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Added count_digits()

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This commit is contained in:
Andreas Tsouchlos
2021-11-26 23:19:57 +01:00
parent 9b430b9902
commit ffa4a6a501
155 changed files with 12192 additions and 12 deletions
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8
inc/format.h
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@@ -43,15 +43,17 @@ constexpr inline void check_fmt_params() {
// TODO: Error handling
template <fmt_data_t fmt_data, std::integral arg_t>
constexpr inline void format_arg(char* dest, arg_t arg) {
auto error_array = get_init_array<fmt_data.length>('f');
constexpr auto error_array = get_init_array<fmt_data.length>('f');
detail::format_integral(dest, arg, fmt_data);
detail::format_int(dest, arg, fmt_data);
};
// TODO: Error handling
template <fmt_data_t fmt_data, std::floating_point arg_t>
constexpr inline void format_arg(char* dest, arg_t) {
constexpr inline void format_arg(char* dest, arg_t arg) {
*(dest) = 'f';
*(dest + fmt_data.length - fmt_data.precision - 1) = '.';
//detail::format_float(dest, arg, fmt_data);
};
// TODO: Error handling
template<fmt_data_t fmt_data>

57
inc/format_impl.h
View File

@@ -11,6 +11,8 @@
*/
#include <cstdint>
#include "utility.h"
@@ -24,6 +26,12 @@ namespace detail {
*/
#define FMT_POWERS_OF_10(factor) \
factor * 10, (factor)*100, (factor)*1000, (factor)*10000, (factor)*100000, \
(factor)*1000000, (factor)*10000000, (factor)*100000000, \
(factor)*1000000000
// Converts value in the range [0, 100) to a string.
constexpr inline const char* digits2(size_t value) {
// GCC generates slightly better code when value is pointer-size.
@@ -40,13 +48,12 @@ constexpr inline void copy2(char* dst, const char* src) {
std::memcpy(dst, src, 2);
return;
}
*dst++ = static_cast<char>(*src++);
*dst = static_cast<char>(*src);
}
template <typename UInt>
constexpr inline void format_decimal(char* out, UInt value, int size) {
template <typename uint_t>
constexpr inline void format_decimal(char* out, uint_t value, int size) {
out += size;
while (value >= 100) {
out -= 2;
@@ -60,6 +67,40 @@ constexpr inline void format_decimal(char* out, UInt value, int size) {
copy2(out, digits2(static_cast<size_t>(value)));
}
template <typename T>
constexpr int count_digits_fallback(T n) {
int count = 1;
for (;;) {
if (n < 10) return count;
if (n < 100) return count + 1;
if (n < 1000) return count + 2;
if (n < 10000) return count + 3;
n /= 10000u;
count += 4;
}
}
inline int do_count_digits(uint64_t n) {
// Maps bsr(n) to ceil(log10(pow(2, bsr(n) + 1) - 1)).
static constexpr uint8_t bsr2log10[] = {
1, 1, 1, 2, 2, 2, 3, 3, 3, 4, 4, 4, 4, 5, 5, 5,
6, 6, 6, 7, 7, 7, 7, 8, 8, 8, 9, 9, 9, 10, 10, 10,
10, 11, 11, 11, 12, 12, 12, 13, 13, 13, 13, 14, 14, 14, 15, 15,
15, 16, 16, 16, 16, 17, 17, 17, 18, 18, 18, 19, 19, 19, 19, 20};
auto t = bsr2log10[__builtin_clzll(n | 1) ^ 63];
static constexpr const uint64_t zero_or_powers_of_10[] = {
0, 0, FMT_POWERS_OF_10(1U), FMT_POWERS_OF_10(1000000000ULL),
10000000000000000000ULL};
return t - (n < zero_or_powers_of_10[t]);
}
constexpr inline auto count_digits(uint64_t n) -> int {
if (!std::is_constant_evaluated()) {
return do_count_digits(n);
}
return count_digits_fallback(n);
}
/*
*
@@ -69,14 +110,12 @@ constexpr inline void format_decimal(char* out, UInt value, int size) {
template <std::unsigned_integral uint_t>
constexpr inline void format_integral(char* out, uint_t value,
fmt_data_t fmt_node) {
constexpr inline void format_int(char* out, uint_t value, fmt_data_t fmt_node) {
format_decimal(out, value, fmt_node.length);
}
template <std::signed_integral uint_t>
constexpr inline void format_integral(char* out, uint_t value,
fmt_data_t fmt_node) {
constexpr inline void format_int(char* out, uint_t value, fmt_data_t fmt_node) {
if (value < 0) value = -value;
format_decimal(out, value, fmt_node.length);
}
@@ -90,8 +129,8 @@ constexpr inline void format_integral(char* out, uint_t value,
template <std::floating_point float_t>
constexpr inline void format_floating_point(char* out, float_t value,
fmt_data_t fmt_node) {
constexpr inline void format_float(char* out, float_t value,
fmt_data_t fmt_node) {
// TODO
}