Experimental alignment layout manager using a property on the views

base/set_template.h

+// Copyright (c) 2016 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#ifndef BASE_SET_TEMPLATE_H_
+#define BASE_SET_TEMPLATE_H_
+
+#include <initializer_list>
+#include <type_traits>
+
+namespace base {
+
+template <class T, unsigned char maxEl>
+class SetCore {
+ public:
+  typedef
+      typename std::conditional<((maxEl / 8 + 1) == 1), unsigned char,
+      typename std::conditional<((maxEl / 8 + 1) == 2), unsigned short,
+      unsigned int>::type>::type _Ty;
+
+ private:
+  static_assert(std::is_enum<T>::value, "T must be an enumeration");
+  static_assert(maxEl < 32, "Sets can only contain up to 32 elements");
+
+ protected:
+  SetCore() : data(0) {}
+
+ public:
+  _Ty data;
+};
+
+template <class T, T maxEl>
+class SetOf : public SetCore<T, static_cast<unsigned char>(maxEl)> {
+  static constexpr unsigned char NumElms =
+      static_cast<unsigned char>(maxEl) + 1;
+  static constexpr unsigned char MaxEl = NumElms - 1;
+
+ public:
+  class ElemRef {
+    friend class SetOf<T, maxEl>;
+   public:
+    ~ElemRef() {}
+
+    ElemRef& operator=(bool rhs) {
+      if (rhs)
+        set_->Include(el_);
+      else
+        set_->Exclude(el_);
+      return *this;
+    }
+
+    ElemRef& operator=(const ElemRef& elemref) {
+      return set_->operator=(bool(elemref));
+    }
+
+    operator bool() const {
+      return set_->Contains(el_);
+    }
+
+   private:
+    ElemRef() : set_(nullptr), el_(static_cast<T>(0)) {}
+    ElemRef(SetOf<T, maxEl>& set, T el) : set_(&set), el_(el)  {}
+
+    SetOf<T, maxEl>* set_;
+    T el_;
+  };
+
+  SetOf() : SetCore<T, MaxEl>() {}
+
+  SetOf(const SetOf& src) : SetCore<T, MaxEl>() {
+    this->data = src.data;
+  }
+
+  explicit SetOf(const int& src) : SetCore<T, MaxEl>() {
+    union {
+      typename SetCore<T, MaxEl>::_Ty data;
+      unsigned int IntData;
+    } overlay;
+    overlay.IntData = src;
+    this->data = overlay.data;
+  }
+
+  SetOf(const std::initializer_list<T>& src) : SetCore<T, MaxEl>() {
+    Include(src);
+  }
+
+  SetOf& operator=(const SetOf& rhs) {
+    if (this != &rhs)
+      this->data = rhs.data;
+    return *this;
+  }
+
+  SetOf& operator+=(const SetOf& rhs) {
+    this->data |= rhs.data;
+    return *this;
+  }
+
+  SetOf& operator-=(const SetOf& rhs) {
+    this->data ^= rhs.data;
+    return *this;
+  }
+
+  SetOf& operator*=(const SetOf& rhs) {
+    this->data &= rhs.data;
+    return *this;
+  }
+
+  SetOf operator+(const SetOf& rhs) {
+    SetOf<T, maxEl> s;
+    s.data = this->data | rhs.data;
+    return s;
+  }
+
+  SetOf operator-(const SetOf& rhs) {
+    SetOf<T, maxEl> s;
+    s.data = this->data ^ rhs.data;
+    return s;
+  }
+
+  SetOf operator*(const SetOf& rhs) {
+    SetOf<T, maxEl> s;
+    s.data = this->data & rhs.data;
+    return s;
+  }
+
+  SetOf& operator<<(const T el) {
+    return Include(el);
+  }
+
+  SetOf& operator>>(const T el) {
+    return Exclude(el);
+  }
+
+  bool operator==(const SetOf& rhs) const {
+    static const typename SetCore<T, MaxEl>::_Ty Mask =
+        static_cast<typename SetCore<T, MaxEl>::_Ty>(-1) >>
+          (sizeof(this->data) * 8 - NumElms);
+    return !(this->data != rhs.data &&
+        (Mask & this->data) != (Mask & rhs.data));
+  }
+
+  bool operator!=(const SetOf& rhs) const {
+    return !operator==(rhs);
+  }
+
+  constexpr bool operator[](const T el) const {
+    return Contains(el);
+  }
+
+  ElemRef operator[](T el) {
+    return ElemRef(*this, el);
+  }
+
+  SetOf& Clear() {
+    this->data = 0;
+    return *this;
+  }
+
+  bool Contains(const T el) const {
+    return static_cast<int>(el) >= 0 && static_cast<int>(el) < NumElms &&
+           (this->data & static_cast<int>(1) << static_cast<int>(el)) != 0;
+  }
+
+  bool ContainsAll(const std::initializer_list<T>& els) const {
+    for (const T& el : els)
+      if (!Contains(el))
+        return false;
+    return true;
+  }
+
+  bool ContainsSome(const std::initializer_list<T>& els) const {
+    for (const T& el : els)
+      if (Contains(el))
+        return true;
+    return false;
+  }
+
+  bool Equals(const std::initializer_list<T>& rhs) const {
+    SetOf<T, maxEl> s(rhs);
+    return operator==(s);
+  }
+
+  bool Equals(const std::initializer_list<T>& mask,
+              const std::initializer_list<T>& rhs) const {
+    SetOf<T, maxEl> s_mask(mask);
+    SetOf<T, maxEl> s_rhs(rhs);
+    return (s_mask * *this) == s_rhs;
+  }
+
+  bool Equals(const SetOf& mask,
+              const std::initializer_list<T>& rhs) const {
+    SetOf<T, maxEl> s_rhs(rhs);
+    return (mask * *this) == s_rhs;
+  }
+
+  bool Equals(const SetOf& rhs) const {
+    return *this == rhs;
+  }
+
+  SetOf& Exclude(const T el) {
+    if (static_cast<int>(el) >= 0 && static_cast<int>(el) < NumElms)
+      this->data &= ~(static_cast<int>(1) << static_cast<int>(el));
+    return *this;
+  }
+
+  SetOf& Exclude(const std::initializer_list<T>& els) {
+    for (const T& el : els)
+      Exclude(el);
+    return *this;
+  }
+
+  SetOf& Include(const T el) {
+    if (static_cast<int>(el) >= 0 && static_cast<int>(el) < NumElms)
+      this->data |= (static_cast<int>(1) << static_cast<int>(el));
+    return *this;
+  }
+
+  SetOf& Include(const std::initializer_list<T>& els) {
+    for (const T& el : els)
+      Include(el);
+    return *this;
+  }
+
+  bool IsEmpty() const { return this->data == 0; }
+};
+
+} // namespace base
+
+#endif  // BASE_SET_TEMPLATE_H_