From e0dd50831fd19e1145897de8af909002c2821376 Mon Sep 17 00:00:00 2001
From: Charles <sircharlesaze@gmail.com>
Date: Sat, 7 Dec 2019 17:27:41 +0100
Subject: Basic Queue package

---
 main.adb  |  2 ++
 queue.adb | 50 ++++++++++++++++++++++++++++++++++++++++++++++++++
 queue.ads | 28 ++++++++++++++++------------
 snake.gpr |  2 +-
 4 files changed, 69 insertions(+), 13 deletions(-)

diff --git a/main.adb b/main.adb
index 65c37f1..59d6fe7 100644
--- a/main.adb
+++ b/main.adb
@@ -4,6 +4,8 @@ use  Ada.Text_IO;
 with Graphics;
 use  Graphics;
 
+with Queue;
+
 procedure Main is
 	state: T_State;
 begin
diff --git a/queue.adb b/queue.adb
index e69de29..2869984 100644
--- a/queue.adb
+++ b/queue.adb
@@ -0,0 +1,50 @@
+package body Queue is
+
+	procedure Enqueue(queue: in out T_Queue; data: T_Data) is
+		element: T_List_Node;
+		new_back: T_List;
+	begin
+		element.data := data;
+		element.next := null;
+		new_back := new T_List_Node'(element);
+
+		if Empty(queue) then
+			queue.front := new_back;
+			queue.back := new_back;
+			return;
+		end if;
+
+		queue.back.next := new_back;
+		queue.back := new_back;
+	end Enqueue;
+
+	procedure Dequeue(queue: in out T_Queue) is
+	begin
+		if Empty(queue) then
+			return;
+		end if;
+		if queue.front.next = null then
+			queue.front := null;
+			queue.back := null;
+			return;
+		end if;
+		queue.front := queue.front.next;
+	end Dequeue;
+
+	function Length(queue: T_Queue) return Natural is
+		tmp: T_List := queue.front;
+		i:   Natural := 0;
+	begin
+		while tmp /= null loop
+			tmp := tmp.next;
+			i := i + 1;
+		end loop;
+		return i;
+	end Length;
+
+	function Empty(queue: T_Queue) return Boolean is
+	begin
+		return queue.front = null and queue.back = null;
+	end Empty;
+
+end Queue;
diff --git a/queue.ads b/queue.ads
index e0da54c..d573490 100644
--- a/queue.ads
+++ b/queue.ads
@@ -1,21 +1,25 @@
 generic
-	type T_Data is limited private;
+	type T_Data is private;
 package Queue is
 
-	type T_Queue is record
-		front: T_List;
-		back:  T_List;
-	end record;
-
-	type T_List_Cell;
-	type T_List is access T_List_Cell;
-	type T_List_Cell is record
+	type T_List_Node;
+	type T_List is access all T_List_Node;
+	type T_List_Node is record
 		data: T_Data;
 		next: T_List;
 	end record;
 
-	procedure Enqueue(queue: T_Queue;
-		              data: T_Data);
-	procedure Dequeue(queue: T_Queue);
+	type T_Queue is record
+		front: T_List := null;
+		back:  T_List := null;
+	end record;
+
+	procedure Enqueue(queue: in out T_Queue; data: T_Data);
+	procedure Dequeue(queue: in out T_Queue);
+	function Length(queue: T_Queue) return Natural;
+
+private
+
+	function Empty(queue: T_Queue) return Boolean;
 
 end Queue;
diff --git a/snake.gpr b/snake.gpr
index d3f1454..06b348d 100644
--- a/snake.gpr
+++ b/snake.gpr
@@ -2,6 +2,6 @@ with "./vendor/sdlada/share/gpr/sdlada.gpr";
 
 project Snake is
 	for Source_Dirs use ("./");
-	for Source_Files use ("main.adb", "graphics.adb", "game.adb");
+	for Source_Files use ("main.adb", "graphics.adb", "game.adb", "queue.adb");
 	for Main use ("main.adb");
 end Snake;
-- 
cgit