|
// Licensed to the .NET Foundation under one or more agreements.
// The .NET Foundation licenses this file to you under the MIT license.
// See the LICENSE file in the project root for more information.
//
// Description: A component of the list data structure used for live shaping.
//
namespace MS.Internal.Data
{
internal class LiveShapingBlock : RBNode<LiveShapingItem>
{
internal LiveShapingBlock() : base() { }
internal LiveShapingBlock(bool b) : base(b) { }
LiveShapingBlock ParentBlock { get { return Parent as LiveShapingBlock; } }
LiveShapingBlock LeftChildBlock { get { return (LiveShapingBlock)LeftChild; } }
LiveShapingBlock RightChildBlock { get { return (LiveShapingBlock)RightChild; } }
internal LiveShapingList List
{
get { return ((LiveShapingTree)GetRoot(this)).List; }
}
public override LiveShapingItem SetItemAt(int offset, LiveShapingItem lsi)
{
base.SetItemAt(offset, lsi);
if (lsi != null)
lsi.Block = this;
return lsi;
}
protected override void Copy(RBNode<LiveShapingItem> sourceNode, int sourceOffset, RBNode<LiveShapingItem> destNode, int destOffset, int count)
{
#if LiveShapingInstrumentation
++_copies;
_totalCopySize += count;
#endif
base.Copy(sourceNode, sourceOffset, destNode, destOffset, count);
if (sourceNode != destNode)
{
LiveShapingBlock destBlock = (LiveShapingBlock)destNode;
for (int k = 0; k < count; ++k, ++destOffset)
{
destNode.GetItemAt(destOffset).Block = destBlock;
}
}
}
internal RBFinger<LiveShapingItem> GetFinger(LiveShapingItem lsi)
{
int baseIndex;
int offset = OffsetOf(lsi);
GetRootAndIndex(this, out baseIndex);
return new RBFinger<LiveShapingItem>() { Node = this, Offset = offset, Index = baseIndex + offset, Found = true };
}
// find the current and desired position of the given item (called while restoring live sorting)
// The hurdle here is that items marked IsSortDirty should be ignored - their sort property
// has changed, so they are possibly not in the right place.
internal void FindPosition(LiveShapingItem item, out RBFinger<LiveShapingItem> oldFinger, out RBFinger<LiveShapingItem> newFinger, Comparison<LiveShapingItem> comparison)
{
// within this block, find the first and last sort-clean items, the given item
// itself, and the nearest sort-clean items on either side of the given item
int size = Size;
int index;
int first = -1, last, left = -1, right;
LiveShapingItem lsi;
for (index = 0; index < size; ++index)
{ // linear search finds the item, the first clean item, and the left-nearest
lsi = GetItemAt(index);
if (item == lsi)
break;
if (!lsi.IsSortDirty)
{
left = index;
if (first < 0)
first = index;
}
}
Debug.Assert(index < size, "FindPosition called with item not in its block");
for (right = index + 1; right < size; ++right)
{ // continue the linear search to find the right-nearest
lsi = GetItemAt(right);
if (!lsi.IsSortDirty)
break;
}
last = right;
for (int k = size - 1; k > last; --k)
{ // reverse linear search to find the last clean item
lsi = GetItemAt(k);
if (!lsi.IsSortDirty)
last = k;
}
// now we know enough to create the oldFinger
int baseIndex;
GetRootAndIndex(this, out baseIndex);
oldFinger = new RBFinger<LiveShapingItem>() { Node = this, Offset = index, Index = baseIndex + index, Found = true };
// find the newFinger
// The current picture is:
// first left index right last
// |----v-----------v-------v-----------v-----------v-----------|
// |****| |*******|***********| |***********|
// |------------------------------------------------------------|
// Items under the pointers are clean (unless the pointers fall off the
// end). The shaded regions are dirty, the unshaded regions can be
// a mixture of clean and dirty. Any of the regions might be empty,
// as the pointers can coincide.
