Fix float calculations

Fix float calculations in range from 0 to -1 (#5386)

sonoff/_changelog.ino

@@ -3,6 +3,7 @@
  * Add Korean language translations (#5344)
  * Fix Energy TotalStartTime when commands EnergyReset0 and/or EnergyReset3 used (#5373)
  * Fix DS18S20 temperature calculation (#5375)
+ * Fix float calculations in range from 0 to -1 (#5386)
  *
  * 6.4.1.18 20190221
  * Fix some exceptions and watchdogs due to lack of stack space - part 1 (#5215)

sonoff/support.ino

@@ -154,34 +154,39 @@ char* subStr(char* dest, char* str, const char *delim, int index)
   return sub;
 }
 
-double CharToDouble(const char *str)
+double CharToDouble(char *str)
 {
   // simple ascii to double, because atof or strtod are too large
   char strbuf[24];
 
   strlcpy(strbuf, str, sizeof(strbuf));
-  char *pt;
-  double left = atoi(strbuf);
+  char *pt = strbuf;
+  while ((*pt != '\0') && isblank(*pt)) { pt++; }  // Trim leading spaces
+
+  signed char sign = 1;
+  if (*pt == '-') { sign = -1; }
+  if (*pt == '-' || *pt=='+') { pt++; }            // Skip any sign
+
+  double left = 0;
+  if (*pt != '.') {
+    left = atoi(pt);                               // Get left part
+    while (isdigit(*pt)) { pt++; }                 // Skip number
+  }
+
   double right = 0;
-  short len = 0;
-  pt = strtok (strbuf, ".");
-  if (pt) {
-    pt = strtok (NULL, ".");
-    if (pt) {
-      right = atoi(pt);
-      len = strlen(pt);
-      double fac = 1;
-      while (len) {
-        fac /= 10.0;
-        len--;
-      }
-      // pow is also very large
-      //double fac=pow(10,-len);
-      right *= fac;
+  if (*pt == '.') {
+    pt++;
+    right = atoi(pt);                              // Decimal part
+    while (isdigit(*pt)) {
+      pt++;
+      right /= 10.0;
     }
   }
+
   double result = left + right;
-  if (left < 0) { result = left - right; }
+  if (sign < 0) {
+    return -result;                                // Add negative sign
+  }
   return result;
 }