P/Invoke and CIL functions in COM objects, C/C++ DLLs, etc. E.g. - PDF document

2/15/2008 P/Invoke  Allows managed code to call unmanaged P/Invoke and CIL functions in COM objects, C/C++ DLLs, etc.  E.g. access to Win32 API Mingsheng Hong  To declare unmanaged functions CS 215, Spring 2008  Use DllImport attribute and static extern [DllImport(“kernel32.dll”)] static extern int GetProcessHeap(); P/Invoke Example Steps in P/Invoke using System.Runtime.InteropServices;  Locates implementing DLL namespace HelloWorld { class MyClass {  Loads DLL into memory [DllImport (“user32.dll”, CharSet=CharSet.Ansi)] static extern int MessageBox(int hwnd,  Finds function address string msg, string caption, int t);  Pushes arguments on stack, marshalling data public static void Main() {  Transfers control to unmanaged code MessageBox(0, "Hello World!", "Caption", 0); } } } P/Invoke Callbacks Callback Example public class SampleClass {  Unmanaged code can call back to managed delegate bool CallBack(int hwnd, int lParam); code Unmanaged parameter is function pointer [DllImport("user32.dll")]  static extern int EnumWindows(CallBack x, int lParam); In managed code, must supply parameter as delegate  P/Invoke creates callback thunk  // report the window handle  Passes address of thunk as callback parameter public bool Report(int hwnd, int lParam) { Console.Write(“Window handle is ” + hwnd); Unmanaged Code Managed Code return true; } .NET Application DLL Call passes pointer to public static void Main() { DLL function callback function CallBack myCallBack = new CallBack(Report); EnumWindows(myCallBack, 0); Implementation of callback } function } 1

2/15/2008 C++/CLI CIL  Write managed C++ code  Recall: two stage compilation  compile with /clr  C# compiler: C# code  CIL code  Just-in-time (JIT) compiler: CIL  native code  generates CIL from C++  new key words  Common Intermediate Language  __gc, __box, __typeof, __interface, __property  very close to C# (and other OO languages)  #pragma managed/unmanaged  define classes, structs, inheritance, methods  Very useful for native access to C++ libraries  assembly-like statements  build a “managed wrapper” CIL Hello World Example .assembly extern mscorlib {} //automatically added  Stack language .assembly hello {} Compile with  instead of registers, everything is from stack ilasm /exe /debug hello.il .class Program { .method static public void Main() cil managed {  main operations take operands from stack .entrypoint //designates this method as the entry pt  e.g. .locals init (string name) //create a local var int i = 137; 138 137 1 ldstr “World" //load the string onto eval stack 137 int j = 1; stloc.0 //store the string into the first local var int k = i + j; ldstr "Hello, {0}!" ldloc name //load local var onto eval stack call void [mscorlib] System.Console::WriteLine( string, object) //call method with stack items as params ret } } CIL Directives Load/Store Operations  .assembly  ldloc / stloc  pushes contents of local var (or index) onto stack  . class  pops and stores in local var (or index)  define any type  ldc  extends: extend some other type  ldc.i4 50000  if extend System.ValueType , then value type  ldc.i4.1  . method, .field, .property, .event  ldc.i4.m1  .locals: names and types for local vars  ldnull  . entrypoint  ldfld / stfld  .maxstack  ldsfld int32 A::fielda 2

2/15/2008 Load/Store Example CIL Operations .locals init ([1] int32 a, [0] int32 b)  Integer operations ldc.i4.5  add, mul, sub, div, rem, neg stloc.0 ldc.i4 10  Boxing stloc.1  removes the value type from stack ldloc a  creates an object on the managed heap that call void [mscorlib] boxes the value type System.Console::WriteLine(int32)  places a reference to the newly created object ldloc b back on the evaluation stack call void [mscorlib]  e.g. ldc.i4.3 System.Console::WriteLine(int32) box int32  Data type conversions: conv.* CIL Operations Control Flow Operations  ceq/cgt/clt  Construct objects  newobj instance void A::.ctor()  pop top two elements of stack  check =, >, <  Invoke functions call void [mscorlib]  push true or false onto stack  System.Console::WriteLine(string, object)  br/beq/bne/bgt/blt/brfalse/brtrue call instance int32 A::F()  callvirt instance int32 A::G()  do the comparison and jump   use to implement structured control flow Control Flow Example CIL Tools ldc.i4.3 CIL ldc.i4.1 binary cgt brtrue greater C# C# compiler ILDASM ILASM Native code ldstr "{0} is less than or equal {1}" code br end CIL textual greater: ldstr "{0} is greater than {1}" end: ldc.i4.3  Roundtripping box int32 ldc.i4.1  ildasm /out=new_program.il program.exe box int32  Edit the CIL code in new_program.il call void [mscorlib]  ilasm newadd.il System.Console::WriteLine(string, object, object) 3