Introduce CSSNodeGetInstanceCount API

Summary:
- Add CSSNodeGetInstanceCount API to get the number of native instances.
- It makes testing easy.

Reviewed By: emilsjolander

Differential Revision: D3981990

fbshipit-source-id: 98005ae1fc21d4c8802f24030fff9ffb00bd292d

CSSLayout/CSSLayout.c

@@ -129,9 +129,12 @@ computedEdgeValue(const float edges[CSSEdgeCount], const CSSEdge edge, const flo
   return defaultValue;
 }
 
+static int32_t gNodeInstanceCount = 0;
+
 CSSNodeRef CSSNodeNew() {
   const CSSNodeRef node = calloc(1, sizeof(CSSNode));
   CSS_ASSERT(node, "Could not allocate memory for node");
+  gNodeInstanceCount++;
 
   CSSNodeInit(node);
   return node;
@@ -140,6 +143,7 @@ CSSNodeRef CSSNodeNew() {
 void CSSNodeFree(const CSSNodeRef node) {
   CSSNodeListFree(node->children);
   free(node);
+  gNodeInstanceCount--;
 }
 
 void CSSNodeFreeRecursive(const CSSNodeRef root) {
@@ -151,6 +155,10 @@ void CSSNodeFreeRecursive(const CSSNodeRef root) {
   CSSNodeFree(root);
 }
 
+int32_t CSSNodeGetInstanceCount() {
+  return gNodeInstanceCount;
+}
+
 void CSSNodeInit(const CSSNodeRef node) {
   node->parent = NULL;
   node->children = CSSNodeListNew(4);

CSSLayout/CSSLayout.h

@@ -127,6 +127,7 @@ WIN_EXPORT CSSNodeRef CSSNodeNew();
 WIN_EXPORT void CSSNodeInit(const CSSNodeRef node);
 WIN_EXPORT void CSSNodeFree(const CSSNodeRef node);
 WIN_EXPORT void CSSNodeFreeRecursive(const CSSNodeRef node);
+WIN_EXPORT int32_t CSSNodeGetInstanceCount();
 
 WIN_EXPORT void CSSNodeInsertChild(const CSSNodeRef node, const CSSNodeRef child, const uint32_t index);
 WIN_EXPORT void CSSNodeRemoveChild(const CSSNodeRef node, const CSSNodeRef child);

csharp/Facebook.CSSLayout/CSSNode.cs

@@ -711,5 +711,10 @@ namespace Facebook.CSSLayout
         {
             return ((IEnumerable<CSSNode>)_children).GetEnumerator();
         }
+
+        public static int GetInstanceCount()
+        {
+            return Native.CSSNodeGetInstanceCount();
+        }
     }
 }

csharp/Facebook.CSSLayout/Native.cs

@@ -29,6 +29,9 @@ namespace Facebook.CSSLayout
         [DllImport(DllName)]
         public static extern void CSSNodeFree(IntPtr cssNode);
 
+        [DllImport(DllName)]
+        public static extern int CSSNodeGetInstanceCount();
+
         [DllImport(DllName)]
         public static extern void CSSNodeInsertChild(IntPtr node, IntPtr child, uint index);
 

tests/csharp/Facebook.CSSLayout/CSSNodeTest.cs

@@ -8,6 +8,7 @@
  */
 
 using NUnit.Framework;
+using System;
 
 /**
  * Tests for {@link CSSNode}.
@@ -87,16 +88,53 @@ namespace Facebook.CSSLayout
         [Test]
         public void TestDispose()
         {
+            ForceGC();
+            Assert.AreEqual(0, CSSNode.GetInstanceCount());
             CSSNode node = new CSSNode();
+            Assert.AreEqual(0, CSSNode.GetInstanceCount());
             node.Initialize();
+            Assert.AreEqual(1, CSSNode.GetInstanceCount());
             node.Dispose();
+            Assert.AreEqual(0, CSSNode.GetInstanceCount());
+        }
+
+        [Test]
+        public void TestDisposeWithUsing()
+        {
+            ForceGC();
+            Assert.AreEqual(0, CSSNode.GetInstanceCount());
+            using (CSSNode node = new CSSNode())
+            {
+                Assert.AreEqual(0, CSSNode.GetInstanceCount());
+                node.Initialize();
+                Assert.AreEqual(1, CSSNode.GetInstanceCount());
+            }
+            Assert.AreEqual(0, CSSNode.GetInstanceCount());
         }
 
         [Test]
         public void TestDestructor()
+        {
+            ForceGC();
+            Assert.AreEqual(0, CSSNode.GetInstanceCount());
+            TestDestructorFunc();
+            ForceGC();
+            Assert.AreEqual(0, CSSNode.GetInstanceCount());
+        }
+
+        private void TestDestructorFunc()
         {
             CSSNode node = new CSSNode();
+            Assert.AreEqual(0, CSSNode.GetInstanceCount());
             node.Initialize();
+            Assert.AreEqual(1, CSSNode.GetInstanceCount());
+            node = null;
+        }
+
+        private void ForceGC()
+        {
+            GC.Collect(GC.MaxGeneration);
+            GC.WaitForPendingFinalizers();
         }
     }
 }