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//-----------------------------------------------------------------------------
// Copyright (c) Microsoft Corporation. All rights reserved.
//-----------------------------------------------------------------------------
namespace System.Runtime.Serialization
{
using System.Collections;
using System.Collections.Generic;
using System.Runtime.CompilerServices;
using System.Security;
class ObjectToIdCache
{
internal int m_currentCount;
internal int[] m_ids;
internal Object[] m_objs;
bool[] m_isWrapped;
public ObjectToIdCache()
{
m_currentCount = 1;
m_ids = new int[GetPrime(1)];
m_objs = new Object[m_ids.Length];
m_isWrapped = new bool[m_ids.Length];
}
public int GetId(object obj, ref bool newId)
{
bool isEmpty, isWrapped;
int position = FindElement(obj, out isEmpty, out isWrapped);
if (!isEmpty)
{
newId = false;
return m_ids[position];
}
if (!newId)
return -1;
int id = m_currentCount++;
m_objs[position] = obj;
m_ids[position] = id;
m_isWrapped[position] = isWrapped;
if (m_currentCount >= (m_objs.Length - 1))
Rehash();
return id;
}
#if NotUsed
public bool Remove(object obj)
{
bool isEmpty;
int position = FindElement(obj, out isEmpty);
if(isEmpty)
return false;
RemoveAt(position);
return true;
}
#endif
// (oldObjId, oldObj-id, newObj-newObjId) => (oldObj-oldObjId, newObj-id, newObjId )
public int ReassignId(int oldObjId, object oldObj, object newObj)
{
bool isEmpty, isWrapped;
int position = FindElement(oldObj, out isEmpty, out isWrapped);
if (isEmpty)
return 0;
int id = m_ids[position];
if (oldObjId > 0)
m_ids[position] = oldObjId;
else
RemoveAt(position);
position = FindElement(newObj, out isEmpty, out isWrapped);
int newObjId = 0;
if (!isEmpty)
newObjId = m_ids[position];
m_objs[position] = newObj;
m_ids[position] = id;
m_isWrapped[position] = isWrapped;
return newObjId;
}
private int FindElement(object obj, out bool isEmpty, out bool isWrapped)
{
isWrapped = false;
int position = ComputeStartPosition(obj);
for (int i = position; i != (position - 1); i++)
{
if (m_objs[i] == null)
{
isEmpty = true;
return i;
}
if (m_objs[i] == obj)
{
isEmpty = false;
return i;
}
if (i == (m_objs.Length - 1))
{
isWrapped = true;
i = -1;
}
}
// m_obj must ALWAYS have atleast one slot empty (null).
Fx.Assert("Object table overflow");
throw System.Runtime.Serialization.DiagnosticUtility.ExceptionUtility.ThrowHelperError(XmlObjectSerializer.CreateSerializationException(SR.GetString(SR.ObjectTableOverflow)));
}
private void RemoveAt(int position)
{
int cacheSize = m_objs.Length;
int lastVacantPosition = position;
for (int next = (position == cacheSize - 1) ? 0 : position + 1; next != position; next++)
{
if (m_objs[next] == null)
{
m_objs[lastVacantPosition] = null;
m_ids[lastVacantPosition] = 0;
m_isWrapped[lastVacantPosition] = false;
return;
}
int nextStartPosition = ComputeStartPosition(m_objs[next]);
// If we wrapped while placing an object, then it must be that the start position wasn't wrapped to begin with
bool isNextStartPositionWrapped = next < position && !m_isWrapped[next];
bool isLastVacantPositionWrapped = lastVacantPosition < position;
// We want to avoid moving objects in the cache if the next bucket position is wrapped, but the last vacant position isn't
// and we want to make sure to move objects in the cache when the last vacant position is wrapped but the next bucket position isn't
if ((nextStartPosition <= lastVacantPosition && !(isNextStartPositionWrapped && !isLastVacantPositionWrapped)) ||
(isLastVacantPositionWrapped && !isNextStartPositionWrapped))
{
m_objs[lastVacantPosition] = m_objs[next];
m_ids[lastVacantPosition] = m_ids[next];
// A wrapped object might become unwrapped if it moves from the front of the array to the end of the array
m_isWrapped[lastVacantPosition] = m_isWrapped[next] && next > lastVacantPosition;
lastVacantPosition = next;
}
if (next == (cacheSize - 1))
{
next = -1;
}
}
// m_obj must ALWAYS have atleast one slot empty (null).
Fx.Assert("Object table overflow");
throw System.Runtime.Serialization.DiagnosticUtility.ExceptionUtility.ThrowHelperError(XmlObjectSerializer.CreateSerializationException(SR.GetString(SR.ObjectTableOverflow)));
}
private int ComputeStartPosition(object o)
{
return (RuntimeHelpers.GetHashCode(o) & 0x7FFFFFFF) % m_objs.Length;
}
private void Rehash()
{
int size = GetPrime(m_objs.Length * 2);
int[] oldIds = m_ids;
object[] oldObjs = m_objs;
m_ids = new int[size];
m_objs = new Object[size];
m_isWrapped = new bool[size];
for (int j = 0; j < oldObjs.Length; j++)
{
object obj = oldObjs[j];
if (obj != null)
{
bool found, isWrapped;
int position = FindElement(obj, out found, out isWrapped);
m_objs[position] = obj;
m_ids[position] = oldIds[j];
m_isWrapped[position] = isWrapped;
}
}
}
static int GetPrime(int min)
{
for (int i = 0; i < primes.Length; i++)
{
int prime = primes[i];
if (prime >= min) return prime;
}
//outside of our predefined table.
//compute the hard way.
for (int i = (min | 1); i < Int32.MaxValue; i += 2)
{
if (IsPrime(i))
return i;
}
return min;
}
static bool IsPrime(int candidate)
{
if ((candidate & 1) != 0)
{
int limit = (int)Math.Sqrt(candidate);
for (int divisor = 3; divisor <= limit; divisor += 2)
{
if ((candidate % divisor) == 0)
return false;
}
return true;
}
return (candidate == 2);
}
[Fx.Tag.SecurityNote(Miscellaneous = "RequiresReview - Static fields are marked SecurityCritical or readonly to prevent"
+ " data from being modified or leaked to other components in appdomain.")]
internal static readonly int[] primes =
{
3, 7, 17, 37, 89, 197, 431, 919, 1931, 4049, 8419, 17519, 36353,
75431, 156437, 324449, 672827, 1395263, 2893249, 5999471,
};
}
}
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