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Add string concatenation function

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Add variadic concat() function for concatenating char *, char, and
string types.
This commit is contained in:
Florian Albrechtskirchinger 2022-04-03 17:43:39 +02:00
parent b9d27b6a1f
commit 10e451b58d
4 changed files with 396 additions and 0 deletions
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139
include/nlohmann/detail/string_concat.hpp Normal file
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@ -0,0 +1,139 @@
#pragma once
#include <cstring> // strlen
#include <string> // string
#include <utility> // forward
#include <nlohmann/detail/meta/cpp_future.hpp>
#include <nlohmann/detail/meta/detected.hpp>
namespace nlohmann
{
namespace detail
{
inline std::size_t concat_length()
{
return 0;
}
template<typename... Args>
inline std::size_t concat_length(const char* cstr, Args&& ... rest);
template<typename StringType, typename... Args>
inline std::size_t concat_length(const StringType& str, Args&& ... rest);
template<typename... Args>
inline std::size_t concat_length(const char /*c*/, Args&& ... rest)
{
return 1 + concat_length(std::forward<Args>(rest)...);
}
template<typename... Args>
inline std::size_t concat_length(const char* cstr, Args&& ... rest)
{
// cppcheck-suppress ignoredReturnValue
return ::strlen(cstr) + concat_length(std::forward<Args>(rest)...);
}
template<typename StringType, typename... Args>
inline std::size_t concat_length(const StringType& str, Args&& ... rest)
{
return str.size() + concat_length(std::forward<Args>(rest)...);
}
template<typename OutStringType>
inline void concat_into(OutStringType& /*out*/)
{}
template<typename StringType, typename Arg>
using string_can_append = decltype(std::declval<StringType&>().append(std::declval < Arg && > ()));
template<typename StringType, typename Arg>
using detect_string_can_append = is_detected<string_can_append, StringType, Arg>;
template<typename StringType, typename Arg>
using string_can_append_op = decltype(std::declval<StringType&>() += std::declval < Arg && > ());
template<typename StringType, typename Arg>
using detect_string_can_append_op = is_detected<string_can_append_op, StringType, Arg>;
template<typename StringType, typename Arg>
using string_can_append_iter = decltype(std::declval<StringType&>().append(std::declval<const Arg&>().begin(), std::declval<const Arg&>().end()));
template<typename StringType, typename Arg>
using detect_string_can_append_iter = is_detected<string_can_append_iter, StringType, Arg>;
template<typename StringType, typename Arg>
using string_can_append_data = decltype(std::declval<StringType&>().append(std::declval<const Arg&>().data(), std::declval<const Arg&>().size()));
template<typename StringType, typename Arg>
using detect_string_can_append_data = is_detected<string_can_append_data, StringType, Arg>;
template < typename OutStringType, typename Arg, typename... Args,
enable_if_t < !detect_string_can_append<OutStringType, Arg>::value
&& detect_string_can_append_op<OutStringType, Arg>::value, int > = 0 >
inline void concat_into(OutStringType& out, Arg && arg, Args && ... rest);
template < typename OutStringType, typename Arg, typename... Args,
enable_if_t < !detect_string_can_append<OutStringType, Arg>::value
&& !detect_string_can_append_op<OutStringType, Arg>::value
&& detect_string_can_append_iter<OutStringType, Arg>::value, int > = 0 >
inline void concat_into(OutStringType& out, const Arg& arg, Args && ... rest);
template < typename OutStringType, typename Arg, typename... Args,
enable_if_t < !detect_string_can_append<OutStringType, Arg>::value
&& !detect_string_can_append_op<OutStringType, Arg>::value
&& !detect_string_can_append_iter<OutStringType, Arg>::value
&& detect_string_can_append_data<OutStringType, Arg>::value, int > = 0 >
inline void concat_into(OutStringType& out, const Arg& arg, Args && ... rest);
template<typename OutStringType, typename Arg, typename... Args,
enable_if_t<detect_string_can_append<OutStringType, Arg>::value, int> = 0>
inline void concat_into(OutStringType& out, Arg && arg, Args && ... rest)
{
out.append(std::forward<Arg>(arg));
concat_into(out, std::forward<Args>(rest)...);
}
template < typename OutStringType, typename Arg, typename... Args,
enable_if_t < !detect_string_can_append<OutStringType, Arg>::value
&& detect_string_can_append_op<OutStringType, Arg>::value, int > >
inline void concat_into(OutStringType& out, Arg&& arg, Args&& ... rest)
{
out += std::forward<Arg>(arg);
concat_into(out, std::forward<Args>(rest)...);
}
template < typename OutStringType, typename Arg, typename... Args,
enable_if_t < !detect_string_can_append<OutStringType, Arg>::value
&& !detect_string_can_append_op<OutStringType, Arg>::value
&& detect_string_can_append_iter<OutStringType, Arg>::value, int > >
inline void concat_into(OutStringType& out, const Arg& arg, Args&& ... rest)
{
out.append(arg.begin(), arg.end());
concat_into(out, std::forward<Args>(rest)...);
}
template < typename OutStringType, typename Arg, typename... Args,
enable_if_t < !detect_string_can_append<OutStringType, Arg>::value
&& !detect_string_can_append_op<OutStringType, Arg>::value
&& !detect_string_can_append_iter<OutStringType, Arg>::value
&& detect_string_can_append_data<OutStringType, Arg>::value, int > >
inline void concat_into(OutStringType& out, const Arg& arg, Args&& ... rest)
{
out.append(arg.data(), arg.size());
concat_into(out, std::forward<Args>(rest)...);
}
template<typename OutStringType = std::string, typename... Args>
inline OutStringType concat(Args && ... args)
{
OutStringType str;
str.reserve(concat_length(std::forward<Args>(args)...));
concat_into(str, std::forward<Args>(args)...);
return str;
}
} // namespace detail
} // namespace nlohmann

1
include/nlohmann/json.hpp
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@ -83,6 +83,7 @@ SOFTWARE.
