From: Richard Kettlewell <rjk@greenend.org.uk>
Date: Sat, 28 Nov 2009 10:59:49 +0000 (+0000)
Subject: Improve scratch handling to cope better with slow decoding.  The
X-Git-Tag: 5.0~34^2~3
X-Git-Url: http://www.chiark.greenend.org.uk/ucgi/~mdw/git/disorder/commitdiff_plain/4857234e09030f35e1c58b966991c00231eb90eb

Improve scratch handling to cope better with slow decoding.  The
scratch is now chosen and prepared (i.e. starts filling a buffer in
the speaker) whenever something is playing, so it can be played
immediately once something is scratched.
---

diff --git a/server/disorder-server.h b/server/disorder-server.h
index f980b6f..e8f4dab 100644
--- a/server/disorder-server.h
+++ b/server/disorder-server.h
@@ -140,6 +140,7 @@ struct queue_entry *queue_add(const char *track, const char *submitter,
 #define WHERE_END 1			/* Add to end of queue */
 #define WHERE_BEFORE_RANDOM 2		/* End, or before random track */
 #define WHERE_AFTER 3                   /* After the target */
+#define WHERE_NOWHERE 4                 /* Don't add to queue at all */
 /* add an entry to the queue.  Return a pointer to the new entry. */
 
 void queue_remove(struct queue_entry *q, const char *who);
diff --git a/server/play.c b/server/play.c
index f93fd5a..b66bbbc 100644
--- a/server/play.c
+++ b/server/play.c
@@ -39,6 +39,7 @@ static int start_child(struct queue_entry *q,
 static int prepare_child(struct queue_entry *q, 
                          const struct pbgc_params *params,
                          void attribute((unused)) *bgdata);
+static void ensure_next_scratch(ev_source *ev);
 
 /** @brief File descriptor of our end of the socket to the speaker */
 static int speaker_fd = -1;
@@ -195,7 +196,9 @@ static void finished(ev_source *ev) {
  * some time before the speaker reports it as finished) or when a non-raw
  * (i.e. non-speaker) player terminates.  In the latter case it's imaginable
  * that the OS has buffered the last few samples.
- * 
+ *
+ * NB.  The finished track might NOT be in the queue (yet) - it might be a
+ * pre-chosen scratch.
  */
 static int player_finished(ev_source *ev,
 			   pid_t pid,
@@ -609,6 +612,8 @@ void play(ev_source *ev) {
      * potentially be a just-added random track. */
     if(qhead.next != &qhead)
       prepare(ev, qhead.next);
+    /* Make sure there is a prepared scratch */
+    ensure_next_scratch(ev);
     break;
   }
 }
@@ -656,12 +661,27 @@ void disable_random(const char *who) {
 
 /* Scratching --------------------------------------------------------------- */
 
+/** @brief Track to play next time something is scratched */
+static struct queue_entry *next_scratch;
+
+/** @brief Ensure there isa prepared scratch */
+static void ensure_next_scratch(ev_source *ev) {
+  if(next_scratch)                      /* There's one already */
+    return;
+  if(!config->scratch.n)                /* There are no scratches */
+    return;
+  int r = rand() * (double)config->scratch.n / (RAND_MAX + 1.0);
+  next_scratch = queue_add(config->scratch.s[r], NULL,
+                           WHERE_NOWHERE, NULL, origin_scratch);
+  if(ev)
+    prepare(ev, next_scratch);
+}
+
 /** @brief Scratch a track
  * @param who User responsible (or NULL)
  * @param id Track ID (or NULL for current)
  */
 void scratch(const char *who, const char *id) {
-  struct queue_entry *q;
   struct speaker_message sm;
 
   D(("scratch playing=%p state=%d id=%s playing->id=%s",
@@ -692,12 +712,13 @@ void scratch(const char *who, const char *id) {
       speaker_send(speaker_fd, &sm);
       D(("sending SM_CANCEL for %s", playing->id));
     }
-    /* put a scratch track onto the front of the queue (but don't
-     * bother if playing is disabled) */
-    if(playing_is_enabled() && config->scratch.n) {
-      int r = rand() * (double)config->scratch.n / (RAND_MAX + 1.0);
-      q = queue_add(config->scratch.s[r], who, WHERE_START, NULL, 
-                    origin_scratch);
+    /* Try to make sure there is a scratch */
+    ensure_next_scratch(NULL);
+    /* Insert it at the head of the queue */
+    if(next_scratch){
+      next_scratch->submitter = who;
+      queue_insert_entry(&qhead, next_scratch);
+      next_scratch = NULL;
     }
     notify_scratch(playing->track, playing->submitter, who,
 		   xtime(0) - playing->played);
diff --git a/server/queue-ops.c b/server/queue-ops.c
index e513d16..7dcaa84 100644
--- a/server/queue-ops.c
+++ b/server/queue-ops.c
@@ -104,6 +104,8 @@ struct queue_entry *queue_add(const char *track, const char *submitter,
     }
     queue_insert_entry(afterme, q);
     break;
+  case WHERE_NOWHERE:
+    return q;
   }
   /* submitter will be a null pointer for a scratch */
   if(submitter)