source: branches/PersistentDataStructures/HeuristicLab.ExtLibs/HeuristicLab.AvalonEdit/5.0.1/AvalonEdit-5.0.1/Utils/RopeNode.cs

// Copyright (c) 2014 AlphaSierraPapa for the SharpDevelop Team
// 
// Permission is hereby granted, free of charge, to any person obtaining a copy of this
// software and associated documentation files (the "Software"), to deal in the Software
// without restriction, including without limitation the rights to use, copy, modify, merge,
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// to whom the Software is furnished to do so, subject to the following conditions:
// 
// The above copyright notice and this permission notice shall be included in all copies or
// substantial portions of the Software.
// 
// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED,
// INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR
// PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE
// FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR
// OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
// DEALINGS IN THE SOFTWARE.

using System;
using System.Diagnostics;
using System.Runtime.Serialization;

using System.Text;

namespace ICSharpCode.AvalonEdit.Utils
{
  // Class used to represent a node in the tree.
  // There are three types of nodes:
  // Concat nodes: height>0, left!=null, right!=null, contents==null
  // Leaf nodes: height==0, left==null, right==null, contents!=null
  // Function nodes: height==0, left==null, right==null, contents==null, are of type FunctionNode<T>
  
  [Serializable]
  class RopeNode<T>
  {
    internal const int NodeSize = 256;
    
    internal static readonly RopeNode<T> emptyRopeNode = new RopeNode<T> { isShared = true, contents = new T[RopeNode<T>.NodeSize] };
    
    // Fields for pointers to sub-nodes. Only non-null for concat nodes (height>=1)
    internal RopeNode<T> left, right;
    internal volatile bool isShared; // specifies whether this node is shared between multiple ropes
    // the total length of all text in this subtree
    internal int length;
    // the height of this subtree: 0 for leaf nodes; 1+max(left.height,right.height) for concat nodes
    internal byte height;
    
    // The character data. Only non-null for leaf nodes (height=0) that aren't function nodes.
    internal T[] contents;
    
    internal int Balance {
      get { return right.height - left.height; }
    }
    
    [Conditional("DATACONSISTENCYTEST")]
    internal void CheckInvariants()
    {
      if (height == 0) {
        Debug.Assert(left == null && right == null);
        if (contents == null) {
          Debug.Assert(this is FunctionNode<T>);
          Debug.Assert(length > 0);
          Debug.Assert(isShared);
        } else {
          Debug.Assert(contents != null && contents.Length == NodeSize);
          Debug.Assert(length >= 0 && length <= NodeSize);
        }
      } else {
        Debug.Assert(left != null && right != null);
        Debug.Assert(contents == null);
        Debug.Assert(length == left.length + right.length);
        Debug.Assert(height == 1 + Math.Max(left.height, right.height));
        Debug.Assert(Math.Abs(this.Balance) <= 1);
        
        // this is an additional invariant that forces the tree to combine small leafs to prevent excessive memory usage:
        Debug.Assert(length > NodeSize);
        // note that this invariant ensures that all nodes except for the empty rope's single node have at least length 1
        
        if (isShared)
          Debug.Assert(left.isShared && right.isShared);
        left.CheckInvariants();
        right.CheckInvariants();
      }
    }
    
    internal RopeNode<T> Clone()
    {
      if (height == 0) {
        // If a function node needs cloning, we'll evaluate it.
        if (contents == null)
          return GetContentNode().Clone();
        T[] newContents = new T[NodeSize];
        contents.CopyTo(newContents, 0);
        return new RopeNode<T> {
          length = this.length,
          contents = newContents
        };
      } else {
        return new RopeNode<T> {
          left = this.left,
          right = this.right,
          length = this.length,
          height = this.height
        };
      }
    }
    
    internal RopeNode<T> CloneIfShared()
    {
      if (isShared)
        return Clone();
      else
        return this;
    }
    
    internal void Publish()
    {
      if (!isShared) {
        if (left != null)
          left.Publish();
        if (right != null)
          right.Publish();
        // it's important that isShared=true is set at the end:
        // Publish() must not return until the whole subtree is marked as shared, even when
        // Publish() is called concurrently.
        isShared = true;
      }
    }
    
