Introduce equality comparers for OpenXmlElement

src/DocumentFormat.OpenXml.Framework/Equality/FrameworkHashCode.cs

@@ -0,0 +1,31 @@
+// Copyright (c) Microsoft. All rights reserved.
+// Licensed under the MIT license. See LICENSE file in the project root for full license information.
+
+namespace DocumentFormat.OpenXml
+{
+    internal ref struct FrameworkHashCode
+    {
+        private const int Seed = 23;
+        private const int Combinator = 37;
+
+        private int _code;
+
+        public FrameworkHashCode()
+        {
+            this._code = Seed;
+        }
+
+        internal void Add(object? value)
+        {
+            if (value != null)
+            {
+                unchecked
+                {
+                    this._code += value.GetHashCode() * Combinator;
+                }
+            }
+        }
+
+        internal readonly int GetHash => this._code;
+    }
+}

src/DocumentFormat.OpenXml.Framework/Equality/OpenXmlElementComparers.cs

@@ -0,0 +1,28 @@
+// Copyright (c) Microsoft. All rights reserved.
+// Licensed under the MIT license. See LICENSE file in the project root for full license information.
+
+using System.Collections.Generic;
+
+namespace DocumentFormat.OpenXml
+{
+    /// <summary>
+    /// Equality comparer for determining value equality for <see cref="OpenXmlElement"/>.
+    /// </summary>
+    public static class OpenXmlElementComparers
+    {
+        /// <summary>
+        /// Gets the default equality comparer.
+        /// </summary>
+        public static readonly IEqualityComparer<OpenXmlElement> Default = GetEqualityComparer(new OpenXmlElementEqualityOptions());
+
+        /// <summary>
+        /// Gets the <see cref="IEqualityComparer{OpenXmlElement}"/> based on the given options./>
+        /// </summary>
+        /// <param name="openXmlElementEqualityOptions">The options defining equality.</param>
+        /// <returns></returns>
+        public static IEqualityComparer<OpenXmlElement> GetEqualityComparer(OpenXmlElementEqualityOptions openXmlElementEqualityOptions)
+        {
+            return new OpenXmlElementEqualityComparer(openXmlElementEqualityOptions);
+        }
+    }
+}

