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//
// Copyright Aliaksei Levin (levlam@telegram.org), Arseny Smirnov (arseny30@gmail.com) 2014-2026
//
// Distributed under the Boost Software License, Version 1.0. (See accompanying
// file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
//
#pragma once
#include "td/utils/common.h"
#include <array>
#include <iterator>
namespace td {
namespace detail {
template <class T, class InnerT>
class SpanImpl {
InnerT *data_{nullptr};
size_t size_{0};
public:
SpanImpl() = default;
SpanImpl(InnerT *data, size_t size) : data_(data), size_(size) {
}
SpanImpl(InnerT &data) : SpanImpl(&data, 1) {
}
template <class OtherInnerT>
SpanImpl(const SpanImpl<T, OtherInnerT> &other) : SpanImpl(other.data(), other.size()) {
}
template <size_t N>
SpanImpl(const std::array<T, N> &arr) : SpanImpl(arr.data(), arr.size()) {
}
template <size_t N>
SpanImpl(std::array<T, N> &arr) : SpanImpl(arr.data(), arr.size()) {
}
template <size_t N>
SpanImpl(const T (&arr)[N]) : SpanImpl(arr, N) {
}
template <size_t N>
SpanImpl(T (&arr)[N]) : SpanImpl(arr, N) {
}
SpanImpl(const vector<T> &v) : SpanImpl(v.data(), v.size()) {
}
SpanImpl(vector<T> &v) : SpanImpl(v.data(), v.size()) {
}
template <class OtherInnerT>
SpanImpl &operator=(const SpanImpl<T, OtherInnerT> &other) {
SpanImpl copy{other};
*this = copy;
return *this;
}
template <class OtherInnerT>
bool operator==(const SpanImpl<T, OtherInnerT> &other) const {
if (size() != other.size()) {
return false;
}
for (size_t i = 0; i < size(); i++) {
if (!((*this)[i] == other[i])) {
return false;
}
}
return true;
}
InnerT &operator[](size_t i) {
DCHECK(i < size());
return data_[i];
}
const InnerT &operator[](size_t i) const {
DCHECK(i < size());
return data_[i];
}
InnerT &back() {
DCHECK(!empty());
return data_[size() - 1];
}
const InnerT &back() const {
DCHECK(!empty());
return data_[size() - 1];
}
InnerT &front() {
DCHECK(!empty());
return data_[0];
}
const InnerT &front() const {
DCHECK(!empty());
return data_[0];
}
InnerT *data() const {
return data_;
}
InnerT *begin() const {
return data_;
}
InnerT *end() const {
return data_ + size_;
}
std::reverse_iterator<InnerT *> rbegin() const {
return std::reverse_iterator<InnerT *>(end());
}
std::reverse_iterator<InnerT *> rend() const {
return std::reverse_iterator<InnerT *>(begin());
}
size_t size() const {
return size_;
}
bool empty() const {
return size() == 0;
}
SpanImpl &truncate(size_t size) {
if (size < size_) {
size_ = size;
}
return *this;
}
SpanImpl substr(size_t offset) const {
CHECK(offset <= size_);
return SpanImpl(begin() + offset, size_ - offset);
}
SpanImpl substr(size_t offset, size_t size) const {
CHECK(offset <= size_);
CHECK(size_ - offset >= size);
return SpanImpl(begin() + offset, size);
}
};
} // namespace detail
template <class T>
using Span = detail::SpanImpl<T, const T>;
template <class T>
using MutableSpan = detail::SpanImpl<T, T>;
template <class T>
Span<T> as_span(const std::vector<T> &vec) {
return Span<T>(vec);
}
template <class T>
MutableSpan<T> as_mutable_span(std::vector<T> &vec) {
return MutableSpan<T>(vec);
}
} // namespace td
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