Add RefCounted

4 files changed, 462 insertions, 4 deletions

diff --git a/source/tanya/memory/allocator.d b/source/tanya/memory/allocator.d
index df2c77c..16309e1 100644
--- a/source/tanya/memory/allocator.d
+++ b/source/tanya/memory/allocator.d
@@ -11,7 +11,6 @@
 module tanya.memory.allocator;
 
 import std.experimental.allocator;
-import std.traits;
 import std.typecons;
 
 /**
@@ -178,5 +177,39 @@ unittest
     assert(p is null);
 }
 
-enum bool isFinalizable(T) = is(T == class) || is(T == interface)
-                           || hasElaborateDestructor!T || isDynamicArray!T;
+/**
+ * Mixin to get around the impossibility to define a default constructor for
+ * structs. It can be used for the structs that don't disable the default
+ * constructor and don't wan't to force passing the allocator each time to
+ * the constructor.
+ *
+ * It defines the private property `allocator`, a constructor that accepts only
+ * an allocator instance and the method `checkAllocator` that checks if an
+ * allocator is set and sets it to ` $(D_PSYMBOL theAllocator) if not.
+ *
+ * `checkAllocator` should be used at beginning of functions that
+ * allocate/free memory.
+ */
+mixin template StructAllocator()
+{
+	private IAllocator allocator;
+
+	this(IAllocator allocator)
+	in
+	{
+		assert(allocator !is null);
+	}
+	body
+	{
+		this.allocator = allocator;
+	}
+
+	pragma(inline, true)
+	private void checkAllocator() nothrow @safe @nogc
+	{
+		if (allocator is null)
+		{
+			allocator = theAllocator;
+		}
+	}
+}
diff --git a/source/tanya/memory/package.d b/source/tanya/memory/package.d
index 2893849..a524504 100644
--- a/source/tanya/memory/package.d
+++ b/source/tanya/memory/package.d
@@ -10,5 +10,6 @@
  */
 module tanya.memory;
 
