From ab23e8a65678d62323e023f4b9069378a3053bd2 Mon Sep 17 00:00:00 2001
From: "Dirk O. Kaar" <19971886+dok-net@users.noreply.github.com>
Date: Wed, 30 Sep 2020 13:28:51 +0200
Subject: [PATCH] Greatly reduces error rate (half, or 0 zero errors, depends
 on in/out ranges) for round-trip mapping at the same performance. (#3655)

(Based on "improved_map" from ESP8266's Servo.cpp)
---
 cores/esp32/WMath.cpp | 10 +++++-----
 1 file changed, 5 insertions(+), 5 deletions(-)

diff --git a/cores/esp32/WMath.cpp b/cores/esp32/WMath.cpp
index abec110b..eafff903 100644
--- a/cores/esp32/WMath.cpp
+++ b/cores/esp32/WMath.cpp
@@ -66,11 +66,11 @@ long random(long howsmall, long howbig)
 }
 
 long map(long x, long in_min, long in_max, long out_min, long out_max) {
-    long divisor = (in_max - in_min);
-    if(divisor == 0){
-        return -1; //AVR returns -1, SAM returns 0
-    }
-    return (x - in_min) * (out_max - out_min) / divisor + out_min;
+    const long dividend = out_max - out_min;
+    const long divisor = in_max - in_min;
+    const long delta = x - in_min;
+
+    return (delta * dividend + (divisor / 2)) / divisor + out_min;
 }
 
 unsigned int makeWord(unsigned int w)