Added custom implementation of ftoa (issues #266, #267, #269 and #270)

include/ArduinoJson/Internals/JsonWriter.hpp

@@ -8,6 +8,9 @@
 #pragma once
 
 #include "../Arduino/Print.hpp"
+#include "../Polyfills/isNaN.hpp"
+#include "../Polyfills/isInfinity.hpp"
+#include "../Polyfills/normalize.hpp"
 #include "Encoding.hpp"
 #include "ForceInline.hpp"
 #include "JsonFloat.hpp"
@@ -63,10 +66,70 @@ class JsonWriter {
     }
   }
 
-  void writeInteger(JsonUInt value) { _length += _sink.print(value); }
+  void writeFloat(JsonFloat value, int digits = 2) {
+    if (Polyfills::isNaN(value)) return writeRaw("NaN");
 
-  void writeFloat(JsonFloat value, uint8_t decimals) {
-    _length += _sink.print(value, decimals);
+    if (value < 0.0) {
+      writeRaw('-');
+      value = -value;
+    }
+
+    if (Polyfills::isInfinity(value)) return writeRaw("Infinity");
+
+    short powersOf10;
+    if (value > 1000 || value < 0.001) {
+      powersOf10 = Polyfills::normalize(value);
+    } else {
+      powersOf10 = 0;
+    }
+
+    // Round correctly so that print(1.999, 2) prints as "2.00"
+    JsonFloat rounding = 0.5;
+    for (uint8_t i = 0; i < digits; ++i) rounding /= 10.0;
+
+    value += rounding;
+
+    // Extract the integer part of the value and print it
+    JsonUInt int_part = static_cast<JsonUInt>(value);
+    JsonFloat remainder = value - static_cast<JsonFloat>(int_part);
+    writeInteger(int_part);
+
+    // Print the decimal point, but only if there are digits beyond
+    if (digits > 0) {
+      writeRaw('.');
+    }
+
+    // Extract digits from the remainder one at a time
+    while (digits-- > 0) {
+      remainder *= 10.0;
+      JsonUInt toPrint = JsonUInt(remainder);
+      writeInteger(JsonUInt(remainder));
+      remainder -= static_cast<JsonFloat>(toPrint);
+    }
+
+    if (powersOf10 < 0) {
+      writeRaw("e-");
+      writeInteger(-powersOf10);
+    }
+
+    if (powersOf10 > 0) {
+      writeRaw('e');
+      writeInteger(powersOf10);
+    }
+  }
+
+  void writeInteger(JsonUInt value) {
+    char buffer[22];
+
+    uint8_t i = 0;
+    do {
+      buffer[i++] = static_cast<char>(value % 10 + '0');
+      value /= 10;
+    } while (value);
+
+    while (i > 0) {
+      writeRaw(buffer[--i]);
+    }
   }
 
   void writeRaw(const char *s) { _length += _sink.print(s); }