-public import tanya.memory.allocator;
 public import std.experimental.allocator;
+public import tanya.memory.allocator;
+public import tanya.memory.types;
diff --git a/source/tanya/memory/types.d b/source/tanya/memory/types.d
new file mode 100644
index 0000000..655740d
--- /dev/null
+++ b/source/tanya/memory/types.d
@@ -0,0 +1,401 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+/**
+ * Copyright: Eugene Wissner 2016.
+ * License: $(LINK2 https://www.mozilla.org/en-US/MPL/2.0/,
+ *                  Mozilla Public License, v. 2.0).
+ * Authors: $(LINK2 mailto:belka@caraus.de, Eugene Wissner)
+ */
+module tanya.memory.types;
+
+import core.exception;
+import std.algorithm.comparison;
+import std.algorithm.mutation;
+import std.conv;
+import std.traits;
+import tanya.memory;
+import tanya.traits;
+
+/**
+ * Reference-counted object containing a $(D_PARAM T) value as payload.
+ * $(D_PSYMBOL RefCounted) keeps track of all references of an object, and
+ * when the reference count goes down to zero, frees the underlying store.
+ *
+ * Params:
+ * 	T = Type of the reference-counted value.
+ */
+struct RefCounted(T)
+{
+	static if (isReference!T)
+	{
+		private T payload;
+	}
+	else
+	{
+		private T* payload;
+	}
+
+	private uint *counter;
+
+	invariant
+	{
+		assert(counter is null || allocator !is null);
+	}
+
+	/**
+	 * Takes ownership over $(D_PARAM value), setting the counter to 1.
+	 *
+	 * Params:
+	 * 	value     = Value whose ownership is taken over.
+	 * 	allocator = Allocator used to destroy the $(D_PARAM value) and to
+	 * 	            allocate/deallocate internal storage.
+
+	 * Precondition: $(D_INLINECODE allocator !is null)
+	 */
+	this(T value, IAllocator allocator = theAllocator)
+	in
+	{
+		assert(allocator !is null);
+	}
+	body
+	{
+		this.allocator = allocator;
+		initialize();
+		move(value, get);
+	}
+
+	/// Ditto.
+	this(IAllocator allocator)
+	in
+	{
+		assert(allocator !is null);
+	}
+	body
+	{
+		this.allocator = allocator;
+	}
+
+	/**
+	 * Allocates the internal storage.
+	 */
+	private void initialize()
+	{
+		static if (isReference!T)
+		{
+			counter = allocator.make!uint(1);
+		}
+		else
+		{
+			// Allocate for the counter and the payload together.
+			auto p = allocator.allocate(uint.sizeof + T.sizeof);
+			if (p is null)
+			{
+				onOutOfMemoryError();
+			}
+			counter = emplace(cast(uint*) p.ptr, 1);
+			payload = cast(T*) p[uint.sizeof .. $].ptr;
+		}
+	}
+
+	/**
+	 * Increases the reference counter by one.
+	 */
+	this(this) pure nothrow @safe @nogc
+	{
+		if (isInitialized)
+		{
+			++(*counter);
+		}
+	}
+
+	/**
+	 * Decreases the reference counter by one.
+	 *
+	 * If the counter reaches 0, destroys the owned value.
+	 */
+	~this()
+	{
+		if (!isInitialized || (--(*counter)))
+		{
+			return;
+		}
+		allocator.dispose(payload);
+		payload = null;
+
+		allocator.dispose(counter);
+		counter = null;
+	}
+
+	/**
+	 * Takes ownership over $(D_PARAM rhs). Initializes this
+	 * $(D_PSYMBOL RefCounted) if needed.
+	 *
+	 * If it is the last reference of the previously owned object,
+	 * it will be destroyed.
+	 *
+	 * If the allocator wasn't set before, $(D_PSYMBOL theAllocator) will
+	 * be used. If you need a different allocator, create a new
+	 * $(D_PSYMBOL RefCounted).
+	 *
+	 * Params:
+	 * 	rhs = Object whose ownership is taken over.
+	 */
+	ref T opAssign(T rhs)
+	{
+		checkAllocator();
+		if (isInitialized)
+		{
+			static if (isReference!T)
+			{
+				if (!--(*counter))
+				{
+					allocator.dispose(payload);
+					*counter = 1;
+				}
+			}
+		}
+		else
+		{
+			initialize();
+		}
+		move(rhs, get);
+		return get;
+	}
+
+	/// Ditto.
+	ref typeof(this) opAssign(typeof(this) rhs)
+	{
+		swap(counter, rhs.counter);
+		swap(get, rhs.get);
+		swap(allocator, rhs.allocator);
+
+		return this;
+	}
+
+	/**
+	 * Defines the casting to the original type.
+	 *
+	 * Params:
+	 * 	T = Target type.
+	 *
+	 * Returns: Owned value.
+	 */
+	inout(T2) opCast(T2)() inout pure nothrow @safe @nogc
+		if (is(T : T2))
+	in
+	{
+		assert(payload !is null, "Attempted to access an uninitialized reference.");
+	}
+	body
+	{
+		return get;
+	}
+
+	ref inout(T) get() inout return pure nothrow @safe @nogc
+	{
+		static if (isReference!T)
+		{
+			return payload;
+		}
+		else
+		{
+			return *payload;
+		}
+	}
+
+	/**
+	 * Returns: The number of $(D_PSYMBOL RefCounted) instances that share
+	 *          ownership over the same pointer (including $(D_KEYWORD this)).
