source: branches/2839_HiveProjectManagement/HeuristicLab.ExtLibs/HeuristicLab.AvalonEdit/5.0.1/AvalonEdit-5.0.1/Utils/RopeTextReader.cs @ 15866

// 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,
// publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons
// 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
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// DEALINGS IN THE SOFTWARE.

using System;
using System.Collections.Generic;
using System.Diagnostics;
using System.IO;

namespace ICSharpCode.AvalonEdit.Utils
{
  /// <summary>
  /// TextReader implementation that reads text from a rope.
  /// </summary>
  public sealed class RopeTextReader : TextReader
  {
    Stack<RopeNode<char>> stack = new Stack<RopeNode<char>>();
    RopeNode<char> currentNode;
    int indexInsideNode;
    
    /// <summary>
    /// Creates a new RopeTextReader.
    /// Internally, this method creates a Clone of the rope; so the text reader will always read through the old
    /// version of the rope if it is modified. <seealso cref="Rope{T}.Clone()"/>
    /// </summary>
    public RopeTextReader(Rope<char> rope)
    {
      if (rope == null)
        throw new ArgumentNullException("rope");
      
      // We force the user to iterate through a clone of the rope to keep the API contract of RopeTextReader simple
      // (what happens when a rope is modified while iterating through it?)
      rope.root.Publish();
      
      // special case for the empty rope:
      // leave currentNode initialized to null (RopeTextReader doesn't support empty nodes)
      if (rope.Length != 0) {
        currentNode = rope.root;
        GoToLeftMostLeaf();
      }
    }
    
    void GoToLeftMostLeaf()
    {
      while (currentNode.contents == null) {
        if (currentNode.height == 0) {
          // this is a function node - move to its contained rope
          currentNode = currentNode.GetContentNode();
          continue;
        }
        Debug.Assert(currentNode.right != null);
        stack.Push(currentNode.right);
        currentNode = currentNode.left;
      }
      Debug.Assert(currentNode.height == 0);
    }
    
    /// <inheritdoc/>
    public override int Peek()
    {
      if (currentNode == null)
        return -1;
      return currentNode.contents[indexInsideNode];
    }
    
    /// <inheritdoc/>
    public override int Read()
    {
      if (currentNode == null)
        return -1;
      char result = currentNode.contents[indexInsideNode++];
      if (indexInsideNode >= currentNode.length)
        GoToNextNode();
      return result;
    }
    
    void GoToNextNode()
    {
      if (stack.Count == 0) {
        currentNode = null;
      } else {
        indexInsideNode = 0;
        currentNode = stack.Pop();
        GoToLeftMostLeaf();
      }
    }
    
    /// <inheritdoc/>
    public override int Read(char[] buffer, int index, int count)
    {
      if (currentNode == null)
        return 0;
      int amountInCurrentNode = currentNode.length - indexInsideNode;
      if (count < amountInCurrentNode) {
        Array.Copy(currentNode.contents, indexInsideNode, buffer, index, count);
        indexInsideNode += count;
        return count;
      } else {
        // read to end of current node
        Array.Copy(currentNode.contents, indexInsideNode, buffer, index, amountInCurrentNode);
        GoToNextNode();
        return amountInCurrentNode;
      }
    }
  }
}