Passing Structure Example

DPI allows to pass the structs and Unions . This can be done by passing pointers or by packing.

In the following example, a "struct" is passed from SystemVerilog to C and also from C to Systemverilog using import and export functions.

While passing the "struct" data type, the data is packed in to array and passed from SV to C and then the array is decoded back to Struct in C. The same when the Struct is passed from C to SystemVerilog.

CODE: C_file.c

#include "stdio.h"

#include "vc_hdrs.h"

#include "svdpi.h"

extern "C" {

typedef struct{

int a;

int b;

char c;

} C_struct;

extern void export_func(svBitVec32 x[3] );

void import_func()

{

C_struct s_data;

unsigned int arr[3];

s_data.a = 51;

s_data.b = 242;

s_data.c = 35;

printf( "C : s_data.a = %d\n", s_data.a );

printf( "C : s_data.b = %d\n", s_data.b );

printf( "C : s_data.c = %d\n\n", s_data.c );

arr[0] = s_data.a ;

arr[1] = s_data.b ;

arr[2] = s_data.c ;

export_func(arr);

}

}

CODE: SV_file.sv

program main;

export "DPI-C" function export_func;

import "DPI-C" function void import_func();

typedef struct packed{

int a;

int b;

byte c;

} SV_struct;

function void export_func(input int arr[3]);

SV_struct s_data;

s_data.a = arr[0];

s_data.b = arr[1];

s_data.c = arr[2];

$display("SV: s_data.a = %0d", s_data.a );

$display("SV: s_data.b = %0d", s_data.b );

$display("SV: s_data.c = %0d \n", s_data.c );

endfunction

initial

begin

import_func();

end

endprogram

RESULTS:

C : s_data.a = 51

C : s_data.b = 242

C : s_data.c = 35

SV: s_data.a = 51

SV: s_data.b = 242

SV: s_data.c = 35

Passing Openarray Structs

CODE: C_file.c

#include "svdpi.h"

typedef struct {int p; int q} PkdStru;

void send2c(const svOpenArrayHandle dyn_arr)

{

int i;

PkdStru Sele;

printf("\n \n Array Left %d, Array Right %d \n\n", svLeft(dyn_arr,1), svRight(dyn_arr, 1) );

for (i= svLeft(dyn_arr,1); i <= svRight(dyn_arr,1); i++) {

Sele = *(PkdStru*)svGetArrElemPtr1(dyn_arr, i);

printf("C : %d : [%d,%d]\n",i, Sele.q,Sele.p );

}

printf("\n\n");

}

CODE: SV_file.sv

program open_array_struct ();

typedef struct packed { int p; int q; } PkdStru;

import "DPI-C" function void send2c (input PkdStru arr []);

PkdStru arr_data [0:4];

initial begin

foreach (arr_data[i]) begin

arr_data[i] = {$random,$random};

$display("SV: %0d : [%0d,%0d]",i,arr_data[i].p,arr_data[i].q);

end

send2c(arr_data);

end

endprogram

RESULTS:

SV: 0 : [303379748,-1064739199]

SV: 1 : [-2071669239,-1309649309]

SV: 2 : [112818957,1189058957]

SV: 3 : [-1295874971,-1992863214]

SV: 4 : [15983361,114806029]

Array Left 0, Array Right 4

C : 0 : [303379748,-1064739199]

C : 1 : [-2071669239,-1309649309]

C : 2 : [112818957,1189058957]

C : 3 : [-1295874971,-1992863214]

C : 4 : [15983361,114806029]

Passing Union Example

CODE:SV_file

module m;

typedef bit [2:0] A;

typedef union packed { A a; S s; } U;

U u;

A a;

// Import function takes three arguments

import "DPI-C" function void foo8(input A fa, input U fu);

initial begin

a = 3'b100;

u.a = 3'b100;

foo8(a, u);

end

endmodule

CODE:C_file

#include "svdpi.h"

void foo8(

const svBitVecVal* fa,

const svBitVecVal* fu)

{

printf("fa is %d, fu is %d\n", *fa, *fu);

}