Fix ESP.getSketchSize, add ESP.getSketchMD5 (#2158)

* return true sketch size using ESP.getSketchSize() https://github.com/esp8266/Arduino/issues/2153
add MD5 for current binary ESP.getSketchMD5()

* Simplify ESP.getSketchSize, fix ESP.getSketchMD5

cores/esp8266/Esp.cpp

@@ -23,6 +23,7 @@
 #include "eboot_command.h"
 #include <memory>
 #include "interrupts.h"
+#include "MD5Builder.h"
 
 extern "C" {
 #include "user_interface.h"
@@ -443,7 +444,7 @@ uint32_t EspClass::getSketchSize() {
         DEBUG_SERIAL.printf("section=%u size=%u pos=%u\r\n", section_index, section_header.size, pos);
 #endif
     }
-    result = pos;
+    result = (pos + 16) & ~15;
     return result;
 }
 
@@ -519,3 +520,33 @@ bool EspClass::flashRead(uint32_t offset, uint32_t *data, size_t size) {
     ets_isr_unmask(FLASH_INT_MASK);
     return rc == 0;
 }
+
+String EspClass::getSketchMD5()
+{
+    static String result;
+    if (result.length()) {
+        return result;
+    }
+    uint32_t lengthLeft = getSketchSize();
+    const size_t bufSize = 512;
+    std::unique_ptr<uint8_t[]> buf(new uint8_t[bufSize]);
+    uint32_t offset = 0;
+    if(!buf.get()) {
+        return String();
+    }
+    MD5Builder md5;
+    md5.begin();
+    while( lengthLeft > 0) {
+        size_t readBytes = (lengthLeft < bufSize) ? lengthLeft : bufSize;
+        if (!flashRead(offset, reinterpret_cast<uint32_t*>(buf.get()), (readBytes + 3) & ~3)) {
+            return String();
+        }
+        md5.add(buf.get(), readBytes);
+        lengthLeft -= readBytes;
+        offset += readBytes;
+    }
+    md5.calculate();
+    result = md5.toString();
+    return result;
+} 
+

cores/esp8266/Esp.h

@@ -133,6 +133,7 @@ class EspClass {
         bool flashRead(uint32_t offset, uint32_t *data, size_t size);
 
         uint32_t getSketchSize();
+        String getSketchMD5();
         uint32_t getFreeSketchSpace();
         bool updateSketch(Stream& in, uint32_t size, bool restartOnFail = false, bool restartOnSuccess = true);