MATLAB: How to call a C# function, foo(out byte [])? — help passing a byte pointer

c# function pointerlibpointer

Been struggling to call the following function in a C# dll:
public bool GetLatestBuffer(out byte[] buffer)
I've allocated the buffer in Matlab and tried various castings with libpointer, but keep getting the result:
No method 'GetLatestBuffer' with matching signature found for class ...
I could write a wrapper in C# that allocates the buffer … but would rather do the memory management in Matlab.
My pseudocode is basically:
   NET.addAssembly(dllLoc)
   ls = luma_ns.Luma(initParams);
   ls.function1(params) % --> it works passing parameters by value
   buf = zeros(10000,'uint8'); % tried uint16, int16, etc.
   pbuf = libpointer('uint8Ptr',buf); 
   ls.GetLatestBuffer(pbuf) % doesn't match the prototype of out byte []
No method 'GetLatestBuffer' with matching signature found for class 'Luma_ns.Luma'.
Thanks!!

Best Answer

Hi,
have you tried calling it like this
[bool_val, byte_array] = obj.GetLatestBuffer();
This works fine for me in 14a with the following example
C#
            public bool GetLatestBuffer(out byte[] Buffer)
            {
                Buffer = new byte[10];
                for (int i = 0; i < 10;i++)
                {
                    Buffer[i] = (byte)i;
                }
                return true;
            }
ML:
>> a = ClassLibrary1.Class1
a = 
Class1 with no properties.
>> [bool,array] = a.GetLatestBuffer()
bool =
       1
array = 
Byte[] with properties:
            Length: 10
        LongLength: 10
              Rank: 1
          SyncRoot: [1x1 System.Byte[]]
        IsReadOnly: 0
       IsFixedSize: 1
    IsSynchronized: 0
>>
SideNote: The out keyword forces the routine GetLatestBuffer to assign Buffer to some value. So you do NOT need to pass down a preallocated array and since you dont need to do this it appears as output in MATLAB directly.
Also in C# when using OUT you never pass down a preallocated array. So what MATLAB does is correct here and matches the .NET programming.
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