Optimize array access and add ability to hint array size

Jint.Tests.CommonScripts/Jint.Tests.CommonScripts.csproj

@@ -1,5 +1,4 @@
 <Project Sdk="Microsoft.NET.Sdk">
-
   <PropertyGroup>
     <TargetFrameworks>netcoreapp2.0</TargetFrameworks>
     <AssemblyName>Jint.Tests.CommonScripts</AssemblyName>
@@ -14,21 +13,18 @@
     <GenerateAssemblyVersionAttribute>false</GenerateAssemblyVersionAttribute>
     <GenerateAssemblyFileVersionAttribute>false</GenerateAssemblyFileVersionAttribute>
   </PropertyGroup>
-
   <ItemGroup>
     <EmbeddedResource Include="Scripts\*.*" Exclude="bin\**;obj\**;**\*.xproj;packages\**;@(EmbeddedResource)" />
   </ItemGroup>
-
   <ItemGroup>
     <ProjectReference Include="..\Jint\Jint.csproj" />
   </ItemGroup>
-
   <ItemGroup>
     <PackageReference Include="Microsoft.NET.Test.Sdk" Version="15.3.0" />
     <PackageReference Include="xunit" Version="2.3.1" />
+    <PackageReference Include="xunit.analyzers" Version="0.8.0" />
     <PackageReference Include="xunit.runner.visualstudio" Version="2.3.1" />
-    <PackageReference Include="xunit.analyzers" Version="0.7.0" />
     <PackageReference Include="xunit.runner.console" Version="2.3.1" />
+    <DotNetCliToolReference Include="dotnet-xunit" Version="2.3.1" />
   </ItemGroup>
-
-</Project>
+</Project>

Jint.Tests.Ecma/Jint.Tests.Ecma.csproj

@@ -1,5 +1,4 @@
 <Project Sdk="Microsoft.NET.Sdk">
-
   <PropertyGroup>
     <TargetFramework>netcoreapp2.0</TargetFramework>
     <AssemblyName>Jint.Tests.Ecma</AssemblyName>
@@ -15,21 +14,19 @@
     <GenerateAssemblyVersionAttribute>false</GenerateAssemblyVersionAttribute>
     <GenerateAssemblyFileVersionAttribute>false</GenerateAssemblyFileVersionAttribute>
   </PropertyGroup>
-
   <ItemGroup>
     <ProjectReference Include="..\Jint\Jint.csproj" />
   </ItemGroup>
-
   <ItemGroup>
     <PackageReference Include="Microsoft.NET.Test.Sdk" Version="15.0.0" />
-    <PackageReference Include="xunit" Version="2.2.0" />
-    <PackageReference Include="xunit.runner.visualstudio" Version="2.2.0" />
-    <PackageReference Include="xunit.analyzers" Version="0.3.0" />
+    <PackageReference Include="xunit" Version="2.3.1" />
+    <PackageReference Include="xunit.analyzers" Version="0.8.0" />
+    <PackageReference Include="xunit.runner.visualstudio" Version="2.3.1" />
+    <PackageReference Include="xunit.runner.console" Version="2.3.1" />
+    <DotNetCliToolReference Include="dotnet-xunit" Version="2.3.1" />
   </ItemGroup>
-
   <ItemGroup Condition=" '$(TargetFramework)' == 'net451' ">
     <Reference Include="System" />
     <Reference Include="Microsoft.CSharp" />
   </ItemGroup>
-
-</Project>
+</Project>

Jint.Tests/Jint.Tests.csproj

@@ -22,8 +22,9 @@
   <ItemGroup>
     <PackageReference Include="Microsoft.NET.Test.Sdk" Version="15.3.0" />
     <PackageReference Include="xunit" Version="2.3.1" />
+    <PackageReference Include="xunit.analyzers" Version="0.8.0" />
     <PackageReference Include="xunit.runner.visualstudio" Version="2.3.1" />
-    <PackageReference Include="xunit.analyzers" Version="0.7.0" />
     <PackageReference Include="xunit.runner.console" Version="2.3.1" />
+    <DotNetCliToolReference Include="dotnet-xunit" Version="2.3.1" />
   </ItemGroup>
 </Project>

Jint.Tests/Runtime/EngineTests.cs

@@ -310,6 +310,28 @@ public void ArrayIndexerIsAssigned()
             ");
         }
 
+        [Fact]
+        public void DenseArrayTurnsToSparseArrayWhenSizeGrowsTooMuch()
+        {
+            RunTest(@"
+                var n = 1024*10+2;
+                var o = Array(n);
+                for (var i = 0; i < n; i++) o[i] = i;
+                assert(o[0] == 0);
+                assert(o[n - 1] == n -1);
+            ");
+        }
+
+        [Fact]
+        public void DenseArrayTurnsToSparseArrayWhenSparseIndexed()
+        {
+            RunTest(@"
+                var o = Array();
+                o[100] = 1;
+                assert(o[100] == 1);
+            ");
+        }
+
         [Fact]
         public void ArrayPopShouldDecrementLength()
         {
@@ -1893,7 +1915,7 @@ public void ShouldStringifyNumWithoutV8DToA()
 
