upload android base code part3

android/art/runtime/base/bit_utils_iterator.h

@@ -0,0 +1,112 @@
+/*
+ * Copyright (C) 2015 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#ifndef ART_RUNTIME_BASE_BIT_UTILS_ITERATOR_H_
+#define ART_RUNTIME_BASE_BIT_UTILS_ITERATOR_H_
+
+#include <iterator>
+#include <limits>
+#include <type_traits>
+
+#include "base/bit_utils.h"
+#include "base/iteration_range.h"
+#include "base/logging.h"
+#include "base/stl_util.h"
+
+namespace art {
+
+// Using the Curiously Recurring Template Pattern to implement everything shared
+// by LowToHighBitIterator and HighToLowBitIterator, i.e. everything but operator*().
+template <typename T, typename Iter>
+class BitIteratorBase
+    : public std::iterator<std::forward_iterator_tag, uint32_t, ptrdiff_t, void, void> {
+  static_assert(std::is_integral<T>::value, "T must be integral");
+  static_assert(std::is_unsigned<T>::value, "T must be unsigned");
+
+  static_assert(sizeof(T) == sizeof(uint32_t) || sizeof(T) == sizeof(uint64_t), "Unsupported size");
+
+ public:
+  BitIteratorBase() : bits_(0u) { }
+  explicit BitIteratorBase(T bits) : bits_(bits) { }
+
+  Iter& operator++() {
+    DCHECK_NE(bits_, 0u);
+    uint32_t bit = *static_cast<Iter&>(*this);
+    bits_ &= ~(static_cast<T>(1u) << bit);
+    return static_cast<Iter&>(*this);
+  }
+
+  Iter& operator++(int) {
+    Iter tmp(static_cast<Iter&>(*this));
+    ++*this;
+    return tmp;
+  }
+
+ protected:
+  T bits_;
+
+  template <typename U, typename I>
+  friend bool operator==(const BitIteratorBase<U, I>& lhs, const BitIteratorBase<U, I>& rhs);
+};
+
+template <typename T, typename Iter>
+bool operator==(const BitIteratorBase<T, Iter>& lhs, const BitIteratorBase<T, Iter>& rhs) {
+  return lhs.bits_ == rhs.bits_;
+}
+
+template <typename T, typename Iter>
+bool operator!=(const BitIteratorBase<T, Iter>& lhs, const BitIteratorBase<T, Iter>& rhs) {
+  return !(lhs == rhs);
+}
+
+template <typename T>
+class LowToHighBitIterator : public BitIteratorBase<T, LowToHighBitIterator<T>> {
+ public:
+  using BitIteratorBase<T, LowToHighBitIterator<T>>::BitIteratorBase;
+
+  uint32_t operator*() const {
+    DCHECK_NE(this->bits_, 0u);
+    return CTZ(this->bits_);
+  }
+};
+
+template <typename T>
+class HighToLowBitIterator : public BitIteratorBase<T, HighToLowBitIterator<T>> {
+ public:
+  using BitIteratorBase<T, HighToLowBitIterator<T>>::BitIteratorBase;
+
+  uint32_t operator*() const {
+    DCHECK_NE(this->bits_, 0u);
+    static_assert(std::numeric_limits<T>::radix == 2, "Unexpected radix!");
+    return std::numeric_limits<T>::digits - 1u - CLZ(this->bits_);
+  }
+};
+
+template <typename T>
+IterationRange<LowToHighBitIterator<T>> LowToHighBits(T bits) {
+  return IterationRange<LowToHighBitIterator<T>>(
+      LowToHighBitIterator<T>(bits), LowToHighBitIterator<T>());
+}
+
+template <typename T>
+IterationRange<HighToLowBitIterator<T>> HighToLowBits(T bits) {
+  return IterationRange<HighToLowBitIterator<T>>(
+      HighToLowBitIterator<T>(bits), HighToLowBitIterator<T>());
+}
+
+}  // namespace art
+
+#endif  // ART_RUNTIME_BASE_BIT_UTILS_ITERATOR_H_