CfExecute function usage

Diakov Dmytro 1

Hi!
I am using CfExecute function in my .Net Core application.
For this purpose I have marshalled it this way:

[DllImport(Lib.CldApi, SetLastError = false, ExactSpelling = true)]
[PInvokeData("cfapi.h", MSDNShortId = "6AC8958D-B060-4468-9811-9BAB0E6A06D3")]
public static extern HRESULT CfExecute(in CF_OPERATION_INFO OpInfo, ref CF_OPERATION_PARAMETERS OpParams);

I have noticed that it does not working correctly with arrays. When I am trying to pass an array of placeholders to it I got memory corrupt error.

var transferPlaceholders = new CF_OPERATION_PARAMETERS.TRANSFERPLACEHOLDERS();
            transferPlaceholders.CompletionStatus = completionStatus;
            transferPlaceholders.PlaceholderArray = Marshal.AllocHGlobal(Marshal.SizeOf(typeof(CF_PLACEHOLDER_CREATE_INFO)) * aPlaceholders.Length);
            transferPlaceholders.PlaceholderArray.Write<CF_PLACEHOLDER_CREATE_INFO>(aPlaceholders, 0, Marshal.SizeOf(typeof(CF_PLACEHOLDER_CREATE_INFO)) * aPlaceholders.Length);
            transferPlaceholders.PlaceholderCount = (uint)aPlaceholders.Length;
            transferPlaceholders.PlaceholderTotalCount = (uint)aPlaceholders.Length;
            transferPlaceholders.Flags = flags;

var opParams = CF_OPERATION_PARAMETERS.Create<CF_OPERATION_PARAMETERS.TRANSFERPLACEHOLDERS>(transferPlaceholders);

var opInfo = new CF_OPERATION_INFO()
            {
                StructSize = (uint)Marshal.SizeOf<CF_OPERATION_INFO>(),
                Type = operationType,
                ConnectionKey = CallbackInfo.ConnectionKey,
                TransferKey = CallbackInfo.TransferKey,
                RequestKey = CallbackInfo.RequestKey,
                CorrelationVector = CallbackInfo.CorrelationVector
                //SyncStatus = IntPtr.Zero
            };

            ThrowIfError(CfExecute(opInfo, ref opParams));

Is there any advices how to fix it ?
Thanks

Drake Wu - MSFT 991 Reputation points

2020-11-18T03:21:43.403+00:00

Hi,@Diakov Dmytro How do you define the CF_OPERATION_PARAMETERS structure, do you initialize CF_OPERATION_PARAMETERS.ParamSize? Also notice that the assignment type of PlaceholderTotalCount is uint (4 bytes), and the original type in win32 is LARGE_INTEGER (usually 8 bytes). You can use type long instead. And how do you implement Write and Create Method? This will help us to solve the problem.

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Diakov Dmytro 1 Reputation point

2020-11-18T12:53:58.987+00:00

Hi, @Drake Wu - MSFT
My CF_OPERATION_PARAMETERS looks this way: https://justpaste.it/933bs
Param size initialized this way: var op = new CF_OPERATION_PARAMETERS { ParamSize = CF_SIZE_OF_OP_PARAM<T>() };
Problem appears when I am trying to execute TransferPlaceholders operation and passing array with more then one item in it.

Diakov Dmytro 1

@Drake Wu - MSFT Also Create method:

public static CF_OPERATION_PARAMETERS Create<T>(T paramValue = default) where T : struct  
			{  
				var op = new CF_OPERATION_PARAMETERS { ParamSize = CF_SIZE_OF_OP_PARAM<T>() };  
				op.SetParam(paramValue);  
				return op;  
			}

Drake Wu - MSFT 991 Reputation points

2020-11-19T07:20:42.92+00:00

Hi,@Diakov Dmytro Ok, the problem may appear in PlaceholderArray.Write, how do you implement this method? The 3rd parameter you use should probably be the number of elements in the array. Could you try the method(call Marshal.StructureToPtr in a loop) in this example to fill the array into a pointer? Also there is a usage on github you could refer to: https://github.com/legsak1mbo/CSMirrorCloud/blob/master/FakeCloudProvider.cs#L253 (This whole sample has a BUG that calls CF_CALLBACK_TYPE_FETCH_PLACEHOLDERS cyclically, but CfExecute returns S_OK correctly even if count> 1, you can only refer to the CfExecute usage part)

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