Imported Upstream version 4.6.0.125

Former-commit-id: a2155e9bd80020e49e72e86c44da02a8ac0e57a4

mcs/class/referencesource/System.Data.DataSetExtensions/System/Data/DataRowComparer.cs

@@ -0,0 +1,246 @@
+//------------------------------------------------------------------------------
+// <copyright file="DataRowComparer.cs" company="Microsoft">
+//     Copyright (c) Microsoft Corporation.  All rights reserved.
+// </copyright>
+// <owner current="true" primary="true">[....]</owner>
+// <owner current="true" primary="false">spather</owner>
+//------------------------------------------------------------------------------
+using System;
+using System.Data;
+using System.Collections;
+using System.Collections.Generic;
+using System.Diagnostics;
+using System.Data.DataSetExtensions;
+
+namespace System.Data
+{
+    /// <summary>
+    /// This class implements IEqualityComparer using value based semantics
+    /// when comparing DataRows.
+    /// </summary>
+    public static class DataRowComparer
+    {
+        /// <summary>
+        /// Gets the singleton instance of the data row comparer.
+        /// </summary>
+        public static DataRowComparer<DataRow> Default { get { return DataRowComparer<DataRow>.Default; } }
+
+        internal static bool AreEqual(object a, object b)
+        {
+            if (Object.ReferenceEquals(a, b))
+            {   // same reference or (null, null) or (DBNull.Value, DBNull.Value)
+                return true;
+            }
+            if (Object.ReferenceEquals(a, null) || Object.ReferenceEquals(a, DBNull.Value) ||
+                Object.ReferenceEquals(b, null) || Object.ReferenceEquals(b, DBNull.Value))
+            {   // (null, non-null) or (null, DBNull.Value) or vice versa
+                return false;
+            }
+            return (a.Equals(b) || (a.GetType().IsArray && CompareArray((Array)a, b as Array)));
+        }
+
+        private static bool AreElementEqual(object a, object b)
+        {
+            if (Object.ReferenceEquals(a, b))
+            {   // same reference or (null, null) or (DBNull.Value, DBNull.Value)
+                return true;
+            }
+            if (Object.ReferenceEquals(a, null) || Object.ReferenceEquals(a, DBNull.Value) ||
+                Object.ReferenceEquals(b, null) || Object.ReferenceEquals(b, DBNull.Value))
+            {   // (null, non-null) or (null, DBNull.Value) or vice versa
+                return false;
+            }
+            return a.Equals(b);
+        }
+
+        private static bool CompareArray(Array a, Array b)
+        {
+            if ((null == b) ||
+                (1 != a.Rank) ||
+                (1 != b.Rank) ||
+                (a.Length != b.Length))
+            {   // automatically consider array's with Rank>1 not-equal
+                return false;
+            }
+
+            int index1 = a.GetLowerBound(0);
+            int index2 = b.GetLowerBound(0);
+            if (a.GetType() == b.GetType() && (0 == index1) && (0 == index2))
+            {
+                switch (Type.GetTypeCode(a.GetType().GetElementType()))
+                {
+                    case TypeCode.Byte:
+                        return DataRowComparer.CompareEquatableArray<Byte>((Byte[])a, (Byte[])b);
+                    case TypeCode.Int16:
+                        return DataRowComparer.CompareEquatableArray<Int16>((Int16[])a, (Int16[])b);
+                    case TypeCode.Int32:
+                        return DataRowComparer.CompareEquatableArray<Int32>((Int32[])a, (Int32[])b);
+                    case TypeCode.Int64:
+                        return DataRowComparer.CompareEquatableArray<Int64>((Int64[])a, (Int64[])b);
+                    case TypeCode.String:
+                        return DataRowComparer.CompareEquatableArray<String>((String[])a, (String[])b);
+                }
+            }
+
+            //Compare every element. But don't recurse if we have Array of array.
+            int length = index1 + a.Length;
+            for (; index1 < length; ++index1, ++index2)
+            {
+                if (!AreElementEqual(a.GetValue(index1), b.GetValue(index2)))
+                {
+                    return false;
+                }
+            }
+            return true;
+        }
+
+        private static bool CompareEquatableArray<TElem>(TElem[] a, TElem[] b) where TElem : IEquatable<TElem>
+        {
+            if (Object.ReferenceEquals(a, b))
+            {
+                return true;
+            }
+            if (Object.ReferenceEquals(a, null) ||
