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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_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_;
}
bool Contains(const T* element) const {
return &AtUnchecked(0) <= element && element < &AtUnchecked(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_
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