pattern: Add lua 4.0 pattern (#465)

* add lua 4.0 pattern

* fix offset the top level function is at

* Update README.md

---------

Co-authored-by: Nik <werwolv98@gmail.com>

README.md

@@ -111,6 +111,7 @@ Everything will immediately show up in ImHex's Content Store and gets bundled wi
 | JPEG | `image/jpeg` | [`patterns/jpeg.hexpat`](patterns/jpeg.hexpat) | JPEG Image Format |
 | KTX | `image/ktx` | [`patterns/ktx.hexpat`](patterns/ktx.hexpat) | Khronos TeXture 1.0 |
 | LOC | | [`patterns/loc.hexpat`](patterns/loc.hexpat) | Minecraft Legacy Console Edition Language file |
+| Lua 4.0 | | [`patterns/lua40.hexpat`](patterns/lua40.hexpat) | Lua 4.0 bytecode |
 | LUC | | [`patterns/popcap_luc.hexpat`](patterns/popcap_luc.hexpat) | PopCap's proprietary Lua bytecode |
 | Lua 5.1 | | [`patterns/lua51.hexpat`](patterns/lua51.hexpat) | Lua 5.1 bytecode |
 | Lua 5.2 | | [`patterns/lua52.hexpat`](patterns/lua52.hexpat) | Lua 5.2 bytecode |

patterns/lua40.hexpat

@@ -0,0 +1,133 @@
+#pragma description Lua 4.0 bytecode
+#pragma magic [ 1B 4C 75 61 40 ] @ 0x00
+// based off of https://www.lua.org/source/4.0/dump.c.html
+
+import std.io;
+
+namespace impl {
+    fn format_LuaString(auto string) {
+       if (string.size == 0) {
+           return "None";
+        }
+        return std::format("\"{}\"", string.data);
+    };
+
+    fn format_Version(auto ver) {
+       return std::format("Ver. {}.{}", ver.major, ver.minor);
+    };
+}
+using LuaFunction;
+
+bitfield Version {
+    minor : 4;
+    major : 4;
+} [[format("impl::format_Version")]];
+
+struct LuaBinaryHeader {
+    u8 id_chunk;
+    char magic[3];       
+    Version version;
+    u8 endianness;
+    u8 size_of_int;
+    u8 size_of_size_t;
+    u8 size_of_instruction; // ???
+    u8 size_INSTRUCTION;      // SIZE_INSTRUCTION in Lua 4 source
+    u8 size_OP;          // SIZE_OP
+    u8 size_B;           // SIZE_B
+    u8 size_number;      // sizeof(Number)
+    
+    if (size_number == 4) {
+        u32 TEST_NUMBER;
+    } else {
+        u64 TEST_NUMBER;
+    }
+};
+
+LuaBinaryHeader header @ 0;
+
+struct LuaString {
+    if (header.size_of_size_t == 4) {
+        u32 size;
+    } else {
+        u64 size;
+    }
+    
+    if (size > 0) {
+        char data[size];
+    }
+}[[format("impl::format_LuaString")]];
+
+struct Vector<T> {
+    if (header.size_of_int == 4) {
+        u32 size;
+    } else {
+        u64 size;
+    }
+    if (size > 0) {
+        T values[size];
+    }
+};
+
+struct LocalVar {
+    LuaString varname;
+    if (header.size_of_int == 4) {
+        u32 startpc;
+        u32 endpc;
+    } else {
+        u64 startpc;
+        u64 endpc;
+        
+    }
+};
+
+struct LuaDebugInfo {
+    Vector<LocalVar> localVar;
+    if (header.size_of_int == 4) {
+        Vector<u32> lineInfo;     // i think this is correct
+    } else {
+        Vector<u64> lineInfo;
+    }
+
+};
+
+bitfield LuaNumber {
+    raw : header.size_number;
+};
+
+struct LuaConstants{
+    Vector<LuaString> stringConstants;
+    if (header.size_of_int == 4) {
+        Vector<u32> intConstants;
+    } else {
+        Vector<u64> intConstants;
+    }
+    Vector<LuaFunction> protos;    
+};
+
+struct LuaFunction {
+    LuaString source;
+    if (header.size_of_int == 4) {
+        u32 linedefined;
+        u32 numparams;    
+    } else {
+        u64 linedefined;
+        u64 numparams;   
+    }
+    u8 is_vararg;
+    
+    if (header.size_of_int == 4) {
+        u32 maxstacksize;
+    } else {
+        u64 maxstacksize;
+    }
+    
+    LuaDebugInfo debugInfo;
+    LuaConstants luaConstants;
+    if (header.size_of_int == 4) {
+        Vector<u32> code;
+    } else {
+        Vector<u64> code;
+    }
+};
+
+LuaFunction toplevelFunction @ sizeof(header);; // Lua header size is not always the same