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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.Diagnostics;
using System.Text;
using Tango.Scripting.Editors.Utils;
namespace Tango.Scripting.Editors.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;
}
}
*/
}
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