Bound channel storage, use correctly typed JACK callbacks, and fix reinitialization.

--- a/ddb_jack.c
+++ b/ddb_jack.c
@@ -20,6 +20,8 @@
 #include <signal.h>
 #include <limits.h>
 
+#define DDB_JACK_MAX_CHANNELS 32
+
 //#define trace(...) { fprintf(stderr, __VA_ARGS__); }
 #define trace(fmt,...)
 
@@ -34,7 +36,7 @@
     char connect;
     ddb_waveformat_t *fmt;
     unsigned short state;
-    jack_port_t   *ports[];
+    jack_port_t   *ports[DDB_JACK_MAX_CHANNELS];
 } ddb_client_t;
 
 static DB_output_t plugin;
@@ -124,10 +126,11 @@
     }
 }
 
-static int jack_rate_callback (void *arg)
+static int jack_rate_callback (jack_nframes_t nframes, void *arg)
 {
     trace (__func__);
-    ddb_client_t *dbc = &ddb_client;
+    ddb_client_t *dbc = arg;
+    (void)nframes;
 
     if (!dbc->connect)
         return EPERM;
@@ -136,13 +139,13 @@
     return 0;
 }
 
-static int jack_shutdown_callback (void *arg)
+static void jack_shutdown_callback (void *arg)
 {
     trace (__func__);
     ddb_client_t *dbc = arg;
 
     if (!dbc->connect)
-        return EPERM;
+        return;
     dbc->connect = 0;
 
     // if JACK crashes or is shut down, start a new server instance
@@ -155,8 +158,6 @@
         fprintf (stderr, "%s: JACK server shut down unexpectedly, stopping playback\n", DB_PLUG_NAME);
         ddb_api->streamer_reset (1);
     }
-
-    return 0;
 }
 
 static int ddb_jack_init (void)
@@ -170,7 +171,8 @@
     dbc->autoconnect  = (char)ddb_api->conf_get_int("ddb_jack.autoconnect", 1);
 
     // create new client on JACK server
-    jack_options_t options = JackNullOption|(JackNoStartServer && !dbc->autostart);
+    jack_options_t options = JackNullOption |
+        (dbc->autostart ? 0 : JackNoStartServer);
     dbc->client = jack_client_open (dbc->name, options, &dbc->status);
     if (dbc->status & JackInitFailure) {
         fprintf (stderr, "%s: Could not connect to JACK server\n", DB_PLUG_NAME);
@@ -194,21 +196,21 @@
     }
 
     // set sample rate callback 
-    if (jack_set_sample_rate_callback(dbc->client, (JackSampleRateCallback)&jack_rate_callback, NULL)) {
+    if (jack_set_sample_rate_callback(dbc->client, jack_rate_callback, dbc)) {
         fprintf (stderr, "%s: Could not set sample rate callback\n", DB_PLUG_NAME);
         plugin.free();
         return ESRCH;
     }
 
     // set shutdown callback
-    jack_on_shutdown (dbc->client, (JackShutdownCallback)&jack_shutdown_callback, dbc);
+    jack_on_shutdown (dbc->client, jack_shutdown_callback, dbc);
 
     // register ports
     for (unsigned short i=0; i < dbc->fmt->channels; i++) {
-        char port_name[16];
+        char port_name[32];
 
         // i+1 used to adhere to JACK convention of counting ports from 1, not 0
-        sprintf (port_name, "ddb_playback_%d", i+1);
+        snprintf (port_name, sizeof(port_name), "ddb_playback_%hu", (unsigned short)(i+1));
         jack_options_t options = JackPortIsOutput|JackPortIsTerminal;
         dbc->ports[i] = jack_port_register(dbc->client, (const char*)&port_name,
                 JACK_DEFAULT_AUDIO_TYPE, options, 0);
@@ -241,14 +243,22 @@
         else {
             int ret;
             for (unsigned short i=0; i < dbc->fmt->channels; i++) {
+                if (!playback_ports[i]) {
+                    fprintf (stderr, "%s: Not enough playback ports\n", DB_PLUG_NAME);
+                    jack_free (playback_ports);
+                    plugin.free();
+                    return ENXIO;
+                }
                 ret = jack_connect(dbc->client, jack_port_name (dbc->ports[i]), playback_ports[i]); 
                 if (ret != 0 && ret != EEXIST) {
                     fprintf (stderr, "%s: Could not create connection from %s to %s\n",
                             DB_PLUG_NAME, jack_port_name (dbc->ports[i]), playback_ports[i]);
+                    jack_free (playback_ports);
                     plugin.free();
                     return EACCES;
                 }
             }
+            jack_free (playback_ports);
         }
     }
 
@@ -259,15 +269,24 @@
 {
     trace (__func__);
 
+    if (fmt->channels < 1 || fmt->channels > DDB_JACK_MAX_CHANNELS)
+        return EINVAL;
+
     /* Support only changing channels numbers */
     if (plugin.fmt.channels == fmt->channels)
         return 0;
 
     if (ddb_client.active) {
-        /* FIXME: just return and let the user restart deadbeef for now */
-        return 0;
+        if (ddb_playback_stop())
+            return EPERM;
+        if (jack_client_close(ddb_client.client))
+            return ESRCH;
+        ddb_client.client = NULL;
+        ddb_client.active = 0;
     }
-    if(!ddb_jack_init())
+
+    plugin.fmt.channels = fmt->channels;
+    if (ddb_jack_init())
         return ENOEXEC;
 
     return 0;
@@ -343,6 +362,7 @@
 {
     trace (__func__);
     ddb_client.connect = 0;
+    ddb_client.active = 0;
 
     // stop playback if we didn't start jack
     // this prevents problems with not disconnecting gracefully