SystemVerilog中的Queue Methods

队列提供了许多内置方法。如下表所示:

module dq;
 bit[7:0] dq1[$]; // A unbounded queue of unsigned 8-bit
 int q3[$:5] = {0,1,2,3,4,5}; //bounded queue
 int a;
 initial begin
 a = dq1.size( ); //empty queue
 $display ($stime,,, "empty dq1 size = %0d",a);
 dq1[0] = 0; dq1[1] = 1; dq1[2] = 2;
 $display ($stime,,, "dq1 SIZE = %0d",dq1.size( ));
 $display ($stime,,, "dq1=",dq1);
 dq1.insert (3,3); //index, value
 $display($stime,,, "After Insert dq1 SIZE = %0d",dq1.size( ));
 $display ($stime,,, "dq1=",dq1);
 dq1.delete (3); //index
 $display ($stime,,, "After delete dq1 SIZE = %0d",dq1.size( ));
 $display ($stime,,, "dq1=",dq1);
 a = dq1.pop_front( ); //pop frst entry of the queue
 $display ($stime,,, "dq1 pop front = %0d ",a);
 $display ($stime,,, "dq1=",dq1);
 a = dq1.pop_back( ); //pop last entry of the queue
 $display ($stime,,, "dq1 pop back = %0d ",a);
 $display ($stime,,, "dq1=",dq1);
 //push the frst entry of the queue with '4'
 dq1.push_front(4);
 $display ($stime,,, "push front dq1=",dq1);
 //push the last entry of the queue with '5'
 dq1.push_back(5);
 $display ($stime,,, "push back dq1=",dq1);
 
 q3_size = q3.size + 5; //size > q3 size
 //underfow : pop from index 6,7,8,9,10 – run time Warning
 for (int i = 0; i < q3_size; i++)
 $display($stime,,,"q3[%0d] = %0d", i, q3.pop_front( ) );
 end
 //Solution for underfow - check for size before pop
 while (q3.size( ) > 0)
 $display($stime,,,"q3 = %0d", q3.pop_front ( ));
 //overfow : push over the bound limit – run time Warning
 for (int i = 0; i < q3_size; i++) begin
 q3.push_front( i );
 $display($stime,,,"q3[%0d] :: q3 = %p", i , q3);
 end
 endmodule

仿真log:

 0 empty dq1 size = 0 //empty queue size
 0 dq1 SIZE = 3 //size after providing values to frst three elements
 0 dq1='{'h0, 'h1, 'h2} //assigned frst three elements
 0 After Insert dq1 SIZE = 4 //Insert value 3 at index 3.
 0 dq1='{'h0, 'h1, 'h2, 'h3} //shows inserted value
 0 After delete dq1 SIZE = 3 //delete value at index 3
 0 dq1='{'h0, 'h1, 'h2} //shows dq1 after deletion
 0 dq1 pop front = 0 //pop the front index of the queue
 0 dq1='{'h1, 'h2} //dq1 after element at index 0 is gone (popped)
 0 dq1 pop back = 2 //pop the back (last) index of the queue
 0 dq1='{'h1} //the last index/value is gone
 0 push front dq1='{'h4, 'h1} //push at the front of the queue (value 4)
 0 push back dq1='{'h4, 'h1, 'h5} //push at the end of the queue (value 5)

上面我们通过队列dq1展示了push和pop的行为。然后我们声明了有界队列q3，最大的index限制是5，所以这个队列最大的size是6.
将队列q3初始化为{0,1,2,3,4,5}，然后pop超过6次。

q3_size = q3.size + 5; //size > q3 size
 //underfow : pop from index 6,7,8,9,10 – run time Warning
 //Queue 'q3' is empty after index 5.
 for (int i = 0; i < q3_size; i++)
 $display($stime,,,"q3[%0d] = %0d", i, q3.pop_front( ) );
 end

这个时候仿真器会上报warnnin：

# RUNTIME: Warning: RUNTIME_0219 testbench.sv (54): Cannot pop from an 
empty queue.

审核编辑：汤梓红