/// <summary>
/// Pop an item from the head of the queue.
/// </summary>
/// <remarks>
/// NOTE: TrySteal() can be invoked from any thread.
/// </remarks>
/// <param name="item">Head item of the queue when operation is successful.</param>
/// <returns><see langword="True"/> if operation was successful.</returns>
public bool TrySteal(out T item)
{
// read top
TopData curTop = _top;
// read bottom
BottomData curBottom = _bottom;
if (IsEmpty(curBottom, curTop, _capacity))
{
item = default(T);
if (ReferenceEquals(curTop, _top))
{
return(false);
}
else
{
// NOTE (steveb): this is contentious access case; we currently return 'false' but may want to differentiate in the future
return(false);
}
}
// if deque isn't empty, calcuate next top pointer
TopData newTop;
if (curTop.Index != 0)
{
// stay at current node
newTop = new TopData(curTop.Tag, curTop.Node, curTop.Index - 1);
}
else
{
// move to next node and update tag
newTop = new TopData(curTop.Tag + 1, curTop.Node.Prev, _capacity - 1);
}
// read value
T retVal = curTop.Node.Data[curTop.Index];
// try updating _top using CAS
if (SysUtil.CAS(ref _top, curTop, newTop))
{
// clear out the entry we read, so the GC can reclaim it
SysUtil.CAS(ref curTop.Node.Data[curTop.Index], retVal, default(T));
// free old node
curTop.Node.Next = null;
item = retVal;
return(true);
}
else
{
item = default(T);
// NOTE (steveb): this is contentious access case; we currently return 'false' but may want to differentiate in the future
return(false);
}
}
/// <summary>
/// Create a new instance.
/// </summary>
/// <param name="capacity">Maximum number of items in the queue.</param>
public WorkStealingDeque(int capacity)
{
_capacity = capacity;
DequeNode nodeB = new DequeNode(_capacity, null);
DequeNode nodeA = new DequeNode(_capacity, nodeB);
_bottom = new BottomData(nodeA, _capacity - 1);
_top = new TopData(0, nodeA, _capacity - 1);
}
//--- Class Methods ---
private static bool IsEmpty(BottomData bottom, TopData top, int capacity)
{
if (ReferenceEquals(bottom.Node, top.Node) && ((bottom.Index == top.Index) || (bottom.Index == (top.Index + 1))))
{
return(true);
}
else if (ReferenceEquals(bottom.Node, top.Node.Next) && (bottom.Index == 0) && (top.Index == (capacity - 1)))
{
return(true);
}
return(false);
}
static public void ShowPanel(List <KeyValuePair <string, string> > showText, string imageLocation, Control panel2)
{
BottomData bottomData;
///创建BottomData
if (!_dicBottomData.TryGetValue(showText.Count + (string.IsNullOrEmpty(imageLocation) ? 0 : 10000), out bottomData))
{
///初始化bottomData
if (string.IsNullOrEmpty(imageLocation))
{
bottomData = new BottomData(panel2, new TableLayoutPanel(), new KeyValuePair <Control, Control> [showText.Count]);
}
else
{
bottomData = new BottomData(panel2, new TableLayoutPanel(), new KeyValuePair <Control, Control> [showText.Count], new PictureBox(), new SplitContainer());
}
_dicBottomData.Add(showText.Count + (string.IsNullOrEmpty(imageLocation) ? 0 : 10000), bottomData);
}
///将其添加到底部
if (bottomData.HasImage)
{
if (panel2.Controls.Count == 0 || panel2.Controls[0] != bottomData.ImageSplitContainer)
{
panel2.Controls.Clear();
panel2.Controls.Add(bottomData.ImageSplitContainer);
}
}
else
{
if (panel2.Controls.Count == 0 || panel2.Controls[0] != bottomData.MainTableLayoutPanel)
{
panel2.Controls.Clear();
panel2.Controls.Add(bottomData.MainTableLayoutPanel);
}
}
///设置Text值
KeyValuePair <Control, Control>[] keyvalues = bottomData.KeyValueControls;
for (int i = 0; i < showText.Count; i++)
{
keyvalues[i].Key.Text = showText[i].Key;
keyvalues[i].Value.Text = showText[i].Value;
}
///设置图片地址
if (!string.IsNullOrEmpty(imageLocation))
{
bottomData.PictureBox.ImageLocation = imageLocation;
}
}
//--- Methods ---
/// <summary>
/// Push an item onto the tail of the queue.
/// </summary>
/// <remarks>
/// NOTE: Push() and TryPop() <strong>MUST</strong> be called from the same thread.
/// </remarks>
/// <param name="data">Item to push onto the tail of the queue.</param>
public void Push(T data)
{
// read bottom data
BottomData curBottom = _bottom;
// write data in current bottom cell
curBottom.Node.Data[curBottom.Index] = data;
BottomData newBottom;
if (curBottom.Index != 0)
{
newBottom = new BottomData(curBottom.Node, curBottom.Index - 1);
}
else
{
// allocate and link a new node
DequeNode newNode = new DequeNode(_capacity, curBottom.Node);
newBottom = new BottomData(newNode, _capacity - 1);
}
// update bottom
_bottom = newBottom;
}
private static void OnValueChanged(DependencyObject d, DependencyPropertyChangedEventArgs e)
{
BottomData bd = d as BottomData;
bd.NotifyPropertyChanged("Value");
}
/// <summary>
/// Pop an item from the tail of the queue.
/// </summary>
/// <remarks>
/// NOTE: Push() and TryPop() <strong>MUST</strong> be called from the same thread.
/// </remarks>
/// <param name="item">Tail item of the queue when operation is successful.</param>
/// <returns><see langword="True"/> if operation was successful.</returns>
public bool TryPop(out T item)
{
item = default(T);
// read bottom data
BottomData curBottom = _bottom;
BottomData newBottom;
if (curBottom.Index != (_capacity - 1))
{
newBottom = new BottomData(curBottom.Node, curBottom.Index + 1);
}
else
{
newBottom = new BottomData(curBottom.Node.Next, 0);
}
// update bottom
_bottom = newBottom;
// read top
TopData curTop = _top;
// read data to be popped
T retVal = newBottom.Node.Data[newBottom.Index];
// case 1: if _top has crossed _bottom
if (ReferenceEquals(curBottom.Node, curTop.Node) && (curBottom.Index == curTop.Index))
{
// return bottom to its old position
_bottom = curBottom;
return(false);
}
// case 2: when popping the last entry in the deque (i.e. deque is empty after the update of bottom)
if (ReferenceEquals(newBottom.Node, curTop.Node) && (newBottom.Index == curTop.Index))
{
// try to update _top's tag so no concurrent Steal operation will also pop the same entry
TopData newTopVal = new TopData(curTop.Tag + 1, curTop.Node, curTop.Index);
if (SysUtil.CAS(ref _top, curTop, newTopVal))
{
// TODO (steveb): clear out the entry we read, so the GC can reclaim it
// free old node if needed
if (!ReferenceEquals(curBottom.Node, newBottom.Node))
{
newBottom.Node.Prev = null;
}
item = retVal;
return(true);
}
else
{
// if CAS failed (i.e. a concurrent Steal operation alrady popped that last entry)
// return bottom to its old position
_bottom = curBottom;
return(false);
}
}
// case 3: regular case (i.e. there was a least one entry in the deque _after_ bottom's update)
// free old node if needed
if (!ReferenceEquals(curBottom.Node, newBottom.Node))
{
newBottom.Node.Prev = null;
}
item = retVal;
return(true);
}
