"
53#include "version.h"
54
55static DB_TXN *global_tid;
56
57static const struct option options[] = {
58 { "help", no_argument, 0, 'h' },
59 { "version", no_argument, 0, 'V' },
60 { "config", required_argument, 0, 'c' },
61 { "debug", no_argument, 0, 'd' },
62 { "no-debug", no_argument, 0, 'D' },
63 { "syslog", no_argument, 0, 's' },
64 { "no-syslog", no_argument, 0, 'S' },
65 { 0, 0, 0, 0 }
66};
67
68/* display usage message and terminate */
69static void help(void) {
70 xprintf("Usage:\n"
71 " disorder-choose [OPTIONS]\n"
72 "Options:\n"
73 " --help, -h Display usage message\n"
74 " --version, -V Display version number\n"
75 " --config PATH, -c PATH Set configuration file\n"
76 " --debug, -d Turn on debugging\n"
77 " --[no-]syslog Enable/disable logging to syslog\n"
78 "\n"
79 "Track choose for DisOrder. Not intended to be run\n"
80 "directly.\n");
81 xfclose(stdout);
82 exit(0);
83}
84
85/** @brief Weighted track record */
86struct weighted_track {
87 /** @brief Next track in the list */
88 struct weighted_track *next;
89 /** @brief Track name */
90 const char *track;
91 /** @brief Weight for this track (always positive) */
92 unsigned long weight;
93};
94
95/** @brief List of tracks with nonzero weight */
96static struct weighted_track *tracks;
97
98/** @brief Sum of all weights */
99static unsigned long long total_weight;
100
101/** @brief Count of tracks */
102static long ntracks;
103
104/** @brief Compute the weight of a track
105 * @param track Track name (UTF-8)
106 * @param data Track data
107 * @param prefs Track preferences
108 * @return Track weight (non-negative)
109 *
110 * Tracks to be excluded entirely are given a weight of 0.
111 */
112static unsigned long compute_weight(const char attribute((unused)) *track,
113 struct kvp attribute((unused)) *data,
114 struct kvp *prefs) {
115 const char *s;
116
117 /* Firstly, tracks with random play disabled always have weight 0 and that's
118 * that */
119 if((s = kvp_get(prefs, "pick_at_random"))
120 && !strcmp(s, "0"))
121 return 0;
122 return 90000;
123}
124
125/** @brief Called for each track */
126static int collect_tracks_callback(const char *track,
127 struct kvp *data,
128 struct kvp *prefs,
129 void attribute((unused)) *u,
130 DB_TXN attribute((unused)) *tid) {
131 const unsigned long weight = compute_weight(track, data, prefs);
132
133 if(weight) {
134 struct weighted_track *const t = xmalloc(sizeof *t);
135
136 t->next = tracks;
137 t->track = track;
138 t->weight = weight;
139 tracks = t;
140 total_weight += weight;
141 ++ntracks;
142 }
143 return 0;
144}
145
146/** @brief Pick a random integer uniformly from [0, limit) */
147static unsigned long long pick_weight(unsigned long long limit) {
148 unsigned long long n;
149 static int fd = -1;
150 int r;
151
152 if(fd < 0) {
153 if((fd = open("/dev/urandom", O_RDONLY)) < 0)
154 fatal(errno, "opening /dev/urandom");
155 }
156 if((r = read(fd, &n, sizeof n)) < 0)
157 fatal(errno, "reading /dev/urandom");
158 if((size_t)r < sizeof n)
159 fatal(0, "short read from /dev/urandom");
160 return n % limit;
161}
162
163/** @brief Pick a track at random and write it to stdout */
164static void pick_track(void) {
165 long long w;
166 struct weighted_track *t;
167
168 w = pick_weight(total_weight);
169 t = tracks;
170 while(t && w >= t->weight) {
171 w -= t->weight;
172 t = t->next;
173 }
174 if(!t)
175 fatal(0, "ran out of tracks but %lld weighting left", w);
176 xprintf("%s", t->track);
177}
178
179int main(int argc, char **argv) {
180 int n, logsyslog = !isatty(2);
181
182 set_progname(argv);
183 mem_init();
184 if(!setlocale(LC_CTYPE, "")) fatal(errno, "error calling setlocale");
185 while((n = getopt_long(argc, argv, "hVc:dDSs", options, 0)) >= 0) {
186 switch(n) {
187 case 'h': help();
188 case 'V': version("disorder-choose");
189 case 'c': configfile = optarg; break;
190 case 'd': debugging = 1; break;
191 case 'D': debugging = 0; break;
192 case 'S': logsyslog = 0; break;
193 case 's': logsyslog = 1; break;
194 default: fatal(0, "invalid option");
195 }
196 }
197 if(logsyslog) {
198 openlog(progname, LOG_PID, LOG_DAEMON);
199 log_default = &log_syslog;
200 }
201 if(config_read(0)) fatal(0, "cannot read configuration");
202 /* Generate the candidate track list */
203 trackdb_init(TRACKDB_NO_RECOVER);
204 trackdb_open(TRACKDB_NO_UPGRADE|TRACKDB_READ_ONLY);
205 global_tid = trackdb_begin_transaction();
206 if(trackdb_scan(0, collect_tracks_callback, 0, global_tid))
207 exit(1);
208 trackdb_commit_transaction(global_tid);
209 trackdb_close();
210 trackdb_deinit();
211 //info("ntracks=%ld total_weight=%lld", ntracks, total_weight);
212 if(!total_weight)
213 fatal(0, "no tracks match random choice criteria");
214 /* Pick a track */
215 pick_track();
216 xfclose(stdout);
217 return 0;
218}
219
220/*
221Local Variables:
222c-basic-offset:2
223comment-column:40
224fill-column:79
225indent-tabs-mode:nil
226End:
227*/