reducing the overhead of 'json' and 'allow plus' options

Author: lemire

include/fast_float/ascii_number.h

@@ -279,7 +279,7 @@ report_parse_error(UC const *p, parse_error error) {
 
 // Assuming that you use no more than 19 digits, this will
 // parse an ASCII string.
-template <typename UC>
+template <bool allow_leading_plus, bool basic_json_fmt, typename UC>
 fastfloat_really_inline FASTFLOAT_CONSTEXPR20 parsed_number_string_t<UC>
 parse_number_string(UC const *p, UC const *pend,
                     parse_options_t<UC> options) noexcept {
@@ -293,14 +293,14 @@ parse_number_string(UC const *p, UC const *pend,
   answer.negative = (*p == UC('-'));
   // C++17 20.19.3.(7.1) explicitly forbids '+' sign here
   if ((*p == UC('-')) ||
-      (uint64_t(fmt & chars_format::allow_leading_plus) &&
-       !uint64_t(fmt & detail::basic_json_fmt) && *p == UC('+'))) {
+      (allow_leading_plus &&
+       !basic_json_fmt && *p == UC('+'))) {
     ++p;
     if (p == pend) {
       return report_parse_error<UC>(
           p, parse_error::missing_integer_or_dot_after_sign);
     }
-    if (uint64_t(fmt & detail::basic_json_fmt)) {
+    if (basic_json_fmt) {
       if (!is_integer(*p)) { // a sign must be followed by an integer
         return report_parse_error<UC>(p,
                                       parse_error::missing_integer_after_sign);
@@ -329,7 +329,7 @@ parse_number_string(UC const *p, UC const *pend,
   UC const *const end_of_integer_part = p;
   int64_t digit_count = int64_t(end_of_integer_part - start_digits);
   answer.integer = span<UC const>(start_digits, size_t(digit_count));
-  if (uint64_t(fmt & detail::basic_json_fmt)) {
+  if (basic_json_fmt) {
     // at least 1 digit in integer part, without leading zeros
     if (digit_count == 0) {
       return report_parse_error<UC>(p, parse_error::no_digits_in_integer_part);
@@ -358,7 +358,7 @@ parse_number_string(UC const *p, UC const *pend,
     answer.fraction = span<UC const>(before, size_t(p - before));
     digit_count -= exponent;
   }
-  if (uint64_t(fmt & detail::basic_json_fmt)) {
+  if (basic_json_fmt) {
     // at least 1 digit in fractional part
     if (has_decimal_point && exponent == 0) {
       return report_parse_error<UC>(p,
@@ -470,11 +470,11 @@ parse_number_string(UC const *p, UC const *pend,
   return answer;
 }
 
-template <typename T, typename UC>
+template <bool allow_leading_plus = false, typename T, typename UC>
 fastfloat_really_inline FASTFLOAT_CONSTEXPR20 from_chars_result_t<UC>
 parse_int_string(UC const *p, UC const *pend, T &value,
                  parse_options_t<UC> options) {
-  chars_format const fmt = detail::adjust_for_feature_macros(options.format);
+  //chars_format const fmt = detail::adjust_for_feature_macros(options.format);
   int const base = options.base;
 
   from_chars_result_t<UC> answer;
@@ -495,7 +495,7 @@ parse_int_string(UC const *p, UC const *pend, T &value,
     return answer;
   }
   if ((*p == UC('-')) ||
-      (uint64_t(fmt & chars_format::allow_leading_plus) && (*p == UC('+')))) {
+      (allow_leading_plus && (*p == UC('+')))) {
     ++p;
   }
 

include/fast_float/parse_number.h

@@ -304,8 +304,11 @@ from_chars_float_advanced(UC const *first, UC const *last, T &value,
     answer.ptr = first;
     return answer;
   }
-  parsed_number_string_t<UC> pns =
-      parse_number_string<UC>(first, last, options);
+  bool allow_leading_plus = uint64_t(fmt & chars_format::allow_leading_plus);
+  bool basic_json_fmt = uint64_t(fmt & detail::basic_json_fmt);
+  parsed_number_string_t<UC> pns = allow_leading_plus ?
+    (basic_json_fmt ? parse_number_string<true, true, UC>(first, last, options): parse_number_string<true, false, UC>(first, last, options)) :
+    (basic_json_fmt ? parse_number_string<false, true,  UC>(first, last, options): parse_number_string<false, false, UC>(first, last, options));
   if (!pns.valid) {
     if (uint64_t(fmt & chars_format::no_infnan)) {
       answer.ec = std::errc::invalid_argument;

tests/json_fmt.cpp

@@ -131,7 +131,7 @@ int main() {
   for (std::size_t i = 0; i < reject.size(); ++i) {
     auto const &f = reject[i].input;
     auto const &expected_reason = reject[i].reason;
-    auto answer = fast_float::parse_number_string(
+    auto answer = fast_float::parse_number_string<true, true>(
         f.data(), f.data() + f.size(),
         fast_float::parse_options(
             fast_float::chars_format::json |