private static Func <IAsyncStateMachine, Task> CompileGetCompletionTaskFunc(AsyncStateMachineMetadata metadata)
{
var stateMachineArg = Expression.Variable(typeof(IAsyncStateMachine), "sm");
var stateMachine = Expression.Convert(stateMachineArg, metadata.StateMachineType);
var accessBuilder = Expression.MakeMemberAccess(stateMachine, metadata.Builder.FieldInfo);
var taskProperty = metadata.Builder.FieldInfo.FieldType.GetProperty(nameof(AsyncTaskMethodBuilder.Task));
var getTask = Expression.MakeMemberAccess(accessBuilder, taskProperty);
var lambda = Expression.Lambda(getTask, stateMachineArg);
return((Func <IAsyncStateMachine, Task>)lambda.Compile());
}
public IAsyncStateMachineAccessor Create(AsyncStateMachineMetadata metadata)
{
lock (_accessorMap)
{
if (!_accessorMap.TryGetValue(metadata, out var accessor))
{
accessor = new AsyncStateMachineAccessor(metadata);
_accessorMap.Add(metadata, accessor);
}
return(accessor);
}
}
private static Func <IAsyncStateMachine> CompileCreateInstanceFunc(AsyncStateMachineMetadata metadata)
{
var stateMachine = Expression.Variable(metadata.StateMachineType, "sm");
var newInstance = Expression.New(metadata.StateMachineType);
var newStateMachine = Expression.Assign(stateMachine, newInstance);
var newBuilder = Expression.Call(null, metadata.Builder.FieldInfo.FieldType.GetMethod(nameof(AsyncTaskMethodBuilder.Create)));
var setBuilder = Expression.Assign(Expression.MakeMemberAccess(stateMachine, metadata.Builder.FieldInfo), newBuilder);
var setState = Expression.Assign(Expression.MakeMemberAccess(stateMachine, metadata.State.FieldInfo), Expression.Constant(-1));
var funcBody = Expression.Block(new[] { stateMachine }, newStateMachine, setBuilder, setState, Expression.Convert(stateMachine, typeof(IAsyncStateMachine)));
var lambda = Expression.Lambda(funcBody);
return((Func <IAsyncStateMachine>)lambda.Compile());
}
public AsyncStateMachineAccessor(AsyncStateMachineMetadata metadata)
{
_createInstanceFunc = CompileCreateInstanceFunc(metadata);
_getCompletionTaskFunc = CompileGetCompletionTaskFunc(metadata);
}