+	 *          If this $(D_PSYMBOL RefCounted) isn't initialized, returns 0.
+	 */
+	@property uint count() const pure nothrow @safe @nogc
+	{
+		return counter is null ? 0 : *counter;
+	}
+
+	/**
+	 * Returns: Whether tihs $(D_PSYMBOL RefCounted) is initialized.
+	 */
+	@property bool isInitialized() const pure nothrow @safe @nogc
+	{
+		return counter !is null;
+	}
+
+	mixin StructAllocator;
+
+	alias get this;
+}
+
+version (unittest)
+{
+	class A
+	{
+		uint *destroyed;
+
+		this(ref uint destroyed)
+		{
+			this.destroyed = &destroyed;
+		}
+
+		~this()
+		{
+			++(*destroyed);
+		}
+	}
+
+	struct B
+	{
+		@disable this();
+		this(int param1)
+		{
+		}
+	}
+}
+
+///
+unittest
+{
+	struct S
+	{
+		RefCounted!(ubyte[]) member;
+
+		this(ref ubyte[] member)
+		{
+			assert(!this.member.isInitialized);
+			this.member = member;
+			assert(this.member.isInitialized);
+		}
+	}
+
+	auto arr = theAllocator.makeArray!ubyte(2);
+	{
+		auto a = S(arr);
+		assert(a.member.count == 1);
+
+		void func(S a)
+		{
+			assert(a.member.count == 2);
+		}
+		func(a);
+
+		assert(a.member.count == 1);
+	}
+	// arr is destroyed.
+}
+
+private unittest
+{
+	uint destroyed;
+	auto a = theAllocator.make!A(destroyed);
+
+	assert(destroyed == 0);
+	{
+		auto rc = RefCounted!A(a);
+		assert(rc.count == 1);
+
+		void func(RefCounted!A rc)
+		{
+			assert(rc.count == 2);
+		}
+		func(rc);
+
+		assert(rc.count == 1);
+	}
+	assert(destroyed == 1);
+
+	RefCounted!int rc;
+	rc = 8;
+}
+
+private unittest
+{
+	auto rc = RefCounted!int(5);
+
+	static assert(is(typeof(rc.payload) == int*));
+	static assert(is(typeof(cast(int) rc) == int));
+
+	static assert(is(typeof(RefCounted!(int*).payload) == int*));
+
+	static assert(is(typeof(cast(A) (RefCounted!A())) == A));
+	static assert(is(typeof(cast(Object) (RefCounted!A())) == Object));
+	static assert(!is(typeof(cast(int) (RefCounted!A()))));
+
+	static assert(is(RefCounted!B));
+}
+
+/**
+ * Constructs a new object of type $(D_PARAM T) and wraps it in a
+ * $(D_PSYMBOL RefCounted) using $(D_PARAM args) as the parameter list for
+ * the constructor of $(D_PARAM T).
+ *
+ * This function is more efficient than using $(D_PSYMBOL RefCounted)
+ * for the new objects directly, since $(D_PSYMBOL refCounted) allocates
+ * only once (the object and the internal storage are allocated at once).
+ *
+ * Params:
+ * 	T    = Type of the constructed object.
+ * 	A    = Types of the arguments to the constructor of $(D_PARAM T).
+ * 	args = Constructor arguments of $(D_PARAM T).
+ * 
+ * Returns: Newly created $(D_PSYMBOL RefCounted!T).
+ */
+RefCounted!T refCounted(T, A...)(IAllocator allocator, auto ref A args)
+	if (!is(T == interface) && !isAbstractClass!T)
+{
+	auto rc = typeof(return)(allocator);
+
+	immutable toAllocate = max(stateSize!T, 1) + uint.sizeof;
+	auto p = allocator.allocate(toAllocate);
+	if (p is null)
+	{
+		onOutOfMemoryError();
+	}
+	scope (failure)
+	{
+		allocator.deallocate(p);
+	}
+
+	rc.counter = emplace(cast(uint*) p.ptr, 1);
+
+	static if (is(T == class))
+	{
+		rc.payload = emplace!T(p[uint.sizeof .. $], args);
+	}
+	else
+	{
+		rc.payload = emplace(cast(T*) p[uint.sizeof .. $].ptr, args);
+	}
+
+	return rc;
+}
+
+///
+unittest
+{
+	auto rc = theAllocator.refCounted!int(5);
+	assert(rc.count == 1);
+
+	void func(RefCounted!int param)
+	{
+		if (param.count == 2)
+		{
+			func(param);
+		}
+		else
+		{
+			assert(param.count == 3);
+		}
+	}
+	func(rc);
+
+	assert(rc.count == 1);
+}
+
+private unittest
+{
+	static assert(!is(theAllocator.refCounted!A));
+	static assert(!is(typeof(theAllocator.refCounted!B())));
+	static assert(is(typeof(theAllocator.refCounted!B(5))));
+}
diff --git a/source/tanya/traits.d b/source/tanya/traits.d
new file mode 100644
index 0000000..74e18be
--- /dev/null
+++ b/source/tanya/traits.d
@@ -0,0 +1,23 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+/**
+ * Copyright: Eugene Wissner 2016.
+ * License: $(LINK2 https://www.mozilla.org/en-US/MPL/2.0/,
+ *                  Mozilla Public License, v. 2.0).
+ * Authors: $(LINK2 mailto:belka@caraus.de, Eugene Wissner)
+ */
+module tanya.traits;
+
+import std.traits;
+
+/**
+ * Params:
+ * 	T = Type.
+ *
+ * Returns: $(D_KEYWORD true) if $(D_PARAM T) is a reference type or a pointer,
+ *          $(D_KEYWORD false) otherwise.
+ */
+enum bool isReference(T) = isDynamicArray!T || isPointer!T
+                        || is(T == class) || is(T == interface);