    internal static RopeNode<T> CreateFromArray(T[] arr, int index, int length)
    {
      if (length == 0) {
        return emptyRopeNode;
      }
      RopeNode<T> node = CreateNodes(length);
      return node.StoreElements(0, arr, index, length);
    }
    
    internal static RopeNode<T> CreateNodes(int totalLength)
    {
      int leafCount = (totalLength + NodeSize - 1) / NodeSize;
      return CreateNodes(leafCount, totalLength);
    }
    
    static RopeNode<T> CreateNodes(int leafCount, int totalLength)
    {
      Debug.Assert(leafCount > 0);
      Debug.Assert(totalLength > 0);
      RopeNode<T> result = new RopeNode<T>();
      result.length = totalLength;
      if (leafCount == 1) {
        result.contents = new T[NodeSize];
      } else {
        int rightSide = leafCount / 2;
        int leftSide = leafCount - rightSide;
        int leftLength = leftSide * NodeSize;
        result.left = CreateNodes(leftSide, leftLength);
        result.right = CreateNodes(rightSide, totalLength - leftLength);
        result.height = (byte)(1 + Math.Max(result.left.height, result.right.height));
      }
      return result;
    }
    
    /// <summary>
    /// Balances this node and recomputes the 'height' field.
    /// This method assumes that the children of this node are already balanced and have an up-to-date 'height' value.
    /// </summary>
    internal void Rebalance()
    {
      // Rebalance() shouldn't be called on shared nodes - it's only called after modifications!
      Debug.Assert(!isShared);
      // leaf nodes are always balanced (we don't use 'height' to detect leaf nodes here
      // because Balance is supposed to recompute the height).
      if (left == null)
        return;
      
      // ensure we didn't miss a MergeIfPossible step
      Debug.Assert(this.length > NodeSize);
      
      // We need to loop until it's balanced. Rotations might cause two small leaves to combine to a larger one,
      // which changes the height and might mean we need additional balancing steps.
      while (Math.Abs(this.Balance) > 1) {
        // AVL balancing
        // note: because we don't care about the identity of concat nodes, this works a little different than usual
        // tree rotations: in our implementation, the "this" node will stay at the top, only its children are rearranged
        if (this.Balance > 1) {
          if (right.Balance < 0) {
            right = right.CloneIfShared();
            right.RotateRight();
          }
          this.RotateLeft();
          // If 'this' was unbalanced by more than 2, we've shifted some of the inbalance to the left node; so rebalance that.
          this.left.Rebalance();
        } else if (this.Balance < -1) {
          if (left.Balance > 0) {
            left = left.CloneIfShared();
            left.RotateLeft();
          }
          this.RotateRight();
          // If 'this' was unbalanced by more than 2, we've shifted some of the inbalance to the right node; so rebalance that.
          this.right.Rebalance();
        }
      }
      
      Debug.Assert(Math.Abs(this.Balance) <= 1);
      this.height = (byte)(1 + Math.Max(left.height, right.height));
    }
    
    void RotateLeft()
    {
      Debug.Assert(!isShared);
      
      /* Rotate tree to the left
       * 
       *       this               this
       *       /  \               /  \
       *      A   right   ===>  left  C
       *           / \          / \
       *          B   C        A   B
       */
      RopeNode<T> a = left;
      RopeNode<T> b = right.left;
      RopeNode<T> c = right.right;
      // reuse right concat node, if possible
      this.left = right.isShared ? new RopeNode<T>() : right;
      this.left.left = a;
      this.left.right = b;
      this.left.length = a.length + b.length;
      this.left.height = (byte)(1 + Math.Max(a.height, b.height));
      this.right = c;
      
      this.left.MergeIfPossible();
    }
    
    void RotateRight()
    {
      Debug.Assert(!isShared);
      
