From a6457aea04d1705f5b03f9c9e628bebbefdcf64c Mon Sep 17 00:00:00 2001
From: Dan Goodliffe <dan@randomdan.homeip.net>
Date: Mon, 1 May 2023 18:14:49 +0100
Subject: Add the pack container

Keeps its elements densely packed together without any interest in order
---
 lib/pack.h         | 42 ++++++++++++++++++++++++++++++++++++++++++
 test/Jamfile.jam   |  1 +
 test/test-pack.cpp | 41 +++++++++++++++++++++++++++++++++++++++++
 3 files changed, 84 insertions(+)
 create mode 100644 lib/pack.h
 create mode 100644 test/test-pack.cpp

diff --git a/lib/pack.h b/lib/pack.h
new file mode 100644
index 0000000..92c8b20
--- /dev/null
+++ b/lib/pack.h
@@ -0,0 +1,42 @@
+#pragma once
+
+#include <utility>
+
+template<typename T, template<typename... S> typename Container> class pack : protected Container<T> {
+public:
+	using Container<T>::Container;
+
+	using Container<T>::begin;
+	using Container<T>::end;
+	using Container<T>::rbegin;
+	using Container<T>::rend;
+	using Container<T>::cbegin;
+	using Container<T>::cend;
+	using Container<T>::crbegin;
+	using Container<T>::crend;
+	using Container<T>::clear;
+	using Container<T>::empty;
+	using Container<T>::size;
+	using Container<T>::capacity;
+	using Container<T>::shrink_to_fit;
+	using Container<T>::at;
+	using Container<T>::data;
+	using Container<T>::operator[];
+
+	template<typename... Ps>
+	decltype(auto)
+	emplace(Ps &&... ps)
+	{
+		return Container<T>::emplace_back(std::forward<Ps>(ps)...);
+	}
+
+	void
+	erase(typename Container<T>::iterator pos)
+	{
+		pos->~T();
+		if (&*pos != &Container<T>::back()) {
+			new (&*pos) T(std::move(Container<T>::back()));
+		}
+		Container<T>::pop_back();
+	}
+};
diff --git a/test/Jamfile.jam b/test/Jamfile.jam
index fb9a996..3b4e891 100644
--- a/test/Jamfile.jam
+++ b/test/Jamfile.jam
@@ -59,6 +59,7 @@ run perf-persistence.cpp : -- : test-persistence : <library>benchmark <library>t
 run test-worker.cpp ;
 run test-instancing.cpp : : : <library>test ;
 run test-glContainer.cpp : : : <library>test ;
+run test-pack.cpp : : : <library>test ;
 compile test-static-enumDetails.cpp ;
 compile test-static-stream_support.cpp ;
 explicit perf-assetFactory ;
diff --git a/test/test-pack.cpp b/test/test-pack.cpp
new file mode 100644
index 0000000..1f9f061
--- /dev/null
+++ b/test/test-pack.cpp
@@ -0,0 +1,41 @@
+#define BOOST_TEST_MODULE pack
+
+#include <boost/test/data/test_case.hpp>
+#include <boost/test/unit_test.hpp>
+
+#include "pack.h"
+#include <vector>
+
+using IntegerVectorPack = pack<int, std::vector>;
+
+BOOST_FIXTURE_TEST_SUITE(pint, IntegerVectorPack)
+
+BOOST_AUTO_TEST_CASE(basics)
+{
+	BOOST_CHECK_EQUAL(size(), 0);
+	BOOST_CHECK_NO_THROW(emplace(1));
+	BOOST_CHECK_NO_THROW(emplace(2));
+	BOOST_CHECK_NO_THROW(emplace(3));
+	BOOST_CHECK_NO_THROW(emplace(4));
+	BOOST_CHECK_EQUAL(size(), 4);
+	{
+		std::array expected1 {1, 2, 3, 4};
+		BOOST_CHECK_EQUAL_COLLECTIONS(begin(), end(), expected1.begin(), expected1.end());
+	}
+
+	BOOST_CHECK_NO_THROW(erase(begin() + 1));
+	BOOST_CHECK_EQUAL(size(), 3);
+	{
+		std::array expected1 {1, 4, 3};
+		BOOST_CHECK_EQUAL_COLLECTIONS(begin(), end(), expected1.begin(), expected1.end());
+	}
+
+	BOOST_CHECK_NO_THROW(erase(--end()));
+	BOOST_CHECK_EQUAL(size(), 2);
+	{
+		std::array expected1 {1, 4};
+		BOOST_CHECK_EQUAL_COLLECTIONS(begin(), end(), expected1.begin(), expected1.end());
+	}
+}
+
+BOOST_AUTO_TEST_SUITE_END()
-- 
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