Resizing dynamic array in SystemVerilog

Question

In SystemVerilog, I have a dynamic array of ints. I need to modify this array so as to skip the first 2 elements. For backward compatibility, I cannot change the data type to a queue. (which would allow me to do pop_front). So I came up with this hacky code that copies the array at least twice. Is there a better way?

tmp_arr = new[dyn_arr.size() -2];         
for(int i = 0; i < tmp_arr.size(); i++) begin
  tmp_arr[i] = dyn_arr[i + 2];           // First Copy
end
dyn_arr = tmp_arr;                       // Second Copy

My test is also on edaplayground. https://www.edaplayground.com/x/2VPm

dave_59 · Accepted Answer · 2018-08-16 16:59:09Z

2

Not really. The streaming operator can do this but might be more expensive.

You might try

for(int i=2;i < dyn_arr.size(); i++)
   dyn_arr[i-2] = dyn_arr[i];
dyn_arr = new[dyn_arr.size-2] dyn_arr;

And hope the compiler is smart enough to optimize that without copying.

answered Aug 16, 2018 at 16:59

dave_59

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Unn · Accepted Answer · 2018-08-16 16:58:34Z

1

Depending on how much support your tools have for the stream operator, you can just use that like so:

dyn_arr = {>>$size(dyn_arr[0]){dyn_arr with [2:dyn_arr.size()-1]}};

This assumes the dyn_arr is at least 3 elements long (ie, that the resulting array will be at least 1 element long).

Otherwise, you can always just use a loop to shift the whole array down rather than making a new one:

for (int i = 2; i < dyn_arr.size(); i++) begin
  dyn_arr[i - 2] = dyn_arr[i];
end
dyn_arr = new[dyn_arr.size()-2] (dyn_arr); // Only include this if you need to use dyn_arr.size with the smaller size after the operation is complete

answered Aug 16, 2018 at 16:58

Unn

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