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Queues
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A queue is a variable-size, ordered collection of homogeneous elements. Each element in a queue is identified by an ordinal number that represents its position within the queue, with 0 representing the first, and $ representing the last. A queue is analogous to a one-dimensional unpacked array that grows and shrinks automatically. Thus, like arrays, queues can be manipulated using the indexing, concatenation, slicing operator syntax, and equality operators. |
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Syntax |
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variable_dimension ::=
{ sized_or_unsized_dimension }
| associative_dimension
| queue_dimension
queue_dimension ::= [ $ [ : constant_expression ] ]
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Queue Operators
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Following operators are used in working with queues |
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- 0 : Used to access first element of queue
- $ : Used to access last element of queue
- {} : Used along with first and last operator to add/delete elements
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Queues methods
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SystemVerilog provides following methods to work with queues |
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Method
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Description
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insert()
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The insert() method inserts the given item at the specified index position.
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delete()
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The delete() method deletes the item at the specified index position.
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pop_front()
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The pop_front() method removes and returns the first element of the queue.
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pop_back()
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The pop_back() method removes and returns the last element of the queue.
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push_front()
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The push_front() method inserts the given element at the front of the queue.
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push_back()
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The push_back() method inserts the given element at the end of the queue.
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size()
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The size() method returns the number of items in the queue. If the queue is empty, it returns 0.
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Example - Queues
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1 module queue_data();
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3 // Queue is declated with $ in array size
4 integer queue[$] = { 0, 1, 2, 3, 4 };
5 integer i;
6
7 initial begin
8 $display ("Initial value of queue");
9 print_queue;
10 // Insert new element at begin of queue
11 queue = {5, queue};
12 $display ("new element added using concate");
13 print_queue;
14 // Insert using method at begining
15 queue.push_front(6);
16 $display ("new element added using push_front");
17 print_queue;
18 // Insert using method at end
19 queue.push_back(7);
20 $display ("new element added using push_back");
21 print_queue;
22 // Using insert to insert, here 4 is index
23 // and 8 is value
24 queue.insert(4,8);
25 $display ("new element added using insert(index,value)");
26 print_queue;
27 // get first queue element method at begining
28 i = queue.pop_front();
29 $display ("element poped using pop_front");
30 print_queue;
31 // get last queue element method at end
32 i = queue.pop_back();
33 $display ("element poped using pop_end");
34 print_queue;
35 // Use delete method to delete element at index 4 in queue
36 queue.delete(4);
37 $display ("deleted element at index 4");
38 print_queue;
39 #1 $finish;
40 end
41
42 task print_queue;
43 integer i;
44 $write("Queue contains ");
45 for (i = 0; i < queue.size(); i ++) begin
46 $write (" %g", queue[i]);
47 end
48 $write("\n");
49 endtask
50
51 endmodule
You could download file queue_data.sv here
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Simulation Output - Queues
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Initial value of queue
Queue contains 0 1 2 3 4
new element added using concate
Queue contains 5 0 1 2 3 4
new element added using push_front
Queue contains 6 5 0 1 2 3 4
new element added using push_back
Queue contains 6 5 0 1 2 3 4 7
new element added using insert(index,value)
Queue contains 6 5 0 1 8 2 3 4 7
element poped using pop_front
Queue contains 5 0 1 8 2 3 4 7
element poped using pop_end
Queue contains 5 0 1 8 2 3 4
deleted element at index 4
Queue contains 5 0 1 8 3 4
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Copyright © 1998-2014 |
Deepak Kumar Tala - All rights reserved |
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Do you have any Comment? mail me at:deepak@asic-world.com
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