New syntax for reversed structs (#324)

* Initial commit

Co-Authored-By: BobTheBob <32057864+BobTheBob9@users.noreply.github.com>

* Format change

* Revert `VPKData` definition

* Add `FIELDS` macro

Co-authored-by: BobTheBob <32057864+BobTheBob9@users.noreply.github.com>

7 files changed, 106 insertions, 55 deletions

diff --git a/NorthstarDLL/NorthstarDLL.vcxproj b/NorthstarDLL/NorthstarDLL.vcxproj
index 9d66b854..c1532157 100644
--- a/NorthstarDLL/NorthstarDLL.vcxproj
+++ b/NorthstarDLL/NorthstarDLL.vcxproj
@@ -558,6 +558,7 @@
     <ClInclude Include="sourceinterface.h" />

     <ClInclude Include="squirrel.h" />

     <ClInclude Include="exploitfixes_utf8parser.cpp" />

+    <ClInclude Include="structs.h" />

     <ClInclude Include="squirrelautobind.h" />

     <ClInclude Include="tier0.h" />

     <ClInclude Include="vector.h" />

diff --git a/NorthstarDLL/NorthstarDLL.vcxproj.filters b/NorthstarDLL/NorthstarDLL.vcxproj.filters
index 024274cf..8ff5f461 100644
--- a/NorthstarDLL/NorthstarDLL.vcxproj.filters
+++ b/NorthstarDLL/NorthstarDLL.vcxproj.filters
@@ -1494,6 +1494,9 @@
     <ClInclude Include="keyvalues.h">

       <Filter>Header Files</Filter>

     </ClInclude>

+    <ClInclude Include="structs.h">

+      <Filter>Header Files</Filter>

+    </ClInclude>

     <ClInclude Include="loghooks.h">

       <Filter>Header Files\Console</Filter>

     </ClInclude>

diff --git a/NorthstarDLL/filesystem.h b/NorthstarDLL/filesystem.h
index c326b419..9a22893a 100644
--- a/NorthstarDLL/filesystem.h
+++ b/NorthstarDLL/filesystem.h
@@ -5,25 +5,32 @@
 typedef void* FileHandle_t;
 
 #pragma pack(push, 1)
-struct VPKFileEntry
+
+// clang-format off
+OFFSET_STRUCT(VPKFileEntry)
 {
-	char* directory;
-	char* filename;
-	char* extension;
-	unsigned char unknown[0x38];
+    STRUCT_SIZE(0x44);
+    FIELDS(0x0, 
+          char* directory;
+          char* filename;
+          char* extension;
+        )
 };
+// clang-format on
 #pragma pack(pop)
 
 #pragma pack(push, 1)
+// clang-format off
 struct VPKData
 {
-	unsigned char unknown[5];
-	char path[255];
-	unsigned char unknown2[0x134];
-	int32_t numEntries;
-	unsigned char unknown3[12];
-	VPKFileEntry* entries;
+	STRUCT_SIZE(0x50);
+	FIELDS(0x0,
+		char* directory;
+		char* filename;
+		char* extension;
+	)
 };
+// clang-format on
 #pragma pack(pop)
 
 enum SearchPathAdd_t
diff --git a/NorthstarDLL/pch.h b/NorthstarDLL/pch.h
index e07c5598..824aaee8 100644
--- a/NorthstarDLL/pch.h
+++ b/NorthstarDLL/pch.h
@@ -20,6 +20,7 @@
 
 namespace fs = std::filesystem;
 
+#include "structs.h"
 #include "color.h"
 #include "spdlog/spdlog.h"
 #include "logging.h"
diff --git a/NorthstarDLL/r2engine.h b/NorthstarDLL/r2engine.h
index e428e1cc..2614b4cc 100644
--- a/NorthstarDLL/r2engine.h
+++ b/NorthstarDLL/r2engine.h
@@ -157,39 +157,17 @@ namespace R2
 		READY_REMOTE
 	};
 
-#pragma pack(push, 1)
-	struct CBaseClient // 0x2D728 bytes
+	// clang-format off
+	OFFSET_STRUCT(CBaseClient)
 	{
-		char pad0[0x16];
-
-		// +0x16
-		char m_Name[64];
-
-		// +0x56
-		char pad1[0x202];
-
-		KeyValues* m_ConVars; // this is a KeyValues* object but not got that struct mapped out atm
-
-		char pad2[0x240];
-
-		// +0x4A0
-		ePersistenceReady m_iPersistenceReady;
-		// +0x4A1
-
-		char pad3[0x59];
-
-		// +0x4FA
-		char m_PersistenceBuffer[PERSISTENCE_MAX_SIZE];
-
-		char pad4[0x1239];
-
-		// +0xF500
-		char m_UID[32];
-		// +0xF520
-
-		char pad5[0x1E208];
+		STRUCT_SIZE(0x2D728)
+		FIELD(0x16, char m_Name[64])
+		FIELD(0x258, KeyValues* m_ConVars)
+		FIELD(0x4A0, ePersistenceReady m_iPersistenceReady)
+		FIELD(0x4FA, char m_PersistenceBuffer[PERSISTENCE_MAX_SIZE])
+		FIELD(0xF500, char m_UID[32])
 	};
-#pragma pack(pop)
+	// clang-format on
 
 	extern CBaseClient* g_pClientArray;
 
diff --git a/NorthstarDLL/r2server.h b/NorthstarDLL/r2server.h
index 235dde7f..aadfdefe 100644
--- a/NorthstarDLL/r2server.h
+++ b/NorthstarDLL/r2server.h
@@ -9,22 +9,20 @@ namespace R2
 	class CBaseEntity;
 	extern CBaseEntity* (*Server_GetEntityByIndex)(int index);
 
