From 01c2ac3369b6e403e5f7a24b91a01b7bb792eed7 Mon Sep 17 00:00:00 2001
From: Scott Wolchok <swolchok@fb.com>
Date: Tue, 25 Oct 2016 17:10:24 -0700
Subject: [PATCH] Don't preallocate child lists

Summary: There is no reason to malloc a list of 4 child pointers for every CSS node eagerly. Instead, we malloc the list (preserving the default size of 4) when we try to put stuff in it.

Reviewed By: emilsjolander

Differential Revision: D4078012

fbshipit-source-id: 7cdcab03ec4067550a5fee5e1baea14344f3a8f9
---
 CSSLayout/CSSLayout.c   |  4 ++--
 CSSLayout/CSSNodeList.c | 25 +++++++++++++++++++------
 CSSLayout/CSSNodeList.h |  4 ++--
 3 files changed, 23 insertions(+), 10 deletions(-)

diff --git a/CSSLayout/CSSLayout.c b/CSSLayout/CSSLayout.c
index 0eb7de4b..1cacc993 100644
--- a/CSSLayout/CSSLayout.c
+++ b/CSSLayout/CSSLayout.c
@@ -195,7 +195,7 @@ int32_t CSSNodeGetInstanceCount(void) {
 
 void CSSNodeInit(const CSSNodeRef node) {
   node->parent = NULL;
-  node->children = CSSNodeListNew(4);
+  node->children = NULL;
   node->hasNewLayout = true;
   node->isDirty = false;
 
@@ -257,7 +257,7 @@ static void _CSSNodeMarkDirty(const CSSNodeRef node) {
 
 void CSSNodeInsertChild(const CSSNodeRef node, const CSSNodeRef child, const uint32_t index) {
   CSS_ASSERT(child->parent == NULL, "Child already has a parent, it must be removed first.");
-  CSSNodeListInsert(node->children, child, index);
+  CSSNodeListInsert(&node->children, child, index);
   child->parent = node;
   _CSSNodeMarkDirty(node);
 }
diff --git a/CSSLayout/CSSNodeList.c b/CSSLayout/CSSNodeList.c
index e10131f4..f9c27c18 100644
--- a/CSSLayout/CSSNodeList.c
+++ b/CSSLayout/CSSNodeList.c
@@ -28,19 +28,32 @@ CSSNodeListRef CSSNodeListNew(const uint32_t initialCapacity) {
 }
 
 void CSSNodeListFree(const CSSNodeListRef list) {
-  free(list->items);
-  free(list);
+  if (list) {
+    free(list->items);
+    free(list);
+  }
 }
 
 uint32_t CSSNodeListCount(const CSSNodeListRef list) {
-  return list->count;
+  if (list) {
+    return list->count;
+  }
+  return 0;
 }
 
-void CSSNodeListAdd(const CSSNodeListRef list, const CSSNodeRef node) {
-  CSSNodeListInsert(list, node, list->count);
+void CSSNodeListAdd(CSSNodeListRef *listp, const CSSNodeRef node) {
+  if (!*listp) {
+    *listp = CSSNodeListNew(4);
+  }
+  CSSNodeListInsert(listp, node, (*listp)->count);
 }
 
-void CSSNodeListInsert(const CSSNodeListRef list, const CSSNodeRef node, const uint32_t index) {
+void CSSNodeListInsert(CSSNodeListRef *listp, const CSSNodeRef node, const uint32_t index) {
+  if (!*listp) {
+    *listp = CSSNodeListNew(4);
+  }
+  CSSNodeListRef list = *listp;
+
   if (list->count == list->capacity) {
     list->capacity *= 2;
     list->items = realloc(list->items, sizeof(void *) * list->capacity);
diff --git a/CSSLayout/CSSNodeList.h b/CSSLayout/CSSNodeList.h
index 6d2ca6ce..155fcf6e 100644
--- a/CSSLayout/CSSNodeList.h
+++ b/CSSLayout/CSSNodeList.h
@@ -24,8 +24,8 @@ typedef struct CSSNodeList *CSSNodeListRef;
 CSSNodeListRef CSSNodeListNew(const uint32_t initialCapacity);
 void CSSNodeListFree(const CSSNodeListRef list);
 uint32_t CSSNodeListCount(const CSSNodeListRef list);
-void CSSNodeListAdd(const CSSNodeListRef list, const CSSNodeRef node);
-void CSSNodeListInsert(const CSSNodeListRef list, const CSSNodeRef node, const uint32_t index);
+void CSSNodeListAdd(CSSNodeListRef *listp, const CSSNodeRef node);
+void CSSNodeListInsert(CSSNodeListRef *listp, const CSSNodeRef node, const uint32_t index);
 CSSNodeRef CSSNodeListRemove(const CSSNodeListRef list, const uint32_t index);
 CSSNodeRef CSSNodeListDelete(const CSSNodeListRef list, const CSSNodeRef node);
 CSSNodeRef CSSNodeListGet(const CSSNodeListRef list, const uint32_t index);