src/DocumentFormat.OpenXml.Framework/Equality/OpenXmlElementEqualityComparer.cs

@@ -0,0 +1,255 @@
+// Copyright (c) Microsoft. All rights reserved.
+// Licensed under the MIT license. See LICENSE file in the project root for full license information.
+
+using DocumentFormat.OpenXml.Framework;
+
+using System;
+using System.Collections.Generic;
+using System.Diagnostics.CodeAnalysis;
+using System.Linq;
+
+namespace DocumentFormat.OpenXml
+{
+    internal sealed class OpenXmlElementEqualityComparer : IEqualityComparer<OpenXmlElement>
+    {
+        /// <summary>
+        /// Gets the options regulating how equality is defined.
+        /// </summary>
+        internal OpenXmlElementEqualityOptions Options { get; }
+
+        internal OpenXmlElementEqualityComparer(OpenXmlElementEqualityOptions options)
+        {
+            this.Options = options;
+        }
+
+        /// <summary>
+        /// Determines equality for two given <see cref="OpenXmlElement"/>.
+        /// </summary>
+        /// <param name="x">First object.</param>
+        /// <param name="y">Second object.</param>
+        /// <returns></returns>
+        public bool Equals(OpenXmlElement? x, OpenXmlElement? y)
+        {
+            if (ReferenceEquals(x, y))
+            {
+                return true;
+            }
+
+            if (x == null || y == null)
+            {
+                return false;
+            }
+
+            if (x.GetType() != y.GetType())
+            {
+                return false;
+            }
+
+            if (!this.Options.RequireParsed)
+            {
+                if (!x.XmlParsed && !y.XmlParsed)
+                {
+                    return string.Equals(x.RawOuterXml, y.RawOuterXml, StringComparison.Ordinal);
+                }
+            }
+
+            x.MakeSureParsed();
+            y.MakeSureParsed();
+
+            if (x.HasChildren != y.HasChildren)
+            {
+                return false;
+            }
+
+            if (!OpenXmlElementEqualityComparer.PrefixAndQNameEqual(x, y, this.Options))
+            {
+                return false;
+            }
+
+            if (x is OpenXmlLeafTextElement)
+            {
+                if (!string.Equals(x.InnerText, y.InnerText, StringComparison.Ordinal))
+                {
+                    return false;
+                }
+            }
+
+            if (x.HasChildren)
+            {
+                // DEVNOTE: Do not refactor this to use "simpler" for construct.
+                // The indexer on ChildElement walks the linked list for each operation,
+                // not maintaining state so it turns into a O(n^2) operation.
+                OpenXmlElementList.Enumerator tChilds = x.ChildElements.GetEnumerator();
+                OpenXmlElementList.Enumerator oChilds = y.ChildElements.GetEnumerator();
+
+                int e1 = 0, e2 = 0;
+                while (OpenXmlElementEqualityComparer.MoveNextAndTrackCount(ref tChilds, ref oChilds, ref e1, ref e2))
+                {
+                    if (!this.Equals(tChilds.Current, oChilds.Current))
+                    {
+                        return false;
+                    }
+                }
+
+                // Different amount of children.
+                if (e1 != e2)
+                {
+                    return false;
+                }
+            }
+
+            if (this.Options.IncludeExtendedAttributes)
+            {
+                if (x.ExtendedAttributes == null != (y.ExtendedAttributes == null))
+                {
+                    return false;
+                }
+
+                if (x.ExtendedAttributes != null && y.ExtendedAttributes != null)
+                {
+                    if (x.ExtendedAttributes.Count() != y.ExtendedAttributes.Count())
+                    {
+                        return false;
+                    }
+
+                    for (int i = 0; i < x.ExtendedAttributes.Count(); i++)
+                    {
+                        if (!x.ExtendedAttributes.ElementAt(i).Equals(y.ExtendedAttributes.ElementAt(i)))
+                        {
+                            return false;
+                        }
+                    }
+                }
+            }
+
+            for (int i = 0; i < x.ParsedState.Attributes.Length; i++)
+            {
+                var tAttr = x.ParsedState.Attributes[i];
+                var oAttr = y.ParsedState.Attributes[i];
+
+                if ((tAttr.Value == null && oAttr.Value != null) || (tAttr.Value != null && oAttr.Value == null))
+                {
+                    return false;
+                }
+
+                if (tAttr.Value == null)
+                {
+                    continue;
+                }
+
+                if (!tAttr.Value.Equals(oAttr.Value))
+                {
+                    return false;
+                }
+            }
+
+            if (this.Options.IncludeMCAttributes)
+            {
+                if (x.MCAttributes == null != (y.MCAttributes == null) || (x.MCAttributes != null && !x.MCAttributes.Equals(y.MCAttributes)))
+                {
+                    return false;
+                }
+            }
+
+            return true;
+        }
+
+        /// <summary>
+        /// Calculates a hashcode based on the given <see cref="OpenXmlElement"/> object.
+        /// </summary>
+        /// <param name="obj">The object to get a hashcode for.</param>
+        /// <returns></returns>
+        public int GetHashCode([DisallowNull] OpenXmlElement obj)
+        {
+            if (obj == null)
+            {
+                return 0;
+            }
+
+            var hc = default(FrameworkHashCode);
+            if (this.Options.IncludeMCAttributes)
+            {
+                hc.Add(obj.MCAttributes);
+            }
+
+            for (int i = 0; i < obj.ParsedState.Attributes.Length; i++)
+            {
+                if (obj.ParsedState.Attributes[i].Value != null)
+                {
+                    hc.Add(obj.ParsedState.Attributes[i].Value);
+                }
+            }
+
+            if (this.Options.IncludeExtendedAttributes)
+            {
+                foreach (OpenXmlAttribute attr in obj.ExtendedAttributes)
+                {
+                    hc.Add(attr);
+                }
+            }
+
+            if (obj.HasChildren)
+            {
+                foreach (OpenXmlElement child in obj.ChildElements)
+                {
+                    hc.Add(child);
+                }
+            }
+
+            return hc.GetHash;
+        }
+
+        internal static bool PrefixAndQNameEqual(OpenXmlElement x, OpenXmlElement y, OpenXmlElementEqualityOptions options)
+        {
+            OpenXmlQualifiedName tQName = x.ParsedState.Metadata.QName;
+            OpenXmlQualifiedName oQName = y.ParsedState.Metadata.QName;
+
+            if (!tQName.Equals(oQName))
+            {
+                return false;
+            }
+
+            if (options.SkipPrefixComparison)
+            {
+                return true;
+            }
+
+            string turi = tQName.Namespace.Uri;
+            string ouri = oQName.Namespace.Uri;
+
+            var tPrefix = x.LookupPrefixLocal(ouri);
+            var oPrefix = y.LookupPrefixLocal(ouri);
+
+            if (string.IsNullOrEmpty(tPrefix))
+            {
+               tPrefix = x.Features.GetNamespaceResolver().LookupPrefix(turi);
+            }
+
+            if (string.IsNullOrEmpty(oPrefix))
+            {
+                oPrefix = y.Features.GetNamespaceResolver().LookupPrefix(ouri);
+            }
+
+            return string.Equals(tPrefix, oPrefix, StringComparison.Ordinal);
+        }
+
+        internal static bool MoveNextAndTrackCount(ref OpenXmlElementList.Enumerator e1, ref OpenXmlElementList.Enumerator e2, ref int e1ctr, ref int e2ctr)
+        {
+            if (e1.MoveNext())
+            {
+                e1ctr++;
+                if (e2.MoveNext())
+                {
+                    e2ctr++;
+                    return true;
+                }
+            }
+            else if (e2.MoveNext())
+            {
+                e2ctr++;
+            }
+
+            return false;
+        }
+    }
+}

src/DocumentFormat.OpenXml.Framework/Equality/OpenXmlElementEqualityOptions.cs

@@ -0,0 +1,31 @@
+// Copyright (c) Microsoft. All rights reserved.
+// Licensed under the MIT license. See LICENSE file in the project root for full license information.
+
+namespace DocumentFormat.OpenXml
+{
+    /// <summary>
+    /// Options defining the behaviour of equality for <see cref="OpenXmlElement"/>.
+    /// </summary>
+    public sealed class OpenXmlElementEqualityOptions
+    {
+        /// <summary>
+        /// Gets or sets a value indicating whether extended attributes should be considered when determining equality.
+        /// </summary>
+        public bool IncludeExtendedAttributes { get; set; } = true;
+
+        /// <summary>
+        /// Gets or sets a value indicating whether mC attributes should be considered when determining equality.
+        /// </summary>
+        public bool IncludeMCAttributes { get; set; } = true;
+
+        /// <summary>
+        /// Gets or sets a value indicating whether namespace should alone be used when comparing idenity of elements, skipping prefix lookup to improve performance.
+        /// </summary>
+        public bool SkipPrefixComparison { get; set; }
+
+        /// <summary>
+        /// Gets or sets a value indicating whether elements must be parsed which ensures order of schema is used instead of input ordering.
+        /// </summary>
+        public bool RequireParsed { get; set; }
+    }
+}