source: branches/2389-EpsLexicase/HeuristicLab.ExtLibs/HeuristicLab.AvalonEdit/5.0.1/AvalonEdit-5.0.1/Document/GapTextBuffer.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,
// 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
// 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.Text;

using ICSharpCode.AvalonEdit.Utils;

namespace ICSharpCode.AvalonEdit.Document
{
  /*
  /// <summary>
  /// Implementation of a gap text buffer.
  /// </summary>
  sealed class GapTextBuffer
  {
    char[] buffer = Empty<char>.Array;
    
    /// <summary>
    /// The current text content.
    /// Is set to null whenever the buffer changes, and gets a value only when the
    /// full text content is requested.
    /// </summary>
    string textContent;
    
    /// <summary>
    /// last GetText result
    /// </summary>
    string lastGetTextResult;
    int lastGetTextRequestOffset;
    
    int gapBeginOffset;
    int gapEndOffset;
    int gapLength; // gapLength == gapEndOffset - gapBeginOffset
    
    /// <summary>
    /// when gap is too small for inserted text or gap is too large (exceeds maxGapLength),
    /// a new buffer is reallocated with a new gap of at least this size.
    /// </summary>
    const int minGapLength = 128;
    
    /// <summary>
    /// when the gap exceeds this size, reallocate a smaller buffer
    /// </summary>
    const int maxGapLength = 4096;
    
    public int Length {
      get {
        return buffer.Length - gapLength;
      }
    }
    
    /// <summary>
    /// Gets the buffer content.
    /// </summary>
    public string Text {
      get {
        if (textContent == null)
          textContent = GetText(0, Length);
        return textContent;
      }
      set {
        Debug.Assert(value != null);
        textContent = value;  lastGetTextResult = null;
        buffer = new char[value.Length + minGapLength];
        value.CopyTo(0, buffer, 0, value.Length);
        gapBeginOffset = value.Length;
        gapEndOffset = buffer.Length;
        gapLength = gapEndOffset - gapBeginOffset;
      }
    }
    
    public char GetCharAt(int offset)
    {
      return offset < gapBeginOffset ? buffer[offset] : buffer[offset + gapLength];
    }
    
    public string GetText(int offset, int length)
    {
      if (length == 0)
        return string.Empty;
      if (lastGetTextRequestOffset == offset && lastGetTextResult != null && length == lastGetTextResult.Length)
        return lastGetTextResult;
      
      int end = offset + length;
      string result;
      if (end < gapBeginOffset) {
        result = new string(buffer, offset, length);
      } else if (offset > gapBeginOffset) {
        result = new string(buffer, offset + gapLength, length);
      } else {
        int block1Size = gapBeginOffset - offset;
        int block2Size = end - gapBeginOffset;
        
        StringBuilder buf = new StringBuilder(block1Size + block2Size);
        buf.Append(buffer, offset,       block1Size);
        buf.Append(buffer, gapEndOffset, block2Size);
        result = buf.ToString();
      }
      lastGetTextRequestOffset = offset;
      lastGetTextResult = result;
      return result;
    }
    
    /// <summary>
    /// Inserts text at the specified offset.
    /// </summary>
    public void Insert(int offset, string text)
    {
      Debug.Assert(offset >= 0 && offset <= Length);
      
      if (text.Length == 0)
        return;
      
      textContent = null; lastGetTextResult = null;
      PlaceGap(offset, text.Length);
      text.CopyTo(0, buffer, gapBeginOffset, text.Length);
      gapBeginOffset += text.Length;
      gapLength = gapEndOffset - gapBeginOffset;
    }
    
    /// <summary>
    /// Remove <paramref name="length"/> characters at <paramref name="offset"/>.
    /// Leave a gap of at least <paramref name="reserveGapSize"/>.
    /// </summary>
    public void Remove(int offset, int length, int reserveGapSize)
    {
      Debug.Assert(offset >= 0 && offset <= Length);
      Debug.Assert(length >= 0 && offset + length <= Length);
      Debug.Assert(reserveGapSize >= 0);
      
      if (length == 0)
        return;
      
      textContent = null; lastGetTextResult = null;
      PlaceGap(offset, reserveGapSize - length);
      gapEndOffset += length; // delete removed text
      gapLength = gapEndOffset - gapBeginOffset;
      if (gapLength - reserveGapSize > maxGapLength && gapLength - reserveGapSize > buffer.Length / 4) {
        // shrink gap
        MakeNewBuffer(gapBeginOffset, reserveGapSize + minGapLength);
      }
    }
    
    void PlaceGap(int newGapOffset, int minRequiredGapLength)
    {
      if (gapLength < minRequiredGapLength) {
        // enlarge gap
        MakeNewBuffer(newGapOffset, minRequiredGapLength + Math.Max(minGapLength, buffer.Length / 8));
      } else {
        while (newGapOffset < gapBeginOffset) {
          buffer[--gapEndOffset] = buffer[--gapBeginOffset];
        }
        while (newGapOffset > gapBeginOffset) {
          buffer[gapBeginOffset++] = buffer[gapEndOffset++];
        }
      }
    }
    
    void MakeNewBuffer(int newGapOffset, int newGapLength)
    {
      char[] newBuffer = new char[Length + newGapLength];
      Debug.WriteLine("GapTextBuffer was reallocated, new size=" + newBuffer.Length);
      if (newGapOffset < gapBeginOffset) {
        // gap is moving backwards
        
        // first part:
        Array.Copy(buffer, 0, newBuffer, 0, newGapOffset);
        // moving middle part:
        Array.Copy(buffer, newGapOffset, newBuffer, newGapOffset + newGapLength, gapBeginOffset - newGapOffset);
        // last part:
        Array.Copy(buffer, gapEndOffset, newBuffer, newBuffer.Length - (buffer.Length - gapEndOffset), buffer.Length - gapEndOffset);
      } else {
        // gap is moving forwards
        // first part:
        Array.Copy(buffer, 0, newBuffer, 0, gapBeginOffset);
        // moving middle part:
        Array.Copy(buffer, gapEndOffset, newBuffer, gapBeginOffset, newGapOffset - gapBeginOffset);
        // last part:
        int lastPartLength = newBuffer.Length - (newGapOffset + newGapLength);
        Array.Copy(buffer, buffer.Length - lastPartLength, newBuffer, newGapOffset + newGapLength, lastPartLength);
      }
      
      gapBeginOffset = newGapOffset;
      gapEndOffset = newGapOffset + newGapLength;
      gapLength = newGapLength;
      buffer = newBuffer;
    }
  }
  */
}