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