#include <nlohmann/detail/json_pointer.hpp>
#include <nlohmann/detail/json_ref.hpp>
#include <nlohmann/detail/macro_scope.hpp>
#include <nlohmann/detail/string_concat.hpp>
#include <nlohmann/detail/string_escape.hpp>
#include <nlohmann/detail/meta/cpp_future.hpp>
#include <nlohmann/detail/meta/type_traits.hpp>

143
single_include/nlohmann/json.hpp
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@ -13187,6 +13187,149 @@ class json_ref
// #include <nlohmann/detail/macro_scope.hpp>
// #include <nlohmann/detail/string_concat.hpp>
#include <cstring> // strlen
#include <string> // string
#include <utility> // forward
// #include <nlohmann/detail/meta/cpp_future.hpp>
// #include <nlohmann/detail/meta/detected.hpp>
namespace nlohmann
{
namespace detail
{
inline std::size_t concat_length()
{
return 0;
}
template<typename... Args>
inline std::size_t concat_length(const char* cstr, Args&& ... rest);
template<typename StringType, typename... Args>
inline std::size_t concat_length(const StringType& str, Args&& ... rest);
template<typename... Args>
inline std::size_t concat_length(const char /*c*/, Args&& ... rest)
{
return 1 + concat_length(std::forward<Args>(rest)...);
}
template<typename... Args>
inline std::size_t concat_length(const char* cstr, Args&& ... rest)
{
// cppcheck-suppress ignoredReturnValue
return ::strlen(cstr) + concat_length(std::forward<Args>(rest)...);
}
template<typename StringType, typename... Args>
inline std::size_t concat_length(const StringType& str, Args&& ... rest)
{
return str.size() + concat_length(std::forward<Args>(rest)...);
}
template<typename OutStringType>
inline void concat_into(OutStringType& /*out*/)
{}
template<typename StringType, typename Arg>
using string_can_append = decltype(std::declval<StringType&>().append(std::declval < Arg && > ()));
template<typename StringType, typename Arg>
using detect_string_can_append = is_detected<string_can_append, StringType, Arg>;
template<typename StringType, typename Arg>
using string_can_append_op = decltype(std::declval<StringType&>() += std::declval < Arg && > ());
template<typename StringType, typename Arg>
using detect_string_can_append_op = is_detected<string_can_append_op, StringType, Arg>;
template<typename StringType, typename Arg>
using string_can_append_iter = decltype(std::declval<StringType&>().append(std::declval<const Arg&>().begin(), std::declval<const Arg&>().end()));
template<typename StringType, typename Arg>
using detect_string_can_append_iter = is_detected<string_can_append_iter, StringType, Arg>;
template<typename StringType, typename Arg>
using string_can_append_data = decltype(std::declval<StringType&>().append(std::declval<const Arg&>().data(), std::declval<const Arg&>().size()));
template<typename StringType, typename Arg>
using detect_string_can_append_data = is_detected<string_can_append_data, StringType, Arg>;
template < typename OutStringType, typename Arg, typename... Args,
enable_if_t < !detect_string_can_append<OutStringType, Arg>::value
&& detect_string_can_append_op<OutStringType, Arg>::value, int > = 0 >
inline void concat_into(OutStringType& out, Arg && arg, Args && ... rest);
template < typename OutStringType, typename Arg, typename... Args,
enable_if_t < !detect_string_can_append<OutStringType, Arg>::value
&& !detect_string_can_append_op<OutStringType, Arg>::value
&& detect_string_can_append_iter<OutStringType, Arg>::value, int > = 0 >
inline void concat_into(OutStringType& out, const Arg& arg, Args && ... rest);
template < typename OutStringType, typename Arg, typename... Args,
enable_if_t < !detect_string_can_append<OutStringType, Arg>::value
&& !detect_string_can_append_op<OutStringType, Arg>::value
&& !detect_string_can_append_iter<OutStringType, Arg>::value
&& detect_string_can_append_data<OutStringType, Arg>::value, int > = 0 >
inline void concat_into(OutStringType& out, const Arg& arg, Args && ... rest);
template<typename OutStringType, typename Arg, typename... Args,
enable_if_t<detect_string_can_append<OutStringType, Arg>::value, int> = 0>
