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/*
* 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 "base/bit_utils.h"
#include "base/casts.h"
#include "base/iteration_range.h"
#include "stride_iterator.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_