LiveShapingItem leftItem = (left >= 0) ? GetItemAt(left) : null;
LiveShapingItem rightItem = (right < size) ? GetItemAt(right) : null;
int cL = 0, cR = 0; // result of comparisons
if (leftItem != null && (cL = comparison(item, leftItem)) < 0)
{
if (first != left)
cL = comparison(item, GetItemAt(first));
if (cL >= 0)
{ // item belongs between first and left
newFinger = LocalSearch(item, first + 1, left, comparison);
}
else
{ // item belongs to the left of this block
newFinger = SearchLeft(item, first, comparison);
}
}
else if (rightItem != null && (cR = comparison(item, rightItem)) > 0)
{
if (last != right)
cR = comparison(item, GetItemAt(last));
if (cR <= 0)
{ // item belongs between right and last
newFinger = LocalSearch(item, right + 1, last, comparison);
}
else
{ // item belongs to the right of this block
newFinger = SearchRight(item, last + 1, comparison);
}
}
else if (leftItem != null) // hence item >= leftItem
{
if (rightItem != null) // hence item <= rightItem
{ // item is already in a good position
newFinger = oldFinger;
}
else
{ // item belongs to the right of this block
newFinger = SearchRight(item, index, comparison);
}
}
else // leftItem == null
{
if (rightItem != null) // hence item <= rightItem
{
newFinger = SearchLeft(item, index, comparison);
}
else
{ // no other clean items in this block - item could belong anywhere
newFinger = SearchLeft(item, index, comparison);
if (newFinger.Node == this)
{ // couldn't find it for sure on the left - look right
newFinger = SearchRight(item, index, comparison);
}
}
}
}
// binary search that ignores dirty items
RBFinger<LiveShapingItem> LocalSearch(LiveShapingItem item, int left, int right, Comparison<LiveShapingItem> comparison)
{
int k;
while (right - left > BinarySearchThreshold)
{
int mid = (left + right) / 2;
for (k = mid; k >= left; --k)
{
if (!GetItemAt(k).IsSortDirty)
break;
}
if (k < left || comparison(GetItemAt(k), item) <= 0)
{
left = mid + 1;
}
else
{
right = k;
}
}
for (k = left; k < right; ++k)
{
if (!GetItemAt(k).IsSortDirty && comparison(item, GetItemAt(k)) <= 0)
break;
}
int index;
GetRootAndIndex(this, out index);
return new RBFinger<LiveShapingItem>() { Node = this, Offset = k, Index = index + k };
}
/* The next two methods - SearchLeft and SearchRight - are called when the item
might belong to a different node. I.e. it compares below the first clean item
in the current node (or there is no first clean item), or it compares above
the last clean item (or there is no last clean item). Here's the picture for
the "left" case.
Legend
[-----] + starting node
/ \ [----] left-ancestor - needs search
* 0 0 right-ancestor - doesn't need search
/ * unexplored left subtree
[-----]
/ \
* +
/
*
To find where the item belongs, we first walk up the tree pausing at
each left-ancestor (so we visit them right-to-left). If it has no clean
items, we learn nothing - instead we add its left subtree * to a list
of unexplored subtrees that we may search later. More likely, it has clean
items, and comparisons will tell us whether the item belongs to the ancestor
itself, to its left, or to its right. This constrains the search:
itself the item belongs to the ancestor - use binary search to find where
left the item can't belong to the unexplored trees - discard them
right the item can't belong any farther left - stop the upward tree walk
When the upward walk stops without finding a home for the item, we start
searching the unexplored subtrees, right-to-left. To search a subtree,
we first look at its root. As above, the bad case is when the root has
no clean items; in that case we need to search both its subtrees, so we push
them on a stack (the stack holds the unexplored roots in right-to-left
order). Here's a picture:
Stack * Stack
/ \ R
* ==> Pop * ==> L R ==> L
x x
With better luck, the subtree root will have clean items, and comparisons
will tell us where the item belongs with respect to the node:
itself use binary search to find where
left push the node's left child onto the stack
right push the node's right child onto the stack
Throughout this search, we keep track of the rightmost node the item
could belong to (the "found node"). Initially this is the original
starting node, but it changes as we move left from a subtree root.
If the stack empties without finding a home, we put the item into
the "found node", to the left of its leftmost clean item.
The "right" search is symmetric. We explore right-ancestors, followed
by unexplored subtrees in left-to-right order.
*/
// find the item in the tree to my left. If it's larger than the nearest clean
// neighbor, return a finger to the given offset within this node
RBFinger<LiveShapingItem> SearchLeft(LiveShapingItem item, int offset, Comparison<LiveShapingItem> comparison)
{
LiveShapingBlock foundBlock = this;
List<LiveShapingBlock> list = new List<LiveShapingBlock>(); // subtrees to explore
list.Add(LeftChildBlock);
// phase 1, walk up the tree looking for the item in each left-parent
LiveShapingBlock block, parent;
int first, last, size;
for (block = this, parent = block.ParentBlock; parent != null; block = parent, parent = block.ParentBlock)
{
if (parent.RightChildBlock == block)
{
parent.GetFirstAndLastCleanItems(out first, out last, out size);
// find where the search item belongs relative to the clean items
if (first >= size)
{ // no clean items - add the left subtree for later exploration
list.Add(parent.LeftChildBlock);
}
else if (comparison(item, parent.GetItemAt(last)) > 0)
{ // item belongs to the right of parent - no need to climb higher
break;
}
else if (comparison(item, parent.GetItemAt(first)) >= 0)
{ // item belongs in the parent
return parent.LocalSearch(item, first + 1, last, comparison);
}
else
{ // item belongs to the left of parent, thus also left of unexplored subtrees
list.Clear();
list.Add(parent.LeftChildBlock);
foundBlock = parent;
offset = first;
}
}
}
// phase 2, item wasn't found in a left-parent, so it belongs in one of the
// unexplored subtrees. Search them right-to-left, hoping item didn't move far.
