From 8f94758c7862a77964864c2386c2ce425d1f4aab Mon Sep 17 00:00:00 2001
From: Maya Warrier <maya.warrierm@gmail.com>
Date: Mon, 27 Mar 2023 22:50:21 -0400
Subject: [PATCH] Expose parsed string (before computation) so it can be reused

---
 include/fast_float/ascii_number.h |  2 ++
 include/fast_float/fast_float.h   | 12 +++++++++-
 include/fast_float/parse_number.h | 38 +++++++++++++++++++------------
 3 files changed, 36 insertions(+), 16 deletions(-)

diff --git a/include/fast_float/ascii_number.h b/include/fast_float/ascii_number.h
index 72b8098..9ad754e 100644
--- a/include/fast_float/ascii_number.h
+++ b/include/fast_float/ascii_number.h
@@ -96,6 +96,7 @@ typedef span<const char> byte_span;
 struct parsed_number_string {
   int64_t exponent{0};
   uint64_t mantissa{0};
+  uint64_t integer_value{-1};
   const char *lastmatch{nullptr};
   bool negative{false};
   bool valid{false};
@@ -143,6 +144,7 @@ parsed_number_string parse_number_string(const char *p, const char *pend, parse_
   const char *const end_of_integer_part = p;
   int64_t digit_count = int64_t(end_of_integer_part - start_digits);
   answer.integer = byte_span(start_digits, size_t(digit_count));
+  answer.integer_value = i;
   int64_t exponent = 0;
   if ((p != pend) && (*p == decimal_point)) {
     ++p;
diff --git a/include/fast_float/fast_float.h b/include/fast_float/fast_float.h
index 65704da..d84405d 100644
--- a/include/fast_float/fast_float.h
+++ b/include/fast_float/fast_float.h
@@ -62,6 +62,16 @@ FASTFLOAT_CONSTEXPR20
 from_chars_result from_chars_advanced(const char *first, const char *last,
                                       T &value, parse_options options)  noexcept;
 
-} // namespace fast_float
+} 
+
+#include "ascii_number.h" // parsed_number_string
+
+namespace fast_float {
+template <typename T>
+FASTFLOAT_CONSTEXPR20
+from_chars_result from_chars_preparsed(parsed_number_string parsed, T& value) noexcept;
+}
+
+// namespace fast_float
 #include "parse_number.h"
 #endif // FASTFLOAT_FAST_FLOAT_H
diff --git a/include/fast_float/parse_number.h b/include/fast_float/parse_number.h
index d16a25d..c880f1e 100644
--- a/include/fast_float/parse_number.h
+++ b/include/fast_float/parse_number.h
@@ -141,24 +141,12 @@ from_chars_result from_chars(const char *first, const char *last,
 
 template<typename T>
 FASTFLOAT_CONSTEXPR20
-from_chars_result from_chars_advanced(const char *first, const char *last,
-                                      T &value, parse_options options)  noexcept  {
-
+from_chars_result from_chars_preparsed(parsed_number_string pns, T& value) noexcept
+{
   static_assert (std::is_same<T, double>::value || std::is_same<T, float>::value, "only float and double are supported");
 
-
+  
   from_chars_result answer;
-#if FASTFLOAT_SKIP_WHITE_SPACE  // disabled by default
-  while ((first != last) && fast_float::is_space(uint8_t(*first))) {
-    first++;
-  }
-#endif
-  if (first == last) {
-    answer.ec = std::errc::invalid_argument;
-    answer.ptr = first;
-    return answer;
-  }
-  parsed_number_string pns = parse_number_string(first, last, options);
   if (!pns.valid) {
     return detail::parse_infnan(first, last, value);
   }
@@ -217,6 +205,26 @@ from_chars_result from_chars_advanced(const char *first, const char *last,
   return answer;
 }
 
+template<typename T>
+FASTFLOAT_CONSTEXPR20
+from_chars_result from_chars_advanced(const char *first, const char *last,
+                                      T &value, parse_options options)  noexcept  {
+
+  from_chars_result answer;
+#if FASTFLOAT_SKIP_WHITE_SPACE  // disabled by default
+  while ((first != last) && fast_float::is_space(uint8_t(*first))) {
+    first++;
+  }
+#endif
+  if (first == last) {
+    answer.ec = std::errc::invalid_argument;
+    answer.ptr = first;
+    return answer;
+  }
+  answer = from_chars_preparsed(parse_number_string(first, last, options), value);
+  return answer;
+}
+
 } // namespace fast_float
 
 #endif