strcat.hpp

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#ifndef STRCAT_HPP
#define STRCAT_HPP

#include "string_view.hpp"
#include <array>
#include <cstdint>
#include <string>
#include <type_traits>

namespace BT {

// -----------------------------------------------------------------------------
// StrCat()
// -----------------------------------------------------------------------------
//
// Merges given strings, using no delimiter(s).
//
// `StrCat()` is designed to be the fastest possible way to construct a string
// out of a mix of raw C strings, string_views, strings.

namespace strings_internal {

inline void AppendPieces(std::string* dest,
                         std::initializer_list<nonstd::string_view> pieces)
{
    size_t size = 0;
    for (const auto& piece: pieces)
    {
        size += piece.size();
    }
    dest->reserve(dest->size() + size);
    for (const auto& piece: pieces)
    {
        dest->append( piece.data(), piece.size() );
    }
}

inline std::string CatPieces(std::initializer_list<nonstd::string_view> pieces)
{
    std::string out;
    AppendPieces(&out, std::move(pieces));
    return out;
}

}  // namespace strings_internal

inline std::string StrCat() { return std::string(); }

inline std::string StrCat(const nonstd::string_view& a) {
    return std::string(a.data(), a.size());
}

inline std::string StrCat(const nonstd::string_view& a,
                   const nonstd::string_view& b)
{
    return strings_internal::CatPieces( {a, b} );
}

inline std::string StrCat(const nonstd::string_view& a,
                          const nonstd::string_view& b,
                          const nonstd::string_view& c)
{
    return strings_internal::CatPieces( {a, b, c} );
}

// Support 4 or more arguments
template <typename... AV>
inline std::string StrCat(const nonstd::string_view& a,
                          const nonstd::string_view& b,
                          const nonstd::string_view& c,
                          const nonstd::string_view& d,
                          const AV&... args)
{
    return strings_internal::CatPieces( {a, b, c, d,  static_cast<const nonstd::string_view&>(args)...});
}

//-----------------------------------------------


inline void StrAppend(std::string* destination,
                      const nonstd::string_view& a)
{
    destination->append( a.data(), a.size());
}

inline void StrAppend(std::string* destination,
                      const nonstd::string_view& a,
                      const nonstd::string_view& b)
{
    strings_internal::AppendPieces( destination, {a, b} );
}

inline void StrAppend(std::string* destination,
                      const nonstd::string_view& a,
                      const nonstd::string_view& b,
                      const nonstd::string_view& c)
{
    strings_internal::AppendPieces( destination, {a, b, c} );
}

// Support 4 or more arguments
template <typename... AV>
inline void StrAppend(std::string* destination,
                      const nonstd::string_view& a,
                      const nonstd::string_view& b,
                      const nonstd::string_view& c,
                      const nonstd::string_view& d,
                      const AV&... args)
{
    strings_internal::AppendPieces( destination, {a, b, c, d,  static_cast<const nonstd::string_view&>(args)...});
}


}  // namespace BT


#endif // STRCAT_HPP