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//------------------------------------------------------------------------------
// <copyright file="StringConcat.cs" company="Microsoft">
// Copyright (c) Microsoft Corporation. All rights reserved.
// </copyright>
// <owner current="true" primary="true">Microsoft</owner>
//------------------------------------------------------------------------------
using System;
using System.Collections.Generic;
using System.Diagnostics;
using System.ComponentModel;
namespace System.Xml.Xsl.Runtime {
/// <summary>
/// Efficiently concatenates strings when the number of string is not known beforehand, and
/// yet it is common for only one string to be concatenated. StringBuilder is not good for
/// this purpose, since it *always* allocates objects, even if only one string is appended.
/// </summary>
[EditorBrowsable(EditorBrowsableState.Never)]
public struct StringConcat {
private string s1, s2, s3, s4;
private string delimiter;
private List<string> strList;
int idxStr;
/// <summary>
/// Clear the result string.
/// </summary>
public void Clear() {
this.idxStr = 0;
this.delimiter = null;
}
/// <summary>
/// Gets or sets the string that delimits concatenated strings.
/// </summary>
public string Delimiter {
get { return this.delimiter; }
set { this.delimiter = value; }
}
/// <summary>
/// Return the number of concatenated strings, including delimiters.
/// </summary>
internal int Count {
get { return this.idxStr; }
}
/// <summary>
/// Concatenate a new string to the result.
/// </summary>
public void Concat(string value) {
Debug.Assert(value != null);
if (this.delimiter != null && this.idxStr != 0) {
// Add delimiter
ConcatNoDelimiter(this.delimiter);
}
ConcatNoDelimiter(value);
}
/// <summary>
/// Get the result string.
/// </summary>
public string GetResult() {
switch (this.idxStr) {
case 0: return string.Empty;
case 1: return this.s1;
case 2: return string.Concat(this.s1, this.s2);
case 3: return string.Concat(this.s1, this.s2, this.s3);
case 4: return string.Concat(this.s1, this.s2, this.s3, this.s4);
}
return string.Concat(this.strList.ToArray());
}
/// <summary>
/// Concatenate a new string to the result without adding a delimiter.
/// </summary>
internal void ConcatNoDelimiter(string s) {
switch (this.idxStr) {
case 0: this.s1 = s; break;
case 1: this.s2 = s; break;
case 2: this.s3 = s; break;
case 3: this.s4 = s; break;
case 4:
// Calling Clear() is expensive, allocate a new List instead
int capacity = (this.strList == null) ? 8 : this.strList.Count;
List<string> strList = this.strList = new List<string>(capacity);
strList.Add(this.s1);
strList.Add(this.s2);
strList.Add(this.s3);
strList.Add(this.s4);
goto default;
default:
this.strList.Add(s);
break;
}
this.idxStr++;
}
}
}
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