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// Copyright (c) AlphaSierraPapa for the SharpDevelop Team (for details please see \doc\copyright.txt)
// This code is distributed under the GNU LGPL (for details please see \doc\license.txt)
using System;
using System.Collections.Generic;
using System.Diagnostics;
using System.IO;
namespace Tango.Scripting.Editors.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;
}
}
}
}
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