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FifoQueueBase

FifoQueueBase is a class template defined in Fw/DataStructures. It represents an abstract base class for a FIFO queue.

1. Template Parameters

FifoQueueBase has the following template parameters.

Kind Name Purpose
typename T The type of an item on the queue

2. Base Class

FifoQueueBase<T> is publicly derived from SizedContainer.

3. Private Constructors

3.1. Copy Constructor

FifoQueueBase(const FifoQueueBase<T>& queue)

Defined as = delete.

4. Protected Constructors and Destructors

4.1. Zero-Argument Constructor

FifoQueueBase()

Use default initialization of members.

4.2. Destructor

virtual ~FifoQueueBase()

Defined as = default.

5. Private Member Functions

5.1. operator=

FifoQueueBase& operator=(const FifoQueueBase&)

Defined as = delete.

6. Public Member Functions

6.1. at

virtual const T& at(FwSizeType index) const = 0

Return the item at the specified index. Index 0 is the leftmost (earliest) element in the queue. Increasing indices go from left to right. Fails an assertion if the index is out of range.

Example: 

void f(FifoQueueBase<U32>& queue) {
    queue.clear();
    const auto status = queue.enqueue(3);
    ASSERT_EQ(status, Success::SUCCESS);
    const auto status = queue.enqueue(4);
    ASSERT_EQ(status, Success::SUCCESS);
    ASSERT_EQ(queue.at(0), 3);
    ASSERT_EQ(queue.at(1), 4);
    ASSERT_DEATH(queue.at(2), "Assert");
}

6.2. copyDataFrom

void copyDataFrom(const FifoQueueBase<T>& queue)

  1. If &queue != this then

    1. Call clear().

    2. Let size be the minimum of queue.getSize() and getCapacity().

    3. For i in [0, size)

      1. Set e = at(i).

      2. Set status = enqueue(e).

      3. Assert status == Success::SUCCESS.

Example: 

void f(FifoQueueBase<U32>& q1, FifoQueueBase<U32>& q2) {
    q1.clear();
    // Enqueue an item
    U32 value = 42;
    (void) q1.enqueue(value);
    q2.clear();
    ASSERT_EQ(q2.getSize(), 0);
    q2.copyDataFrom(q1);
    ASSERT_EQ(q2.getSize(), 1);
}

6.3. dequeue

virtual Success dequeue(T& e) = 0

  1. Set status = Success::FAILURE.

  2. If size > 0

    1. Remove the leftmost item from the queue and store it into e.

    2. Set status = Success::SUCCESS.

  3. Return status.

Example: 

void f(FifoQueueBase<U32>& queue) {
    queue.clear();
    U32 val = 0;
    auto status = queue.dequeue(val);
    ASSERT_EQ(status, Success::FAILURE);
    status = queue.enqueue(3);
    ASSERT_EQ(status, Success::SUCCESS);
    status = queue.dequeue(val);
    ASSERT_EQ(status, Success::SUCCESS);
    ASSERT_EQ(val, 3);
}

6.4. enqueue

virtual Success enqueue(const T& e) = 0

  1. Set status = Success::FAILURE.

  2. If there is room on the queue for a new item, then

    1. Add e to the right of the queue.

    2. Set status = Success::SUCCESS.

  3. Return status.

Example: 

void f(FifoQueueBase<U32>& queue) {
    queue.clear();
    const auto status = queue.enqueue(3);
    ASSERT_EQ(status, Success::SUCCESS);
}

6.5. peek

Success peek(T& e, FwSizeType index = 0) const

  1. Set status = Success::FAILURE.

  2. If index < getSize()

    1. Set e = at(index).

    2. Set status = Success::SUCCESS.

  3. Return status.

Example: 

void f(FifoQueueBase<U32>& queue) {
    queue.clear();
    U32 value = 0;
    auto status = queue.peek(value);
    ASSERT_EQ(status, Success::FAILURE);
    status = queue.enqueue(3);
    status = queue.peek(value);
    ASSERT_EQ(status, Success::SUCCESS);
    ASSERT_EQ(value, 3);
    status = queue.peek(value, 1);
    ASSERT_EQ(status, Success::FAILURE);
    status = queue.enqueue(4);
    status = queue.peek(value, 1);
    ASSERT_EQ(status, Success::SUCCESS);
    ASSERT_EQ(value, 4);
}