ExpandoClass.cs source code in C# .NET

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/ 4.0 / 4.0 / untmp / DEVDIV_TFS / Dev10 / Releases / RTMRel / ndp / fx / src / Core / Microsoft / Scripting / Actions / ExpandoClass.cs / 1305376 / ExpandoClass.cs

                            /* **************************************************************************** 
 *
 * Copyright (c) Microsoft Corporation.
 *
 * This source code is subject to terms and conditions of the Microsoft Public License. A 
 * copy of the license can be found in the License.html file at the root of this distribution. If
 * you cannot locate the  Microsoft Public License, please send an email to 
 * dlr@microsoft.com. By using this source code in any fashion, you are agreeing to be bound 
 * by the terms of the Microsoft Public License.
 * 
 * You must not remove this notice, or any other, from this software.
 *
 *
 * ***************************************************************************/ 

using System; 
using System.Collections.Generic; 
using System.Diagnostics;
using System.Linq.Expressions; 
using System.Dynamic.Utils;
using System.Text;

namespace System.Dynamic { 
    /// 
    /// Represents a dynamically assigned class.  Expando objects which share the same 
    /// members will share the same class.  Classes are dynamically assigned as the 
    /// expando object gains members.
    ///  
    internal class ExpandoClass {
        private readonly string[] _keys;                            // list of names associated with each element in the data array, sorted
        private readonly int _hashCode;                             // pre-calculated hash code of all the keys the class contains
        private Dictionary> _transitions;  // cached transitions 

        private const int EmptyHashCode = 6551;                     // hash code of the empty ExpandoClass. 
 
        internal static ExpandoClass Empty = new ExpandoClass();    // The empty Expando class - all Expando objects start off w/ this class.
 
        /// 
        /// Constructs the empty ExpandoClass.  This is the class used when an
        /// empty Expando object is initially constructed.
        ///  
        internal ExpandoClass() {
            _hashCode = EmptyHashCode; 
            _keys = new string[0]; 
        }
 
        /// 
        /// Constructs a new ExpandoClass that can hold onto the specified keys.  The
        /// keys must be sorted ordinally.  The hash code must be precalculated for
        /// the keys. 
        /// 
        internal ExpandoClass(string[] keys, int hashCode) { 
            _hashCode = hashCode; 
            _keys = keys;
        } 

        /// 
        /// Finds or creates a new ExpandoClass given the existing set of keys
        /// in this ExpandoClass plus the new key to be added. Members in an 
        /// ExpandoClass are always stored case sensitively.
        ///  
        internal ExpandoClass FindNewClass(string newKey) { 
            // just XOR the newKey hash code
            int hashCode = _hashCode ^ newKey.GetHashCode(); 

            lock (this) {
                List infos = GetTransitionList(hashCode);
 
                for (int i = 0; i < infos.Count; i++) {
                    ExpandoClass klass = infos[i].Target as ExpandoClass; 
                    if (klass == null) { 
                        infos.RemoveAt(i);
                        i--; 
                        continue;
                    }

                    if (string.Equals(klass._keys[klass._keys.Length - 1], newKey, StringComparison.Ordinal)) { 
                        // the new key is the key we added in this transition
                        return klass; 
                    } 
                }
 
                // no applicable transition, create a new one
                string[] keys = new string[_keys.Length + 1];
                Array.Copy(_keys, keys, _keys.Length);
                keys[_keys.Length] = newKey; 
                ExpandoClass ec = new ExpandoClass(keys, hashCode);
 
                infos.Add(new WeakReference(ec)); 
                return ec;
            } 
        }

        /// 
        /// Gets the lists of transitions that are valid from this ExpandoClass 
        /// to an ExpandoClass whos keys hash to the apporopriate hash code.
        ///  
        private List GetTransitionList(int hashCode) { 
            if (_transitions == null) {
                _transitions = new Dictionary>(); 
            }

            List infos;
            if (!_transitions.TryGetValue(hashCode, out infos)) { 
                _transitions[hashCode] = infos = new List();
            } 
 
            return infos;
        } 

        /// 
        /// Gets the index at which the value should be stored for the specified name.
        ///  
        internal int GetValueIndex(string name, bool caseInsensitive, ExpandoObject obj) {
            if (caseInsensitive) { 
                return GetValueIndexCaseInsensitive(name, obj); 
            } else {
                return GetValueIndexCaseSensitive(name); 
            }
        }

        ///  
        /// Gets the index at which the value should be stored for the specified name
        /// case sensitively. Returns the index even if the member is marked as deleted. 
        ///  
        internal int GetValueIndexCaseSensitive(string name) {
            for (int i = 0; i < _keys.Length; i++) { 
                if (string.Equals(
                    _keys[i],
                    name,
                    StringComparison.Ordinal)) { 
                    return i;
                } 
            } 
            return ExpandoObject.NoMatch;
        } 

        /// 
        /// Gets the index at which the value should be stored for the specified name,
        /// the method is only used in the case-insensitive case. 
        /// 
        /// the name of the member 
        /// The ExpandoObject associated with the class 
        /// that is used to check if a member has been deleted.
        ///  
        /// the exact match if there is one
        /// if there is exactly one member with case insensitive match, return it
        /// otherwise we throw AmbiguousMatchException.
        ///  
        private int GetValueIndexCaseInsensitive(string name, ExpandoObject obj) {
            int caseInsensitiveMatch = ExpandoObject.NoMatch; //the location of the case-insensitive matching member 
            lock (obj.LockObject) { 
                for (int i = _keys.Length - 1; i >= 0; i--) {
                    if (string.Equals( 
                        _keys[i],
                        name,
                        StringComparison.OrdinalIgnoreCase)) {
                        //if the matching member is deleted, continue searching 
                        if (!obj.IsDeletedMember(i)) {
                            if (caseInsensitiveMatch == ExpandoObject.NoMatch) { 
                                caseInsensitiveMatch = i; 
                            } else {
                                //Ambigous match, stop searching 
                                return ExpandoObject.AmbiguousMatchFound;
                            }
                        }
                    } 
                }
            } 
            //There is exactly one member with case insensitive match. 
            return caseInsensitiveMatch;
        } 

        /// 
        /// Gets the names of the keys that can be stored in the Expando class.  The
        /// list is sorted ordinally. 
        /// 
        internal string[] Keys { 
            get { 
                return _keys;
            } 
        }
    }
}

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

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