int trackdb_scan(const char *root,
int (*callback)(const char *track,
struct kvp *data,
+ struct kvp *prefs,
void *u,
DB_TXN *tid),
void *u,
DB_TXN *tid) {
DBC *cursor;
- DBT k, d;
+ DBT k, d, pd;
const size_t root_len = root ? strlen(root) : 0;
int err, cberr;
- struct kvp *data;
+ struct kvp *data, *prefs;
const char *track;
cursor = trackdb_opencursor(trackdb_tracksdb, tid);
data = kvp_urldecode(d.data, d.size);
if(kvp_get(data, "_path")) {
track = xstrndup(k.data, k.size);
+ /* TODO: trackdb_prefsdb is currently a DB_HASH. This means we have to
+ * do a lookup for every single track. In fact this is quite quick:
+ * with around 10,000 tracks a complete scan is around 0.3s on my
+ * 2.2GHz Athlon. However, if it were a DB_BTREE, we could do the same
+ * linear walk as we already do over trackdb_tracksdb, and probably get
+ * even higher performance. That would require upgrade logic to
+ * translate old databases though.
+ */
+ switch(err = trackdb_prefsdb->get(trackdb_prefsdb, tid, &k,
+ prepare_data(&pd), 0)) {
+ case 0:
+ prefs = kvp_urldecode(pd.data, pd.size);
+ break;
+ case DB_NOTFOUND:
+ prefs = 0;
+ break;
+ case DB_LOCK_DEADLOCK:
+ error(0, "getting prefs: %s", db_strerror(err));
+ trackdb_closecursor(cursor);
+ return err;
+ default:
+ fatal(0, "getting prefs: %s", db_strerror(err));
+ }
/* Advance to the next track before the callback so that the callback
* may safely delete the track */
err = cursor->c_get(cursor, &k, &d, DB_NEXT);
- if((cberr = callback(track, data, u, tid))) {
+ if((cberr = callback(track, data, prefs, u, tid))) {
err = cberr;
break;
}
--- /dev/null
+/*
+ * This file is part of DisOrder
+ * Copyright (C) 2008 Richard Kettlewell
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful, but
+ * WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
+ * General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software
+ * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307
+ * USA
+ */
+/** @file choose.c
+ * @brief Random track chooser
+ *
+ * Picks a track at random and writes it to standard output. If for
+ * any reason no track can be picked - even a trivial reason like a
+ * deadlock - it just exits and expects the server to try again.
+ */
+
+#include <config.h>
+#include "types.h"
+
+#include <getopt.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <db.h>
+#include <locale.h>
+#include <errno.h>
+#include <sys/types.h>
+#include <unistd.h>
+#include <pcre.h>
+#include <string.h>
+#include <fcntl.h>
+#include <syslog.h>
+
+#include "configuration.h"
+#include "log.h"
+#include "defs.h"
+#include "mem.h"
+#include "kvp.h"
+#include "syscalls.h"
+#include "printf.h"
+#include "trackdb.h"
+#include "trackdb-int.h"
+#include "version.h"
+
+static DB_TXN *global_tid;
+
+static const struct option options[] = {
+ { "help", no_argument, 0, 'h' },
+ { "version", no_argument, 0, 'V' },
+ { "config", required_argument, 0, 'c' },
+ { "debug", no_argument, 0, 'd' },
+ { "no-debug", no_argument, 0, 'D' },
+ { "syslog", no_argument, 0, 's' },
+ { "no-syslog", no_argument, 0, 'S' },
+ { 0, 0, 0, 0 }
+};
+
+/* display usage message and terminate */
+static void help(void) {
+ xprintf("Usage:\n"
+ " disorder-choose [OPTIONS]\n"
+ "Options:\n"
+ " --help, -h Display usage message\n"
+ " --version, -V Display version number\n"
+ " --config PATH, -c PATH Set configuration file\n"
+ " --debug, -d Turn on debugging\n"
+ " --[no-]syslog Enable/disable logging to syslog\n"
+ "\n"
+ "Track choose for DisOrder. Not intended to be run\n"
+ "directly.\n");
+ xfclose(stdout);
+ exit(0);
+}
+
+/** @brief Weighted track record */
+struct weighted_track {
+ /** @brief Next track in the list */
+ struct weighted_track *next;
+ /** @brief Track name */
+ const char *track;
+ /** @brief Weight for this track (always positive) */
+ unsigned long weight;
+};
+
+/** @brief List of tracks with nonzero weight */
+static struct weighted_track *tracks;
+
+/** @brief Sum of all weights */
+static unsigned long long total_weight;
+
+/** @brief Count of tracks */
+static long ntracks;
+
+/** @brief Compute the weight of a track
+ * @param track Track name (UTF-8)
+ * @param data Track data
+ * @param prefs Track preferences
+ * @return Track weight (non-negative)
+ *
+ * Tracks to be excluded entirely are given a weight of 0.
