Implement destroy_n

include/preview/__memory/destroy_n.h

@@ -0,0 +1,22 @@
+//
+// Created by yonggyulee on 2024. 8. 4.
+//
+
+#ifndef PREVIEW_MEMORY_DESTROY_N_H_
+#define PREVIEW_MEMORY_DESTROY_N_H_
+
+#include "preview/__memory/addressof.h"
+#include "preview/__memory/destroy_at.h"
+
+namespace preview {
+
+template<typename NothrowForwardIterator, typename Size>
+constexpr NothrowForwardIterator destroy_n(NothrowForwardIterator first, Size n) {
+  for (; n > 0; (void)++first, --n)
+    preview::destroy_at(preview::addressof(*first));
+  return first;
+}
+
+} // namespace preview
+
+#endif // PREVIEW_MEMORY_DESTROY_N_H_

include/preview/memory.h

@@ -9,6 +9,7 @@
 #include "preview/__memory/construct_at.h"
 #include "preview/__memory/destroy.h"
 #include "preview/__memory/destroy_at.h"
+#include "preview/__memory/destroy_n.h"
 #include "preview/__memory/make_obj_using_allocator.h"
 #include "preview/__memory/pointer_traits.h"
 #include "preview/__memory/to_address.h"

test/memory.cc

@@ -12,6 +12,9 @@
 #include "preview/bit.h"
 #include "preview/ranges.h"
 
+namespace ranges = preview::ranges;
+namespace views = preview::views;
+
 struct bizarre_object {
   int operator&() const {
     return 3;
@@ -109,6 +112,22 @@ TEST(VERSIONED(Memory), destroy_at) {
   }
 }
 
+TEST(VERSIONED(Memory), destroy_n) {
+  alignas(Tracer) unsigned char buffer[sizeof(Tracer) * 8];
+  bool destroyed[8]{};
+
+  for (int i = 0; i < 8; ++i)
+    new(buffer + sizeof(Tracer) * i) Tracer{i, [&](int x) { destroyed[i] = true; }}; //manually construct objects
+
+  auto ptr = reinterpret_cast<Tracer*>(buffer);
+
+  EXPECT_TRUE(ranges::equal(destroyed, views::repeat(false, 8)));
+  preview::destroy_n(ptr, 4);
+  EXPECT_TRUE(ranges::equal(destroyed, views::concat(views::repeat(true, 4), views::repeat(false, 4))));
+  preview::destroy_n(ptr + 4, 4);
+  EXPECT_TRUE(ranges::equal(destroyed, views::repeat(true, 8)));
+}
+
 template<class Ptr>
 struct BlockList
 {