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// Copyright (c) Microsoft. All rights reserved.
// Licensed under the MIT license. See LICENSE file in the project root for full license information.
//
//
////////////////////////////////////////////////////////////////////////////
//
// Class: TextElementEnumerator
//
// Purpose:
//
// Date: March 31, 1999
//
////////////////////////////////////////////////////////////////////////////
using System.Collections;
using System.Diagnostics.Contracts;
namespace System.Globalization
{
//
// This is public because GetTextElement() is public.
//
[System.Runtime.InteropServices.ComVisible(true)]
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)
{
Contract.Assert(str != null, "TextElementEnumerator(): str != null");
Contract.Assert(startIndex >= 0 && strLen >= 0, "TextElementEnumerator(): startIndex >= 0 && strLen >= 0");
Contract.Assert(strLen >= startIndex, "TextElementEnumerator(): strLen >= startIndex");
this.str = str;
this.startIndex = startIndex;
this.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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