Reuse the objects to improve the performance of parsing WKTs. (#548)

Parsing of every WKT through WKTReader.Read() is initailizing new object of 'StreamTokenizerSettings' with default values and then overwritting it. Changes are done to initialize it once and re-use it with every WKTReader.Read() method.

src/NetTopologySuite/ApiCompatBaseline.txt

@@ -0,0 +1,3 @@
+Compat issues with assembly NetTopologySuite:
+CannotChangeAttribute : Attribute 'System.Runtime.CompilerServices.IteratorStateMachineAttribute' on 'RTools_NTS.Util.StreamTokenizer.GetEnumerator()' changed from '[IteratorStateMachineAttribute(typeof(StreamTokenizer.<GetEnumerator>d__33))]' in the contract to '[IteratorStateMachineAttribute(typeof(StreamTokenizer.<GetEnumerator>d__34))]' in the implementation.
+Total Issues: 1

src/NetTopologySuite/IO/WKTReader.cs

@@ -44,6 +44,8 @@ public class WKTReader
 
         private static readonly CoordinateSequenceFactory CoordinateSequenceFactoryXYZM = CoordinateArraySequenceFactory.Instance;
 
+        private static readonly StreamTokenizerSettings tokenizerSettings;
+
         private NtsGeometryServices _ntsGeometryServices;
 
         private int? _overriddenDefaultSRID;
@@ -56,6 +58,23 @@ public class WKTReader
          */
         private bool _isStrict = true;
 
+        static WKTReader()
+        {
+            tokenizerSettings = new StreamTokenizerSettings();
+            tokenizerSettings.SetDefaults();
+            // set tokenizer to NOT parse numbers
+            tokenizerSettings.ResetCharTypeTable();
+            tokenizerSettings.WordChars('a', 'z');
+            tokenizerSettings.WordChars('A', 'Z');
+            ////tokenizer.Settings.WordChars(128 + 32, 255);
+            tokenizerSettings.WordChars('0', '9');
+            tokenizerSettings.WordChars('-', '-');
+            tokenizerSettings.WordChars('+', '+');
+            tokenizerSettings.WordChars('.', '.');
+            tokenizerSettings.WhitespaceChars(0, ' ');
+            tokenizerSettings.CommentChar('#');
+        }
+
         /// <summary>
         /// Creates a <c>WKTReader</c> that creates objects using a basic GeometryFactory.
         /// </summary>
@@ -203,19 +222,7 @@ public Geometry Read(TextReader reader)
 
         internal TokenStream Tokenizer(TextReader reader)
         {
-            var tokenizer = new StreamTokenizer(reader);
-
-            // set tokenizer to NOT parse numbers
-            tokenizer.Settings.ResetCharTypeTable();
-            tokenizer.Settings.WordChars('a', 'z');
-            tokenizer.Settings.WordChars('A', 'Z');
-            ////tokenizer.Settings.WordChars(128 + 32, 255);
-            tokenizer.Settings.WordChars('0', '9');
-            tokenizer.Settings.WordChars('-', '-');
-            tokenizer.Settings.WordChars('+', '+');
-            tokenizer.Settings.WordChars('.', '.');
-            tokenizer.Settings.WhitespaceChars(0, ' ');
-            tokenizer.Settings.CommentChar('#');
+            var tokenizer = new StreamTokenizer(reader, tokenizerSettings);
             return new TokenStream(tokenizer.GetEnumerator());
         }
 

src/NetTopologySuite/Utilities/RToolsUtil/StreamTokenizer.cs

@@ -704,6 +704,18 @@ public StreamTokenizer(TextReader sr)
             textReader = sr;
         }
 
+        /// <summary>
+        /// Construct and set this object's TextReader to the one specified.
+        /// </summary>
+        /// <param name="sr">The TextReader to read from.</param>
+        /// <param name="tokenizerSettings">Tokenizer settings.</param>
+        public StreamTokenizer(TextReader sr, StreamTokenizerSettings tokenizerSettings)
+        {
+            settings = tokenizerSettings;
+            Initialize();
+            textReader = sr;
+        }
+
         /// <summary>
         /// Construct and set a string to tokenize.
         /// </summary>
@@ -723,8 +735,11 @@ void Initialize()
             nextTokenSb = new CharBuffer(1024);
 
             InitializeStream();
-            settings = new StreamTokenizerSettings();
-            settings.SetDefaults();
+            if (null == settings)
+            {
+                settings = new StreamTokenizerSettings();
+                settings.SetDefaults();
+            }
 
             expSb = new CharBuffer();
             tmpSb = new CharBuffer();