Use Bitfield in YGNode and YGStyle

Summary:
@public

Replaces the usage of C++ bitfields with our portable `Bitfield` class.

Reviewed By: SidharthGuglani

Differential Revision: D16649875

fbshipit-source-id: 539f016d5e1c9a8c48cc9bacbbf6ed985e385e69

yoga/YGNode.h

@@ -7,6 +7,7 @@
 #pragma once
 #include <cstdint>
 #include <stdio.h>
+#include "Bitfield.h"
 #include "CompactValue.h"
 #include "YGConfig.h"
 #include "YGLayout.h"
@@ -23,15 +24,20 @@ struct YGNode {
   using PrintWithContextFn = void (*)(YGNode*, void*);
 
 private:
+  static constexpr size_t hasNewLayout_ = 0;
+  static constexpr size_t isReferenceBaseline_ = 1;
+  static constexpr size_t isDirty_ = 2;
+  static constexpr size_t nodeType_ = 3;
+  static constexpr size_t measureUsesContext_ = 4;
+  static constexpr size_t baselineUsesContext_ = 5;
+  static constexpr size_t printUsesContext_ = 6;
+  static constexpr size_t useWebDefaults_ = 7;
+
   void* context_ = nullptr;
-  bool hasNewLayout_ : 1;
-  bool isReferenceBaseline_ : 1;
-  bool isDirty_ : 1;
-  YGNodeType nodeType_ : 1;
-  bool measureUsesContext_ : 1;
-  bool baselineUsesContext_ : 1;
-  bool printUsesContext_ : 1;
-  bool useWebDefaults_ : 1;
+  using Flags = facebook::yoga::
+      Bitfield<uint8_t, bool, bool, bool, YGNodeType, bool, bool, bool, bool>;
+  Flags flags_ =
+      {true, false, false, YGNodeTypeDefault, false, false, false, false};
   uint8_t reserved_ = 0;
   union {
     YGMeasureFunc noContext;
@@ -63,7 +69,7 @@ private:
   void setBaselineFunc(decltype(baseline_));
 
   void useWebDefaults() {
-    useWebDefaults_ = true;
+    flags_.at<useWebDefaults_>() = true;
     style_.flexDirection() = YGFlexDirectionRow;
     style_.alignContent() = YGAlignStretch;
   }
@@ -79,17 +85,8 @@ private:
 
 public:
   YGNode() : YGNode{YGConfigGetDefault()} {}
-  explicit YGNode(const YGConfigRef config)
-      : hasNewLayout_{true},
-        isReferenceBaseline_{false},
-        isDirty_{false},
-        nodeType_{YGNodeTypeDefault},
-        measureUsesContext_{false},
-        baselineUsesContext_{false},
-        printUsesContext_{false},
-        useWebDefaults_{config->useWebDefaults},
-        config_{config} {
-    if (useWebDefaults_) {
+  explicit YGNode(const YGConfigRef config) : config_{config} {
+    if (config->useWebDefaults) {
       useWebDefaults();
     }
   };
@@ -116,9 +113,9 @@ public:
 
   void print(void*);
 
-  bool getHasNewLayout() const { return hasNewLayout_; }
+  bool getHasNewLayout() const { return flags_.at<hasNewLayout_>(); }
 
-  YGNodeType getNodeType() const { return nodeType_; }
+  YGNodeType getNodeType() const { return flags_.at<nodeType_>(); }
 
   bool hasMeasureFunc() const noexcept { return measure_.noContext != nullptr; }
 
@@ -144,7 +141,7 @@ public:
 
   uint32_t getLineIndex() const { return lineIndex_; }
 
-  bool isReferenceBaseline() { return isReferenceBaseline_; }
+  bool isReferenceBaseline() { return flags_.at<isReferenceBaseline_>(); }
 
   // returns the YGNodeRef that owns this YGNode. An owner is used to identify
   // the YogaTree that a YGNode belongs to. This method will return the parent
@@ -177,7 +174,7 @@ public:
 
   YGConfigRef getConfig() const { return config_; }
 
-  bool isDirty() const { return isDirty_; }
+  bool isDirty() const { return flags_.at<isDirty_>(); }
 
   std::array<YGValue, 2> getResolvedDimensions() const {
     return resolvedDimensions_;
@@ -225,17 +222,19 @@ public:
 
   void setPrintFunc(YGPrintFunc printFunc) {
     print_.noContext = printFunc;
-    printUsesContext_ = false;
+    flags_.at<printUsesContext_>() = false;
   }
   void setPrintFunc(PrintWithContextFn printFunc) {
     print_.withContext = printFunc;
-    printUsesContext_ = true;
+    flags_.at<printUsesContext_>() = true;
   }
   void setPrintFunc(std::nullptr_t) { setPrintFunc(YGPrintFunc{nullptr}); }
 
-  void setHasNewLayout(bool hasNewLayout) { hasNewLayout_ = hasNewLayout; }
+  void setHasNewLayout(bool hasNewLayout) {
+    flags_.at<hasNewLayout_>() = hasNewLayout;
+  }
 
-  void setNodeType(YGNodeType nodeType) { nodeType_ = nodeType; }
+  void setNodeType(YGNodeType nodeType) { flags_.at<nodeType_>() = nodeType; }
 
   void setMeasureFunc(YGMeasureFunc measureFunc);
   void setMeasureFunc(MeasureWithContextFn);
@@ -244,11 +243,11 @@ public:
   }
 
   void setBaselineFunc(YGBaselineFunc baseLineFunc) {
-    baselineUsesContext_ = false;
+    flags_.at<baselineUsesContext_>() = false;
     baseline_.noContext = baseLineFunc;
   }
   void setBaselineFunc(BaselineWithContextFn baseLineFunc) {
-    baselineUsesContext_ = true;
+    flags_.at<baselineUsesContext_>() = true;
     baseline_.withContext = baseLineFunc;
   }
   void setBaselineFunc(std::nullptr_t) {
@@ -264,7 +263,7 @@ public:
   void setLineIndex(uint32_t lineIndex) { lineIndex_ = lineIndex; }
 
   void setIsReferenceBaseline(bool isReferenceBaseline) {
-    isReferenceBaseline_ = isReferenceBaseline;
+    flags_.at<isReferenceBaseline_>() = isReferenceBaseline;
   }
 
   void setOwner(YGNodeRef owner) { owner_ = owner; }