mdw@git.distorted.org.uk Git - disorder/blob - server/choose.c

   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 #include <time.h>
  44
  45 #include "configuration.h"
  46 #include "log.h"
  47 #include "defs.h"
  48 #include "mem.h"
  49 #include "kvp.h"
  50 #include "syscalls.h"
  51 #include "printf.h"
  52 #include "trackdb.h"
  53 #include "trackdb-int.h"
  54 #include "version.h"
  55 #include "trackname.h"
  56 #include "queue.h"
  57 #include "server-queue.h"
  58
  59 static DB_TXN *global_tid;
  60
  61 static const struct option options[] = {
  62   { "help", no_argument, 0, 'h' },
  63   { "version", no_argument, 0, 'V' },
  64   { "config", required_argument, 0, 'c' },
  65   { "debug", no_argument, 0, 'd' },
  66   { "no-debug", no_argument, 0, 'D' },
  67   { "syslog", no_argument, 0, 's' },
  68   { "no-syslog", no_argument, 0, 'S' },
  69   { 0, 0, 0, 0 }
  70 };
  71
  72 /* display usage message and terminate */
  73 static void help(void) {
  74   xprintf("Usage:\n"
  75           "  disorder-choose [OPTIONS]\n"
  76           "Options:\n"
  77           "  --help, -h              Display usage message\n"
  78           "  --version, -V           Display version number\n"
  79           "  --config PATH, -c PATH  Set configuration file\n"
  80           "  --debug, -d             Turn on debugging\n"
  81           "  --[no-]syslog           Enable/disable logging to syslog\n"
  82           "\n"
  83           "Track choose for DisOrder.  Not intended to be run\n"
  84           "directly.\n");
  85   xfclose(stdout);
  86   exit(0);
  87 }
  88
  89 /** @brief Weighted track record */
  90 struct weighted_track {
  91   /** @brief Next track in the list */
  92   struct weighted_track *next;
  93   /** @brief Track name */
  94   const char *track;
  95   /** @brief Weight for this track (always positive) */
  96   unsigned long weight;
  97 };
  98
  99 /** @brief List of tracks with nonzero weight */
 100 static struct weighted_track *tracks;
 101
 102 /** @brief Sum of all weights */
 103 static unsigned long long total_weight;
 104
 105 /** @brief Count of tracks */
 106 static long ntracks;
 107
 108 static char **required_tags;
 109 static char **prohibited_tags;
 110
 111 static int queue_contains(const struct queue_entry *head,
 112                           const char *track) {
 113   const struct queue_entry *q;
 114
 115   for(q = head->next; q != head; q = q->next)
 116     if(!strcmp(q->track, track))
 117       return 1;
 118   return 0;
 119 }
 120
 121 /** @brief Compute the weight of a track
 122  * @param track Track name (UTF-8)
 123  * @param data Track data
 124  * @param prefs Track preferences
 125  * @return Track weight (non-negative)
 126  *
 127  * Tracks to be excluded entirely are given a weight of 0.
 128  */
 129 static unsigned long compute_weight(const char *track,
 130                                     struct kvp *data,
 131                                     struct kvp *prefs) {
 132   const char *s;
 133   char **track_tags;
 134   time_t last, now;
 135
 136   /* Reject tracks not in any collection (race between edit config and
 137    * rescan) */
 138   if(!find_track_root(track)) {
 139     info("found track not in any collection: %s", track);
 140     return 0;
 141   }
 142
 143   /* Reject aliases to avoid giving aliased tracks extra weight */
 144   if(kvp_get(data, "_alias_for"))
 145     return 0;
 146
 147   /* Reject tracks with random play disabled */
 148   if((s = kvp_get(prefs, "pick_at_random"))
 149      && !strcmp(s, "0"))
 150     return 0;
 151
 152   /* Reject tracks played within the last 8 hours */
 153   if((s = kvp_get(prefs, "played_time"))) {
 154     last = atoll(s);
 155     now = time(0);
 156     if(now < last + config->replay_min)
 157       return 0;
 158   }
 159
 160   /* Reject tracks currently in the queue or in the recent list */
 161   if(queue_contains(&qhead, track)
 162      || queue_contains(&phead, track))
 163     return 0;
 164
 165   /* We'll need tags for a number of things */
 166   track_tags = parsetags(kvp_get(prefs, "tags"));
 167
 168   /* Reject tracks with prohibited tags */
 169   if(prohibited_tags && tag_intersection(track_tags, prohibited_tags))
 170     return 0;
 171
 172   /* Reject tracks that lack required tags */
