pos/is4c-nf/scale-drivers/drivers/NewMagellan/Newtonsoft.Json/Utilities/PropertyNameTable.cs
#region License
// Copyright (c) 2007 James Newton-King
//
// Permission is hereby granted, free of charge, to any person
// obtaining a copy of this software and associated documentation
// files (the "Software"), to deal in the Software without
// restriction, including without limitation the rights to use,
// copy, modify, merge, publish, distribute, sublicense, and/or sell
// copies of the Software, and to permit persons to whom the
// Software is furnished to do so, subject to the following
// conditions:
//
// The above copyright notice and this permission notice shall be
// included in all copies or substantial portions of the Software.
//
// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
// EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES
// OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
// NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT
// HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY,
// WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
// FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR
// OTHER DEALINGS IN THE SOFTWARE.
#endregion
using System;
namespace Newtonsoft.Json.Utilities
{
internal class PropertyNameTable
{
// used to defeat hashtable DoS attack where someone passes in lots of strings that hash to the same hash code
private static readonly int HashCodeRandomizer;
private int _count;
private Entry[] _entries;
private int _mask = 31;
static PropertyNameTable()
{
HashCodeRandomizer = Environment.TickCount;
}
public PropertyNameTable()
{
_entries = new Entry[_mask + 1];
}
public string Get(char[] key, int start, int length)
{
if (length == 0)
return string.Empty;
int hashCode = length + HashCodeRandomizer;
hashCode += (hashCode << 7) ^ key[start];
int end = start + length;
for (int i = start + 1; i < end; i++)
{
hashCode += (hashCode << 7) ^ key[i];
}
hashCode -= hashCode >> 17;
hashCode -= hashCode >> 11;
hashCode -= hashCode >> 5;
for (Entry entry = _entries[hashCode & _mask]; entry != null; entry = entry.Next)
{
if (entry.HashCode == hashCode && TextEquals(entry.Value, key, start, length))
return entry.Value;
}
return null;
}
public string Add(string key)
{
if (key == null)
throw new ArgumentNullException("key");
int length = key.Length;
if (length == 0)
return string.Empty;
int hashCode = length + HashCodeRandomizer;
for (int i = 0; i < key.Length; i++)
{
hashCode += (hashCode << 7) ^ key[i];
}
hashCode -= hashCode >> 17;
hashCode -= hashCode >> 11;
hashCode -= hashCode >> 5;
for (Entry entry = _entries[hashCode & _mask]; entry != null; entry = entry.Next)
{
if (entry.HashCode == hashCode && entry.Value.Equals(key))
return entry.Value;
}
return AddEntry(key, hashCode);
}
private string AddEntry(string str, int hashCode)
{
int index = hashCode & _mask;
Entry entry = new Entry(str, hashCode, _entries[index]);
_entries[index] = entry;
if (_count++ == _mask)
{
Grow();
}
return entry.Value;
}
private void Grow()
{
Entry[] entries = _entries;
int newMask = (_mask * 2) + 1;
Entry[] newEntries = new Entry[newMask + 1];
for (int i = 0; i < entries.Length; i++)
{
Entry next;
for (Entry entry = entries[i]; entry != null; entry = next)
{
int index = entry.HashCode & newMask;
next = entry.Next;
entry.Next = newEntries[index];
newEntries[index] = entry;
}
}
_entries = newEntries;
_mask = newMask;
}
private static bool TextEquals(string str1, char[] str2, int str2Start, int str2Length)
{
if (str1.Length != str2Length)
return false;
for (int i = 0; i < str1.Length; i++)
{
if (str1[i] != str2[str2Start + i])
return false;
}
return true;
}
private class Entry
{
internal readonly string Value;
internal readonly int HashCode;
internal Entry Next;
internal Entry(string value, int hashCode, Entry next)
{
Value = value;
HashCode = hashCode;
Next = next;
}
}
}
}