Stack<LiveShapingBlock> stack = new Stack<LiveShapingBlock>(list);
while (stack.Count > 0)
{
block = stack.Pop();
if (block == null)
continue;
block.GetFirstAndLastCleanItems(out first, out last, out size);
if (first >= size)
{ // no clean items - explore the subtrees
stack.Push(block.LeftChildBlock);
stack.Push(block.RightChildBlock);
}
else if (comparison(item, block.GetItemAt(last)) > 0)
{ // item belongs to the right
stack.Clear();
stack.Push(block.RightChildBlock);
}
else if (comparison(item, block.GetItemAt(first)) >= 0)
{ // item belongs in the current block
return block.LocalSearch(item, first + 1, last, comparison);
}
else
{ // item belongs to the left of the block, or possibly in it
foundBlock = block;
offset = first;
stack.Push(block.LeftChildBlock);
}
}
// phase 3, item wasn't found within any block, so put it at the
// edge of the "found" block
int baseIndex;
GetRootAndIndex(foundBlock, out baseIndex);
return new RBFinger<LiveShapingItem>() { Node = foundBlock, Offset = offset, Index = baseIndex + offset };
}
// find the item in the tree to my right. If it's smaller than the nearest clean
// neighbor, return a finger to the given offset within this node
RBFinger<LiveShapingItem> SearchRight(LiveShapingItem item, int offset, Comparison<LiveShapingItem> comparison)
{
LiveShapingBlock foundBlock = this;
List<LiveShapingBlock> list = new List<LiveShapingBlock>(); // subtrees to explore
list.Add(RightChildBlock);
// phase 1, walk up the tree looking for the item in each right-parent
LiveShapingBlock block, parent;
int first, last, size;
for (block = this, parent = block.ParentBlock; parent != null; block = parent, parent = block.ParentBlock)
{
if (parent.LeftChildBlock == block)
{
parent.GetFirstAndLastCleanItems(out first, out last, out size);
// find where the search item belongs relative to the clean items
if (first >= size)
{ // no clean items - add the right subtree for later exploration
list.Add(parent.RightChildBlock);
}
else if (comparison(item, parent.GetItemAt(first)) < 0)
{ // item belongs to the left of parent - no need to climb higher
break;
}
else if (comparison(item, parent.GetItemAt(last)) <= 0)
{ // item belongs in the parent
return parent.LocalSearch(item, first + 1, last, comparison);
}
else
{ // item belongs to the right of parent, thus also right of unexplored subtrees
list.Clear();
list.Add(parent.RightChildBlock);
foundBlock = parent;
offset = last + 1;
}
}
}
// phase 2, item wasn't found in a right-parent, so it belongs in one of the
// unexplored subtrees. Search them left-to-right, hoping item didn't move far.
Stack<LiveShapingBlock> stack = new Stack<LiveShapingBlock>(list);
while (stack.Count > 0)
{
block = stack.Pop();
if (block == null)
continue;
block.GetFirstAndLastCleanItems(out first, out last, out size);
if (first >= size)
{ // no clean items - explore the subtrees
stack.Push(block.RightChildBlock);
stack.Push(block.LeftChildBlock);
}
else if (comparison(item, block.GetItemAt(first)) < 0)
{ // item belongs to the left
stack.Clear();
stack.Push(block.LeftChildBlock);
}
else if (comparison(item, block.GetItemAt(last)) <= 0)
{ // item belongs in the current block
return block.LocalSearch(item, first + 1, last, comparison);
}
else
{ // item belongs to the right of the block, or possibly in it
foundBlock = block;
offset = last + 1;
stack.Push(block.RightChildBlock);
}
}
// phase 3, item wasn't found within any block, so put it at the
// edge of the "found" block
int baseIndex;
GetRootAndIndex(foundBlock, out baseIndex);
return new RBFinger<LiveShapingItem>() { Node = foundBlock, Offset = offset, Index = baseIndex + offset };
}
void GetFirstAndLastCleanItems(out int first, out int last, out int size)
{
size = Size;
for (first = 0; first < size; ++first)
{
if (!GetItemAt(first).IsSortDirty)
break;
}
for (last = size - 1; last > first; --last)
{
if (!GetItemAt(last).IsSortDirty)
break;
}
}
#if LiveShapingInstrumentation
static internal void SetNodeSize(int nodeSize)
{
MaxSize = nodeSize;
}
static internal int _copies, _totalCopySize;
#endif // LiveShapingInstrumentation
}
}
|