From 2d77eae5999bd803429bc73949690a7234352e83 Mon Sep 17 00:00:00 2001
From: Raheel Hameed <raheel.hameed@gmail.com>
Date: Sun, 28 Feb 2016 02:50:48 -0600
Subject: [PATCH] Leverage realloc() in String::changeBuffer()

---
 cores/esp8266/WString.cpp | 9 ++++-----
 1 file changed, 4 insertions(+), 5 deletions(-)

diff --git a/cores/esp8266/WString.cpp b/cores/esp8266/WString.cpp
index 95a515c24..5e7b3fcc9 100644
--- a/cores/esp8266/WString.cpp
+++ b/cores/esp8266/WString.cpp
@@ -153,13 +153,12 @@ unsigned char ICACHE_FLASH_ATTR String::reserve(unsigned int size) {
 
 unsigned char ICACHE_FLASH_ATTR String::changeBuffer(unsigned int maxStrLen) {
     size_t newSize = (maxStrLen + 16) & (~0xf);
-    char *newbuffer = (char *) malloc(newSize);
+    char *newbuffer = (char *) realloc(buffer, newSize);
     if(newbuffer) {
-        memset(newbuffer, 0, newSize);
-        if (buffer)
+        size_t oldSize = capacity + 1; // include NULL.
+        if (newSize > oldSize)
         {
-            memcpy(newbuffer, buffer, len);
-            free(buffer);
+            memset(newbuffer + oldSize, 0, newSize - oldSize);
         }
         capacity = newSize - 1;
         buffer = newbuffer;