From 2dbd94951c6c77a27a6c9c50ebb393c0ac550d32 Mon Sep 17 00:00:00 2001
From: Benoit Blanchon <github@benoitblanchon.fr>
Date: Sun, 10 Jul 2016 16:12:49 +0200
Subject: [PATCH] Improved speed of float serialization (about twice faster)

---
 CHANGELOG.md                                 |  5 +++++
 include/ArduinoJson/Internals/JsonWriter.hpp | 18 +++++++++---------
 2 files changed, 14 insertions(+), 9 deletions(-)

diff --git a/CHANGELOG.md b/CHANGELOG.md
index e9966083..4ca44885 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -1,6 +1,11 @@
 ArduinoJson: change log
 =======================
 
+HEAD
+----
+
+* Improved speed of float serialization (about twice faster)
+
 v5.6.2
 ------
 
diff --git a/include/ArduinoJson/Internals/JsonWriter.hpp b/include/ArduinoJson/Internals/JsonWriter.hpp
index 5df2e68f..c7f26b26 100644
--- a/include/ArduinoJson/Internals/JsonWriter.hpp
+++ b/include/ArduinoJson/Internals/JsonWriter.hpp
@@ -98,12 +98,6 @@ class JsonWriter {
       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);
@@ -116,10 +110,16 @@ class JsonWriter {
 
     // Extract digits from the remainder one at a time
     while (digits-- > 0) {
+      // Extract digit
       remainder *= 10.0;
-      JsonUInt toPrint = JsonUInt(remainder);
-      writeInteger(JsonUInt(remainder));
-      remainder -= static_cast<JsonFloat>(toPrint);
+      char currentDigit = char(remainder);
+      remainder -= static_cast<JsonFloat>(currentDigit);
+
+      // Round up last digit (so that print(1.999, 2) prints as "2.00")
+      if (digits == 0 && remainder >= 0.5) currentDigit++;
+
+      // Print
+      writeRaw(char('0' + currentDigit));
     }
 
     if (powersOf10 < 0) {