Replace try parse double

tiny_obj_loader.h

@@ -62,6 +62,14 @@ THE SOFTWARE.
 #include <map>
 #include <string>
 #include <vector>
+#include <math.h>
+#include <stdlib.h>
+
+#if defined(__APPLE__)
+#include <xlocale.h>
+#else
+#include <locale.h>
+#endif
 
 namespace tinyobj {
 
@@ -839,125 +847,20 @@ static bool tryParseDouble(const char *s, const char *s_end, double *result) {
     return false;
   }
 
-  double mantissa = 0.0;
-  // This exponent is base 2 rather than 10.
-  // However the exponent we parse is supposed to be one of ten,
-  // thus we must take care to convert the exponent/and or the
-  // mantissa to a * 2^E, where a is the mantissa and E is the
-  // exponent.
-  // To get the final double we will use ldexp, it requires the
-  // exponent to be in base 2.
-  int exponent = 0;
-
-  // NOTE: THESE MUST BE DECLARED HERE SINCE WE ARE NOT ALLOWED
-  // TO JUMP OVER DEFINITIONS.
-  char sign = '+';
-  char exp_sign = '+';
-  char const *curr = s;
-
-  // How many characters were read in a loop.
-  int read = 0;
-  // Tells whether a loop terminated due to reaching s_end.
-  bool end_not_reached = false;
-  bool leading_decimal_dots = false;
-
-  /*
-          BEGIN PARSING.
-  */
-
-  // Find out what sign we've got.
-  if (*curr == '+' || *curr == '-') {
-    sign = *curr;
-    curr++;
-    if ((curr != s_end) && (*curr == '.')) {
-      // accept. Somethig like `.7e+2`, `-.5234`
-      leading_decimal_dots = true;
-    }
-  } else if (IS_DIGIT(*curr)) { /* Pass through. */
-  } else if (*curr == '.') {
-    // accept. Somethig like `.7e+2`, `-.5234`
-    leading_decimal_dots = true;
-  } else {
-    goto fail;
-  }
-
-  // Read the integer part.
-  end_not_reached = (curr != s_end);
-  if (!leading_decimal_dots) {
-    while (end_not_reached && IS_DIGIT(*curr)) {
-      mantissa *= 10;
-      mantissa += static_cast<int>(*curr - 0x30);
-      curr++;
-      read++;
-      end_not_reached = (curr != s_end);
-    }
-
-    // We must make sure we actually got something.
-    if (read == 0) goto fail;
-  }
+#if defined(__APPLE__)
+  static locale_t c_locale = newlocale(LC_ALL_MASK, NULL, NULL);
+#else
+  static locale_t c_locale = newlocale(LC_ALL_MASK, "C", (locale_t)0);
+#endif
 
-  // We allow numbers of form "#", "###" etc.
-  if (!end_not_reached) goto assemble;
-
-  // Read the decimal part.
-  if (*curr == '.') {
-    curr++;
-    read = 1;
-    end_not_reached = (curr != s_end);
-    while (end_not_reached && IS_DIGIT(*curr)) {
-      static const double pow_lut[] = {
-          1.0, 0.1, 0.01, 0.001, 0.0001, 0.00001, 0.000001, 0.0000001,
-      };
-      const int lut_entries = sizeof pow_lut / sizeof pow_lut[0];
-
-      // NOTE: Don't use powf here, it will absolutely murder precision.
-      mantissa += static_cast<int>(*curr - 0x30) *
-                  (read < lut_entries ? pow_lut[read] : std::pow(10.0, -read));
-      read++;
-      curr++;
-      end_not_reached = (curr != s_end);
-    }
-  } else if (*curr == 'e' || *curr == 'E') {
+  char *str_end = NULL;
+  const double val = strtod_l(s, &str_end, c_locale);
+  if (str_end != s && isfinite(val)) {
+    *result = val;
+    return true;
   } else {
-    goto assemble;
-  }
-
-  if (!end_not_reached) goto assemble;
-
-  // Read the exponent part.
-  if (*curr == 'e' || *curr == 'E') {
-    curr++;
-    // Figure out if a sign is present and if it is.
-    end_not_reached = (curr != s_end);
-    if (end_not_reached && (*curr == '+' || *curr == '-')) {
-      exp_sign = *curr;
-      curr++;
-    } else if (IS_DIGIT(*curr)) { /* Pass through. */
-    } else {
-      // Empty E is not allowed.
-      goto fail;
-    }
-
-    read = 0;
-    end_not_reached = (curr != s_end);
-    while (end_not_reached && IS_DIGIT(*curr)) {
-      exponent *= 10;
-      exponent += static_cast<int>(*curr - 0x30);
-      curr++;
-      read++;
-      end_not_reached = (curr != s_end);
-    }
-    exponent *= (exp_sign == '+' ? 1 : -1);
-    if (read == 0) goto fail;
+    return false;
   }
-
-assemble:
-  *result = (sign == '+' ? 1 : -1) *
-            (exponent ? std::ldexp(mantissa * std::pow(5.0, exponent), exponent)
-                      : mantissa);
-  return true;
-fail:
-  return false;
 }
 
 static inline real_t parseReal(const char **token, double default_value = 0.0) {