Open Arrays

The size of the packed dimension, the unpacked dimension, or both dimensions can remain unspecified,such cases are referred to as open arrays (or unsized arrays). Open arrays allow the use of generic code to handle different sizes.

Formal arguments in SystemVerilog can be specified as open arrays solely in import declarations, exported. SystemVerilog functions cannot have formal arguments specified as open arrays.

OpenArrays are good for generic programming, since C language doesn't have concept of parameterizable arguments. Standared query and library functions are provided to determine array information to acess array elements.

EXAMPLE: open arrays

CODE:SV_file.sv

program main;

int fxd_arr_1[8:3];

int fxd_arr_2[12:1];

import "DPI-C" context function void pass_array(input int dyn_arr[] );

initial

begin

for (int i = 3; i<=8 ; i++)

begin

fxd_arr_1[i] = $random() ;

$display("SV:fxd_arr_1 %0d %d ",i, fxd_arr_1[i] );

end

$display("\n Passing fxd_arr_1 to C \n");

pass_array( fxd_arr_1 );

for (int i = 1; i<=12 ; i++)

begin

fxd_arr_2[i] = $random() ;

$display("SV: fxd_arr_2 %0d %d ",i, fxd_arr_2[i] );

end

$display("\n Passing fxd_arr_2 to C \n");

pass_array( fxd_arr_2 );

end

endprogram

CODE: C_file.c

#include

#include

void pass_array(const svOpenArrayHandle dyn_arr ) {

int i;

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

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

printf("C: %d %d \n", i, *(int*)svGetArrElemPtr1(dyn_arr, i) );

}

printf("\n\n");

}

RESULTS:

SV:fxd_arr_1 3 303379748

SV:fxd_arr_1 4 -1064739199

SV:fxd_arr_1 5 -2071669239

SV:fxd_arr_1 6 -1309649309

SV:fxd_arr_1 7 112818957

SV:fxd_arr_1 8 1189058957

Passing fxd_arr_1 to C

Array Left 8, Array Right 3

C: 3 303379748

C: 4 -1064739199

C: 5 -2071669239

C: 6 -1309649309

C: 7 112818957

C: 8 1189058957

SV: fxd_arr_2 1 -1295874971

SV: fxd_arr_2 2 -1992863214

SV: fxd_arr_2 3 15983361

SV: fxd_arr_2 4 114806029

SV: fxd_arr_2 5 992211318

SV: fxd_arr_2 6 512609597

SV: fxd_arr_2 7 1993627629

SV: fxd_arr_2 8 1177417612

SV: fxd_arr_2 9 2097015289

SV: fxd_arr_2 10 -482925370

SV: fxd_arr_2 11 -487095099

SV: fxd_arr_2 12 -720121174

Passing fxd_arr_2 to C

Array Left 12, Array Right 1

C: 1 -1295874971

C: 2 -1992863214

C: 3 15983361

C: 4 114806029

C: 5 992211318

C: 6 512609597

C: 7 1993627629

C: 8 1177417612

C: 9 2097015289

C: 10 -482925370

C: 11 -487095099

C: 12 -720121174

Packed Arrays

A packed array is represented as an array of one or more elements (of type svBitVecVal for 2-state values and svLogicVecVal for 4-state values), each element representing a group of 32 bits.

CODE:SV_file.sv

program main;

import "DPI-C" function void get_nums(output logic [15:0] nums[10]);

logic [15:0] nums[10];

initial begin

get_nums(nums);

foreach (nums[i]) $display(i,nums[i]);

end

endprogram

CODE:C_file.c

#include "svdpi.h"

void fib(svLogicVecVal nums[10]) {

int i;

for (i=0; i<10; i++) {

nums[i] = i ;

}

}

RESULTS:

0 0

1 1

2 2

3 3

4 4

5 5

6 6

7 7

8 8

9 9

Linearized And Normalized

Arrays use normalized ranges for the packed [n-1:0] and the unpacked part [0:n-1]

For example, if SV code defines an array as follows:

logic [2:3][1:3][2:0] b [1:10][31:0];

Then C code would see it as defined like this:

logic [17:0] b [0:9][0:31];

Array Querying Functions

svLeft() shall return the left bound (MSB) of the dimension.

svRight() shall return the right bound (LSB) of the dimension.

svLow() shall return the minimum of left index and right index of the dimension.

svHigh() shall return the maximum of left index and right index of the dimension.

svIncrement() shall return 1 if left index is greater than or equal to right index and -1 if left index is less than right index.

svLength() shall return the number of elements in the dimension, which is equivalent to high index - low index + 1.

svDimensions() shell return total number of dimensions in the array

CODE: SV_file.sv

program main;

int fxd_arr_1[8:3];

int fxd_arr_2[1:13];

import "DPI-C" context function void pass_array(input int dyn_arr[] );

initial

begin

$display("\n Passing fxd_arr_1 to C \n");

pass_array( fxd_arr_1 );

$display("\n Passing fxd_arr_2 to C \n");

pass_array( fxd_arr_2 );

end

endprogram

CODE: C_file.c

#include

#include

void pass_array(const svOpenArrayHandle dyn_arr ) {

printf("Array Pointer is %x \n", svGetArrayPtr(dyn_arr) );

printf(" Lower index %d \n", svLow(dyn_arr,1));

printf(" Higher index %d \n", svHigh(dyn_arr, 1) );

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

printf(" Right index %d \n", svRight(dyn_arr, 1) );

printf(" Length of array %d \n", svLength(dyn_arr,1) );

printf(" Incremental %d \n",svIncrement(dyn_arr,1));

printf("Dimentions of Array %d \n", svDimensions(dyn_arr ));

printf("Size of Array in bytes %d \n", svSizeOfArray(dyn_arr) );

}

RESULTS:

Passing fxd_arr_1 to C

Array Pointer is 80fdc58

Lower index 3

Higher index 8

Left index 8

Right index 3

Length of array 6

Incremental 1

Dimentions of Array 1

Size of Array in bytes 24

Passing fxd_arr_2 to C

Array Pointer is 80fdc70

Lower index 1

Higher index 13

Left index 1

Right index 13

Length of array 13

Incremental -1

Dimentions of Array 1

Size of Array in bytes 52