clyne/constexpr-to-string
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Remove redundant length calculation; expand base support to 36

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Clyne 2020-06-26 13:12:14 -04:00 committed by GitHub
parent aa85b760a8
commit 796eb3e7ee
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1 changed files with 6 additions and 7 deletions
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13
to_string.hpp
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@ -13,9 +13,11 @@
* @struct to_string_t
* @brief Provides the ability to convert any integral to a string at compile-time.
* @tparam N Number to convert
* @tparam base Desired base, can be from 2 to 16 (though no checking is done)
* @tparam base Desired base, can be from 2 to 36
*/
template<auto N, unsigned int base = 10, std::enable_if_t<std::is_integral_v<decltype(N)>, int> = 0>
template<auto N, unsigned int base,
std::enable_if_t<std::is_integral_v<decltype(N)>, int> = 0,
std::enable_if_t<(base > 1 && base < 37), int> = 0>
struct to_string_t {
// The lambda calculates what the string length of N will be, so that `buf`
// fits to the number perfectly.
@ -29,13 +31,10 @@ struct to_string_t {
* Constructs the object, filling `buf` with the string representation of N.
*/
constexpr to_string_t() {
unsigned int len = N >= 0 ? 1 : 2;
for (auto n = N < 0 ? -N : N; n; len++, n /= base);
auto ptr = buf + len;
auto ptr = buf + sizeof(buf) / sizeof(buf[0]);
*--ptr = '\0';
for (auto n = N < 0 ? -N : N; n; n /= base)
*--ptr = "0123456789ABCDEF"[n % base];
*--ptr = "0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZ"[n % base];
if (N < 0)
*--ptr = '-';
}