-#pragma pack(push, 1)
-	struct CBasePlayer
+	// clang-format off
+	OFFSET_STRUCT(CBasePlayer)
 	{
-		char pad[0x58];
-		uint32_t m_nPlayerIndex;
+		STRUCT_SIZE(0x1D02);
+		FIELD(0x58, uint32_t m_nPlayerIndex)
 
-		// +0x5C
-		char pad1[0x1C34];
-		bool m_hasBadReputation; // 0x1C90
-		char m_communityName[64]; // 0x1C91
-		char m_communityClanTag[16]; // 0x1CD1
-		char m_factionName[16]; // 0x1CE1
-		char m_hardwareIcon[16]; // 0x1CF1
-		bool m_happyHourActive; // 0x1D01
+		FIELD(0x1C90, bool m_hasBadReputation)
+		FIELD(0x1C91, char m_communityName[64])
+		FIELD(0x1CD1, char m_communityClanTag[16])
+		FIELD(0x1CE1, char m_factionName[16])
+		FIELD(0x1CF1, char m_hardwareIcon[16])
+		FIELD(0x1D01, bool m_happyHourActive)
 	};
-#pragma pack(pop)
+	// clang-format on
 
 	extern CBasePlayer*(__fastcall* UTIL_PlayerByIndex)(int playerIndex);
 } // namespace R2
diff --git a/NorthstarDLL/structs.h b/NorthstarDLL/structs.h
new file mode 100644
index 00000000..939fd302
--- /dev/null
+++ b/NorthstarDLL/structs.h
@@ -0,0 +1,63 @@
+#pragma once
+//clang-format off
+// About this file:
+// This file contains several macros used to define reversed structs
+// The reason we use these macros is to make it easier to update existing structs
+// when new fields are reversed
+// This means we dont have to manually add padding, and recalculate when updating
+
+// Technical note:
+// While functionally, these structs act like a regular struct, they are actually
+// defined as unions with anonymous structs in them.
+// This means that each field is essentially an offset into a union.
+// We acknowledge that this goes against C++'s active-member guideline for unions
+// However, this is not such a big deal here as these structs will not be constructed
+
+// Usage:
+// To use these macros, define a struct like so:
+/*
+OFFSET_STRUCT(Name)
+{
+	STRUCT_SIZE(0x100)		// Total in-memory struct size
+	FIELD(0x0, int field)	// offset, signature
+}
+*/
+
+#define OFFSET_STRUCT(name) union name
+#define STRUCT_SIZE(size) char __size[size];
+#define STRUCT_FIELD_OFFSET(offset, signature)                                                                                             \
+	struct                                                                                                                                 \
+	{                                                                                                                                      \
+		char CONCAT2(pad, __LINE__)[offset];                                                                                               \
+		signature;                                                                                                                         \
+	};
+
+// Special case for a 0-offset field
+#define STRUCT_FIELD_NOOFFSET(offset, signature) signature;
+
+// Based on: https://stackoverflow.com/questions/11632219/c-preprocessor-macro-specialisation-based-on-an-argument
+// Yes, this is hacky, but it works quite well actually
+// This basically makes sure that when the offset is 0x0, no padding field gets generated
+#define OFFSET_0x0 ()
+
+#define IIF(c) CONCAT2(IIF_, c)
+#define IIF_0(t, ...) __VA_ARGS__
+#define IIF_1(t, ...) t
+
+#define PROBE(x) x, 1
+
+#define MSVC_VA_ARGS_WORKAROUND(define, args) define args
+#define CHECK(...) MSVC_VA_ARGS_WORKAROUND(CHECK_N, (__VA_ARGS__, 0))
+#define CHECK_N(x, n, ...) n
+
+#define DO_PROBE(offset) PROBE_PROXY(OFFSET_##offset) // concatenate prefix with offset
+#define PROBE_PROXY(...) PROBE_PRIMITIVE(__VA_ARGS__) // expand arguments
+#define PROBE_PRIMITIVE(x) PROBE_COMBINE_##x // merge
+#define PROBE_COMBINE_(...) PROBE(~) // if merge successful, expand to probe
+
+#define IS_0(offset) CHECK(DO_PROBE(offset))
+
+#define FIELD(offset, signature) IIF(IS_0(offset))(STRUCT_FIELD_NOOFFSET, STRUCT_FIELD_OFFSET)(offset, signature)
+#define FIELDS FIELD
+
+//clang-format on