Fix short unaligned writes in SPIFFS HAL, 2nd attempt (#924)

Author: igrr

hardware/esp8266com/esp8266/cores/esp8266/spiffs_hal.cpp

@@ -109,12 +109,11 @@ int32_t spiffs_hal_write(uint32_t addr, uint32_t size, uint8_t *src) {
     }
 
     if (addr < alignedBegin) {
-        uint32_t nb = alignedBegin - addr;
-        if (nb > size)
-            nb = size;
-        uint32_t tmp = 0xffffffff;
-        memcpy(((uint8_t* )&tmp) + 4 - nb, src, nb);
-        if (!ESP.flashWrite(alignedBegin - 4, &tmp, 4)) {
+        uint32_t ofs = alignedBegin - addr;
+        uint32_t nb = (size < ofs) ? size : ofs;
+        uint8_t tmp[4] __attribute__((aligned(4))) = {0xff, 0xff, 0xff, 0xff};
+        memcpy(tmp + 4 - ofs, src, nb);
+        if (!ESP.flashWrite(alignedBegin - 4, (uint32_t*) tmp, 4)) {
             DEBUGV("_spif_write(%d) addr=%x size=%x ab=%x ae=%x\r\n",
                 __LINE__, addr, size, alignedBegin, alignedEnd);
             return SPIFFS_ERR_INTERNAL;