alloc error

cores/esp8266/Updater.cpp

@@ -176,9 +176,7 @@ bool UpdaterClass::begin(size_t size, int command, int ledPin, uint8_t ledOn) {
   }
   _buffer = new (std::nothrow) uint8_t[_bufferSize];
   if (!_buffer) {
-#ifdef DEBUG_UPDATER
-    DEBUG_UPDATER.println(F("[begin] Unable to allocate a temporary buffer."));
-#endif
+    _setError(UPDATE_ERROR_OOM);
     _reset(false);
     return false;
   }
@@ -307,7 +305,7 @@ bool UpdaterClass::end(bool evenIfRemaining){
       const uint32_t sigAddr = _startAddress + binSize;
       sig.reset(new (std::nothrow) uint8_t[sigLen]);
       if (!sig) {
-        _setError(UPDATE_ERROR_SIGN);
+        _setError(UPDATE_ERROR_OOM);
         _reset();
         return false;
       }
@@ -622,17 +620,11 @@ String UpdaterClass::getErrorString() const {
   case UPDATE_ERROR_STREAM:
     out = F("Stream Read Timeout");
     break;
-  case UPDATE_ERROR_NO_DATA:
-    out = F("No data supplied");
-    break;
   case UPDATE_ERROR_MD5:
     out += F("MD5 verification failed: ");
     out += F("expected: ") + _target_md5;
     out += F(", calculated: ") + _md5.toString();
     break;
-  case UPDATE_ERROR_SIGN:
-    out = F("Signature verification failed");
-    break;
   case UPDATE_ERROR_FLASH_CONFIG:
     out += F("Flash config wrong: ");
     out += F("real: ") + String(ESP.getFlashChipRealSize(), 10);
@@ -648,6 +640,15 @@ String UpdaterClass::getErrorString() const {
   case UPDATE_ERROR_BOOTSTRAP:
     out = F("Invalid bootstrapping state, reset ESP8266 before updating");
     break;
+  case UPDATE_ERROR_SIGN:
+    out = F("Signature verification failed");
+    break;
+  case UPDATE_ERROR_NO_DATA:
+    out = F("No data supplied");
+    break;
+  case UPDATE_ERROR_OOM:
+    out = F("Out of memory");
+    break;
   default:
     out = F("UNKNOWN");
     break;

cores/esp8266/Updater.h

@@ -20,6 +20,7 @@
 #define UPDATE_ERROR_BOOTSTRAP          (11)
 #define UPDATE_ERROR_SIGN               (12)
 #define UPDATE_ERROR_NO_DATA            (13)
+#define UPDATE_ERROR_OOM                (14)
 
 #define U_FLASH   0
 #define U_FS      100

doc/ota_updates/readme.rst

@@ -668,9 +668,29 @@ Updater class
 
 Updater is in the Core and deals with writing the firmware to the flash, checking its integrity and telling the bootloader (eboot) to load the new firmware on the next boot.
 
-**Note:** The bootloader command will be stored into the first 128 bytes of user RTC memory, then it will be retrieved by eboot on boot. That means that user data present there will be lost `(per discussion in #5330) <https://github.com/esp8266/Arduino/pull/5330#issuecomment-437803456>`__.
+The following `Updater <https://github.com/esp8266/Arduino/tree/master/cores/esp8266/Updater.h` methods could be used to be notified about OTA progress:
 
-**Note:** For uncompressed firmware images, the Updater will change the flash mode bits if they differ from the flash mode the device is currently running at. This ensures that the flash mode is not changed to an incompatible mode when the device is in a remote or hard to access area. Compressed images are not modified, thus changing the flash mode in this instance could result in damage to the ESP8266 and/or flash memory chip or your device no longer be accessible via OTA, and requiring re-flashing via a serial connection `(per discussion in #7307) <https://github.com/esp8266/Arduino/issues/7307#issuecomment-631523053>`__.
+.. code:: cpp
+
+    using THandlerFunction_Progress = std::function<void(size_t, size_t)>;
+    void onProgress(THandlerFunction_Progress); // current and total number of bytes
+
+    using THandlerFunction_Error = std::function<void(uint8_t)>;
+    void onStart(THandlerFunction_Error); // error code
+
+    using THandlerFunction = std::function<void()>;
+    void onEnd(THandlerFunction);
+    void onError(THandlerFunction);
+
+Using RTC memory
+~~~~~~~~~~~~~~~~
+
+The bootloader command will be stored into the first 128 bytes of user RTC memory, then it will be retrieved by eboot on boot. That means that user data present there will be lost `(per discussion in #5330) <https://github.com/esp8266/Arduino/pull/5330#issuecomment-437803456>`__.
+
+Flash mode and size
+~~~~~~~~~~~~~~~~~~~
+
+For uncompressed firmware images, the Updater will change the flash mode bits if they differ from the flash mode the device is currently running at. This ensures that the flash mode is not changed to an incompatible mode when the device is in a remote or hard to access area. Compressed images are not modified, thus changing the flash mode in this instance could result in damage to the ESP8266 and/or flash memory chip or your device no longer be accessible via OTA, and requiring re-flashing via a serial connection `(per discussion in #7307) <https://github.com/esp8266/Arduino/issues/7307#issuecomment-631523053>`__.
 
 Update process - memory view
 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~