From 58061b5f45f4d3d91fe9342c2cd7f54e45d1b482 Mon Sep 17 00:00:00 2001
From: Kp <kp@valhallalegends.com>
Date: Sat, 30 Jul 2022 17:42:59 +0000
Subject: [PATCH] Use C++20 std::span for morph_data

---
 common/include/compiler-span.h | 46 ----------------------------------
 common/main/morph.h            |  8 +++---
 similar/main/morph.cpp         | 18 +++++++------
 3 files changed, 14 insertions(+), 58 deletions(-)
 delete mode 100644 common/include/compiler-span.h

diff --git a/common/include/compiler-span.h b/common/include/compiler-span.h
deleted file mode 100644
index 7a829a76f..000000000
--- a/common/include/compiler-span.h
+++ /dev/null
@@ -1,46 +0,0 @@
-/*
- * This file is part of the DXX-Rebirth project <https://www.dxx-rebirth.com/>.
- * It is copyright by its individual contributors, as recorded in the
- * project's Git history.  See COPYING.txt at the top level for license
- * terms and a link to the Git history.
- */
-#pragma once
-
-#include <cstddef>
-
-/* Partial implementation of std::span (C++20) for pre-C++20 compilers.
- * As of this writing, there are no released compilers with C++20
- * support, so this implementation is always used.
- *
- * This implementation covers only the minimal functionality used by
- * Rebirth.  It is not intended as a drop-in replacement for arbitrary
- * use of std::span.
- */
-
-template <typename T>
-class span
-{
-	std::size_t extent;
-	T *ptr;
-public:
-	span(T *p, std::size_t l) :
-		extent(l), ptr(p)
-	{
-	}
-	T *begin() const
-	{
-		return ptr;
-	}
-	T *end() const
-	{
-		return ptr + extent;
-	}
-	std::size_t size() const
-	{
-		return extent;
-	}
-	T &operator[](std::size_t i) const
-	{
-		return *(ptr + i);
-	}
-};
diff --git a/common/main/morph.h b/common/main/morph.h
index d0d0a8f96..f5c23046c 100644
--- a/common/main/morph.h
+++ b/common/main/morph.h
@@ -34,10 +34,10 @@ COPYRIGHT 1993-1999 PARALLAX SOFTWARE CORPORATION.  ALL RIGHTS RESERVED.
 #include "dsx-ns.h"
 
 #ifdef dsx
-#include "compiler-span.h"
 #include "object.h"
 #include <array>
 #include <memory>
+#include <span>
 
 namespace dcx {
 
@@ -89,9 +89,9 @@ struct morph_data : prohibit_void_ptr<morph_data>
 		n_morphing_points,       // how many active points in each part
 		submodel_startpoints;    // first point for each submodel
 	static ptr create(object_base &, const polymodel &, polymodel_idx);
-	span<fix> get_morph_times();
-	span<vms_vector> get_morph_vecs();
-	span<vms_vector> get_morph_deltas();
+	std::span<fix> get_morph_times();
+	std::span<vms_vector> get_morph_vecs();
+	std::span<vms_vector> get_morph_deltas();
 private:
 	static void *operator new(std::size_t bytes, max_vectors);
 	explicit morph_data(object_base &o, max_vectors);
diff --git a/similar/main/morph.cpp b/similar/main/morph.cpp
index ef87af1ea..2c27818cb 100644
--- a/similar/main/morph.cpp
+++ b/similar/main/morph.cpp
@@ -204,28 +204,30 @@ morph_data::morph_data(object_base &o, const max_vectors m) :
 {
 	DXX_POISON_VAR(submodel_active, 0xcc);
 	const auto morph_times = get_morph_times();
-	DXX_POISON_MEMORY(morph_times.begin(), morph_times.end(), 0xcc);
+	DXX_POISON_MEMORY(morph_times.data(), morph_times.size(), 0xcc);
 	const auto morph_vecs = get_morph_times();
-	DXX_POISON_MEMORY(morph_vecs.begin(), morph_vecs.end(), 0xcc);
+	DXX_POISON_MEMORY(morph_vecs.data(), morph_vecs.size(), 0xcc);
 	const auto morph_deltas = get_morph_times();
-	DXX_POISON_MEMORY(morph_deltas.begin(), morph_deltas.end(), 0xcc);
+	DXX_POISON_MEMORY(morph_deltas.data(), morph_deltas.size(), 0xcc);
 	DXX_POISON_VAR(n_morphing_points, 0xcc);
 	DXX_POISON_VAR(submodel_startpoints, 0xcc);
 }
 
-span<fix> morph_data::get_morph_times()
+std::span<fix> morph_data::get_morph_times()
 {
 	return {reinterpret_cast<fix *>(this + 1), max_vecs.count};
 }
 
-span<vms_vector> morph_data::get_morph_vecs()
+std::span<vms_vector> morph_data::get_morph_vecs()
 {
-	return {reinterpret_cast<vms_vector *>(get_morph_times().end()), max_vecs.count};
+	const auto t = get_morph_times();
+	return {reinterpret_cast<vms_vector *>(t.data() + t.size()), max_vecs.count};
 }
 
-span<vms_vector> morph_data::get_morph_deltas()
+std::span<vms_vector> morph_data::get_morph_deltas()
 {
-	return {get_morph_vecs().end(), max_vecs.count};
+	const auto v = get_morph_vecs();
+	return {v.data() + v.size(), max_vecs.count};
 }
 
 d_level_unique_morph_object_state::~d_level_unique_morph_object_state() = default;