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// Copyright 2019 The Chromium Authors
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.
#ifndef V8_CRDTP_SPAN_H_
#define V8_CRDTP_SPAN_H_
#include <cstdint>
#include <cstring>
#include <string>
#include <type_traits>
#include "export.h"
namespace v8_crdtp {
// =============================================================================
// span - sequence of bytes
// =============================================================================
// This template is similar to std::span, which will be included in C++20.
template <typename T>
class span {
public:
using index_type = size_t;
constexpr span() : data_(nullptr), size_(0) {}
constexpr span(const T* data, index_type size) : data_(data), size_(size) {}
constexpr const T* data() const { return data_; }
constexpr const T* begin() const { return data_; }
constexpr const T* end() const { return data_ + size_; }
constexpr const T& operator[](index_type idx) const { return data_[idx]; }
constexpr span<T> subspan(index_type offset, index_type count) const {
return span(data_ + offset, count);
}
constexpr span<T> subspan(index_type offset) const {
return span(data_ + offset, size_ - offset);
}
constexpr bool empty() const { return size_ == 0; }
constexpr index_type size() const { return size_; }
constexpr index_type size_bytes() const { return size_ * sizeof(T); }
private:
const T* data_;
index_type size_;
};
template <size_t N>
constexpr span<char> MakeSpan(const char (&str)[N]) {
return span<char>(str, N - 1);
}
template <size_t N>
constexpr span<uint8_t> SpanFrom(const char (&str)[N]) {
return span<uint8_t>(reinterpret_cast<const uint8_t*>(str), N - 1);
}
constexpr inline span<uint8_t> SpanFrom(const char* str) {
return str ? span<uint8_t>(reinterpret_cast<const uint8_t*>(str), strlen(str))
: span<uint8_t>();
}
inline span<uint8_t> SpanFrom(const std::string& v) {
return span<uint8_t>(reinterpret_cast<const uint8_t*>(v.data()), v.size());
}
// This SpanFrom routine works for std::vector<uint8_t> and
// std::vector<uint16_t>, but also for base::span<const uint8_t> in Chromium.
template <typename C>
inline span<typename C::value_type> SpanFrom(const C& v)
requires(std::is_unsigned_v<typename C::value_type> &&
std::is_member_function_pointer_v<decltype(&C::size)>)
{
return span<typename C::value_type>(v.data(), v.size());
}
// Less than / equality comparison functions for sorting / searching for byte
// spans.
bool SpanLessThan(span<uint8_t> x, span<uint8_t> y) noexcept;
bool SpanEquals(span<uint8_t> x, span<uint8_t> y) noexcept;
// Less than / equality comparison functions for sorting / searching for byte
// spans.
bool SpanLessThan(span<char> x, span<char> y) noexcept;
bool SpanEquals(span<char> x, span<char> y) noexcept;
struct SpanLt {
bool operator()(span<uint8_t> l, span<uint8_t> r) const {
return SpanLessThan(l, r);
}
};
} // namespace v8_crdtp
#endif // V8_CRDTP_SPAN_H_
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