DPI import C function pass by reference to int array

[marco5polo]

My system verification makes use of C function for some processing calculation. The C function needs to pass in a pointer of integer array, where the result will be calculated. Can you show me an example how it could be done? I want to print out the result calculated by my_lib_cal(). There's not much literature about how to implement pass by reference.

Here's how to C function looks like:

void my_lib_cal(int * out, int size)

Here's how I import the fnction intp my SV environment and execute them.

import "DPI-C" function void my_lib_cal(int out[9:0], int size);

initial begin
int result[9:0];
int cycle=24;

int (int i=0; i<cycle; i++) begin
  my_lib_cal(result,10);
  for (int j=0; j<10; j++) begin
    $display("%d",result[j]);
  end
end

end

 

[RCircuit]

So, did you mean your code doesn't work? The array in c side can be definedas svOpenArrayHandle, and RTL side should be defined as inout

 

[dave_59]

Obviously you never tried to compile this code. If you use ModelSim/Questa, always use the -dpiheader switch to create the C prototypes needed for your C code.

module top;

import "DPI-C" function void my_lib_cal(output int out[9:0], input int size);

int result[9:0];
int cycle=24;
initial begin

for (int i=0; i<cycle; i++) begin
  my_lib_cal(result,10);
  for (int j=0; j<10; j++) begin
    $display("%d",result[j]);
  end
end

end
endmodule

the vlog -dpiheader switch will produce

DPI_LINK_DECL DPI_DLLESPEC
void
my_lib_cal(
    int* out,
    int size);

The C side thinks it is has an array of ints, but the SV side uses copy value semantics. Use an output or inout argument on the SV side.