upload android base code part3

android/art/runtime/base/length_prefixed_array.h

@@ -0,0 +1,121 @@
+/*
+ * 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_LENGTH_PREFIXED_ARRAY_H_
+#define ART_RUNTIME_BASE_LENGTH_PREFIXED_ARRAY_H_
+
+#include <stddef.h>  // for offsetof()
+#include <string.h>  // for memset()
+
+#include "stride_iterator.h"
+#include "base/bit_utils.h"
+#include "base/casts.h"
+#include "base/iteration_range.h"
+
+namespace art {
+
+template<typename T>
+class LengthPrefixedArray {
+ public:
+  explicit LengthPrefixedArray(size_t length)
+      : size_(dchecked_integral_cast<uint32_t>(length)) {}
+
+  T& At(size_t index, size_t element_size = sizeof(T), size_t alignment = alignof(T)) {
+    DCHECK_LT(index, size_);
+    return AtUnchecked(index, element_size, alignment);
+  }
+
+  const T& At(size_t index, size_t element_size = sizeof(T), size_t alignment = alignof(T)) const {
+    DCHECK_LT(index, size_);
+    return AtUnchecked(index, element_size, alignment);
+  }
+
+  StrideIterator<T> begin(size_t element_size = sizeof(T), size_t alignment = alignof(T)) {
+    return StrideIterator<T>(&AtUnchecked(0, element_size, alignment), element_size);
+  }
+
+  StrideIterator<const T> begin(size_t element_size = sizeof(T),
+                                size_t alignment = alignof(T)) const {
+    return StrideIterator<const T>(&AtUnchecked(0, element_size, alignment), element_size);
+  }
+
+  StrideIterator<T> end(size_t element_size = sizeof(T), size_t alignment = alignof(T)) {
+    return StrideIterator<T>(&AtUnchecked(size_, element_size, alignment), element_size);
+  }
+
+  StrideIterator<const T> end(size_t element_size = sizeof(T),
+                              size_t alignment = alignof(T)) const {
+    return StrideIterator<const T>(&AtUnchecked(size_, element_size, alignment), element_size);
+  }
+
+  static size_t OffsetOfElement(size_t index,
+                                size_t element_size = sizeof(T),
+                                size_t alignment = alignof(T)) {
+    DCHECK_ALIGNED_PARAM(element_size, alignment);
+    return RoundUp(offsetof(LengthPrefixedArray<T>, data_), alignment) + index * element_size;
+  }
+
+  static size_t ComputeSize(size_t num_elements,
+                            size_t element_size = sizeof(T),
+                            size_t alignment = alignof(T)) {
+    size_t result = OffsetOfElement(num_elements, element_size, alignment);
+    DCHECK_ALIGNED_PARAM(result, alignment);
+    return result;
+  }
+
+  size_t size() const {
+    return size_;
+  }
+
+  // Update the length but does not reallocate storage.
+  void SetSize(size_t length) {
+    size_ = dchecked_integral_cast<uint32_t>(length);
+  }
+
+  // Clear the potentially uninitialized padding between the size_ and actual data.
+  void ClearPadding(size_t element_size = sizeof(T), size_t alignment = alignof(T)) {
+    size_t gap_offset = offsetof(LengthPrefixedArray<T>, data_);
+    size_t gap_size = OffsetOfElement(0, element_size, alignment) - gap_offset;
+    memset(reinterpret_cast<uint8_t*>(this) + gap_offset, 0, gap_size);
+  }
+
+ private:
+  T& AtUnchecked(size_t index, size_t element_size, size_t alignment) {
+    return *reinterpret_cast<T*>(
+        reinterpret_cast<uintptr_t>(this) + OffsetOfElement(index, element_size, alignment));
+  }
+
+  const T& AtUnchecked(size_t index, size_t element_size, size_t alignment) const {
+    return *reinterpret_cast<T*>(
+        reinterpret_cast<uintptr_t>(this) + OffsetOfElement(index, element_size, alignment));
+  }
+
+  uint32_t size_;
+  uint8_t data_[0];
+};
+
+// Returns empty iteration range if the array is null.
+template<typename T>
+IterationRange<StrideIterator<T>> MakeIterationRangeFromLengthPrefixedArray(
+    LengthPrefixedArray<T>* arr, size_t element_size = sizeof(T), size_t alignment = alignof(T)) {
+  return arr != nullptr ?
+      MakeIterationRange(arr->begin(element_size, alignment), arr->end(element_size, alignment)) :
+      MakeEmptyIterationRange(StrideIterator<T>(nullptr, 0));
+}
+
+}  // namespace art
+
+#endif  // ART_RUNTIME_BASE_LENGTH_PREFIXED_ARRAY_H_