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xo-flatstring: undercap flastring_concat instead of char arrays

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This commit is contained in:
Roland Conybeare 2024-04-18 13:27:06 -04:00
commit 0a03aa949b
3 changed files with 34 additions and 4 deletions
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6
example/ex1/ex1.cpp
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@ -136,12 +136,12 @@ main() {
static_assert(sizeof(s14) == 7);
constexpr flatstring s15 = flatstring_concat(flatstring("hello"),
", ",
flatstring("world"));
flatstring(", "),
flatstring("world"));
static_assert(s15.fixed_capacity == 13);
static_assert(sizeof(s15) == 13);
constexpr auto s16 = xo::flatstring_concat("foo", "bar");
constexpr auto s16 = xo::flatstring_concat(flatstring("foo"), flatstring("bar"));
static_assert(s16.fixed_capacity == 7);

13
include/xo/flatstring/flatstring.hpp
View file

@ -452,7 +452,18 @@ namespace xo {
std::size_t pos = 0;
auto detail_concat = [ &pos, &result ](auto && arg) {
constexpr auto count = (sizeof(arg) - sizeof(value_type)) / sizeof(value_type);
/* tradeoff here:
* 1. flatstring::size() is constexpr, so we can concat strings with size() < capacity().
* (note flatstring::from_int() likely creates such strings)
* 2. ..but no size() method on char arrays.
* 3. std::size() not suitable: size of char array includes null terminator,
* while flatstring.size() excludes it, and flatstring behavior is consistent with
* std::string.size()
* Consequence of using arg.size() here; have to wrap char arrays with
* flatstring() to use them with flatstring_concat()
*/
auto count = arg.size();
//constexpr auto count = (sizeof(arg) - sizeof(value_type)) / sizeof(value_type);
std::copy_n(/*arg.c_str()*/ static_cast<const char *>(arg), count, result.value_ + pos);
pos += count;

19
utest/flatstring.test.cpp
View file

@ -231,6 +231,25 @@ namespace xo {
REQUIRE(::strcmp(concat.c_str(), req_str.c_str()) == 0);
}
#ifdef NOT_USING
{
auto concat4 = flatstring_concat(str,
flatstring(text2),
str,
flatstring(text2));
auto req_str = string(text) + string(text2) + string(text) + string(text2);
REQUIRE(::strcmp(concat4.c_str(), req_str.c_str()) == 0);
}
#endif
{
auto concat4 = flatstring_concat(str, str2, str, str2);
auto req_str = string(text) + string(text2) + string(text) + string(text2);
REQUIRE(::strcmp(concat4.c_str(), req_str.c_str()) == 0);
}
}
template <typename String>