/*
* This file is part of DisOrder
- * Copyright (C) 2008 Richard Kettlewell
+ * Copyright (C) 2008, 2009, 2011 Richard Kettlewell
+ * Copyright (C) 2008 Mark Wooding
*
- * This program is free software; you can redistribute it and/or modify
+ * 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
+ * the Free Software Foundation, either version 3 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.
- *
+ *
+ * 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
+ * along with this program. If not, see <http://www.gnu.org/licenses/>.
*/
-/** @file choose.c
+/** @file server/choose.c
* @brief Random track chooser
*
* Picks a track at random and writes it to standard output. If for
* 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 <time.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"
-#include "trackname.h"
+#include "disorder-server.h"
+
+#define BASE_WEIGHT 90000
static DB_TXN *global_tid;
};
/* display usage message and terminate */
-static void help(void) {
+static void attribute((noreturn)) help(void) {
xprintf("Usage:\n"
" disorder-choose [OPTIONS]\n"
"Options:\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"
+ "Track chooser 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 The winning track */
+static const char *winning = 0;
+
/** @brief Count of tracks */
static long ntracks;
static char **required_tags;
static char **prohibited_tags;
+static int queue_contains(const struct queue_entry *head,
+ const char *track) {
+ const struct queue_entry *q;
+
+ for(q = head->next; q != head; q = q->next)
+ if(!strcmp(q->track, track))
+ return 1;
+ return 0;
+}
+
/** @brief Compute the weight of a track
* @param track Track name (UTF-8)
* @param data Track data
struct kvp *prefs) {
const char *s;
char **track_tags;
- time_t last, now;
+ time_t last, now = xtime(0);
/* Reject tracks not in any collection (race between edit config and
* rescan) */
if(!find_track_root(track)) {
- info("found track not in any collection: %s", track);
+ disorder_info("found track not in any collection: %s", track);
return 0;
}
/* Reject tracks played within the last 8 hours */
if((s = kvp_get(prefs, "played_time"))) {
last = atoll(s);
- now = time(0);
- if(now < last + 8 * 3600) /* TODO configurable */
+ if(now < last + config->replay_min)
return 0;
}
+ /* Reject tracks currently in the queue or in the recent list */
+ if(queue_contains(&qhead, track)
+ || queue_contains(&phead, track))
+ return 0;
+
/* We'll need tags for a number of things */
track_tags = parsetags(kvp_get(prefs, "tags"));
if(*required_tags && !tag_intersection(track_tags, required_tags))
return 0;
- return 90000;
-}
+ /* Use the configured weight if available */
+ if((s = kvp_get(prefs, "weight"))) {
+ long n;
+ errno = 0;
-/** @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);
+ n = strtol(s, 0, 10);
+ if((errno == 0 || errno == ERANGE) && n >= 0)
+ return n;
+ }
- if(weight) {
- struct weighted_track *const t = xmalloc(sizeof *t);
+ /* Bias up tracks that were recently added */
+ if((s = kvp_get(data, "_noticed"))) {
+ const time_t noticed = atoll(s);
- t->next = tracks;
- t->track = track;
- t->weight = weight;
- tracks = t;
- total_weight += weight;
- ++ntracks;
+ if(noticed + config->new_bias_age < now)
+ /* Currently we just step up the weight of tracks that are in range. A
+ * more sophisticated approach would be to linearly decay from new_bias
+ * down to BASE_WEIGHT over the course of the new_bias_age interval
+ * starting when the track is added. */
+ return config->new_bias;
}
- return 0;
+
+ return BASE_WEIGHT;
}
/** @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;
+ unsigned char buf[(sizeof(unsigned long long) * CHAR_BIT + 7)/8], m;
+ unsigned long long t, r, slop;
+ int i, nby, nbi;
- 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;
+ D(("pick_weight: limit = %#016llx", limit));
+
+ /* First, decide how many bits of output we actually need; do bytes first
+ * (they're quicker) and then bits.
+ *
+ * To speed this up, we could use a binary search if we knew where to
+ * start. (Note that shifting by ULLONG_BITS or more (if such a constant
+ * existed) is undefined behaviour, so we mustn't do that.) Figuring out a
+ * start point involves preprocessor and/or autoconf magic.
+ */
+ for (nby = 1, t = (limit - 1) >> 8; t; nby++, t >>= 8)
+ ;
+ nbi = (nby - 1) << 3; t = limit >> nbi;
+ if (t >> 4) { t >>= 4; nbi += 4; }
+ if (t >> 2) { t >>= 2; nbi += 2; }
+ if (t >> 1) { t >>= 1; nbi += 1; }
+ nbi++;
+ D(("nby = %d; nbi = %d", nby, nbi));
+
+ /* Main randomness collection loop. We read a number of bytes from the
+ * randomness source, and glue them together into an integer (dropping
+ * bits off the top byte as necessary). Call the result r; we have
+ * 2^{nbi - 1) <= limit < 2^nbi and r < 2^nbi. If r < limit then we win;
+ * otherwise we try again. Given the above bounds, we expect fewer than 2
+ * iterations.
+ *
+ * Unfortunately there are subtleties. In particular, 2^nbi may in fact be
+ * zero due to overflow. So in fact what we do is compute slop = 2^nbi -
+ * limit > 0; if r < slop then we try again, otherwise r - slop is our
+ * winner.
