[lucenenet] 09/27: Lucene.Net.Util.Automaton: Fixed State class to initialize and trim more efficiently (#295, #261). Fixes the performance of Lucene.Net.Util.Automaton.TestBasicOperations::TestEmptyLanguageConcatenate().

[ni...@apache.org]

This is an automated email from the ASF dual-hosted git repository.

nightowl888 pushed a commit to branch master
in repository https://gitbox.apache.org/repos/asf/lucenenet.git

commit 867834b34068692c8adecff9fee690b9390a4ca5
Author: Shad Storhaug <sh...@shadstorhaug.com>
AuthorDate: Sun Jun 28 21:49:07 2020 +0700

    Lucene.Net.Util.Automaton: Fixed State class to initialize and trim more efficiently (#295, #261). Fixes the performance of Lucene.Net.Util.Automaton.TestBasicOperations::TestEmptyLanguageConcatenate().
---
 Directory.Build.targets                |  8 +++++++-
 src/Lucene.Net/Util/Automaton/State.cs | 20 +++++++++++++-------
 2 files changed, 20 insertions(+), 8 deletions(-)

diff --git a/Directory.Build.targets b/Directory.Build.targets
index a0bdb4d..88f406b 100644
--- a/Directory.Build.targets
+++ b/Directory.Build.targets
@@ -19,8 +19,10 @@
 
 -->
 <Project>
+  <!-- Features in .NET Standard and .NET Core only (no .NET Framework support) -->
   <PropertyGroup Condition=" $(TargetFramework.StartsWith('netstandard')) Or $(TargetFramework.StartsWith('netcoreapp')) ">
     <DefineConstants>$(DefineConstants);NETSTANDARD</DefineConstants>
+    <DefineConstants>$(DefineConstants);FEATURE_ARRAYEMPTY</DefineConstants>
     <DebugType>portable</DebugType>
   </PropertyGroup>
 
@@ -66,7 +68,11 @@
     
   </PropertyGroup>
 
-  <!-- Features in .NET Framework 4.5+ only -->
+  <!-- Features in .NET Framework 4.6+ only -->
+  <PropertyGroup Condition="$(TargetFramework.StartsWith('net46')) Or $(TargetFramework.StartsWith('net47')) Or $(TargetFramework.StartsWith('net48'))">
+    <DefineConstants>$(DefineConstants);FEATURE_ARRAYEMPTY</DefineConstants>
+  </PropertyGroup>
+
   <PropertyGroup Condition="$(TargetFramework.StartsWith('net4'))">
     
     <DefineConstants>$(DefineConstants);FEATURE_SERIALIZABLE_EXCEPTIONS</DefineConstants>
diff --git a/src/Lucene.Net/Util/Automaton/State.cs b/src/Lucene.Net/Util/Automaton/State.cs
index 587c403..1df6c98 100644
--- a/src/Lucene.Net/Util/Automaton/State.cs
+++ b/src/Lucene.Net/Util/Automaton/State.cs
@@ -48,11 +48,15 @@ namespace Lucene.Net.Util.Automaton
         [SuppressMessage("Microsoft.Performance", "CA1819", Justification = "Lucene's design requires some writable array properties")]
         public Transition[] TransitionsArray
         {
-            get { return transitionsArray; }
+            get => transitionsArray;
             // LUCENENET NOTE: Setter removed because it is apparently not in use outside of this class
         }
-        private Transition[] transitionsArray;
-        internal int numTransitions; // LUCENENET NOTE: Made internal because we already have a public property for access
+#if FEATURE_ARRAYEMPTY
+        private Transition[] transitionsArray = Array.Empty<Transition>();
+#else
+        private Transition[] transitionsArray = new Transition[0];
+#endif
+        internal int numTransitions = 0;// LUCENENET NOTE: Made internal because we already have a public property for access
 
         internal int number;
 
@@ -64,7 +68,7 @@ namespace Lucene.Net.Util.Automaton
         /// </summary>
         public State()
         {
-            ResetTransitions();
+            //ResetTransitions(); // LUCENENET: Let class initializer set these
             id = next_id++;
         }
 
@@ -73,7 +77,11 @@ namespace Lucene.Net.Util.Automaton
         /// </summary>
         internal void ResetTransitions()
         {
+#if FEATURE_ARRAYEMPTY
+            transitionsArray = Array.Empty<Transition>();
+#else
             transitionsArray = new Transition[0];
+#endif
             numTransitions = 0;
         }
 
@@ -242,9 +250,7 @@ namespace Lucene.Net.Util.Automaton
         {
             if (numTransitions < transitionsArray.Length)
             {
-                Transition[] newArray = new Transition[numTransitions];
-                Array.Copy(transitionsArray, 0, newArray, 0, numTransitions);
-                transitionsArray = newArray;
+                Array.Resize(ref transitionsArray, numTransitions); // LUCENENET: Resize rather than copy
             }
         }