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//------------------------------------------------------------------------------
// <copyright file="NameTable.cs" company="Microsoft">
// Copyright (c) Microsoft Corporation. All rights reserved.
// </copyright>
// <owner current="true" primary="true">Microsoft</owner>
//------------------------------------------------------------------------------
using System;
namespace System.Xml {
/// <include file='doc\NameTable.uex' path='docs/doc[@for="NameTable"]/*' />
/// <devdoc>
/// <para>
/// XmlNameTable implemented as a simple hash table.
/// </para>
/// </devdoc>
public class NameTable : XmlNameTable {
//
// Private types
//
class Entry {
internal string str;
internal int hashCode;
internal Entry next;
internal Entry( string str, int hashCode, Entry next ) {
this.str = str;
this.hashCode = hashCode;
this.next = next;
}
}
//
// Fields
//
Entry[] entries;
int count;
int mask;
int hashCodeRandomizer;
//
// Constructor
//
/// <include file='doc\NameTable.uex' path='docs/doc[@for="NameTable.NameTable"]/*' />
/// <devdoc>
/// Public constructor.
/// </devdoc>
public NameTable() {
mask = 31;
entries = new Entry[mask+1];
hashCodeRandomizer = Environment.TickCount;
}
//
// XmlNameTable public methods
//
/// <include file='doc\NameTable.uex' path='docs/doc[@for="NameTable.Add"]/*' />
/// <devdoc>
/// Add the given string to the NameTable or return
/// the existing string if it is already in the NameTable.
/// </devdoc>
public override string Add( string key ) {
if ( key == null ) {
throw new ArgumentNullException( "key" );
}
int len = key.Length;
if ( len == 0 ) {
return string.Empty;
}
int hashCode = len + hashCodeRandomizer;
// use key.Length to eliminate the rangecheck
for ( int i = 0; i < key.Length; i++ ) {
hashCode += ( hashCode << 7 ) ^ key[i];
}
// mix it a bit more
hashCode -= hashCode >> 17;
hashCode -= hashCode >> 11;
hashCode -= hashCode >> 5;
for ( Entry e = entries[hashCode & mask]; e != null; e = e.next ) {
if ( e.hashCode == hashCode && e.str.Equals( key ) ) {
return e.str;
}
}
return AddEntry( key, hashCode );
}
/// <include file='doc\NameTable.uex' path='docs/doc[@for="NameTable.Add1"]/*' />
/// <devdoc>
/// Add the given string to the NameTable or return
/// the existing string if it is already in the NameTable.
/// </devdoc>
public override string Add( char[] key, int start, int len ) {
if ( len == 0 ) {
return string.Empty;
}
int hashCode = len + hashCodeRandomizer;
hashCode += ( hashCode << 7 ) ^ key[start]; // this will throw IndexOutOfRangeException in case the start index is invalid
int end = start+len;
for ( int i = start + 1; i < end; i++) {
hashCode += ( hashCode << 7 ) ^ key[i];
}
// mix it a bit more
hashCode -= hashCode >> 17;
hashCode -= hashCode >> 11;
hashCode -= hashCode >> 5;
for ( Entry e = entries[hashCode & mask]; e != null; e = e.next ) {
if ( e.hashCode == hashCode && TextEquals( e.str, key, start, len ) ) {
return e.str;
}
}
return AddEntry( new string( key, start, len ), hashCode );
}
/// <include file='doc\NameTable.uex' path='docs/doc[@for="NameTable.Get"]/*' />
/// <devdoc>
/// Find the matching string in the NameTable.
/// </devdoc>
public override string Get( string value ) {
if ( value == null ) {
throw new ArgumentNullException("value");
}
if ( value.Length == 0 ) {
return string.Empty;
}
int len = value.Length + hashCodeRandomizer;
int hashCode = len;
// use value.Length to eliminate the rangecheck
for ( int i = 0; i < value.Length; i++ ) {
hashCode += ( hashCode << 7 ) ^ value[i];
}
// mix it a bit more
hashCode -= hashCode >> 17;
hashCode -= hashCode >> 11;
hashCode -= hashCode >> 5;
for ( Entry e = entries[hashCode & mask]; e != null; e = e.next ) {
if ( e.hashCode == hashCode && e.str.Equals( value ) ) {
return e.str;
}
}
return null;
}
/// <include file='doc\NameTable.uex' path='docs/doc[@for="NameTable.Get1"]/*' />
/// <devdoc>
/// Find the matching string atom given a range of
/// characters.
/// </devdoc>
public override string Get( char[] key, int start, int len ) {
if ( len == 0 ) {
return string.Empty;
}
int hashCode = len + hashCodeRandomizer;
hashCode += ( hashCode << 7 ) ^ key[start]; // this will throw IndexOutOfRangeException in case the start index is invalid
int end = start+len;
for ( int i = start + 1; i < end; i++) {
hashCode += ( hashCode << 7 ) ^ key[i];
}
// mix it a bit more
hashCode -= hashCode >> 17;
hashCode -= hashCode >> 11;
hashCode -= hashCode >> 5;
for ( Entry e = entries[hashCode & mask]; e != null; e = e.next ) {
if ( e.hashCode == hashCode && TextEquals( e.str, key, start, len ) ) {
return e.str;
}
}
return null;
}
//
// Private methods
//
private string AddEntry( string str, int hashCode ) {
int index = hashCode & mask;
Entry e = new Entry( str, hashCode, entries[index] );
entries[index] = e;
if ( count++ == mask ) {
Grow();
}
return e.str;
}
private void Grow() {
int newMask = mask * 2 + 1;
Entry[] oldEntries = entries;
Entry[] newEntries = new Entry[newMask+1];
// use oldEntries.Length to eliminate the rangecheck
for ( int i = 0; i < oldEntries.Length; i++ ) {
Entry e = oldEntries[i];
while ( e != null ) {
int newIndex = e.hashCode & newMask;
Entry tmp = e.next;
e.next = newEntries[newIndex];
newEntries[newIndex] = e;
e = tmp;
}
}
entries = newEntries;
mask = newMask;
}
private static bool TextEquals( string str1, char[] str2, int str2Start, int str2Length ) {
if ( str1.Length != str2Length ) {
return false;
}
// use array.Length to eliminate the rangecheck
for ( int i = 0; i < str1.Length; i++ ) {
if ( str1[i] != str2[str2Start+i] ) {
return false;
}
}
return true;
}
}
}
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