+                Object.ReferenceEquals(b, null))
+            {
+                return false;
+            }
+            if (a.Length != b.Length)
+            {
+                return false;
+            }
+
+            for (int i = 0; i < a.Length; ++i)
+            {
+                if (!a[i].Equals(b[i]))
+                {
+                    return false;
+                }
+            }
+            return true;
+        }
+    }
+
+    /// <summary>
+    /// This class implements IEqualityComparer using value based semantics
+    /// when comparing DataRows.
+    /// </summary>
+    public sealed class DataRowComparer<TRow> : IEqualityComparer<TRow> where TRow : DataRow
+    {
+        /// <summary>
+        /// Private constructor to prevent initialization outside of Default singleton instance.
+        /// </summary>
+        private DataRowComparer() { }
+
+        private static DataRowComparer<TRow> _instance = new DataRowComparer<TRow>();
+
+        /// <summary>
+        /// Gets the singleton instance of the data row comparer.
+        /// </summary>
+        public static DataRowComparer<TRow> Default { get { return _instance; } }
+
+        /// <summary>
+        /// This method compares to DataRows by doing a column by column value based
+        /// comparision.
+        /// </summary>
+        /// <param name="leftRow">
+        ///   The first input DataRow
+        /// </param>
+        /// <param name="rightRow">
+        ///   The second input DataRow
+        /// </param>
+        /// <returns>
+        ///   True if rows are equal, false if not.
+        /// </returns>
+        public bool Equals(TRow leftRow, TRow rightRow)
+        {
+            if (Object.ReferenceEquals(leftRow, rightRow))
+            {
+                return true;
+            }
+            if (Object.ReferenceEquals(leftRow, null) ||
+                Object.ReferenceEquals(rightRow, null))
+            {
+                return false;
+            }
+
+            if (leftRow.RowState == DataRowState.Deleted || rightRow.RowState == DataRowState.Deleted)
+            {
+                throw DataSetUtil.InvalidOperation(Strings.DataSetLinq_CannotCompareDeletedRow);
+            }
+
+            int count = leftRow.Table.Columns.Count;
+            if (count != rightRow.Table.Columns.Count)
+            {
+                return false;
+            }
+
+            for (int i = 0; i < count; ++i)
+            {
+                if (!DataRowComparer.AreEqual(leftRow[i], rightRow[i]))
+                {
+                    return false;
+                }
+            }
+            return true;
+        }
+
+        /// <summary>
+        /// This mtheod retrieves a hash code for the source row.
+        /// </summary>
+        /// <param name="row">
+        ///   The source DataRow
+        /// </param>
+        /// <returns>
+        ///   HashCode for row based on values in the row.
+        /// </returns>
+        public int GetHashCode(TRow row)
+        {
+            DataSetUtil.CheckArgumentNull(row, "row");
+
+            if (row.RowState == DataRowState.Deleted)
+            {
+                throw DataSetUtil.InvalidOperation(Strings.DataSetLinq_CannotCompareDeletedRow);
+            }
+
+            int hash = 0;
+            Debug.Assert(row.Table != null);
+            if (row.Table.Columns.Count > 0)
+            {
+                // if the row has at least one column, then use the first column value
+                object value = row[0];
+
+                Type valueType = value.GetType();
+                if (valueType.IsArray)
+                {
+                    Array array = value as Array;
+
+                    if (array.Rank > 1)
+                    {
+                        hash = value.GetHashCode();
+                    }
+                    else if (array.Length > 0)
+                    {
+                        hash = array.GetValue(array.GetLowerBound(0)).GetHashCode();
+                    }
+                }
+                else
+                {
+                    System.ValueType vt = value as System.ValueType;
+
+                    // have to unbox value types.
+                    if (vt != null)
+                    {
+                        hash = vt.GetHashCode();
+                    }
+                    else
+                    {
+                        hash = value.GetHashCode();
+                    }
+                }
+            }
+            // if table has no columns, the hash code is 0
+            return hash;
+        }
+    }
+}