 173   if(*required_tags && !tag_intersection(track_tags, required_tags))
 174     return 0;
 175
 176   /* Use the configured weight if available */
 177   if((s = kvp_get(prefs, "weight"))) {
 178     long n;
 179     errno = 0;
 180
 181     n = strtol(s, 0, 10);
 182     if((errno == 0 || errno == ERANGE) && n >= 0)
 183       return n;
 184   }
 185
 186   return 90000;
 187 }
 188
 189 /** @brief Called for each track */
 190 static int collect_tracks_callback(const char *track,
 191                                    struct kvp *data,
 192                                    struct kvp *prefs,
 193                                    void attribute((unused)) *u,
 194                                    DB_TXN attribute((unused)) *tid) {
 195   unsigned long weight = compute_weight(track, data, prefs);
 196
 197   if(weight) {
 198     struct weighted_track *const t = xmalloc(sizeof *t);
 199
 200     /* Clamp weight so that we can fit in billions of tracks when we do
 201      * arithmetic in long long */
 202     if(weight > 0x7fffffff)
 203       weight = 0x7fffffff;
 204     t->next = tracks;
 205     t->track = track;
 206     t->weight = weight;
 207     tracks = t;
 208     total_weight += weight;
 209     ++ntracks;
 210   }
 211   return 0;
 212 }
 213
 214 /** @brief Pick a random integer uniformly from [0, limit) */
 215 static unsigned long long pick_weight(unsigned long long limit) {
 216   unsigned long long n;
 217   static int fd = -1;
 218   int r;
 219
 220   if(fd < 0) {
 221     if((fd = open("/dev/urandom", O_RDONLY)) < 0)
 222       fatal(errno, "opening /dev/urandom");
 223   }
 224   if((r = read(fd, &n, sizeof n)) < 0)
 225     fatal(errno, "reading /dev/urandom");
 226   if((size_t)r < sizeof n)
 227     fatal(0, "short read from /dev/urandom");
 228   return n % limit;
 229 }
 230
 231 /** @brief Pick a track at random and write it to stdout */
 232 static void pick_track(void) {
 233   long long w;
 234   struct weighted_track *t;
 235
 236   w = pick_weight(total_weight);
 237   t = tracks;
 238   while(t && w >= t->weight) {
 239     w -= t->weight;
 240     t = t->next;
 241   }
 242   if(!t)
 243     fatal(0, "ran out of tracks but %lld weighting left", w);
 244   xprintf("%s", t->track);
 245 }
 246
 247 int main(int argc, char **argv) {
 248   int n, logsyslog = !isatty(2), err;
 249   const char *tags;
 250
 251   set_progname(argv);
 252   mem_init();
 253   if(!setlocale(LC_CTYPE, "")) fatal(errno, "error calling setlocale");
 254   while((n = getopt_long(argc, argv, "hVc:dDSs", options, 0)) >= 0) {
 255     switch(n) {
 256     case 'h': help();
 257     case 'V': version("disorder-choose");
 258     case 'c': configfile = optarg; break;
 259     case 'd': debugging = 1; break;
 260     case 'D': debugging = 0; break;
 261     case 'S': logsyslog = 0; break;
 262     case 's': logsyslog = 1; break;
 263     default: fatal(0, "invalid option");
 264     }
 265   }
 266   if(logsyslog) {
 267     openlog(progname, LOG_PID, LOG_DAEMON);
 268     log_default = &log_syslog;
 269   }
 270   if(config_read(0)) fatal(0, "cannot read configuration");
 271   /* Find out current queue/recent list */
 272   queue_read();
 273   recent_read();
 274   /* Generate the candidate track list */
 275   trackdb_init(TRACKDB_NO_RECOVER);
 276   trackdb_open(TRACKDB_NO_UPGRADE|TRACKDB_READ_ONLY);
 277   global_tid = trackdb_begin_transaction();
 278   if((err = trackdb_get_global_tid("required-tags", global_tid, &tags)))
 279     fatal(0, "error getting required-tags: %s", db_strerror(err));
 280   required_tags = parsetags(tags);
 281   if((err = trackdb_get_global_tid("prohibited-tags", global_tid, &tags)))
 282     fatal(0, "error getting prohibited-tags: %s", db_strerror(err));
 283   prohibited_tags = parsetags(tags);
 284   if(trackdb_scan(0, collect_tracks_callback, 0, global_tid))
 285     exit(1);
 286   trackdb_commit_transaction(global_tid);
 287   trackdb_close();
 288   trackdb_deinit();
 289   //info("ntracks=%ld total_weight=%lld", ntracks, total_weight);
 290   if(!total_weight)
 291     fatal(0, "no tracks match random choice criteria");
 292   /* Pick a track */
 293   pick_track();
 294   xfclose(stdout);
 295   return 0;
 296 }
 297
 298 /*
 299 Local Variables:
 300 c-basic-offset:2
 301 comment-column:40
 302 fill-column:79
 303 indent-tabs-mode:nil
 304 End:
 305 */