Clear dirty flag in begin and reallocate only if necessary, add getConstDataPtr method (#2217) (#3849)

Author: devyte

libraries/EEPROM/EEPROM.cpp

@@ -56,16 +56,21 @@ void EEPROMClass::begin(size_t size) {
 
   size = (size + 3) & (~3);
 
-  if (_data) {
+  //In case begin() is called a 2nd+ time, don't reallocate if size is the same
+  if(_data && size != _size) {
     delete[] _data;
+    _data = new uint8_t[size];
+  } else if(!_data) {
+    _data = new uint8_t[size];
   }
 
-  _data = new uint8_t[size];
   _size = size;
 
   noInterrupts();
   spi_flash_read(_sector * SPI_FLASH_SEC_SIZE, reinterpret_cast<uint32_t*>(_data), _size);
   interrupts();
+
+  _dirty = false; //make sure dirty is cleared in case begin() is called 2nd+ time
 }
 
 void EEPROMClass::end() {
@@ -131,6 +136,10 @@ uint8_t * EEPROMClass::getDataPtr() {
   return &_data[0];
 }
 
+uint8_t const * EEPROMClass::getConstDataPtr() {
+  return &_data[0];
+}
+
 #if !defined(NO_GLOBAL_INSTANCES) && !defined(NO_GLOBAL_EEPROM)
 EEPROMClass EEPROM;
 #endif

libraries/EEPROM/EEPROM.h

@@ -38,6 +38,7 @@ class EEPROMClass {
   void end();
 
   uint8_t * getDataPtr();
+  uint8_t const * getConstDataPtr();
 
   template<typename T> 
   T &get(int address, T &t) {