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uint8_t parsing

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Signed-off-by: Shikhar <shikharish05@gmail.com>
This commit is contained in:
Shikhar 2025-12-23 05:59:26 +05:30
parent 0920535f64
commit fce0ab61df
1 changed files with 86 additions and 0 deletions
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86
include/fast_float/ascii_number.h
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@ -509,6 +509,92 @@ parse_int_string(UC const *p, UC const *pend, T &value,
UC const *const start_digits = p; UC const *const start_digits = p;
if constexpr (std::is_same_v<T, std::uint8_t>) {
const size_t len = (size_t)(pend - p);
if (len == 0) {
if (has_leading_zeros) {
value = 0;
answer.ec = std::errc();
answer.ptr = p;
} else {
answer.ec = std::errc::invalid_argument;
answer.ptr = first;
}
return answer;
}
union {
uint8_t as_str[4];
uint32_t as_int;
} digits;
if (cpp20_and_in_constexpr()) {
digits.as_int = 0;
for (size_t j = 0; j < 4 && j < len; ++j) {
digits.as_str[j] = static_cast<uint8_t>(p[j]);
}
} else if (len >= 4) {
memcpy(&digits.as_int, p, 4);
} else {
uint32_t b0 = static_cast<uint8_t>(p[0]);
uint32_t b1 = (len > 1) ? static_cast<uint8_t>(p[1]) : 0xFFu;
uint32_t b2 = (len > 2) ? static_cast<uint8_t>(p[2]) : 0xFFu;
uint32_t b3 = 0xFFu;
#if FASTFLOAT_IS_BIG_ENDIAN
digits.as_int = (b0 << 24) | (b1 << 16) | (b2 << 8) | b3;
#else
digits.as_int = b0 | (b1 << 8) | (b2 << 16) | (b3 << 24);
#endif
}
uint32_t magic =
((digits.as_int + 0x46464646u) | (digits.as_int - 0x30303030u)) &
0x80808080u;
uint32_t tz = (uint32_t)std::__countr_zero(magic); // 7, 15, 23, 31, or 32
uint32_t nd = (tz == 32) ? 4 : (tz >> 3);
nd = (uint32_t)std::min((size_t)nd, len);
if (nd == 0) {
if (has_leading_zeros) {
value = 0;
answer.ec = std::errc();
answer.ptr = p;
return answer;
}
answer.ec = std::errc::invalid_argument;
answer.ptr = first;
return answer;
}
if (nd > 3) {
const UC *q = p + nd;
size_t rem = len - nd;
while (rem) {
if (*q < UC('0') || *q > UC('9'))
break;
++q;
--rem;
}
answer.ec = std::errc::result_out_of_range;
answer.ptr = q;
return answer;
}
digits.as_int ^= 0x30303030u;
digits.as_int <<= ((4 - nd) * 8);
uint32_t check = ((digits.as_int >> 24) & 0xff) |
((digits.as_int >> 8) & 0xff00) |
((digits.as_int << 8) & 0xff0000);
if (check > 0x00020505) {
answer.ec = std::errc::result_out_of_range;
answer.ptr = p + nd;
return answer;
}
value = (uint8_t)((0x640a01 * digits.as_int) >> 24);
answer.ec = std::errc();
answer.ptr = p + nd;
return answer;
}
uint64_t i = 0; uint64_t i = 0;
if (base == 10) { if (base == 10) {
loop_parse_if_eight_digits(p, pend, i); // use SIMD if possible loop_parse_if_eight_digits(p, pend, i); // use SIMD if possible