From 15e24ff7021ecb9646a55d11edef96061e846491 Mon Sep 17 00:00:00 2001
From: Dan Goodliffe <dan@randomdan.homeip.net>
Date: Sat, 29 Aug 2015 01:21:12 +0100
Subject: Move and test lazy pointer

---
 libadhocutil/lazyPointer.h                 | 126 +++++++++++++++++++++++++++++
 libadhocutil/unittests/Jamfile.jam         |  10 +++
 libadhocutil/unittests/testLazyPointer.cpp |  77 ++++++++++++++++++
 3 files changed, 213 insertions(+)
 create mode 100644 libadhocutil/lazyPointer.h
 create mode 100644 libadhocutil/unittests/testLazyPointer.cpp

diff --git a/libadhocutil/lazyPointer.h b/libadhocutil/lazyPointer.h
new file mode 100644
index 0000000..23058c7
--- /dev/null
+++ b/libadhocutil/lazyPointer.h
@@ -0,0 +1,126 @@
+#ifndef LIBADHOC_LAZYPOINTER_H
+#define LIBADHOC_LAZYPOINTER_H
+
+#include <boost/function.hpp>
+#include <boost/variant.hpp>
+#include <boost/intrusive_ptr.hpp>
+
+template <typename T, typename P = boost::intrusive_ptr<T>>
+class LazyPointer {
+	public:
+		typedef T element_type;
+		typedef P pointer_type;
+		typedef boost::function0<P> Factory;
+		typedef boost::variant<P, Factory> Source;
+
+		// Constructors
+		LazyPointer(const Factory & f) :
+			source(f)
+		{
+		}
+
+		LazyPointer(const P & p) :
+			source(p)
+		{
+		}
+
+		LazyPointer(T * p) :
+			source(P(p))
+		{
+		}
+
+		LazyPointer() :
+			source(P(NULL))
+		{
+		}
+
+		// Getters
+		operator P() const
+		{
+			return deref();
+		}
+
+		T * operator->() const
+		{
+			return get();
+		}
+
+		T & operator*() const
+		{
+			return *get();
+		}
+
+		T * get() const
+		{
+			return deref().get();
+		}
+
+		P deref() const
+		{
+			if (Factory * f = boost::get<Factory>(&source)) {
+				P p = (*f)();
+				source = p;
+				return p;
+			}
+			else {
+				return boost::get<P>(source);
+			}
+		}
+
+		bool operator!() const
+		{
+			return get() == nullptr;
+		}
+
+		operator bool() const
+		{
+			return get() != nullptr;
+		}
+
+		bool operator==(const P & o) const
+		{
+			return (deref() == o);
+		}
+
+		bool operator==(const T * o) const
+		{
+			return (deref().get() == o);
+		}
+
+		// Setters
+		LazyPointer<T, P> & operator=(const P & p)
+		{
+			source = p;
+			return *this;
+		}
+
+		LazyPointer<T, P> & operator=(T * t)
+		{
+			source = P(t);
+			return *this;
+		}
+
+		LazyPointer<T, P> & operator=(const Factory & f)
+		{
+			source = f;
+			return *this;
+		}
+
+		bool hasValue() const
+		{
+			return boost::get<P>(&source);
+		}
+
+	private:
+		mutable Source source;
+};
+
+namespace boost {
+	template <typename R, typename T, typename P>
+		R * dynamic_pointer_cast(const LazyPointer<T, P> & p) {
+			return dynamic_cast<R *>(p.get());
+		}
+}
+
+#endif
+
diff --git a/libadhocutil/unittests/Jamfile.jam b/libadhocutil/unittests/Jamfile.jam
index e26825a..4a6b430 100644
--- a/libadhocutil/unittests/Jamfile.jam
+++ b/libadhocutil/unittests/Jamfile.jam
@@ -86,3 +86,13 @@ run
 	testLocks
 	;
 
+run
+	testLazyPointer.cpp
+	: : :
+	<define>BOOST_TEST_DYN_LINK
+	<library>..//adhocutil
+	<library>boost_utf
+	:
+	testLazyPointer
+	;
+
diff --git a/libadhocutil/unittests/testLazyPointer.cpp b/libadhocutil/unittests/testLazyPointer.cpp
new file mode 100644
index 0000000..6c4ddcd
--- /dev/null
+++ b/libadhocutil/unittests/testLazyPointer.cpp
@@ -0,0 +1,77 @@
+#define BOOST_TEST_MODULE LazyPointer
+#include <boost/test/unit_test.hpp>
+
+#include <boost/bind.hpp>
+#include "intrusivePtrBase.h"
+#include "lazyPointer.h"
+
+class Test : public IntrusivePtrBase {
+	public:
+		Test(int v) :
+			val(v)
+		{
+		}
+		const int val;
+};
+
+typedef LazyPointer<Test> TestLazyPointer;
+
+static
+TestLazyPointer::pointer_type
+factory()
+{
+	return new Test(3);
+}
+
+static
+TestLazyPointer::pointer_type
+paramFactory(const std::string & str)
+{
+	return new Test(str.length());
+}
+
+BOOST_AUTO_TEST_CASE ( islazy )
+{
+	TestLazyPointer p(boost::bind(&factory));
+	BOOST_REQUIRE_EQUAL(false, p.hasValue());
+	Test * t = p.get();
+	BOOST_REQUIRE(t);
+	BOOST_REQUIRE_EQUAL(true, p.hasValue());
+	BOOST_REQUIRE_EQUAL(p, t);
+	BOOST_REQUIRE_EQUAL(3, t->val);
+	BOOST_REQUIRE_EQUAL(3, p->val);
+}
+
+BOOST_AUTO_TEST_CASE ( preinit )
+{
+	Test * t = new Test(4);
+	TestLazyPointer p(t);
+	BOOST_REQUIRE_EQUAL(true, p.hasValue());
+	BOOST_REQUIRE_EQUAL(p, t);
+	BOOST_REQUIRE_EQUAL(4, p->val);
+}
+
+BOOST_AUTO_TEST_CASE ( reset )
+{
+	Test * t = new Test(4);
+	TestLazyPointer p(t);
+	BOOST_REQUIRE_EQUAL(true, p.hasValue());
+	BOOST_REQUIRE_EQUAL(4, p->val);
+	p = nullptr;
+	BOOST_REQUIRE_EQUAL(true, p.hasValue());
+	BOOST_REQUIRE_EQUAL(true, !p);
+	p = boost::bind(&factory);
+	BOOST_REQUIRE_EQUAL(false, p.hasValue());
+	p.get();
+	BOOST_REQUIRE_EQUAL(true, p.hasValue());
+	BOOST_REQUIRE_EQUAL(3, p->val);
+}
+
+BOOST_AUTO_TEST_CASE ( nondefault )
+{
+	TestLazyPointer p(boost::bind(&paramFactory, "some string"));
+	BOOST_REQUIRE_EQUAL(false, p.hasValue());
+	BOOST_REQUIRE_EQUAL(11, (*p).val);
+	BOOST_REQUIRE_EQUAL(true, p.hasValue());
+}
+
-- 
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