csharp-sdk-upm/Libs/Newtonsoft.Json.AOT/DefaultJsonNameTable.cs

197 lines
6.6 KiB
C#

#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 LC.Newtonsoft.Json
{
/// <summary>
/// The default JSON name table implementation.
/// </summary>
public class DefaultJsonNameTable : JsonNameTable
{
// 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 DefaultJsonNameTable()
{
HashCodeRandomizer = Environment.TickCount;
}
/// <summary>
/// Initializes a new instance of the <see cref="DefaultJsonNameTable"/> class.
/// </summary>
public DefaultJsonNameTable()
{
_entries = new Entry[_mask + 1];
}
/// <summary>
/// Gets a string containing the same characters as the specified range of characters in the given array.
/// </summary>
/// <param name="key">The character array containing the name to find.</param>
/// <param name="start">The zero-based index into the array specifying the first character of the name.</param>
/// <param name="length">The number of characters in the name.</param>
/// <returns>A string containing the same characters as the specified range of characters in the given array.</returns>
public override 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;
// make sure index is evaluated before accessing _entries, otherwise potential race condition causing IndexOutOfRangeException
var index = hashCode & _mask;
var entries = _entries;
for (Entry entry = entries[index]; entry != null; entry = entry.Next)
{
if (entry.HashCode == hashCode && TextEquals(entry.Value, key, start, length))
{
return entry.Value;
}
}
return null;
}
/// <summary>
/// Adds the specified string into name table.
/// </summary>
/// <param name="key">The string to add.</param>
/// <remarks>This method is not thread-safe.</remarks>
/// <returns>The resolved string.</returns>
public string Add(string key)
{
if (key == null)
{
throw new ArgumentNullException(nameof(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, StringComparison.Ordinal))
{
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;
}
}
}
}