boot_serial: Refactoring writes

     * write.

     */

    rem_bytes = img_chunk_len % flash_area_align(fap);

    if ((curr_off + img_chunk_len < img_size) && rem_bytes) {

    img_chunk_len -= rem_bytes;

    if (curr_off + img_chunk_len + rem_bytes < img_size) {

        rem_bytes = 0;

    }

    BOOT_LOG_INF("Writing at 0x%x until 0x%x", curr_off, curr_off + img_chunk_len);

    if (rem_bytes) {

        /* the last chunk of the image might be unaligned */

    /* Write flash aligned chunk, note that img_chunk_len now holds aligned length */

    rc = flash_area_write(fap, curr_off, img_chunk, img_chunk_len);

    if (rc == 0 && rem_bytes) {

        /* Non-zero rem_bytes means that last chunk needs alignment; the aligned

         * part, in the img_chunk_len - rem_bytes count bytes, has already been

         * written by the above write, so we are left with the rem_bytes.

         */

        uint8_t wbs_aligned[BOOT_MAX_ALIGN];

        size_t w_size = img_chunk_len - rem_bytes;

        if (w_size) {

            rc = flash_area_write(fap, curr_off, img_chunk, w_size);

            if (rc) {

                goto out_invalid_data;

            }

            curr_off += w_size;

            img_chunk_len -= w_size;

            img_chunk += w_size;

        }

        memset(wbs_aligned, flash_area_erased_val(fap), sizeof(wbs_aligned));

        memcpy(wbs_aligned, img_chunk + img_chunk_len, rem_bytes);

        if (img_chunk_len) {

            memcpy(wbs_aligned, img_chunk, rem_bytes);

            memset(wbs_aligned + rem_bytes, flash_area_erased_val(fap),

                   sizeof(wbs_aligned) - rem_bytes);

            rc = flash_area_write(fap, curr_off, wbs_aligned, flash_area_align(fap));

        }

    } else {

        rc = flash_area_write(fap, curr_off, img_chunk, img_chunk_len);

        rc = flash_area_write(fap, curr_off + img_chunk_len, wbs_aligned,

                              flash_area_align(fap));

    }

    if (rc == 0) {

        curr_off += img_chunk_len;

        curr_off += img_chunk_len + rem_bytes;

        if (curr_off == img_size) {

#ifdef MCUBOOT_ERASE_PROGRESSIVELY

            /* Assure that sector for image trailer was erased. */