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add base check for uint8 #358

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Merged
lemire merged 2 commits into from
Dec 31, 2025
+75 −72
Merged

add base check for uint8 #358

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fb522b6
fix endianess bug in uint8 parsing
shikharish Dec 31, 2025
4dc5225
add base check for uint8 parsing
shikharish Dec 31, 2025
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147 changes: 75 additions & 72 deletions include/fast_float/ascii_number.h
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Original file line number Diff line number Diff line change
Expand Up @@ -42,6 +42,11 @@ fastfloat_really_inline constexpr uint64_t byteswap(uint64_t val) {
(val & 0x000000000000FF00) << 40 | (val & 0x00000000000000FF) << 56;
}

fastfloat_really_inline constexpr uint32_t byteswap_32(uint32_t val) {
return (val >> 24) | ((val >> 8) & 0x0000FF00u) | ((val << 8) & 0x00FF0000u) |
(val << 24);
}

// Read 8 UC into a u64. Truncates UC if not char.
template <typename UC>
fastfloat_really_inline FASTFLOAT_CONSTEXPR20 uint64_t
Expand Down Expand Up @@ -510,97 +515,95 @@ parse_int_string(UC const *p, UC const *pend, T &value,
UC const *const start_digits = p;

FASTFLOAT_IF_CONSTEXPR17((std::is_same<T, std::uint8_t>::value)) {
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;
if (base == 10) {
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;
}
return answer;
}

uint32_t digits;
uint32_t digits;

#if FASTFLOAT_HAS_IS_CONSTANT_EVALUATED && FASTFLOAT_HAS_BIT_CAST
if (std::is_constant_evaluated()) {
uint8_t str[4]{};
for (size_t j = 0; j < 4 && j < len; ++j) {
str[j] = static_cast<uint8_t>(p[j]);
}
digits = std::bit_cast<uint32_t>(str);
if (std::is_constant_evaluated()) {
uint8_t str[4]{};
for (size_t j = 0; j < 4 && j < len; ++j) {
str[j] = static_cast<uint8_t>(p[j]);
}
digits = std::bit_cast<uint32_t>(str);
#if FASTFLOAT_IS_BIG_ENDIAN
digits = byteswap(digits);
digits = byteswap_32(digits);
#endif
}
}
#else
if (false) {
}
#endif
else if (len >= 4) {
::memcpy(&digits, p, 4);
#if FASTFLOAT_IS_BIG_ENDIAN
digits = byteswap(digits);
if (false) {
}
#endif
} 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;
else if (len >= 4) {
::memcpy(&digits, p, 4);
#if FASTFLOAT_IS_BIG_ENDIAN
digits = (b0 << 24) | (b1 << 16) | (b2 << 8) | b3;
#else
digits = b0 | (b1 << 8) | (b2 << 16) | (b3 << 24);
digits = byteswap_32(digits);
#endif
}
} 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;
digits = b0 | (b1 << 8) | (b2 << 16) | (b3 << 24);
}

uint32_t magic =
((digits + 0x46464646u) | (digits - 0x30303030u)) & 0x80808080u;
uint32_t tz = (uint32_t)countr_zero_32(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;
uint32_t magic =
((digits + 0x46464646u) | (digits - 0x30303030u)) & 0x80808080u;
uint32_t tz = (uint32_t)countr_zero_32(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;
}
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;
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;
}
answer.ec = std::errc::result_out_of_range;
answer.ptr = q;
return answer;
}

digits ^= 0x30303030u;
digits <<= ((4 - nd) * 8);
digits ^= 0x30303030u;
digits <<= ((4 - nd) * 8);

uint32_t check = ((digits >> 24) & 0xff) | ((digits >> 8) & 0xff00) |
((digits << 8) & 0xff0000);
if (check > 0x00020505) {
answer.ec = std::errc::result_out_of_range;
uint32_t check = ((digits >> 24) & 0xff) | ((digits >> 8) & 0xff00) |
((digits << 8) & 0xff0000);
if (check > 0x00020505) {
answer.ec = std::errc::result_out_of_range;
answer.ptr = p + nd;
return answer;
}
value = (uint8_t)((0x640a01 * digits) >> 24);
answer.ec = std::errc();
answer.ptr = p + nd;
return answer;
}
value = (uint8_t)((0x640a01 * digits) >> 24);
answer.ec = std::errc();
answer.ptr = p + nd;
return answer;
}

uint64_t i = 0;
Expand Down