scylladb/utils/mutable_view.hh

/*
 * Copyright (C) 2017-present ScyllaDB
 */

/*
 * SPDX-License-Identifier: LicenseRef-ScyllaDB-Source-Available-1.1
 */

#pragma once

#include <string_view>
#include <seastar/core/sstring.hh>

#include "seastarx.hh"

template<typename CharT>
class basic_mutable_view {
    CharT* _begin = nullptr;
    CharT* _end = nullptr;
public:
    using value_type = CharT;
    using pointer = CharT*;
    using iterator = CharT*;
    using const_iterator = CharT*;

    basic_mutable_view() = default;

    template<typename U, U N>
    basic_mutable_view(basic_sstring<CharT, U, N>& str)
        : _begin(str.begin())
        , _end(str.end())
    { }

    basic_mutable_view(CharT* ptr, size_t length)
        : _begin(ptr)
        , _end(ptr + length)
    { }

    operator std::basic_string_view<CharT>() const noexcept {
        return std::basic_string_view<CharT>(begin(), size());
    }

    CharT& operator[](size_t idx) const { return _begin[idx]; }

    iterator begin() const { return _begin; }
    iterator end() const { return _end; }

    CharT* data() const { return _begin; }
    size_t size() const { return _end - _begin; }
    bool empty() const { return _begin == _end; }
    CharT& front() const { return *_begin; }

    void remove_prefix(size_t n) {
        _begin += n;
    }
    void remove_suffix(size_t n) {
        _end -= n;
    }

    basic_mutable_view substr(size_t pos, size_t count) {
        size_t n = std::min(count, (_end - _begin) - pos);
        return basic_mutable_view{_begin + pos, n};
    }

    explicit operator std::span<CharT>() const noexcept {
        return std::span<CharT>(_begin, _end);
    }
};