             Assert.True(val.AsString() == "53.6841659");
         }
-		
+
         [Theory]
         [InlineData("", "escape('')")]
         [InlineData("%u0100%u0101%u0102", "escape('\u0100\u0101\u0102')")]

Jint/Jint.csproj

@@ -1,13 +1,11 @@
 <Project Sdk="Microsoft.NET.Sdk">
-
   <PropertyGroup>
     <NeutralLanguage>en-US</NeutralLanguage>
     <TargetFramework>netstandard2.0</TargetFramework>
     <AssemblyOriginatorKeyFile>Jint.snk</AssemblyOriginatorKeyFile>
     <SignAssembly>true</SignAssembly>
   </PropertyGroup>
-
   <ItemGroup>
-    <PackageReference Include="Esprima" Version="1.0.0-beta-1000" /> 
+    <PackageReference Include="Esprima" Version="1.0.0-beta-1011" />
   </ItemGroup>
-</Project>
+</Project>

Jint/Native/Array/ArrayConstructor.cs

@@ -1,4 +1,5 @@
-using System.Collections;
+using System;
+using System.Collections;
 using Jint.Native.Function;
 using Jint.Native.Object;
 using Jint.Runtime;
@@ -19,7 +20,7 @@ public static ArrayConstructor CreateArrayConstructor(Engine engine)
             var obj = new ArrayConstructor(engine);
             obj.Extensible = true;
 
-            // The value of the [[Prototype]] internal property of the Array constructor is the Function prototype object 
+            // The value of the [[Prototype]] internal property of the Array constructor is the Function prototype object
             obj.Prototype = engine.Function.PrototypeObject;
             obj.PrototypeObject = ArrayPrototype.CreatePrototypeObject(engine, obj);
 
@@ -36,7 +37,7 @@ public void Configure()
             FastAddProperty("isArray", new ClrFunctionInstance(Engine, IsArray, 1), true, false, true);
         }
 
-        private JsValue IsArray(JsValue thisObj, JsValue[] arguments)
+        private static JsValue IsArray(JsValue thisObj, JsValue[] arguments)
         {
             if (arguments.Length == 0)
             {
@@ -55,7 +56,36 @@ public override JsValue Call(JsValue thisObject, JsValue[] arguments)
 
         public ObjectInstance Construct(JsValue[] arguments)
         {
-            var instance = new ArrayInstance(Engine);
+            // check if we can figure out good size
+            var capacity = arguments.Length > 0 ? (uint) arguments.Length : 0;
+            if (arguments.Length == 1 && arguments[0].Type == Types.Number)
+            {
+                var number = arguments[0].AsNumber();
+                if (number > 0)
+                {
+                    capacity = (uint) number;
+                }
+            }
+            return Construct(arguments, capacity);
+        }
+
+        public ArrayInstance Construct(int capacity)
+        {
+            if (capacity < 0)
+            {
+                throw new ArgumentException("invalid array length", nameof(capacity));
+            }
+            return Construct(System.Array.Empty<JsValue>(), (uint) capacity);
+        }
+
+        public ArrayInstance Construct(uint capacity)
+        {
+            return Construct(System.Array.Empty<JsValue>(), capacity);
+        }
+
+        public ArrayInstance Construct(JsValue[] arguments, uint capacity)
+        {
+            var instance = new ArrayInstance(Engine, capacity);
             instance.Prototype = PrototypeObject;
             instance.Extensible = true;
 
@@ -66,7 +96,7 @@ public ObjectInstance Construct(JsValue[] arguments)
                 {
                     throw new JavaScriptException(Engine.RangeError, "Invalid array length");
                 }
-                
+
                 instance.FastAddProperty("length", length, true, false, false);
             }
             else if (arguments.Length == 1 && arguments.At(0).IsObject() && arguments.At(0).As<ObjectWrapper>() != null )
@@ -75,7 +105,7 @@ public ObjectInstance Construct(JsValue[] arguments)
 
                 if (enumerable != null)
                 {
-                    var jsArray = Engine.Array.Construct(Arguments.Empty);
+                    var jsArray = (ArrayInstance) Engine.Array.Construct(Arguments.Empty);
                     foreach (var item in enumerable)
                     {
                         var jsItem = JsValue.FromObject(Engine, item);

Jint/Native/Array/ArrayExecutionContext.cs

@@ -0,0 +1,26 @@
+using System.Collections.Generic;
+using System.Threading;
+
+namespace Jint.Native.Array
+{
+    /// <summary>
+    /// Helper to cache common data structures needed in array access on a per thread basis.
+    /// </summary>
+    internal class ArrayExecutionContext
+    {
+        // cache key container for array iteration for less allocations
+        private static readonly ThreadLocal<ArrayExecutionContext> _executionContext = new ThreadLocal<ArrayExecutionContext>(() => new ArrayExecutionContext());
+
+        private ArrayExecutionContext()
+        {
+        }
+
+        public List<uint> KeyCache = new List<uint>();
+
+        public JsValue[] CallArray1 = new JsValue[1];
+        public JsValue[] CallArray3 = new JsValue[3];
+        public JsValue[] CallArray4 = new JsValue[4];
+
+        public static ArrayExecutionContext Current => _executionContext.Value;
+    }
+}