From 66fa3ff4bab5e36066784e61632e07336de7b8d5 Mon Sep 17 00:00:00 2001
From: jadebenn <jonahebenn@yahoo.com>
Date: Mon, 25 Nov 2024 01:40:58 -0600
Subject: [PATCH] created FromBitsUnchecked memcpy wrapper

---
 dCommon/GeneralUtils.h                        | 21 +++++++++++++++++++
 dCommon/dClient/AssetManager.h                |  1 +
 .../02_server/Map/AG/NpcAgCourseStarter.cpp   |  9 ++++----
 dWorldServer/WorldServer.cpp                  |  5 ++---
 4 files changed, 28 insertions(+), 8 deletions(-)

diff --git a/dCommon/GeneralUtils.h b/dCommon/GeneralUtils.h
index 3c4ee285f..b1d497281 100644
--- a/dCommon/GeneralUtils.h
+++ b/dCommon/GeneralUtils.h
@@ -3,6 +3,7 @@
 // C++
 #include <charconv>
 #include <cstdint>
+#include <cstring>
 #include <ctime>
 #include <functional>
 #include <optional>
@@ -152,6 +153,26 @@ namespace GeneralUtils {
 		char_pointer_hash
 	>;
 
+	/**
+	 * A convenience wrapper around std::memcpy that creates a new object
+	 * from the value representation of the provided bytes.Use when
+	 * std::bit_cast is not applicable.
+	 * @warning All restrictions of std::memcpy still apply. Accessing
+	 * outside of the source object is undefined behavior.
+	 * @param from The source of the value representation
+	 * @returns A new object with the given value representation
+	 */
+    template <typename To, typename From>
+    [[nodiscard]]
+    inline To FromBitsUnchecked(const From* from) noexcept 
+    requires (std::is_trivially_copyable_v<To>
+              && std::is_trivially_copyable_v<From>)
+    {
+        To to{};
+        std::memcpy(&to, from, sizeof(To));
+        return to;
+    }
+
 	// Concept constraining to enum types
 	template <typename T>
 	concept Enum = std::is_enum_v<T>;
diff --git a/dCommon/dClient/AssetManager.h b/dCommon/dClient/AssetManager.h
index 2116f2237..73e6162a9 100644
--- a/dCommon/dClient/AssetManager.h
+++ b/dCommon/dClient/AssetManager.h
@@ -54,6 +54,7 @@ struct AssetStream : std::istream {
 	}
 
 	operator bool() {
+		// NEED TO FIX THIS
 		return reinterpret_cast<AssetMemoryBuffer*>(rdbuf())->m_Success;
 	}
 };
diff --git a/dScripts/02_server/Map/AG/NpcAgCourseStarter.cpp b/dScripts/02_server/Map/AG/NpcAgCourseStarter.cpp
index 5bd0ff2bd..c6c3629d9 100644
--- a/dScripts/02_server/Map/AG/NpcAgCourseStarter.cpp
+++ b/dScripts/02_server/Map/AG/NpcAgCourseStarter.cpp
@@ -81,11 +81,10 @@ void NpcAgCourseStarter::OnFireEventServerSide(Entity* self, Entity* sender, std
 		scriptedActivityComponent->RemoveActivityPlayerData(sender->GetObjectID());
 	} else if (args == "course_finish") {
 		const time_t endTime = std::time(0);
-		
-		// Using memcpy since misaligned reads are UB
-		time_t startTime{};
-		std::memcpy(&startTime, &data->values[1], sizeof(time_t));
-		const time_t finish = (endTime - startTime);
+
+		// Using FromBitsUnchecked to create new time_t object since misaligned reads are UB
+		const time_t startTime = GeneralUtils::FromBitsUnchecked<time_t>(&data->values[1]);
+		const time_t finish = endTime - startTime;
 		
 		std::memcpy(&data->values[2], &finish, sizeof(float));
 
diff --git a/dWorldServer/WorldServer.cpp b/dWorldServer/WorldServer.cpp
index 84a0c1a93..c71c4a4fe 100644
--- a/dWorldServer/WorldServer.cpp
+++ b/dWorldServer/WorldServer.cpp
@@ -1396,9 +1396,8 @@ void HandlePacket(Packet* packet) {
 	}
 
 	default:
-		// Need to use memcpy instead of reinterpret_cast to avoid misaligned reads, which are UB
-		auto messageId = MessageType::World::INVALID;
-		std::memcpy(&messageId, &packet->data[3], sizeof(MessageType::World));
+		// Need to use FromBitsUnchecked (aka memcpy) instead of reinterpret_cast to avoid misaligned reads, which are UB
+		const auto messageId = GeneralUtils::FromBitsUnchecked<MessageType::World>(&packet->data[3]);
 
 		const std::string_view messageIdString = StringifiedEnum::ToString(messageId);
 		LOG("Unknown world packet received: %4i, %s", messageId, messageIdString.data());