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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_LIBARTBASE_BASE_ARRAY_SLICE_H_
#define ART_LIBARTBASE_BASE_ARRAY_SLICE_H_
#include "bit_utils.h"
#include "casts.h"
#include "iteration_range.h"
#include "length_prefixed_array.h"
#include "stride_iterator.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:
using value_type = T;
using reference = T&;
using const_reference = const T&;
using pointer = T*;
using const_pointer = const T*;
using iterator = StrideIterator<T>;
using const_iterator = StrideIterator<const T>;
using reverse_iterator = std::reverse_iterator<iterator>;
using const_reverse_iterator = std::reverse_iterator<const_iterator>;
using difference_type = ptrdiff_t;
using size_type = size_t;
// 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);
}
ArraySlice(LengthPrefixedArray<T>* lpa,
size_t element_size = sizeof(T),
size_t alignment = alignof(T))
: ArraySlice(
lpa != nullptr && lpa->size() != 0 ? &lpa->At(0, element_size, alignment) : nullptr,
lpa != nullptr ? lpa->size() : 0,
element_size) {}
// Iterators.
iterator begin() { return iterator(&AtUnchecked(0), element_size_); }
const_iterator begin() const { return const_iterator(&AtUnchecked(0), element_size_); }
const_iterator cbegin() const { return const_iterator(&AtUnchecked(0), element_size_); }
StrideIterator<T> end() { return StrideIterator<T>(&AtUnchecked(size_), element_size_); }
const_iterator end() const { return const_iterator(&AtUnchecked(size_), element_size_); }
const_iterator cend() const { return const_iterator(&AtUnchecked(size_), element_size_); }
reverse_iterator rbegin() { return reverse_iterator(end()); }
const_reverse_iterator rbegin() const { return const_reverse_iterator(end()); }
const_reverse_iterator crbegin() const { return const_reverse_iterator(cend()); }
reverse_iterator rend() { return reverse_iterator(begin()); }
const_reverse_iterator rend() const { return const_reverse_iterator(begin()); }
const_reverse_iterator crend() const { return const_reverse_iterator(cbegin()); }
// Size.
size_type size() const { return size_; }
bool empty() const { return size() == 0u; }
// Element access. NOTE: Not providing at() and data().
reference operator[](size_t index) {
DCHECK_LT(index, size_);
return AtUnchecked(index);
}
const_reference operator[](size_t index) const {
DCHECK_LT(index, size_);
return AtUnchecked(index);
}
reference front() {
DCHECK(!empty());
return (*this)[0];
}
const_reference front() const {
DCHECK(!empty());
return (*this)[0];
}
reference back() {
DCHECK(!empty());
return (*this)[size_ - 1u];
}
const_reference back() const {
DCHECK(!empty());
return (*this)[size_ - 1u];
}
ArraySlice<T> SubArray(size_type pos) {
return SubArray(pos, size() - pos);
}
ArraySlice<const T> SubArray(size_type pos) const {
return SubArray(pos, size() - pos);
}
ArraySlice<T> SubArray(size_type pos, size_type length) {
DCHECK_LE(pos, size());
DCHECK_LE(length, size() - pos);
return ArraySlice<T>(&AtUnchecked(pos), length, element_size_);
}
ArraySlice<const T> SubArray(size_type pos, size_type length) const {
DCHECK_LE(pos, size());
DCHECK_LE(length, size() - pos);
return ArraySlice<const T>(&AtUnchecked(pos), length, element_size_);
}
size_t ElementSize() const {
return element_size_;
}
bool Contains(const T* element) const {
return &AtUnchecked(0) <= element && element < &AtUnchecked(size_) &&
((reinterpret_cast<uintptr_t>(element) -
reinterpret_cast<uintptr_t>(&AtUnchecked(0))) % element_size_) == 0;
}
size_t OffsetOf(const T* element) const {
DCHECK(Contains(element));
// Since it's possible element_size_ != sizeof(T) we cannot just use pointer arithmatic
uintptr_t base_ptr = reinterpret_cast<uintptr_t>(&AtUnchecked(0));
uintptr_t obj_ptr = reinterpret_cast<uintptr_t>(element);
return (obj_ptr - base_ptr) / 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_LIBARTBASE_BASE_ARRAY_SLICE_H_
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