Define Missing MLTYPE Parameter

hello,

i try to call several c/c++ function in a library and have a problem with **void output parameter.

This is the description of the c++ function :

Prototype

int32_t ME100_API ME3_acquireImage(DET_t det, void **dataBuffer, uint32_t *dataSize void **inputsBuffer, uint32_t *inputsSize);

Parameters

• In – det: handle to the detector.
• Out – databuffer: handle to memory allocated by API that stores the lines acquired.
• Out – dataSize: size of allocated buffer.
• Out – inputsBuffer: handle to memory allocated by API that stores the sub-D9 inputs.
• Out – inputsSize: size of allocated buffer.

After using the "clibgen.generateLibraryDefinition" function, i need to missing MLTYPE parameter for this function :

This is what i got for this function :

C++ function ME3_acquireImage with MATLAB name clib.ME100.ME3_acquireImage

C++ Signature: int32_t ME3_acquireImage(DET_t det,void * * dataBuffer,uint32_t * dataSize,void * * inputsBuffer,uint32_t * inputsSize)

%ME3_acquireImageDefinition = addFunction(libDef, ...

% "int32_t ME3_acquireImage(DET_t det,void * * dataBuffer,uint32_t * dataSize,void * * inputsBuffer,uint32_t * inputsSize)", ...

% "MATLABName", "clib.ME100.ME3_acquireImage", ...

% "Description", "clib.ME100.ME3_acquireImage Representation of C++ function ME3_acquireImage." + newline + ...

% "Acquire an image. Must be called between ME3_prepareAcquisition and ME3_unPrepareAcquisition." + newline + ...

% "MUST�NOT�BE�USED when MEDET_startAcquisition has been called", ...

% "DetailedDescription", "This content is from the external library documentation."); % Modify help description values as needed.

%defineArgument(ME3_acquireImageDefinition, "det", "clib.ME100.ME100_base", "input", <SHAPE>, "Description", "[in] det concerned detector");

%defineArgument(ME3_acquireImageDefinition, "dataBuffer", <MLTYPE>, "output", 1, "Description", "[in] buffer memory to store acquired lines"); % <MLTYPE> can be an existing typedef name for void* or a new typedef name to void*.

%defineArgument(ME3_acquireImageDefinition, "dataSize", "clib.array.ME100.UnsignedInt", "input", <SHAPE>, "Description", "[in] size size of buffer, in bytes."); % <MLTYPE> can be "clib.array.ME100.UnsignedInt", or "uint32"

%defineArgument(ME3_acquireImageDefinition, "inputsBuffer", <MLTYPE>, "output", 1); % <MLTYPE> can be an existing typedef name for void* or a new typedef name to void*.

%defineArgument(ME3_acquireImageDefinition, "inputsSize", "clib.array.ME100.UnsignedInt", "input", <SHAPE>); % <MLTYPE> can be "clib.array.ME100.UnsignedInt", or "uint32"

%defineOutput(ME3_acquireImageDefinition, "RetVal", "int32", "Description", "ME_SUCCESS on success, after the image has been acquired.");

%validate(ME3_acquireImageDefinition);

How to define in particular the output parameter "dataBuffer" which is define as a void** in C library and should give the buffer of an 2Dimage ?

This is what i tried :

ME3_acquireImageDefinition = addFunction(libDef, ...

"int32_t ME3_acquireImage(DET_t det,void * * dataBuffer,uint32_t * dataSize,void * * inputsBuffer,uint32_t * inputsSize)", ...

"MATLABName", "clib.ME100.ME3_acquireImage", ...

"Description", "clib.ME100.ME3_acquireImage Representation of C++ function ME3_acquireImage." + newline + ...

"Acquire an image. Must be called between ME3_prepareAcquisition and ME3_unPrepareAcquisition." + newline + ...

"MUST�NOT�BE�USED when MEDET_startAcquisition has been called", ...

"DetailedDescription", "This content is from the external library documentation."); % Modify help description values as needed.

defineArgument(ME3_acquireImageDefinition, "det", "clib.ME100.ME100_base", "input", 1, "Description", "[in] det concerned detector");

defineArgument(ME3_acquireImageDefinition, "dataBuffer", "uint32", "output", "dataSize", "Description", "[in] buffer memory to store acquired lines"); % <MLTYPE> can be an existing typedef name for void* or a new typedef name to void*.

defineArgument(ME3_acquireImageDefinition, "dataSize", "uint32", "output", 1, "Description", "[in] size size of buffer, in bytes."); % <MLTYPE> can be "clib.array.ME100.UnsignedInt", or "uint32"

defineArgument(ME3_acquireImageDefinition, "inputsBuffer", "uint32", "output", "inputsSize"); % <MLTYPE> can be an existing typedef name for void* or a new typedef name to void*.

defineArgument(ME3_acquireImageDefinition, "inputsSize", "uint32", "output", 1); % <MLTYPE> can be "clib.array.ME100.UnsignedInt", or "uint32"

defineOutput(ME3_acquireImageDefinition, "RetVal", "int32", "Description", "ME_SUCCESS on success, after the image has been acquired.");

validate(ME3_acquireImageDefinition);

Building the library give the following error:

>> build(defineME100)

Error using defineME100

Invalid MATLABType specified for argument 'dataBuffer'.

Expected type is one of the following: an existing typedef

name for void* or a new typedef name for void*.

Can you help please?

Thank you

Philippe

Answer 1

[Abhishek Chakram]

Hi philippe duvauchelle,

When working with MATLAB's C/C++ integration features, defining the correct types for interfacing with C/C++ functions is crucial. In your case, the “dataBuffer” parameter is defined as a “void**” in C, which means it is a pointer to a pointer. This is often used in C APIs to allow the function to allocate memory and pass back a pointer to this memory to the caller.

In MATLAB, you'll need to define a new type that corresponds to “void*” and then use that type for “dataBuffer” and “inputsBuffer”. Here is how to do it:

• Define a new type for “void*” using “ addOpaqueType” with a MATLAB type that can hold a pointer. Since MATLAB does not directly support “void*”, you typically use a numeric type like “uint64” to represent it.
• Use this new type for “dataBuffer” and “inputsBuffer” in “defineArgument”.

Here is an example for the same:

% Define a new type for void*, using uint64 as a stand-in
addOpaqueType(libDef, "Name", "voidPtr", "MATLABType", "uint64", "Description", "Pointer type");

% Define the dataBuffer and inputsBuffer arguments using the new type
defineArgument(ME3_acquireImageDefinition, "dataBuffer", "voidPtr", "output", 1, "Description", "[out] dataBuffer    Memory allocated by API to store acquired lines");
defineArgument(ME3_acquireImageDefinition, "inputsBuffer", "voidPtr", "output", 1, "Description", "[out] inputsBuffer  Memory allocated by API to store the sub-D9 inputs");

You can refer to the following documentation to know more about the functions used:

• Define void* and void** Arguments: https://in.mathworks.com/help/matlab/matlab_external/use-void-arguments.html
• defineArgument: https://www.mathworks.com/help/matlab/ref/clibgen.methoddefinition.defineargument.html
• Define Missing MLTYPE Parameter: https://www.mathworks.com/help/matlab/matlab_external/define-missing-mltype-parameter.html
• C++ to MATLAB Data Type Mapping: https://www.mathworks.com/help/matlab/matlab_external/matlab-to-c-data-type-mapping.html
• addOpaqueType: https://in.mathworks.com/help/matlab/ref/clibgen.librarydefinition.addopaquetype.html

Best Regards,

Abhishek Chakram