upnpsoap: Add forced alphasort capability

Add the ability to force title modification for clients that do their own
alphanumeric sorting.  Adding a '!' to the beginning of the
force_sort_criteria value will enable this behavior.

It is implemented by prepending all titles with a zero-padded number, and
possibly season and episode (or disc and track) numbers if they aren't
already in the title.

minidlna.c

@@ -740,6 +740,11 @@ init(int argc, char **argv)
 			break;
 		case FORCE_SORT_CRITERIA:
 			force_sort_criteria = ary_options[i].value;
+			if (force_sort_criteria[0] == '!')
+			{
+				SETFLAG(FORCE_ALPHASORT_MASK);
+				force_sort_criteria++;
+			}
 			break;
 		case MAX_CONNECTIONS:
 			runtime_vars.max_connections = atoi(ary_options[i].value);

minidlna.conf

@@ -80,6 +80,9 @@ model_number=1
 #root_container=.
 
 # always force SortCriteria to this value, regardless of the SortCriteria passed by the client
+# note: you can prepend the sort criteria with "!" to alter the titles of the objects so that they
+# will be alphanumerically sorted in the order you specify here, to work around clients that do their
+# own alphanumeric sorting.
 #force_sort_criteria=+upnp:class,+upnp:originalTrackNumber,+dc:title
 
 # maximum number of simultaneous connections

minidlna.conf.5

@@ -161,6 +161,10 @@ The possible values are:
 .IP "\fBforce_sort_criteria\fP"
 Always force SortCriteria to this value, regardless of the SortCriteria passed by the client.
 .nf
+You may prepend the sort criteria with "!" to alter the titles of the objects so that they
+will be alphanumerically sorted in the order you specify here, to work around clients that do
+their own alphanumeric sorting.
+.nf
 
 Example
 force_sort_criteria=+upnp:class,+upnp:originalTrackNumber,+dc:title

upnpglobalvars.h

@@ -196,6 +196,7 @@ extern uint32_t runtime_flags;
 #define SCANNING_MASK         0x0100
 #define RESCAN_MASK           0x0200
 #define SUBTITLES_MASK        0x0400
+#define FORCE_ALPHASORT_MASK  0x0800
 
 #define SETFLAG(mask)	runtime_flags |= mask
 #define GETFLAG(mask)	(runtime_flags & mask)

upnpsoap.c

@@ -77,6 +77,8 @@
 #else
 # define __SORT_LIMIT
 #endif
+#define NON_ZERO(x) (x && atoi(x))
+#define IS_ZERO(x) (!x || !atoi(x))
 
 /* Standard Errors:
  *
@@ -691,6 +693,35 @@ parse_sort_criteria(char *sortCriteria, int *error)
 	return order;
 }
 
+static void
+_alphasort_alt_title(char **title, char **alt_title, int requested, int returned, const char *disc, const char *track)
+{
+	char *old_title = *alt_title ?: NULL;
+	char buf[8];
+	int pad;
+	int ret;
+
+	snprintf(buf, sizeof(buf), "%d", requested);
+	pad = strlen(buf);
+
+	if (NON_ZERO(track) && !strstr(*title, track)) {
+		if (NON_ZERO(disc))
+			ret = asprintf(alt_title, "%0*d %s.%s %s",
+					pad, returned, disc, track, *title);
+		else
+			ret = asprintf(alt_title, "%0*d %s %s",
+					pad, returned, track, *title);
+	}
+	else
+		ret = asprintf(alt_title, "%0*d %s", pad, returned, *title);
+
+	if (ret > 0)
+		*title = *alt_title;
+	else
+		*alt_title = NULL;
+	free(old_title);
+}
+
 inline static void
 add_resized_res(int srcw, int srch, int reqw, int reqh, char *dlna_pn,
                 char *detailID, struct Response *args)
@@ -796,9 +827,6 @@ object_exists(const char *object)
                 " d.THUMBNAIL, d.CREATOR, d.DLNA_PN, d.MIME, d.ALBUM_ART, d.ROTATION, d.DISC "
 #define SELECT_COLUMNS "SELECT o.OBJECT_ID, o.PARENT_ID, o.REF_ID, " COLUMNS
 
-#define NON_ZERO(x) (x && atoi(x))
-#define IS_ZERO(x) (!x || !atoi(x))
-
 static int
 callback(void *args, int argc, char **argv, char **azColName)
 {
@@ -947,6 +975,9 @@ callback(void *args, int argc, char **argv, char **azColName)
 		}
 		else
 			dlna_flags |= DLNA_FLAG_TM_I;
+		/* Force an alphabetical sort, for clients that like to do their own sorting */
+		if( GETFLAG(FORCE_ALPHASORT_MASK) )
+			_alphasort_alt_title(&title, &alt_title, passed_args->requested, passed_args->returned, disc, track);
 
 		if( passed_args->flags & FLAG_SKIP_DLNA_PN )
 			dlna_pn = NULL;
@@ -1022,7 +1053,7 @@ callback(void *args, int argc, char **argv, char **azColName)
 			if( *mime == 'a' && (passed_args->filter & FILTER_UPNP_ORIGINALTRACKNUMBER) ) {
 				ret = strcatf(str, "<upnp:originalTrackNumber>%s</upnp:originalTrackNumber>", track);
 			} else if( *mime == 'v' ) {
-				if( passed_args->filter & FILTER_UPNP_EPISODESEASON )
+				if( NON_ZERO(disc) && (passed_args->filter & FILTER_UPNP_EPISODESEASON) )
 					ret = strcatf(str, "<upnp:episodeSeason>%s</upnp:episodeSeason>", disc);
 				if( passed_args->filter & FILTER_UPNP_EPISODENUMBER )
 					ret = strcatf(str, "<upnp:episodeNumber>%s</upnp:episodeNumber>", track);