      /* Rotate tree to the right
       * 
       *       this             this
       *       /  \             /  \
       *     left  C   ===>    A  right
       *     / \                   /  \
       *    A   B                 B    C
       */
      RopeNode<T> a = left.left;
      RopeNode<T> b = left.right;
      RopeNode<T> c = right;
      // reuse left concat node, if possible
      this.right = left.isShared ? new RopeNode<T>() : left;
      this.right.left = b;
      this.right.right = c;
      this.right.length = b.length + c.length;
      this.right.height = (byte)(1 + Math.Max(b.height, c.height));
      this.left = a;
      
      this.right.MergeIfPossible();
    }
    
    void MergeIfPossible()
    {
      Debug.Assert(!isShared);
      
      if (this.length <= NodeSize) {
        // Convert this concat node to leaf node.
        // We know left and right cannot be concat nodes (they would have merged already),
        // but they could be function nodes.
        this.height = 0;
        int lengthOnLeftSide = this.left.length;
        if (this.left.isShared) {
          this.contents = new T[NodeSize];
          left.CopyTo(0, this.contents, 0, lengthOnLeftSide);
        } else {
          // must be a leaf node: function nodes are always marked shared
          Debug.Assert(this.left.contents != null);
          // steal buffer from left side
          this.contents = this.left.contents;
          #if DEBUG
          // In debug builds, explicitly mark left node as 'damaged' - but no one else should be using it
          // because it's not shared.
          this.left.contents = Empty<T>.Array;
          #endif
        }
        this.left = null;
        right.CopyTo(0, this.contents, lengthOnLeftSide, this.right.length);
        this.right = null;
      }
    }
    
    /// <summary>
    /// Copies from the array to this node.
    /// </summary>
    internal RopeNode<T> StoreElements(int index, T[] array, int arrayIndex, int count)
    {
      RopeNode<T> result = this.CloneIfShared();
      // result cannot be function node after a call to Clone()
      if (result.height == 0) {
        // leaf node:
        Array.Copy(array, arrayIndex, result.contents, index, count);
      } else {
        // concat node:
        if (index + count <= result.left.length) {
          result.left = result.left.StoreElements(index, array, arrayIndex, count);
        } else if (index >= this.left.length) {
          result.right = result.right.StoreElements(index - result.left.length, array, arrayIndex, count);
        } else {
          int amountInLeft = result.left.length - index;
          result.left = result.left.StoreElements(index, array, arrayIndex, amountInLeft);
          result.right = result.right.StoreElements(0, array, arrayIndex + amountInLeft, count - amountInLeft);
        }
        result.Rebalance(); // tree layout might have changed if function nodes were replaced with their content
      }
      return result;
    }
    
    /// <summary>
    /// Copies from this node to the array.
    /// </summary>
    internal void CopyTo(int index, T[] array, int arrayIndex, int count)
    {
      if (height == 0) {
        if (this.contents == null) {
          // function node
          this.GetContentNode().CopyTo(index, array, arrayIndex, count);
        } else {
          // leaf node
          Array.Copy(this.contents, index, array, arrayIndex, count);
        }
      } else {
        // concat node
        if (index + count <= this.left.length) {
          this.left.CopyTo(index, array, arrayIndex, count);
        } else if (index >= this.left.length) {
          this.right.CopyTo(index - this.left.length, array, arrayIndex, count);
        } else {
          int amountInLeft = this.left.length - index;
          this.left.CopyTo(index, array, arrayIndex, amountInLeft);
          this.right.CopyTo(0, array, arrayIndex + amountInLeft, count - amountInLeft);
        }
      }
    }
    
    internal RopeNode<T> SetElement(int offset, T value)
    {
      RopeNode<T> result = CloneIfShared();
      // result of CloneIfShared() is leaf or concat node
      if (result.height == 0) {
        result.contents[offset] = value;
      } else {
        if (offset < result.left.length) {
          result.left = result.left.SetElement(offset, value);
        } else {
          result.right = result.right.SetElement(offset - result.left.length, value);
        }
        result.Rebalance(); // tree layout might have changed if function nodes were replaced with their content
      }
      return result;
    }
    
    internal static RopeNode<T> Concat(RopeNode<T> left, RopeNode<T> right)
    {
      if (left.length == 0)
        return right;
      if (right.length == 0)
        return left;
      
      if (left.length + right.length <= NodeSize) {
        left = left.CloneIfShared();
        // left is guaranteed to be leaf node after cloning:
        // - it cannot be function node (due to clone)
        // - it cannot be concat node (too short)
        right.CopyTo(0, left.contents, left.length, right.length);
        left.length += right.length;
        return left;
      } else {
        RopeNode<T> concatNode = new RopeNode<T>();
        concatNode.left = left;
        concatNode.right = right;
        concatNode.length = left.length + right.length;
        concatNode.Rebalance();
        return concatNode;
      }
    }
    
