libsaria: Choose the next song based on the random setting

If random is enabled, I choose a random song from the list.  If random
is disabled I choose the next song sequentially.

libsaria/library/list.cpp

@@ -1,8 +1,11 @@
 
+#include <stdlib.h>
+#include <time.h>
 #include <list>
 using namespace std;
 
 #include <libsaria/audio.h>
+#include <libsaria/prefs.h>
 #include <libsaria/print.h>
 #include "library.h"
 
@@ -76,6 +79,21 @@ static void insert_list(list<TrackTag> *tag_list)
 		play_list.push_back(&(*it));
 }
 
+static void random_next()
+{
+	unsigned int index = rand() % play_list.size();
+	cur_track = play_list.begin();
+	for (unsigned int i = 0; i < index; i++)
+		cur_track++;
+}
+
+static void sequential_next()
+{
+	cur_track++;
+	if (cur_track == play_list.end())
+		cur_track = play_list.begin();
+}
+
 namespace libsaria
 {
 
@@ -121,9 +139,10 @@ namespace libsaria
 
 	void library::next()
 	{
-		cur_track++;
-		if (cur_track == play_list.end())
-			cur_track = play_list.begin();
+		if (libsaria::prefs::get_bool("random") == true)
+			random_next();
+		else
+			sequential_next();
 		libsaria::audio::load((*cur_track)->get_filepath());
 	}
 

libsaria/libsaria.cpp

@@ -1,4 +1,6 @@
 
+#include <stdlib.h>
+
 #include <libsaria/libsaria.h>
 #include <libsaria/audio.h>
 #include <libsaria/path.h>
@@ -11,6 +13,7 @@ namespace libsaria
 
 	void init(int argc, char **argv)
 	{
+		srand( time(NULL) );
 		println("Initializing libsaria");
 		audio::init(argc, argv);
 		print("saria dir: ");