From beef9c256748abc60610882dae80739280c31651 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?S=C3=B6nke=20Ludwig?= <sludwig@rejectedsoftware.com>
Date: Fri, 21 Jul 2017 21:34:34 +0200
Subject: [PATCH] Add a doubly linked list implementation.

---
 source/eventcore/internal/dlist.d | 155 ++++++++++++++++++++++++++++++
 1 file changed, 155 insertions(+)
 create mode 100644 source/eventcore/internal/dlist.d

diff --git a/source/eventcore/internal/dlist.d b/source/eventcore/internal/dlist.d
new file mode 100644
index 0000000..5186fc8
--- /dev/null
+++ b/source/eventcore/internal/dlist.d
@@ -0,0 +1,155 @@
+module eventcore.internal.dlist;
+
+struct StackDList(T) {
+	@safe nothrow @nogc:
+
+	private {
+		T* m_first, m_last;
+		size_t m_length;
+	}
+
+	@disable this(this);
+
+	void clear()
+	{
+		T* itm = m_first;
+		while (itm) {
+			auto next = itm.next;
+			itm.prev = null;
+			itm.next = null;
+			itm = next;
+		}
+		m_length = 0;
+	}
+
+	@property bool empty() const { return m_first is null; }
+
+	@property size_t length() const { return m_length; }
+
+	@property T* front() { return m_first; }
+	@property T* back() { return m_last; }
+
+	void insertFront(T* item)
+	{
+		assert(!item.prev && !item.next);
+		item.next = m_first;
+		if (m_first) {
+			m_first.prev = item;
+			m_first = item;
+		} else {
+			m_last = item;
+			m_first = item;
+		}
+		m_length++;
+	}
+
+	void insertBack(T* item)
+	{
+		assert(!item.prev && !item.next);
+		item.prev = m_last;
+		if (m_last) {
+			m_last.next = item;
+			m_last = item;
+		} else {
+			m_first = item;
+			m_last = item;
+		}
+		m_length++;
+	}
+
+	void insertAfter(T* item, T* after)
+	{
+		if (!after) insertBack(item);
+		else {
+			item.prev = after;
+			item.next = after.next;
+			after.next = item;
+			if (item.next) item.next.prev = item;
+			else m_last = item;
+		}
+		m_length++;
+	}
+
+	void remove(T* item)
+	{
+		if (item.prev) item.prev.next = item.next;
+		else m_first = item.next;
+		if (item.next) item.next.prev = item.prev;
+		else m_last = item.prev;
+		item.prev = null;
+		item.next = null;
+		m_length--;
+	}
+
+	void removeFront()
+	{
+		 if (m_first) remove(m_first);
+		m_length--;
+	}
+
+	void removeBack()
+	{
+		 if (m_last) remove(m_last);
+		m_length--;
+	}
+
+	static struct Range {
+		private T* m_first, m_last;
+
+		this(T* first, T* last)
+		{
+			m_first = first;
+			m_last = last;
+		}
+
+		@property bool empty() const { return m_first is null; }
+		@property T* front() { return m_first; }
+		@property T* back() { return m_last; }
+
+		void popFront() {
+			assert(m_first !is null);
+			m_first = m_first.next;
+			if (!m_first) m_last = null;
+		}
+
+		void popBack() {
+			assert(m_last !is null);
+			m_last = m_last.prev;
+			if (!m_last) m_first = null;
+		}
+	}
+
+	Range opSlice() { return Range(m_first, m_last); }
+}
+
+unittest {
+	import std.algorithm.comparison : equal;
+	import std.algorithm.iteration : map;
+
+	struct S { size_t i; S* prev, next; }
+
+	S[10] s;
+	foreach (i, ref rs; s) rs.i = i;
+
+	StackDList!S list;
+
+	assert(list.empty);
+	assert(list[].empty);
+	list.insertBack(&s[0]);
+	assert(list[].map!(s => s.i).equal([0]));
+	list.insertBack(&s[1]);
+	assert(list[].map!(s => s.i).equal([0, 1]));
+	list.insertAfter(&s[2], &s[0]);
+	assert(list[].map!(s => s.i).equal([0, 2, 1]));
+	list.insertFront(&s[3]);
+	assert(list[].map!(s => s.i).equal([3, 0, 2, 1]));
+	list.removeBack();
+	assert(list[].map!(s => s.i).equal([3, 0, 2]));
+	list.remove(&s[0]);
+	assert(list[].map!(s => s.i).equal([3, 2]));
+	list.remove(&s[3]);
+	assert(list[].map!(s => s.i).equal([2]));
+	list.remove(&s[2]);
+	assert(list.empty);
+	assert(list[].empty);
+}