    /// <summary>
    /// Splits this leaf node at offset and returns a new node with the part of the text after offset.
    /// </summary>
    RopeNode<T> SplitAfter(int offset)
    {
      Debug.Assert(!isShared && height == 0 && contents != null);
      RopeNode<T> newPart = new RopeNode<T>();
      newPart.contents = new T[NodeSize];
      newPart.length = this.length - offset;
      Array.Copy(this.contents, offset, newPart.contents, 0, newPart.length);
      this.length = offset;
      return newPart;
    }
    
    internal RopeNode<T> Insert(int offset, RopeNode<T> newElements)
    {
      if (offset == 0) {
        return Concat(newElements, this);
      } else if (offset == this.length) {
        return Concat(this, newElements);
      }
      
      // first clone this node (converts function nodes to leaf or concat nodes)
      RopeNode<T> result = CloneIfShared();
      if (result.height == 0) {
        // leaf node: we'll need to split this node
        RopeNode<T> left = result;
        RopeNode<T> right = left.SplitAfter(offset);
        return Concat(Concat(left, newElements), right);
      } else {
        // concat node
        if (offset < result.left.length) {
          result.left = result.left.Insert(offset, newElements);
        } else {
          result.right = result.right.Insert(offset - result.left.length, newElements);
        }
        result.length += newElements.length;
        result.Rebalance();
        return result;
      }
    }
    
    internal RopeNode<T> Insert(int offset, T[] array, int arrayIndex, int count)
    {
      Debug.Assert(count > 0);
      
      if (this.length + count < RopeNode<char>.NodeSize) {
        RopeNode<T> result = CloneIfShared();
        // result must be leaf node (Clone never returns function nodes, too short for concat node)
        int lengthAfterOffset = result.length - offset;
        T[] resultContents = result.contents;
        for (int i = lengthAfterOffset; i >= 0; i--) {
          resultContents[i + offset + count] = resultContents[i + offset];
        }
        Array.Copy(array, arrayIndex, resultContents, offset, count);
        result.length += count;
        return result;
      } else if (height == 0) {
        // TODO: implement this more efficiently?
        return Insert(offset, CreateFromArray(array, arrayIndex, count));
      } else {
        // this is a concat node (both leafs and function nodes are handled by the case above)
        RopeNode<T> result = CloneIfShared();
        if (offset < result.left.length) {
          result.left = result.left.Insert(offset, array, arrayIndex, count);
        } else {
          result.right = result.right.Insert(offset - result.left.length, array, arrayIndex, count);
        }
        result.length += count;
        result.Rebalance();
        return result;
      }
    }
    
    internal RopeNode<T> RemoveRange(int index, int count)
    {
      Debug.Assert(count > 0);
      
      // produce empty node when one node is deleted completely
      if (index == 0 && count == this.length)
        return emptyRopeNode;
      
      int endIndex = index + count;
      RopeNode<T> result = CloneIfShared(); // convert function node to concat/leaf
      if (result.height == 0) {
        int remainingAfterEnd = result.length - endIndex;
        for (int i = 0; i < remainingAfterEnd; i++) {
          result.contents[index + i] = result.contents[endIndex + i];
        }
        result.length -= count;
      } else {
        if (endIndex <= result.left.length) {
          // deletion is only within the left part
          result.left = result.left.RemoveRange(index, count);
        } else if (index >= result.left.length) {
          // deletion is only within the right part
          result.right = result.right.RemoveRange(index - result.left.length, count);
        } else {
          // deletion overlaps both parts
          int deletionAmountOnLeftSide = result.left.length - index;
          result.left = result.left.RemoveRange(index, deletionAmountOnLeftSide);
          result.right = result.right.RemoveRange(0, count - deletionAmountOnLeftSide);
        }
        // The deletion might have introduced empty nodes. Those must be removed.
        if (result.left.length == 0)
          return result.right;
        if (result.right.length == 0)
          return result.left;
        
        result.length -= count;
        result.MergeIfPossible();
        result.Rebalance();
      }
      return result;
    }
    
