/IronPython_Main/Runtime/Microsoft.Dynamic/Debugging/CollectionUtils.cs

/* ****************************************************************************

 *

 * Copyright (c) Microsoft Corporation. 

 *

 * This source code is subject to terms and conditions of the Apache License, Version 2.0. A 

 * copy of the license can be found in the License.html file at the root of this distribution. If 

 * you cannot locate the  Apache License, Version 2.0, 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 Apache License, Version 2.0.

 *

 * You must not remove this notice, or any other, from this software.

 *

 *

 * ***************************************************************************/



using System;

using System.Collections.Generic;

using System.Text;



namespace Microsoft.Scripting.Debugging {

    internal static class CollectionUtils {

        internal static T[] RemoveLast<T>(this T[] array) {

            T[] result = new T[array.Length - 1];

            Array.Copy(array, 0, result, 0, result.Length);

            return result;

        }



        internal static bool ListEquals<T>(this ICollection<T> first, ICollection<T> second) {

            if (first.Count != second.Count) {

                return false;

            }

            var cmp = EqualityComparer<T>.Default;

            var f = first.GetEnumerator();

            var s = second.GetEnumerator();

            while (f.MoveNext()) {

                s.MoveNext();



                if (!cmp.Equals(f.Current, s.Current)) {

                    return false;

                }

            }

            return true;

        }



        internal static int ListHashCode<T>(this IEnumerable<T> list) {

            var cmp = EqualityComparer<T>.Default;

            int h = 6551;

            foreach (T t in list) {

                h ^= (h << 5) ^ cmp.GetHashCode(t);

            }

            return h;

        }

    }



    // Compares two ICollection<T>'s using element equality

    internal sealed class ListEqualityComparer<T> : EqualityComparer<ICollection<T>> {

        internal static readonly ListEqualityComparer<T> Instance = new ListEqualityComparer<T>();



        private ListEqualityComparer() { }



        // EqualityComparer<T> handles null and object identity for us

        public override bool Equals(ICollection<T> x, ICollection<T> y) {

            return x.ListEquals(y);

        }



        public override int GetHashCode(ICollection<T> obj) {

            return obj.ListHashCode();

        }

    }

}