+ */
+ slop = ((unsigned long long)2 << (nbi - 1)) - limit;
+ m = nbi & 7 ? (1 << (nbi & 7)) - 1 : 0xff;
+ D(("slop = %#016llx", slop));
+ D(("m = 0x%02x", m));
+
+ do {
+ /* Actually get some random data. */
+ random_get(buf, nby);
+
+ /* Clobber the top byte. */
+ buf[0] &= m;
+
+ /* Turn it into an integer. */
+ for (r = 0, i = 0; i < nby; i++)
+ r = (r << 8) | buf[i];
+ D(("r = %#016llx", r));
+ } while (r < slop);
+
+ D((" result=%#016llx", r - slop));
+ return r - slop;
}
-/** @brief Pick a track at random and write it to stdout */
-static void pick_track(void) {
- long long w;
- struct weighted_track *t;
+/** @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) {
+ unsigned long weight = compute_weight(track, data, prefs);
- w = pick_weight(total_weight);
- t = tracks;
- while(t && w >= t->weight) {
- w -= t->weight;
- t = t->next;
+ /* Decide whether this is the winning track.
+ *
+ * Suppose that we have n things, and thing i, for 0 <= i < n, has weight
+ * w_i. Let c_i = w_0 + ... + w_{i-1} be the cumulative weight of the
+ * things previous to thing i, and let W = c_n = w_0 + ... + w_{i-1} be the
+ * total weight. We can clearly choose a random thing with the correct
+ * weightings by picking a random number r in [0, W) and chooeing thing i
+ * where c_i <= r < c_i + w_i. But this involves having an enormous list
+ * and taking two passes over it (which has bad locality and is ugly).
+ *
+ * Here's another way. Initialize v = -1. Examine the things in order;
+ * for thing i, choose a random number r_i in [0, c_i + w_i). If r_i < w_i
+ * then set v <- i.
+ *
+ * Claim. For all 0 <= i < n, the above algorithm chooses thing i with
+ * probability w_i/W.
+ *
+ * Proof. Induction on n. The claim is clear for n = 1. Suppose it's
+ * true for n - 1. Let L be the event that we choose thing n - 1. Clearly
+ * Pr[L] = w_{n-1}/W. Condition on not-L: then the probabilty that we
+ * choose thing i, for 0 <= i < n - 1, is w_i/c_{n-1} (induction
+ * hypothesis); undoing the conditioning gives the desired result.
+ */
+ D(("consider %s", track));
+ if(weight) {
+ total_weight += weight;
+ if (pick_weight(total_weight) < weight)
+ winning = track;
}
- if(!t)
- fatal(0, "ran out of tracks but %lld weighting left", w);
- xprintf("%s", t->track);
+ ntracks++;
+ return 0;
}
int main(int argc, char **argv) {
set_progname(argv);
mem_init();
- if(!setlocale(LC_CTYPE, "")) fatal(errno, "error calling setlocale");
+ if(!setlocale(LC_CTYPE, "")) disorder_fatal(errno, "error calling setlocale");
while((n = getopt_long(argc, argv, "hVc:dDSs", options, 0)) >= 0) {
switch(n) {
case 'h': help();
case 'D': debugging = 0; break;
case 'S': logsyslog = 0; break;
case 's': logsyslog = 1; break;
- default: fatal(0, "invalid option");
+ default: disorder_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");
+ config_per_user = 0;
+ if(config_read(0, NULL)) disorder_fatal(0, "cannot read configuration");
+ /* Find out current queue/recent list */
+ queue_read();
+ recent_read();
/* Generate the candidate track list */
trackdb_init(TRACKDB_NO_RECOVER);
trackdb_open(TRACKDB_NO_UPGRADE|TRACKDB_READ_ONLY);
global_tid = trackdb_begin_transaction();
if((err = trackdb_get_global_tid("required-tags", global_tid, &tags)))
- fatal(0, "error getting required-tags: %s", db_strerror(err));
+ disorder_fatal(0, "error getting required-tags: %s", db_strerror(err));
required_tags = parsetags(tags);
if((err = trackdb_get_global_tid("prohibited-tags", global_tid, &tags)))
- fatal(0, "error getting prohibited-tags: %s", db_strerror(err));
+ disorder_fatal(0, "error getting prohibited-tags: %s", db_strerror(err));
prohibited_tags = parsetags(tags);
- if(trackdb_scan(0, collect_tracks_callback, 0, global_tid))
+ if(trackdb_scan(0, collect_tracks_callback, 0, global_tid)) {
+ global_tid->abort(global_tid);
exit(1);
+ }
trackdb_commit_transaction(global_tid);
trackdb_close();
- trackdb_deinit();
- //info("ntracks=%ld total_weight=%lld", ntracks, total_weight);
+ trackdb_deinit(NULL);
+ D(("ntracks=%ld total_weight=%lld", ntracks, total_weight));
if(!total_weight)
- fatal(0, "no tracks match random choice criteria");
+ disorder_fatal(0, "no tracks match random choice criteria");
+ if(!winning)
+ disorder_fatal(0, "internal: failed to pick a track");
/* Pick a track */
- pick_track();
+ xprintf("%s", winning);
xfclose(stdout);
return 0;
}
~mdw / disorder / blobdiff