    #region Debug Output
    #if DEBUG
    internal virtual void AppendTreeToString(StringBuilder b, int indent)
    {
      b.AppendLine(ToString());
      indent += 2;
      if (left != null) {
        b.Append(' ', indent);
        b.Append("L: ");
        left.AppendTreeToString(b, indent);
      }
      if (right != null) {
        b.Append(' ', indent);
        b.Append("R: ");
        right.AppendTreeToString(b, indent);
      }
    }
    
    public override string ToString()
    {
      if (contents != null) {
        char[] charContents = contents as char[];
        if (charContents != null)
          return "[Leaf length=" + length + ", isShared=" + isShared + ", text=\"" + new string(charContents, 0, length) + "\"]";
        else
          return "[Leaf length=" + length + ", isShared=" + isShared + "\"]";
      } else {
        return "[Concat length=" + length + ", isShared=" + isShared + ", height=" + height + ", Balance=" + this.Balance + "]";
      }
    }
    
    internal string GetTreeAsString()
    {
      StringBuilder b = new StringBuilder();
      AppendTreeToString(b, 0);
      return b.ToString();
    }
    #endif
    #endregion
    
    /// <summary>
    /// Gets the root node of the subtree from a lazily evaluated function node.
    /// Such nodes are always marked as shared.
    /// GetContentNode() will return either a Concat or Leaf node, never another FunctionNode.
    /// </summary>
    internal virtual RopeNode<T> GetContentNode()
    {
      throw new InvalidOperationException("Called GetContentNode() on non-FunctionNode.");
    }
  }
  
  sealed class FunctionNode<T> : RopeNode<T>
  {
    Func<Rope<T>> initializer;
    RopeNode<T> cachedResults;
    
    public FunctionNode(int length, Func<Rope<T>> initializer)
    {
      Debug.Assert(length > 0);
      Debug.Assert(initializer != null);
      
      this.length = length;
      this.initializer = initializer;
      // Function nodes are immediately shared, but cannot be cloned.
      // This ensures we evaluate every initializer only once.
      this.isShared = true;
    }
    
    internal override RopeNode<T> GetContentNode()
    {
      lock (this) {
        if (this.cachedResults == null) {
          if (this.initializer == null)
            throw new InvalidOperationException("Trying to load this node recursively; or: a previous call to a rope initializer failed.");
          Func<Rope<T>> initializerCopy = this.initializer;
          this.initializer = null;
          Rope<T> resultRope = initializerCopy();
          if (resultRope == null)
            throw new InvalidOperationException("Rope initializer returned null.");
          RopeNode<T> resultNode = resultRope.root;
          resultNode.Publish(); // result is shared between returned rope and the rope containing this function node
          if (resultNode.length != this.length)
            throw new InvalidOperationException("Rope initializer returned rope with incorrect length.");
          if (resultNode.height == 0 && resultNode.contents == null) {
            // ResultNode is another function node.
            // We want to guarantee that GetContentNode() never returns function nodes, so we have to
            // go down further in the tree.
            this.cachedResults = resultNode.GetContentNode();
          } else {
            this.cachedResults = resultNode;
          }
        }
        return this.cachedResults;
      }
    }
    
    #if DEBUG
    internal override void AppendTreeToString(StringBuilder b, int indent)
    {
      RopeNode<T> resultNode;
      lock (this) {
        b.AppendLine(ToString());
        resultNode = cachedResults;
      }
      indent += 2;
      if (resultNode != null) {
        b.Append(' ', indent);
        b.Append("C: ");
        resultNode.AppendTreeToString(b, indent);
      }
    }
    
    public override string ToString()
    {
      return "[FunctionNode length=" + length + " initializerRan=" + (initializer == null) + "]";
    }
    #endif
  }
}