Optimize the save performance of page elements

stevencohn#1122

OneMore/Helpers/Extensions/HashAlgorithmExtensions.cs

@@ -0,0 +1,21 @@
+//************************************************************************************************
+// Copyright © 2032 Steven M Cohn. All rights reserved.
+//************************************************************************************************
+
+namespace River.OneMoreAddIn
+{
+ using System.Numerics;
+ using System.Security.Cryptography;
+ using System.Text;
+
+
+ internal static class HashAlgorithmExtensions
+ {
+ public static string GetHashString(this HashAlgorithm algorithm, string s)
+ {
+ var data = Encoding.UTF8.GetBytes(s);
+ var hash = algorithm.ComputeHash(data);
+ return new BigInteger(hash).ToString();
+ }
+ }
+}

OneMore/Models/Page.cs

@@ -17,7 +17,7 @@ namespace River.OneMoreAddIn.Models
  using System.Globalization;
  using System.Linq;
  using System.Media;
- using System.Security.Policy;
+ using System.Security.Cryptography;
  using System.Text;
  using System.Text.RegularExpressions;
  using System.Xml;
@@ -31,6 +31,8 @@ public partial class Page
  {
  public int TopOutlinePosition = 86;
 
+ private const string HashAttributeName = "omHash";
+
 
  /// <summary>
  /// Initialize a new instance with the given page XML root
@@ -40,16 +42,65 @@ public Page(XElement root)
  {
  if (root != null)
  {
- Root = root;
  Namespace = root.GetNamespaceOfPrefix(OneNote.Prefix);
-
  PageId = root.Attribute("ID")?.Value;
+ ComputeHashes(root);
+
+ Root = root;
  }
 
  SelectionScope = SelectionScope.Unknown;
  }
 
 
+ #region Hashing
+ /// <summary>
+ /// Calculates a hash value for each 1st gen child element on the page, which will
+ /// be used to optimize the page just prior to saving.
+ /// </summary>
+ /// <param name="root">The root element of the page</param>
+ private void ComputeHashes(XElement root)
+ {
+ using var algo = MD5.Create();
+
+ // 1st generation child elements of the Page
+ foreach (var child in root.Elements())
+ {
+ child.Add(new XAttribute(
+ HashAttributeName,
+ algo.GetHashString(child.ToString(SaveOptions.DisableFormatting))
+ ));
+ }
+ }
+
+
+ /// <summary>
+ /// Keeps only modified 1st gen child elements of the page to optimize save performance
+ /// especially when the page is loaded with many Ink drawings.
+ /// </summary>
+ public void OptimizeForSave()
+ {
+ // MD5 should be sufficient and performs better than any other algorithm
+ using var algo = MD5.Create();
+
+ // 1st generation child elements of the Page
+ foreach (var child in Root.Elements().ToList())
+ {
+ var att = child.Attribute(HashAttributeName);
+ if (att != null)
+ {
+ att.Remove();
+ var hash = algo.GetHashString(child.ToString(SaveOptions.DisableFormatting));
+ if (hash == att.Value)
+ {
+ child.Remove();
+ }
+ }
+ }
+ }
+ #endregion Hashing
+
+
  public bool IsValid => Root != null;
 
 

OneMore/OneMore.csproj

@@ -241,6 +241,7 @@
  <Compile Include="Helpers\ColorHelper.cs" />
  <Compile Include="Helpers\Extensions\FontFamilyExtensions.cs" />
  <Compile Include="Helpers\Extensions\GraphicsExtensions.cs" />
+ <Compile Include="Helpers\Extensions\HashAlgorithmExtensions.cs" />
  <Compile Include="Helpers\Extensions\ScreenExtensions.cs" />
  <Compile Include="Models\KnownSchemaAttributes.cs" />
  <Compile Include="Models\PageReader.cs" />

OneMore/OneNote.cs

@@ -1047,22 +1047,13 @@ public async Task Update(Page page)
  return;
  }
 
- await Update(page.Root);
- }
+ // must optimize before we can validate schema...
 
+ page.OptimizeForSave();
 
- /// <summary>
- /// Updates the given content, with a unique ID, on the current page.
- /// </summary>
- /// <param name="element">A page or element within a page with a unique objectID</param>
- public async Task Update(XElement element)
- {
- if (element.Name.LocalName == "Page")
+ if (!ValidateSchema(page.Root))
  {
- if (!ValidateSchema(element))
- {
- return;
- }
+ return;
  }
 
  // dateExpectedLastModified is merely a pessimistic-locking safeguard to prevent
@@ -1072,7 +1063,7 @@ public async Task Update(XElement element)
  // ? DateTime.Parse(att.Value).ToUniversalTime()
  // : DateTime.MinValue;
 
- var xml = element.ToString(SaveOptions.DisableFormatting);
+ var xml = page.Root.ToString(SaveOptions.DisableFormatting);
 
  await InvokeWithRetry(() =>
  {