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// Licensed to the .NET Foundation under one or more agreements.
// The .NET Foundation licenses this file to you under the MIT license.
// See the LICENSE file in the project root for more information.
////////////////////////////////////////////////////////////////////////////
//
//
// Purpose:
//
//
////////////////////////////////////////////////////////////////////////////
using System.Collections;
using System.Diagnostics;
namespace System.Globalization
{
//
// This is public because GetTextElement() is public.
//
public class TextElementEnumerator : IEnumerator
{
private string _str;
private int _index;
private int _startIndex;
private int _strLen; // This is the length of the total string, counting from the beginning of string.
private int _currTextElementLen; // The current text element lenght after MoveNext() is called.
private UnicodeCategory _uc;
private int _charLen; // The next abstract char to look at after MoveNext() is called. It could be 1 or 2, depending on if it is a surrogate or not.
internal TextElementEnumerator(string str, int startIndex, int strLen)
{
Debug.Assert(str != null, "TextElementEnumerator(): str != null");
Debug.Assert(startIndex >= 0 && strLen >= 0, "TextElementEnumerator(): startIndex >= 0 && strLen >= 0");
Debug.Assert(strLen >= startIndex, "TextElementEnumerator(): strLen >= startIndex");
_str = str;
_startIndex = startIndex;
_strLen = strLen;
Reset();
}
public bool MoveNext()
{
if (_index >= _strLen)
{
// Make the _index to be greater than _strLen so that we can throw exception if GetTextElement() is called.
_index = _strLen + 1;
return (false);
}
_currTextElementLen = StringInfo.GetCurrentTextElementLen(_str, _index, _strLen, ref _uc, ref _charLen);
_index += _currTextElementLen;
return (true);
}
//
// Get the current text element.
//
public object Current
{
get
{
return (GetTextElement());
}
}
//
// Get the current text element.
//
public string GetTextElement()
{
if (_index == _startIndex)
{
throw new InvalidOperationException(SR.InvalidOperation_EnumNotStarted);
}
if (_index > _strLen)
{
throw new InvalidOperationException(SR.InvalidOperation_EnumEnded);
}
return (_str.Substring(_index - _currTextElementLen, _currTextElementLen));
}
//
// Get the starting index of the current text element.
//
public int ElementIndex
{
get
{
if (_index == _startIndex)
{
throw new InvalidOperationException(SR.InvalidOperation_EnumNotStarted);
}
return (_index - _currTextElementLen);
}
}
public void Reset()
{
_index = _startIndex;
if (_index < _strLen)
{
// If we have more than 1 character, get the category of the current char.
_uc = CharUnicodeInfo.InternalGetUnicodeCategory(_str, _index, out _charLen);
}
}
}
}
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