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46 lines
1.3 KiB
C++
46 lines
1.3 KiB
C++
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#if !defined(PQXX_CONCAT_HXX)
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# define PQXX_CONCAT_HXX
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# include <string>
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# include <string_view>
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# include "pqxx/strconv.hxx"
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namespace pqxx::internal
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{
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/// Convert item to a string, write it into [here, end).
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template<typename TYPE>
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void render_item(TYPE const &item, char *&here, char *end)
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{
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here = string_traits<TYPE>::into_buf(here, end, item) - 1;
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}
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// C++20: Support non-random_access_range ranges.
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/// Efficiently combine a bunch of items into one big string.
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/** Use this as an optimised version of string concatentation. It takes just
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* about any type; it will represent each item as a string according to its
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* @ref string_traits.
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*
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* This is a simpler, more specialised version of @ref separated_list for a
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* statically known series of items, possibly of different types.
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*/
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template<typename... TYPE>
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[[nodiscard]] inline std::string concat(TYPE... item)
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{
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std::string buf;
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// Size to accommodate string representations of all inputs, minus their
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// terminating zero bytes.
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buf.resize(size_buffer(item...));
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char *const data{buf.data()};
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char *here = data;
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char *end = data + std::size(buf);
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(render_item(item, here, end), ...);
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buf.resize(static_cast<std::size_t>(here - data));
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return buf;
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}
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} // namespace pqxx::internal
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#endif
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