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Parse "nan(n-char-seq-opt)" as required by C++17 20.19.3.7 #61

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Mar 1, 2021
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Parse "nan(n-char-seq-opt)" as required by C++17 20.19.3.7 #61

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51 changes: 23 additions & 28 deletions include/fast_float/parse_number.h
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Original file line number Diff line number Diff line change
Expand Up @@ -22,48 +22,43 @@ namespace {
template <typename T>
from_chars_result parse_infnan(const char *first, const char *last, T &value) noexcept {
from_chars_result answer;
answer.ptr = first;
answer.ec = std::errc(); // be optimistic
bool minusSign = false;
if (*first == '-') { // assume first < last, so dereference without checks
minusSign = true;
++first;
} else if( *first == '+' ) { // C++17 20.19.3.7 explicitly forbids '+' here, but anyway
++first;
}
if (last - first >= 3) {
if (fastfloat_strncasecmp(first, "nan", 3)) {
answer.ptr = first + 3;
value = std::numeric_limits<T>::quiet_NaN();
answer.ptr = (first += 3);
value = minusSign ? -std::numeric_limits<T>::quiet_NaN() : std::numeric_limits<T>::quiet_NaN();
// Check for possible nan(n-char-seq-opt), C++17 20.19.3.7, C11 7.20.1.3.3. At least MSVC produces nan(ind) and nan(snan).
if(first != last && *first == '(') {
for(const char* ptr = first + 1; ptr != last; ++ptr) {
if (*ptr == ')') {
answer.ptr = ptr + 1; // valid nan(n-char-seq-opt)
break;
}
else if(!(('a' <= *ptr && *ptr <= 'z') || ('A' <= *ptr && *ptr <= 'Z') || ('0' <= *ptr && *ptr <= '9') || *ptr == '_'))
break; // forbidden char, not nan(n-char-seq-opt)
}
}
return answer;
}
if (fastfloat_strncasecmp(first, "inf", 3)) {
if ((last - first >= 8) && fastfloat_strncasecmp(first, "infinity", 8)) {
if ((last - first >= 8) && fastfloat_strncasecmp(first + 3, "inity", 5)) {
answer.ptr = first + 8;
} else {
answer.ptr = first + 3;
}
value = std::numeric_limits<T>::infinity();
value = minusSign ? -std::numeric_limits<T>::infinity() : std::numeric_limits<T>::infinity();
return answer;
}
if (last - first >= 4) {
if (fastfloat_strncasecmp(first, "+nan", 4) || fastfloat_strncasecmp(first, "-nan", 4)) {
answer.ptr = first + 4;
value = std::numeric_limits<T>::quiet_NaN();
if (first[0] == '-') {
value = -value;
}
return answer;
}

if (fastfloat_strncasecmp(first, "+inf", 4) || fastfloat_strncasecmp(first, "-inf", 4)) {
if ((last - first >= 9) && fastfloat_strncasecmp(first + 1, "infinity", 8)) {
answer.ptr = first + 9;
} else {
answer.ptr = first + 4;
}
value = std::numeric_limits<T>::infinity();
if (first[0] == '-') {
value = -value;
}
return answer;
}
}
}
answer.ec = std::errc::invalid_argument;
answer.ptr = first;
return answer;
}

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