King_DuckZ/duckhandy
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Optimize for base 10 conversions

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King_DuckZ 2018-07-22 00:10:22 +01:00
parent 81f1a2495f
commit 1b73bd49fa
1 changed files with 34 additions and 0 deletions
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34
include/duckhandy/int_conv.hpp
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@ -68,7 +68,9 @@ namespace dhandy {
using CastedType = typename std::conditional<BecomesUnsigned, UnsignedType, I>::type;
template <typename L>
[[gnu::pure,gnu::always_inline]]
static constexpr L abs(L in) { return (not BecomesUnsigned and std::numeric_limits<L>::is_signed and in < L(0) ? -in : in); }
[[gnu::pure,gnu::always_inline]]
static constexpr CastedType cast (I in) { return static_cast<CastedType>(in); }
};
@ -91,6 +93,38 @@ namespace dhandy {
return arr;
}
};
template <typename I, typename Tr>
struct IntConversion<I, 10, Tr> {
static constexpr ReversedSizedArray<std::decay_t<decltype(std::declval<Tr>().to_digit(1))>, implem::int_info<I, 10>::max_len + 1> to_ary (I in) {
using RetType = ReversedSizedArray<std::decay_t<decltype(std::declval<Tr>().to_digit(1))>, implem::int_info<I, 10>::max_len + 1>;
using Num = implem::NumberAdaptation<I, 10>;
const constexpr char lookup[201] = "000102030405060708091011121314"
"1516171819202122232425262728293031323334353637383940414243"
"4445464748495051525354555657585960616263646566676869707172"
"737475767778798081828384858687888990919293949596979899";
const bool was_negative = implem::is_negative<I, 10>(in);
RetType arr;
arr.push_front('\0');
while (Num::abs(in) >= static_cast<I>(100)) {
arr.push_front(Tr::to_digit(static_cast<int>(lookup[(Num::abs(in) % 100) * 2 + 1] - '0')));
arr.push_front(Tr::to_digit(static_cast<int>(lookup[(Num::abs(in) % 100) * 2 + 0] - '0')));
in = static_cast<I>(in / static_cast<I>(100));
};
if (Num::abs(in) < static_cast<I>(10)) {
arr.push_front(Tr::to_digit(static_cast<int>(Num::abs(in))));
}
else {
arr.push_front(Tr::to_digit(static_cast<int>(lookup[Num::abs(in) * 2 + 1] - '0')));
arr.push_front(Tr::to_digit(static_cast<int>(lookup[Num::abs(in) * 2 + 0] - '0')));
}
if (was_negative)
arr.push_front(Tr::minus());
return arr;
}
};
} //namespace implem
template <typename C, C FirstLetter='a'>