fix(zone): align loaded block buffers (#1006)

* fix(zone): align loaded block buffers

* chore: move XBlockTests to correct dir

* chore: align XBlocks to 4096 to match the game

---------

Co-authored-by: LVEIceFire <[email protected]>
Co-authored-by: Jan Laupetin <[email protected]>

src/ZoneCommon/Zone/XBlock.cpp

@@ -1,5 +1,19 @@
 #include "XBlock.h"
 
+#include <new>
+
+namespace
+{
+    // This must be higher or equal to the highest alignment value in any game struct.
+    // The games always seem to align to 4096 up to T6 so we'll keep parity.
+    constexpr std::align_val_t XBLOCK_BUFFER_ALIGNMENT{4096u};
+} // namespace
+
+void XBlockBufferDeleter::operator()(std::uint8_t* buffer) const noexcept
+{
+    ::operator delete[](buffer, XBLOCK_BUFFER_ALIGNMENT);
+}
+
 XBlock::XBlock(std::string name, const unsigned index, const XBlockType type)
     : m_name(std::move(name)),
       m_index(index),
@@ -12,7 +26,7 @@ void XBlock::Alloc(const size_t blockSize)
 {
     if (blockSize > 0)
     {
-        m_buffer = std::make_unique<uint8_t[]>(blockSize);
+        m_buffer.reset(static_cast<std::uint8_t*>(::operator new[](blockSize, XBLOCK_BUFFER_ALIGNMENT)));
         m_buffer_size = blockSize;
     }
     else

src/ZoneCommon/Zone/XBlock.h

@@ -13,6 +13,11 @@ enum class XBlockType : std::uint8_t
     BLOCK_TYPE_NORMAL
 };
 
+struct XBlockBufferDeleter
+{
+    void operator()(std::uint8_t* buffer) const noexcept;
+};
+
 class XBlock
 {
 public:
@@ -24,6 +29,6 @@ public:
     unsigned m_index;
     XBlockType m_type;
 
-    std::unique_ptr<uint8_t[]> m_buffer;
+    std::unique_ptr<uint8_t[], XBlockBufferDeleter> m_buffer;
     size_t m_buffer_size;
 };

test/ZoneCommonTests/Zone/XBlockTests.cpp

@@ -0,0 +1,27 @@
+#include "Zone/XBlock.h"
+
+#include <array>
+#include <catch2/catch_test_macros.hpp>
+#include <cstdint>
+
+namespace
+{
+    TEST_CASE("Zone block buffers provide the maximum asset alignment", "[zone-loading][stream]")
+    {
+        static constexpr std::uintptr_t REQUIRED_ALIGNMENT = 4096u;
+
+        XBlock block("test", 0, XBlockType::BLOCK_TYPE_NORMAL);
+        constexpr size_t sizes[]{1u, 7u, 16u, 4096u, 65537u};
+
+        for (const auto size : sizes)
+        {
+            block.Alloc(size);
+            REQUIRE(reinterpret_cast<std::uintptr_t>(block.m_buffer.get()) % REQUIRED_ALIGNMENT == 0u);
+            REQUIRE(block.m_buffer_size == size);
+        }
+
+        block.Alloc(0u);
+        REQUIRE(block.m_buffer.get() == nullptr);
+        REQUIRE(block.m_buffer_size == 0u);
+    }
+} // namespace