+ */
+static unsigned long compute_weight(const char attribute((unused)) *track,
+ struct kvp attribute((unused)) *data,
+ struct kvp *prefs) {
+ const char *s;
+
+ /* Firstly, tracks with random play disabled always have weight 0 and that's
+ * that */
+ if((s = kvp_get(prefs, "pick_at_random"))
+ && !strcmp(s, "0"))
+ return 0;
+ return 90000;
+}
+
+/** @brief Called for each track */
+static int collect_tracks_callback(const char *track,
+ struct kvp *data,
+ struct kvp *prefs,
+ void attribute((unused)) *u,
+ DB_TXN attribute((unused)) *tid) {
+ const unsigned long weight = compute_weight(track, data, prefs);
+
+ if(weight) {
+ struct weighted_track *const t = xmalloc(sizeof *t);
+
+ t->next = tracks;
+ t->track = track;
+ t->weight = weight;
+ tracks = t;
+ total_weight += weight;
+ ++ntracks;
+ }
+ return 0;
+}
+
+/** @brief Pick a random integer uniformly from [0, limit) */
+static unsigned long long pick_weight(unsigned long long limit) {
+ unsigned long long n;
+ static int fd = -1;
+ int r;
+
+ if(fd < 0) {
+ if((fd = open("/dev/urandom", O_RDONLY)) < 0)
+ fatal(errno, "opening /dev/urandom");
+ }
+ if((r = read(fd, &n, sizeof n)) < 0)
+ fatal(errno, "reading /dev/urandom");
+ if((size_t)r < sizeof n)
+ fatal(0, "short read from /dev/urandom");
+ return n % limit;
+}
+
+/** @brief Pick a track at random and write it to stdout */
+static void pick_track(void) {
+ long long w;
+ struct weighted_track *t;
+
+ w = pick_weight(total_weight);
+ t = tracks;
+ while(t && w >= t->weight) {
+ w -= t->weight;
+ t = t->next;
+ }
+ if(!t)
+ fatal(0, "ran out of tracks but %lld weighting left", w);
+ xprintf("%s", t->track);
+}
+
+int main(int argc, char **argv) {
+ int n, logsyslog = !isatty(2);
+
+ set_progname(argv);
+ mem_init();
+ if(!setlocale(LC_CTYPE, "")) fatal(errno, "error calling setlocale");
+ while((n = getopt_long(argc, argv, "hVc:dDSs", options, 0)) >= 0) {
+ switch(n) {
+ case 'h': help();
+ case 'V': version("disorder-choose");
+ case 'c': configfile = optarg; break;
+ case 'd': debugging = 1; break;
+ case 'D': debugging = 0; break;
+ case 'S': logsyslog = 0; break;
+ case 's': logsyslog = 1; break;
+ default: fatal(0, "invalid option");
+ }
+ }
+ if(logsyslog) {
+ openlog(progname, LOG_PID, LOG_DAEMON);
+ log_default = &log_syslog;
+ }
+ if(config_read(0)) fatal(0, "cannot read configuration");
+ /* Generate the candidate track list */
+ trackdb_init(TRACKDB_NO_RECOVER);
+ trackdb_open(TRACKDB_NO_UPGRADE|TRACKDB_READ_ONLY);
+ global_tid = trackdb_begin_transaction();
+ if(trackdb_scan(0, collect_tracks_callback, 0, global_tid))
+ exit(1);
+ trackdb_commit_transaction(global_tid);
+ trackdb_close();
+ trackdb_deinit();
+ //info("ntracks=%ld total_weight=%lld", ntracks, total_weight);
+ if(!total_weight)
+ fatal(0, "no tracks match random choice criteria");
+ /* Pick a track */
+ pick_track();
+ xfclose(stdout);
+ return 0;
+}
+
+/*
+Local Variables:
+c-basic-offset:2
+comment-column:40
+fill-column:79
+indent-tabs-mode:nil
+End:
+*/
~mdw / disorder / commitdiff