/// <summary>
/// Generate a new DynamicMethod with which you can invoke the previous state.
/// If the NativeDetour holds a reference to a managed method, a copy of the original method is returned.
/// If the NativeDetour holds a reference to a native function, an "undo-call-redo" trampoline with a matching signature is returned.
/// </summary>
public MethodBase GenerateTrampoline(MethodBase signature = null)
{
MethodBase remoteTrampoline = OnGenerateTrampoline?.InvokeWhileNull <MethodBase>(this, signature);
if (remoteTrampoline != null)
{
return(remoteTrampoline);
}
if (_IsFree)
{
throw new InvalidOperationException("Free() has been called on this detour.");
}
if (_BackupMethod != null)
{
// If we're detouring an IL method and have an IL copy, invoke the IL copy.
// Note that this ignores the passed signature.
return(_BackupMethod);
}
/*
* if (signature == null)
* signature = _BackupMethod;
*/
if (signature == null)
{
throw new ArgumentNullException("A signature must be given if the NativeDetour doesn't hold a reference to a managed method.");
}
// Otherwise, undo the detour, call the method and reapply the detour.
MethodBase methodCallable = Method;
if (methodCallable == null)
{
methodCallable = DetourHelper.GenerateNativeProxy(Data.Method, signature);
}
Type returnType = (signature as MethodInfo)?.ReturnType ?? typeof(void);
ParameterInfo[] args = signature.GetParameters();
Type[] argTypes = new Type[args.Length];
for (int i = 0; i < args.Length; i++)
{
argTypes[i] = args[i].ParameterType;
}
using (DynamicMethodDefinition dmd = new DynamicMethodDefinition(
$"Trampoline:Native<{Method?.GetFindableID(simple: true) ?? ((long) Data.Method).ToString("X16")}>?{GetHashCode()}",
returnType, argTypes
)) {
ILProcessor il = dmd.GetILProcessor();
ExceptionHandler eh = new ExceptionHandler(ExceptionHandlerType.Finally);
il.Body.ExceptionHandlers.Add(eh);
il.EmitDetourCopy(_BackupNative, Data.Method, Data.Type);
// Store the return value in a local as we can't preserve the stack across exception block boundaries.
VariableDefinition localResult = null;
if (returnType != typeof(void))
{
il.Body.Variables.Add(localResult = new VariableDefinition(il.Import(returnType)));
}
// Label blockTry = il.BeginExceptionBlock();
int instriTryStart = il.Body.Instructions.Count;
for (int i = 0; i < argTypes.Length; i++)
{
il.Emit(OpCodes.Ldarg, i);
}
if (methodCallable is MethodInfo)
{
il.Emit(OpCodes.Call, (MethodInfo)methodCallable);
}
else if (methodCallable is ConstructorInfo)
{
il.Emit(OpCodes.Call, (ConstructorInfo)methodCallable);
}
else
{
throw new NotSupportedException($"Method type {methodCallable.GetType().FullName} not supported.");
}
if (localResult != null)
{
il.Emit(OpCodes.Stloc, localResult);
}
il.Emit(OpCodes.Leave, (object)null);
Instruction instrLeave = il.Body.Instructions[il.Body.Instructions.Count - 1];
// il.BeginFinallyBlock();
int instriTryEnd = il.Body.Instructions.Count;
int instriFinallyStart = il.Body.Instructions.Count;
// Reapply the detour even if the method threw an exception.
il.EmitDetourApply(Data);
// il.EndExceptionBlock();
int instriFinallyEnd = il.Body.Instructions.Count;
Instruction instrLeaveTarget = null;
if (localResult != null)
{
il.Emit(OpCodes.Ldloc, localResult);
instrLeaveTarget = il.Body.Instructions[il.Body.Instructions.Count - 1];
}
il.Emit(OpCodes.Ret);
instrLeaveTarget = instrLeaveTarget ?? il.Body.Instructions[il.Body.Instructions.Count - 1];
instrLeave.Operand = instrLeaveTarget;
// TODO: Are the exception handler indices correct?
eh.TryStart = il.Body.Instructions[instriTryStart];
eh.TryEnd = il.Body.Instructions[instriTryEnd];
eh.HandlerStart = il.Body.Instructions[instriTryEnd];
eh.HandlerEnd = il.Body.Instructions[instriFinallyEnd];
return(dmd.Generate().Pin());
}
}