ObjectIDGenerator.cs source code in C# .NET

                        Code:
                         / 4.0 / 4.0 / DEVDIV_TFS / Dev10 / Releases / RTMRel / ndp / clr / src / BCL / System / Runtime / Serialization / ObjectIDGenerator.cs / 1305376 / ObjectIDGenerator.cs
                        
                        
                            // ==++== 
//
//   Copyright (c) Microsoft Corporation.  All rights reserved.
//
// ==--== 
/*============================================================
** 
** Class: ObjectIDGenerator 
**
** 
** Purpose: ObjectIDGenerator is a simple id generator that keeps track of
** objects with a hashtable.
**
** 
===========================================================*/
namespace System.Runtime.Serialization { 
    using System; 
    using System.Runtime.CompilerServices;
    using System.Runtime.Remoting; 
    using System.Diagnostics.Contracts;

    [Serializable]
[System.Runtime.InteropServices.ComVisible(true)] 
    public class ObjectIDGenerator {
 
        private const int numbins = 4; 

        internal int m_currentCount; 
        internal int m_currentSize;
        internal long []m_ids;
        internal Object []m_objs;
 
        // Table of prime numbers to use as hash table sizes. Each entry is the
        // smallest prime number larger than twice the previous entry. 
        private static readonly int[] sizes = { 
            5, 11, 29, 47, 97, 197, 397, 797, 1597, 3203, 6421, 12853, 25717, 51437,
            102877, 205759, 411527, 823117, 1646237, 3292489, 6584983}; 

        // Constructs a new ObjectID generator, initalizing all of the necessary variables.
        public ObjectIDGenerator() {
            m_currentCount=1; 
            m_currentSize = sizes[0];
            m_ids = new long[m_currentSize*numbins]; 
            m_objs = new Object[m_currentSize*numbins]; 
        }
 
        // Determines where element obj lives, or should live,
        // within the table. It calculates the hashcode and searches all of the
        // bins where the given object could live.  If it's not found within the bin,
        // we rehash and go look for it in another bin.  If we find the object, we 
        // set found to true and return it's position.  If we can't find the object,
        // we set found to false and return the position where the object should be inserted. 
        // 
        private int FindElement(Object obj, out bool found) {
            //This double-hashing algorithm is recomended by CLR, pg 236. 
            //We're hosed if somebody rehashes the table while we're doing the lookup, but that's
            //generally true for most of these operations.
            int hashcode = RuntimeHelpers.GetHashCode(obj);
            int hashIncrement = (1+((hashcode&0x7FFFFFFF)%(m_currentSize-2))); 
            do {
                int pos = ((hashcode&0x7FFFFFFF)%m_currentSize)*numbins; 
 
                for (int i=pos; i (m_currentSize*numbins)/2) {
                    Rehash();
                }
            } else { 
                BCLDebug.Trace("SER", "[ObjectIDGenerator.GetID] Found objectid: ", (m_ids[pos]), " with hashcode: ", RuntimeHelpers.GetHashCode(obj), " Type: ", obj);
                foundID = m_ids[pos]; 
            } 
            firstTime = !found;
 
            return foundID;
        }

        // Checks to see if obj has already been assigned an id.  If it has, 
        // we return that id, otherwise we return 0.
        // 
        public virtual long HasId(Object obj, out bool firstTime) { 
            bool found;
 
            if (obj==null) {
                throw new ArgumentNullException("obj", Environment.GetResourceString("ArgumentNull_Obj"));
            }
            Contract.EndContractBlock(); 

            int pos = FindElement(obj, out found); 
            if (found) { 
                firstTime = false;
                return m_ids[pos]; 
            }
            firstTime=true;
            return 0;
        } 

        // Rehashes the table by finding the next larger size in the list provided, 
        // allocating two new arrays of that size and rehashing all of the elements in 
        // the old arrays into the new ones.  Expensive but necessary.
        // 
        private void Rehash() {
            int i,pos;
            long [] newIds;
            long [] oldIds; 
            Object[] newObjs;
            Object[] oldObjs; 
            bool found; 
            int currSize;
 
            for (i=0, currSize=m_currentSize; iThis double-hashing algorithm is recomended by CLR, pg 236. 
            //We're hosed if somebody rehashes the table while we're doing the lookup, but that's
            //generally true for most of these operations.
            int hashcode = RuntimeHelpers.GetHashCode(obj);
            int hashIncrement = (1+((hashcode&0x7FFFFFFF)%(m_currentSize-2))); 
            do {
                int pos = ((hashcode&0x7FFFFFFF)%m_currentSize)*numbins; 
 
                for (int i=pos; i (m_currentSize*numbins)/2) {
                    Rehash();
                }
            } else { 
                BCLDebug.Trace("SER", "[ObjectIDGenerator.GetID] Found objectid: ", (m_ids[pos]), " with hashcode: ", RuntimeHelpers.GetHashCode(obj), " Type: ", obj);
                foundID = m_ids[pos]; 
            } 
            firstTime = !found;
 
            return foundID;
        }

        // Checks to see if obj has already been assigned an id.  If it has, 
        // we return that id, otherwise we return 0.
        // 
        public virtual long HasId(Object obj, out bool firstTime) { 
            bool found;
 
            if (obj==null) {
                throw new ArgumentNullException("obj", Environment.GetResourceString("ArgumentNull_Obj"));
            }
            Contract.EndContractBlock(); 

            int pos = FindElement(obj, out found); 
            if (found) { 
                firstTime = false;
                return m_ids[pos]; 
            }
            firstTime=true;
            return 0;
        } 

        // Rehashes the table by finding the next larger size in the list provided, 
        // allocating two new arrays of that size and rehashing all of the elements in 
        // the old arrays into the new ones.  Expensive but necessary.
        // 
        private void Rehash() {
            int i,pos;
            long [] newIds;
            long [] oldIds; 
            Object[] newObjs;
            Object[] oldObjs; 
            bool found; 
            int currSize;
 
            for (i=0, currSize=m_currentSize; i
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