catch_stringref.hpp

//              Copyright Catch2 Authors
// Distributed under the Boost Software License, Version 1.0.
//   (See accompanying file LICENSE_1_0.txt or copy at
//        https://www.boost.org/LICENSE_1_0.txt)

// SPDX-License-Identifier: BSL-1.0
#ifndef CATCH_STRINGREF_HPP_INCLUDED
#define CATCH_STRINGREF_HPP_INCLUDED

#include <cstddef>
#include <string>
#include <iosfwd>
#include <cassert>

namespace Catch {

    /// A non-owning string class (similar to the forthcoming std::string_view)
    /// Note that, because a StringRef may be a substring of another string,
    /// it may not be null terminated.
    class StringRef {
    public:
        using size_type = std::size_t;
        using const_iterator = const char*;

    private:
        static constexpr char const* const s_empty = "";

        char const* m_start = s_empty;
        size_type m_size = 0;

    public: // construction
        constexpr StringRef() noexcept = default;

        StringRef( char const* rawChars ) noexcept;

        constexpr StringRef( char const* rawChars, size_type size ) noexcept
        :   m_start( rawChars ),
            m_size( size )
        {}

        StringRef( std::string const& stdString ) noexcept
        :   m_start( stdString.c_str() ),
            m_size( stdString.size() )
        {}

        explicit operator std::string() const {
            return std::string(m_start, m_size);
        }

    public: // operators
        auto operator == ( StringRef const& other ) const noexcept -> bool;
        auto operator != (StringRef const& other) const noexcept -> bool {
            return !(*this == other);
        }

        constexpr auto operator[] ( size_type index ) const noexcept -> char {
            assert(index < m_size);
            return m_start[index];
        }

        bool operator<(StringRef const& rhs) const noexcept;

    public: // named queries
        constexpr auto empty() const noexcept -> bool {
            return m_size == 0;
        }
        constexpr auto size() const noexcept -> size_type {
            return m_size;
        }

    public: // substrings and searches
        // Returns a substring of [start, start + length).
        // If start + length > size(), then the substring is [start, start + size()).
        // If start > size(), then the substring is empty.
        constexpr StringRef substr(size_type start, size_type length) const noexcept {
            if (start < m_size) {
                const auto shortened_size = m_size - start;
                return StringRef(m_start + start, (shortened_size < length) ? shortened_size : length);
            } else {
                return StringRef();
            }
        }

        // Returns the current start pointer. May not be null-terminated.
        constexpr char const* data() const noexcept {
            return m_start;
        }

    public: // iterators
        constexpr const_iterator begin() const { return m_start; }
        constexpr const_iterator end() const { return m_start + m_size; }


        friend std::string& operator += (std::string& lhs, StringRef const& sr);
        friend std::ostream& operator << (std::ostream& os, StringRef const& sr);
        friend std::string operator+(StringRef lhs, StringRef rhs);
    };


    constexpr auto operator "" _sr( char const* rawChars, std::size_t size ) noexcept -> StringRef {
        return StringRef( rawChars, size );
    }
} // namespace Catch

constexpr auto operator "" _catch_sr( char const* rawChars, std::size_t size ) noexcept -> Catch::StringRef {
    return Catch::StringRef( rawChars, size );
}

#endif // CATCH_STRINGREF_HPP_INCLUDED