inline void concat_into(OutStringType& out, Arg && arg, Args && ... rest)
{
out.append(std::forward<Arg>(arg));
concat_into(out, std::forward<Args>(rest)...);
}
template < typename OutStringType, typename Arg, typename... Args,
enable_if_t < !detect_string_can_append<OutStringType, Arg>::value
&& detect_string_can_append_op<OutStringType, Arg>::value, int > >
inline void concat_into(OutStringType& out, Arg&& arg, Args&& ... rest)
{
out += std::forward<Arg>(arg);
concat_into(out, std::forward<Args>(rest)...);
}
template < typename OutStringType, typename Arg, typename... Args,
enable_if_t < !detect_string_can_append<OutStringType, Arg>::value
&& !detect_string_can_append_op<OutStringType, Arg>::value
&& detect_string_can_append_iter<OutStringType, Arg>::value, int > >
inline void concat_into(OutStringType& out, const Arg& arg, Args&& ... rest)
{
out.append(arg.begin(), arg.end());
concat_into(out, std::forward<Args>(rest)...);
}
template < typename OutStringType, typename Arg, typename... Args,
enable_if_t < !detect_string_can_append<OutStringType, Arg>::value
&& !detect_string_can_append_op<OutStringType, Arg>::value
&& !detect_string_can_append_iter<OutStringType, Arg>::value
&& detect_string_can_append_data<OutStringType, Arg>::value, int > >
inline void concat_into(OutStringType& out, const Arg& arg, Args&& ... rest)
{
out.append(arg.data(), arg.size());
concat_into(out, std::forward<Args>(rest)...);
}
template<typename OutStringType = std::string, typename... Args>
inline OutStringType concat(Args && ... args)
{
OutStringType str;
str.reserve(concat_length(std::forward<Args>(args)...));
concat_into(str, std::forward<Args>(args)...);
return str;
}
} // namespace detail
} // namespace nlohmann
// #include <nlohmann/detail/string_escape.hpp>
// #include <nlohmann/detail/meta/cpp_future.hpp>

113
test/src/unit-convenience.cpp
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@ -37,6 +37,84 @@ using nlohmann::json;
namespace
{
struct alt_string_iter
{
alt_string_iter() = default;
alt_string_iter(const char* cstr)
: impl(cstr)
{}
void reserve(std::size_t s)
{
impl.reserve(s);
}
template<typename Iter>
void append(Iter first, Iter last)
{
impl.append(first, last);
}
std::string::const_iterator begin() const
{
return impl.begin();
}
std::string::const_iterator end() const
{
return impl.end();
}
std::size_t size() const
{
return impl.size();
}
alt_string_iter& operator+=(const char c)
{
impl += c;
return *this;
}
std::string impl{};
};
struct alt_string_data
{
alt_string_data() = default;
alt_string_data(const char* cstr)
: impl(cstr)
{}
void reserve(std::size_t s)
{
impl.reserve(s);
}
void append(const char* p, std::size_t s)
{
impl.append(p, s);
}
const char* data() const
{
return impl.data();
}
std::size_t size() const
{
return impl.size();
}
alt_string_data& operator+=(const char c)
{
impl += c;
return *this;
}
std::string impl{};
};
void check_escaped(const char* original, const char* escaped = "", bool ensure_ascii = false);
void check_escaped(const char* original, const char* escaped, const bool ensure_ascii)
{
@ -110,4 +188,39 @@ TEST_CASE("convenience functions")
CHECK_THROWS_WITH_AS(check_escaped("\xC2"), "[json.exception.type_error.316] incomplete UTF-8 string; last byte: 0xC2", json::type_error&);
}
SECTION("string concat")
{
using nlohmann::detail::concat;
const char* expected = "Hello, world!";
alt_string_iter hello_iter{"Hello, "};
alt_string_data hello_data{"Hello, "};
std::string world = "world";
SECTION("std::string")
{
std::string str1 = concat(hello_iter, world, '!');
std::string str2 = concat(hello_data, world, '!');
std::string str3 = concat("Hello, ", world, '!');
CHECK(str1 == expected);
CHECK(str2 == expected);
CHECK(str3 == expected);
}
SECTION("alt_string_iter")
{
alt_string_iter str = concat<alt_string_iter>(hello_iter, world, '!');
CHECK(str.impl == expected);
}
SECTION("alt_string_data")
{
alt_string_data str = concat<alt_string_data>(hello_data, world, '!');
CHECK(str.impl == expected);
}
}
}