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Diffstat (limited to 'runtime/base/array_slice.h')
-rw-r--r-- | runtime/base/array_slice.h | 148 |
1 files changed, 148 insertions, 0 deletions
diff --git a/runtime/base/array_slice.h b/runtime/base/array_slice.h new file mode 100644 index 0000000000..19ad302c9d --- /dev/null +++ b/runtime/base/array_slice.h @@ -0,0 +1,148 @@ +/* + * 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_ARRAY_SLICE_H_ +#define ART_RUNTIME_BASE_ARRAY_SLICE_H_ + +#include "length_prefixed_array.h" +#include "stride_iterator.h" +#include "base/bit_utils.h" +#include "base/casts.h" +#include "base/iteration_range.h" + +namespace art { + +// An ArraySlice is an abstraction over an array or a part of an array of a particular type. It does +// bounds checking and can be made from several common array-like structures in Art. +template<typename T> +class ArraySlice { + public: + // Create an empty array slice. + ArraySlice() : array_(nullptr), size_(0), element_size_(0) {} + + // Create an array slice of the first 'length' elements of the array, with each element being + // element_size bytes long. + ArraySlice(T* array, + size_t length, + size_t element_size = sizeof(T)) + : array_(array), + size_(dchecked_integral_cast<uint32_t>(length)), + element_size_(element_size) { + DCHECK(array_ != nullptr || length == 0); + } + + // Create an array slice of the elements between start_offset and end_offset of the array with + // each element being element_size bytes long. Both start_offset and end_offset are in + // element_size units. + ArraySlice(T* array, + uint32_t start_offset, + uint32_t end_offset, + size_t element_size = sizeof(T)) + : array_(nullptr), + size_(end_offset - start_offset), + element_size_(element_size) { + DCHECK(array_ != nullptr || size_ == 0); + DCHECK_LE(start_offset, end_offset); + if (size_ != 0) { + uintptr_t offset = start_offset * element_size_; + array_ = *reinterpret_cast<T*>(reinterpret_cast<uintptr_t>(array) + offset); + } + } + + // Create an array slice of the elements between start_offset and end_offset of the array with + // each element being element_size bytes long and having the given alignment. Both start_offset + // and end_offset are in element_size units. + ArraySlice(LengthPrefixedArray<T>* array, + uint32_t start_offset, + uint32_t end_offset, + size_t element_size = sizeof(T), + size_t alignment = alignof(T)) + : array_(nullptr), + size_(end_offset - start_offset), + element_size_(element_size) { + DCHECK(array != nullptr || size_ == 0); + if (size_ != 0) { + DCHECK_LE(start_offset, end_offset); + DCHECK_LE(start_offset, array->size()); + DCHECK_LE(end_offset, array->size()); + array_ = &array->At(start_offset, element_size_, alignment); + } + } + + T& At(size_t index) { + DCHECK_LT(index, size_); + return AtUnchecked(index); + } + + const T& At(size_t index) const { + DCHECK_LT(index, size_); + return AtUnchecked(index); + } + + T& operator[](size_t index) { + return At(index); + } + + const T& operator[](size_t index) const { + return At(index); + } + + StrideIterator<T> begin() { + return StrideIterator<T>(&AtUnchecked(0), element_size_); + } + + StrideIterator<const T> begin() const { + return StrideIterator<const T>(&AtUnchecked(0), element_size_); + } + + StrideIterator<T> end() { + return StrideIterator<T>(&AtUnchecked(size_), element_size_); + } + + StrideIterator<const T> end() const { + return StrideIterator<const T>(&AtUnchecked(size_), element_size_); + } + + IterationRange<StrideIterator<T>> AsRange() { + return size() != 0 ? MakeIterationRange(begin(), end()) + : MakeEmptyIterationRange(StrideIterator<T>(nullptr, 0)); + } + + size_t size() const { + return size_; + } + + size_t ElementSize() const { + return element_size_; + } + + private: + T& AtUnchecked(size_t index) { + return *reinterpret_cast<T*>(reinterpret_cast<uintptr_t>(array_) + index * element_size_); + } + + const T& AtUnchecked(size_t index) const { + return *reinterpret_cast<T*>(reinterpret_cast<uintptr_t>(array_) + index * element_size_); + } + + T* array_; + size_t size_; + size_t element_size_; +}; + +} // namespace art + +#endif // ART_RUNTIME_BASE_ARRAY_SLICE_H_ |