AccessorTable.cs source code in C# .NET

                        Code:
                         / DotNET / DotNET / 8.0 / untmp / WIN_WINDOWS / lh_tools_devdiv_wpf / Windows / wcp / Framework / MS / Internal / Data / AccessorTable.cs / 1 / AccessorTable.cs
                        
                        
                            //---------------------------------------------------------------------------- 
//
// 
//    Copyright (C) Microsoft Corporation.  All rights reserved.
//  
//
// Description: Mapping of (SourceValueType, type, name) to (info, propertyType, args) 
// 
//---------------------------------------------------------------------------
 
/***************************************************************************\
    Data binding uses reflection to obtain accessors for source properties,
    where an "accessor" can be a DependencyProperty, a PropertyInfo, or a
    PropertyDescriptor, depending on the nature of the source item and the 
    property.  We cache the result of this discovery process in the
    AccessorTable;  table lookup is cheaper than doing reflection again. 
\***************************************************************************/ 

using System; 
using System.Collections;
using System.ComponentModel;                // IBindingList
using System.Reflection;                    // TypeDescriptor
using System.Windows;                       // SR 
using System.Windows.Threading;             // Dispatcher
using MS.Internal;                          // Invariant.Assert 
 
namespace MS.Internal.Data
{ 
    internal sealed class AccessorInfo
    {
        internal AccessorInfo(object accessor, Type propertyType, object[] args)
        { 
            _accessor = accessor;
            _propertyType = propertyType; 
            _args = args; 
        }
 
        internal object     Accessor        { get { return _accessor; } }
        internal Type       PropertyType    { get { return _propertyType; } }
        internal object[]   Args            { get { return _args; } }
 
        internal int Generation { get { return _generation; } set { _generation = value; } }
 
        object      _accessor;          // DP, PD, or PI 
        Type        _propertyType;      // type of the property
        object[]    _args;              // args for indexed property 
        int         _generation;        // used for discarding aged entries
    }

 
    internal sealed class AccessorTable
    { 
        internal AccessorTable() 
        {
        } 

        // map (SourceValueType, type, name) to (accessor, propertyType, args)
        internal AccessorInfo this[SourceValueType sourceValueType, Type type, string name]
        { 
            get
            { 
                if (type == null || name == null) 
                    return null;
 
                AccessorInfo info = (AccessorInfo)_table[new AccessorTableKey(sourceValueType, type, name)];

                if (info != null)
                { 
#if DEBUG
                    // record the age of cache hits 
                    int age = _generation - info.Generation; 

                    if (age >= _ages.Length) 
                    {
                        int[] newAges = new int[2*age];
                        _ages.CopyTo(newAges, 0);
                        _ages = newAges; 
                    }
 
                    ++ _ages[age]; 
                    ++ _hits;
#endif 
                    info.Generation = _generation;
                }
#if DEBUG
                else 
                {
                    ++ _misses; 
                } 
#endif
                return info; 
            }
            set
            {
                if (type != null && name != null) 
                {
                    value.Generation = _generation; 
                    _table[new AccessorTableKey(sourceValueType, type, name)] = value; 

                    if (!_cleanupRequested) 
                        RequestCleanup();
                }
            }
        } 

        // request a cleanup pass 
        private void RequestCleanup() 
        {
            _cleanupRequested = true; 
            Dispatcher.CurrentDispatcher.BeginInvoke(DispatcherPriority.ContextIdle, new DispatcherOperationCallback(CleanupOperation), null);
        }

        // run a cleanup pass 
        private object CleanupOperation(object arg)
        { 
            // find entries that are sufficiently old 
            object[] keysToRemove = new object[_table.Count];
            int n = 0; 
            IDictionaryEnumerator ide = _table.GetEnumerator();
            while (ide.MoveNext())
            {
                AccessorInfo info = (AccessorInfo)ide.Value; 
                int age = _generation - info.Generation;
                if (age >= AgeLimit) 
                { 
                    keysToRemove[n++] = ide.Key;
                } 
            }

#if DEBUG
            if (_traceSize) 
            {
                Console.WriteLine("After generation {0}, removing {1} of {2} entries from AccessorTable, new count is {3}", 
                    _generation, n, _table.Count, _table.Count - n); 
            }
#endif 

            // remove those entries
            for (int i=0; i 0)
                { 
                    cumulativeHits += _ages[i];
                    Console.WriteLine("{0,5} {1,6} {2,5} {3,5}", 
                                    i, _ages[i], 100*_ages[i]/_hits, 100*cumulativeHits/_hits); 
                }
            } 
#endif
        }

        internal bool TraceSize 
        {
            get { return _traceSize; } 
            set { _traceSize = value; } 
        }
 
        private const int   AgeLimit = 10;      // entries older than this get removed.

        private Hashtable   _table = new Hashtable();
        private int         _generation; 
        private bool        _cleanupRequested;
        bool                _traceSize; 
#if DEBUG 
        private int[]       _ages = new int[10];
        private int         _hits, _misses; 
#endif

        private struct AccessorTableKey
        { 
            public AccessorTableKey(SourceValueType sourceValueType, Type type, string name)
            { 
                Invariant.Assert(type != null && type != null); 

                _sourceValueType = sourceValueType; 
                _type = type;
                _name = name;
            }
 
            public override bool Equals(object o)
            { 
                if (o is AccessorTableKey) 
                    return this == (AccessorTableKey)o;
                else 
                    return false;
            }

            public static bool operator==(AccessorTableKey k1, AccessorTableKey k2) 
            {
                return  k1._sourceValueType == k2._sourceValueType 
                    &&  k1._type == k2._type 
                    &&  k1._name == k2._name;
            } 

            public static bool operator!=(AccessorTableKey k1, AccessorTableKey k2)
            {
                return !(k1 == k2); 
            }
 
            public override int GetHashCode() 
            {
                return unchecked(_type.GetHashCode() + _name.GetHashCode()); 
            }

            SourceValueType _sourceValueType;
            Type            _type; 
            string          _name;
        } 
    } 
}
 

// File provided for Reference Use Only by Microsoft Corporation (c) 2007.
// Copyright (c) Microsoft Corporation. All rights reserved.
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