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122 lines
4.4 KiB
122 lines
4.4 KiB
/*
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* Copyright (C) 2015 The Android Open Source Project
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*
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* Licensed under the Apache License, Version 2.0 (the "License");
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* you may not use this file except in compliance with the License.
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* You may obtain a copy of the License at
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS,
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* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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* See the License for the specific language governing permissions and
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* limitations under the License.
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*/
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#ifndef ART_LIBARTBASE_BASE_LENGTH_PREFIXED_ARRAY_H_
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#define ART_LIBARTBASE_BASE_LENGTH_PREFIXED_ARRAY_H_
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#include <stddef.h> // for offsetof()
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#include <string.h> // for memset()
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#include "bit_utils.h"
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#include "casts.h"
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#include "iteration_range.h"
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#include "stride_iterator.h"
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namespace art {
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template<typename T>
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class LengthPrefixedArray {
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public:
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explicit LengthPrefixedArray(size_t length)
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: size_(dchecked_integral_cast<uint32_t>(length)) {}
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T& At(size_t index, size_t element_size = sizeof(T), size_t alignment = alignof(T)) {
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DCHECK_LT(index, size_);
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return AtUnchecked(index, element_size, alignment);
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}
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const T& At(size_t index, size_t element_size = sizeof(T), size_t alignment = alignof(T)) const {
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DCHECK_LT(index, size_);
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return AtUnchecked(index, element_size, alignment);
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}
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StrideIterator<T> begin(size_t element_size = sizeof(T), size_t alignment = alignof(T)) {
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return StrideIterator<T>(&AtUnchecked(0, element_size, alignment), element_size);
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}
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StrideIterator<const T> begin(size_t element_size = sizeof(T),
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size_t alignment = alignof(T)) const {
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return StrideIterator<const T>(&AtUnchecked(0, element_size, alignment), element_size);
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}
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StrideIterator<T> end(size_t element_size = sizeof(T), size_t alignment = alignof(T)) {
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return StrideIterator<T>(&AtUnchecked(size_, element_size, alignment), element_size);
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}
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StrideIterator<const T> end(size_t element_size = sizeof(T),
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size_t alignment = alignof(T)) const {
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return StrideIterator<const T>(&AtUnchecked(size_, element_size, alignment), element_size);
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}
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static size_t OffsetOfElement(size_t index,
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size_t element_size = sizeof(T),
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size_t alignment = alignof(T)) {
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DCHECK_ALIGNED_PARAM(element_size, alignment);
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return RoundUp(offsetof(LengthPrefixedArray<T>, data_), alignment) + index * element_size;
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}
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static size_t ComputeSize(size_t num_elements,
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size_t element_size = sizeof(T),
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size_t alignment = alignof(T)) {
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size_t result = OffsetOfElement(num_elements, element_size, alignment);
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DCHECK_ALIGNED_PARAM(result, alignment);
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return result;
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}
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size_t size() const {
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return size_;
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}
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// Update the length but does not reallocate storage.
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void SetSize(size_t length) {
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size_ = dchecked_integral_cast<uint32_t>(length);
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}
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// Clear the potentially uninitialized padding between the size_ and actual data.
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void ClearPadding(size_t element_size = sizeof(T), size_t alignment = alignof(T)) {
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size_t gap_offset = offsetof(LengthPrefixedArray<T>, data_);
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size_t gap_size = OffsetOfElement(0, element_size, alignment) - gap_offset;
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memset(reinterpret_cast<uint8_t*>(this) + gap_offset, 0, gap_size);
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}
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private:
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T& AtUnchecked(size_t index, size_t element_size, size_t alignment) {
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return *reinterpret_cast<T*>(
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reinterpret_cast<uintptr_t>(this) + OffsetOfElement(index, element_size, alignment));
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}
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const T& AtUnchecked(size_t index, size_t element_size, size_t alignment) const {
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return *reinterpret_cast<T*>(
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reinterpret_cast<uintptr_t>(this) + OffsetOfElement(index, element_size, alignment));
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}
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uint32_t size_;
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uint8_t data_[0];
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};
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// Returns empty iteration range if the array is null.
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template<typename T>
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IterationRange<StrideIterator<T>> MakeIterationRangeFromLengthPrefixedArray(
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LengthPrefixedArray<T>* arr, size_t element_size = sizeof(T), size_t alignment = alignof(T)) {
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return arr != nullptr ?
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MakeIterationRange(arr->begin(element_size, alignment), arr->end(element_size, alignment)) :
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MakeEmptyIterationRange(StrideIterator<T>(nullptr, 0));
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}
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} // namespace art
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#endif // ART_LIBARTBASE_BASE_LENGTH_PREFIXED_ARRAY_H_
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