Improve stof (#201)

Use the more correct and fast implementation from the STL to parse floating point numbers.
Upcoming clang release finally implements it and gcc has had this for quite some time now, since gcc 11.1.

Also do some proper pointer checks for the custom implementation.

No functional change

scoreWDLstat.hpp

@@ -1,6 +1,7 @@
 #include <zlib.h>
 
 #include <algorithm>
+#include <charconv>
 #include <cstdint>
 #include <filesystem>
 #include <optional>
@@ -82,37 +83,42 @@ void from_json(const nlohmann::json &nlohmann_json_j, TestMetaData &nlohmann_jso
     nlohmann_json_t.pentanomial = get_optional<std::vector<int>>(jr, "pentanomial");
 }
 
+#if (defined(__clang__) && __clang_major__ < 20) || \
+    !(defined(__GNUC__) && (__GNUC__ >= 11 && __GNUC_MINOR__ >= 1))
 /// @brief Custom stof implementation to avoid locale issues, once clang supports std::from_chars
 /// for floats this can be removed
 /// @param str
 /// @return
-inline float fast_stof(const char *str) {
+inline float fast_stof(std::string_view str) {
     float result   = 0.0f;
     int sign       = 1;
     int decimal    = 0;
     float fraction = 1.0f;
 
+    const char *ptr = str.data();
+    const char *end = ptr + str.size();
+
     // Handle sign
-    if (*str == '-') {
+    if (ptr < end && *ptr == '-') {
         sign = -1;
-        str++;
-    } else if (*str == '+') {
-        str++;
+        ptr++;
+    } else if (ptr < end && *ptr == '+') {
+        ptr++;
     }
 
     // Convert integer part
-    while (*str >= '0' && *str <= '9') {
-        result = result * 10.0f + (*str - '0');
-        str++;
+    while (ptr < end && *ptr >= '0' && *ptr <= '9') {
+        result = result * 10.0f + (*ptr - '0');
+        ptr++;
     }
 
     // Convert decimal part
-    if (*str == '.') {
-        str++;
-        while (*str >= '0' && *str <= '9') {
-            result = result * 10.0f + (*str - '0');
+    if (ptr < end && *ptr == '.') {
+        ptr++;
+        while (ptr < end && *ptr >= '0' && *ptr <= '9') {
+            result = result * 10.0f + (*ptr - '0');
             fraction *= 10.0f;
-            str++;
+            ptr++;
         }
         decimal = 1;
     }
@@ -122,9 +128,29 @@ inline float fast_stof(const char *str) {
     if (decimal) {
         result /= fraction;
     }
-
     return result;
 }
+#else
+inline float fast_stof(std::string_view sw) {
+    if (sw[0] == '+') {
+        sw.remove_prefix(1);
+    }
+
+    float result;
+    const char *str_end  = sw.data() + sw.length();
+    const auto fc_result = std::from_chars(sw.data(), str_end, result);
+
+    if (fc_result.ec == std::errc()) {
+        return result;
+    } else if (fc_result.ec == std::errc::invalid_argument) {
+        throw std::invalid_argument("Invalid float format");
+    } else if (fc_result.ec == std::errc::result_out_of_range) {
+        throw std::out_of_range("Float value out of range");
+    }
+
+    throw std::runtime_error("Unknown error in float conversion");
+}
+#endif
 
 /// @brief Get all files from a directory.
 /// @param path