From 536fa0978010b5ee518ade1981f58deed367e678 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?S=C3=B6nke=20Ludwig?= <sludwig@rejectedsoftware.com>
Date: Thu, 20 Jul 2017 13:34:39 +0200
Subject: [PATCH] Add helper module with intrusive singly and doubly linked
 lists.

---
 source/vibe/internal/list.d | 192 ++++++++++++++++++++++++++++++++++++
 1 file changed, 192 insertions(+)
 create mode 100644 source/vibe/internal/list.d

diff --git a/source/vibe/internal/list.d b/source/vibe/internal/list.d
new file mode 100644
index 0000000..cfc4135
--- /dev/null
+++ b/source/vibe/internal/list.d
@@ -0,0 +1,192 @@
+module vibe.internal.list;
+
+import core.atomic;
+
+struct CircularDList(T)
+{
+	private {
+		T m_pivot;
+	}
+
+	this(T pivot)
+	{
+		assert(pivot.prev is null && pivot.next is null);
+		pivot.next = pivot.prev = pivot;
+		m_pivot = pivot;
+		assert(this.empty);
+	}
+
+	bool empty() const { return m_pivot.next is m_pivot; }
+
+
+	@property T front() { return m_pivot.next is m_pivot ? null : m_pivot.next; }
+	@property T back() { return m_pivot.prev is m_pivot ? null : m_pivot.prev; }
+
+	void remove(T elem)
+	{
+		assert(elem !is m_pivot);
+		elem.prev.next = elem.next;
+		elem.next.prev = elem.prev;
+		elem.prev = elem.next = null;
+	}
+
+	void insertBefore(T elem, T pivot)
+	{
+		assert(elem.prev is null && elem.next is null);
+		elem.prev = pivot.prev;
+		elem.next = pivot;
+		pivot.prev.next = elem;
+		pivot.prev = elem;
+	}
+
+	void insertFront(T elem) { insertBefore(elem, m_pivot.next); }
+
+	void insertBack(T elem) { insertBefore(elem, m_pivot); }
+
+	// NOTE: allowed to remove the current element
+	int opApply(int delegate(T) @safe nothrow del)
+	@safe nothrow {
+		T prev = m_pivot;
+		debug size_t counter = 0;
+		while (prev.next !is m_pivot) {
+			auto el = prev.next;
+			if (auto ret = del(el))
+				return ret;
+			if (prev.next is el)
+				prev = prev.next;
+			debug assert (++counter < 1_000_000, "Cycle in list?");
+		}
+		return 0;
+	}
+}
+
+unittest {
+	static final class C {
+		C prev, next;
+		int i;
+		this(int i) { this.i = i; }
+	}
+
+	alias L = CircularDList!C;
+	auto l = L(new C(0));
+	assert(l.empty);
+
+	auto c = new C(1);
+	l.insertBack(c);
+	assert(!l.empty);
+	assert(l.front is c);
+	assert(l.back is c);
+	foreach (c; l) assert(c.i == 1);
+
+	auto c2 = new C(2);
+	l.insertFront(c2);
+	assert(!l.empty);
+	assert(l.front is c2);
+	assert(l.back is c);
+	foreach (c; l) assert(c.i == 1 || c.i == 2);
+
+	l.remove(c);
+	assert(!l.empty);
+	assert(l.front is c2);
+	assert(l.back is c2);
+	foreach (c; l) assert(c.i == 2);
+
+	l.remove(c2);
+	assert(l.empty);
+}
+
+
+struct StackSList(T)
+{
+@safe nothrow:
+
+	import core.atomic : cas;
+
+	private T m_first;
+
+	@property T first() { return m_first; }
+	@property T front() { return m_first; }
+
+	bool empty() const { return m_first is null; }
+
+	void add(T elem)
+	{
+		debug iterate((el) { assert(el !is elem, "Double-insertion of list element."); return true; });
+		elem.next = m_first;
+		m_first = elem;
+	}
+
+	bool remove(T elem)
+	{
+		debug uint counter = 0;
+		T w = m_first, wp;
+		while (w !is elem) {
+			if (!w) return false;
+			wp = w;
+			w = w.next;
+			debug assert(++counter < 1_000_000, "Cycle in linked list?");
+		}
+		if (wp) wp.next = w.next;
+		else m_first = w.next;
+		return true;
+	}
+
+	void filter(scope bool delegate(T el) @safe nothrow del)
+	{
+		debug uint counter = 0;
+		T w = m_first, pw;
+		while (w !is null) {
+			auto wnext = w.next;
+			if (!del(w)) {
+				if (pw) pw.next = wnext;
+				else m_first = wnext;
+			} else pw = w;
+			w = wnext;
+			debug assert(++counter < 1_000_000, "Cycle in linked list?");
+		}
+	}
+
+	void iterate(scope bool delegate(T el) @safe nothrow del)
+	{
+		debug uint counter = 0;
+		T w = m_first;
+		while (w !is null) {
+			auto wnext = w.next;
+			if (!del(w)) break;
+			w = wnext;
+			debug assert(++counter < 1_000_000, "Cycle in linked list?");
+		}
+	}
+}
+
+unittest {
+	static final class C {
+		C next;
+		int i;
+		this(int i) { this.i = i; }
+	}
+
+	alias L = StackSList!C;
+	L l;
+	assert(l.empty);
+
+	auto c = new C(1);
+	l.add(c);
+	assert(!l.empty);
+	assert(l.front is c);
+	l.iterate((el) { assert(el.i == 1); return true; });
+
+	auto c2 = new C(2);
+	l.add(c2);
+	assert(!l.empty);
+	assert(l.front is c2);
+	l.iterate((el) { assert(el.i == 1 || el.i == 2); return true; });
+
+	l.remove(c);
+	assert(!l.empty);
+	assert(l.front is c2);
+	l.iterate((el) { assert(el.i == 2); return true; });
+
+	l.filter((el) => el.i == 0);
+	assert(l.empty);
+}