How to use the esptool.ESP8266ROM function in esptool

start_sector = offset // sector_size

        head_sectors = sectors_per_block - (start_sector % sectors_per_block)
        if num_sectors < head_sectors:
            head_sectors = num_sectors

        if num_sectors < 2 * head_sectors:
            return (num_sectors + 1) // 2 * sector_size
        else:
            return (num_sectors - head_sectors) * sector_size

    def override_vddsdio(self, new_voltage):
        raise NotImplementedInROMError("Overriding VDDSDIO setting only applies to ESP32")


class ESP8266StubLoader(ESP8266ROM):
    """ Access class for ESP8266 stub loader, runs on top of ROM.
    """
    FLASH_WRITE_SIZE = 0x4000  # matches MAX_WRITE_BLOCK in stub_loader.c
    IS_STUB = True

    def __init__(self, rom_loader):
        self._port = rom_loader._port
        self._trace_enabled = rom_loader._trace_enabled
        self.flush_input()  # resets _slip_reader

    def get_erase_size(self, offset, size):
        return size  # stub doesn't have same size bug as ROM loader


ESP8266ROM.STUB_CLASS = ESP8266StubLoader

print("  Byte 0x%x: new 0x%02x old 0x%02x" % (b, ord(new[k][b]), ord(old[k][b])))

if __name__ == "__main__":
    same = True
    sys.path.append("..")
    import esptool

    old_8266_stub = esptool.ESP8266ROM.STUB_CODE
    old_32_stub = esptool.ESP32ROM.STUB_CODE

    # hackiness: importing this module edits the esptool module
    import esptool_test_stub

    if esptool.ESP8266ROM.STUB_CODE != old_8266_stub:
        print("ESP8266 stub code in esptool.py is different to just-built stub")
        verbose_diff(esptool.ESP8266ROM.STUB_CODE, old_8266_stub)
        same = False
    if esptool.ESP32ROM.STUB_CODE != old_32_stub:
        print("ESP32 stub code in esptool.py is different to just-built stub.")
        verbose_diff(esptool.ESP32ROM.STUB_CODE, old_32_stub)
        same = False
    if same:
        print("Stub code is the same")

    sys.exit(0 if same else 1)

from esptool import ESPLoader, ESP8266ROM, ESP32ROM, DETECTED_FLASH_SIZES
from serial.tools import list_ports as _list_ports

from ampy.core.mpy_boards import MpyBoard, ESP8266Board, ESP32Board


def main(baud: int) -> Generator[MpyBoard, None, None]:
    for port in list_ports():
        try:
            yield detect_board(port, baud)
        except StopIteration:
            pass


CHIP_CLASSES = {
    ESP8266ROM.DATE_REG_VALUE: (ESP8266ROM, ESP8266Board),
    ESP32ROM.DATE_REG_VALUE: (ESP32ROM, ESP32Board),
}


def list_ports() -> List[str]:
    ports = [
        it.device
        for it in _list_ports.comports()
        if "BLUETOOTH" not in it.device.upper()
    ]
    ports.sort(reverse=True)
    return ports


def detect_board(port: str, baud: int) -> MpyBoard:
    board_cls: Type[MpyBoard]

class ESP8266StubLoader(ESP8266ROM):
    """ Access class for ESP8266 stub loader, runs on top of ROM.
    """
    FLASH_WRITE_SIZE = 0x4000  # matches MAX_WRITE_BLOCK in stub_loader.c
    IS_STUB = True

    def __init__(self, rom_loader):
        self._port = rom_loader._port
        self._trace_enabled = rom_loader._trace_enabled
        self.flush_input()  # resets _slip_reader

    def get_erase_size(self, offset, size):
        return size  # stub doesn't have same size bug as ROM loader


ESP8266ROM.STUB_CLASS = ESP8266StubLoader


class ESP32ROM(ESPLoader):
    """Access class for ESP32 ROM bootloader

    """
    CHIP_NAME = "ESP32"
    IS_STUB = False

    DATE_REG_VALUE = 0x15122500

    IROM_MAP_START = 0x400d0000
    IROM_MAP_END   = 0x40400000
    DROM_MAP_START = 0x3F400000
    DROM_MAP_END   = 0x3F800000

for k in [ "data", "text" ]:
        if len(new[k]) != len(old[k]):
            print("New %s %d bytes, old stub code %d bytes" % (k, len(new[k]), len(old)[k]))
        if new[k] != old[k]:
            print("%s is different" % k)
            if len(new[k]) == len(old[k]):
                for b in range(len(new[k])):
                    if new[k][b] != old[k][b]:
                        print("  Byte 0x%x: new 0x%02x old 0x%02x" % (b, ord(new[k][b]), ord(old[k][b])))

if __name__ == "__main__":
    same = True
    sys.path.append("..")
    import esptool

    old_8266_stub = esptool.ESP8266ROM.STUB_CODE
    old_32_stub = esptool.ESP32ROM.STUB_CODE

    # hackiness: importing this module edits the esptool module
    import esptool_test_stub

    if esptool.ESP8266ROM.STUB_CODE != old_8266_stub:
        print("ESP8266 stub code in esptool.py is different to just-built stub")
        verbose_diff(esptool.ESP8266ROM.STUB_CODE, old_8266_stub)
        same = False
    if esptool.ESP32ROM.STUB_CODE != old_32_stub:
        print("ESP32 stub code in esptool.py is different to just-built stub.")
        verbose_diff(esptool.ESP32ROM.STUB_CODE, old_32_stub)
        same = False
    if same:
        print("Stub code is the same")

def is_irom_addr(self, addr):
        """ Returns True if an address starts in the irom region.
        Valid for ESP8266 only.
        """
        return ESP8266ROM.IROM_MAP_START <= addr < ESP8266ROM.IROM_MAP_END

def flash_spi_attach(self, hspi_arg):
        if self.IS_STUB:
            super(ESP8266ROM, self).flash_spi_attach(hspi_arg)
        else:
            # ESP8266 ROM has no flash_spi_attach command in serial protocol,
            # but flash_begin will do it
            self.flash_begin(0, 0)

value = {
                '2m': '256KB',
                '4m': '512KB',
                '8m': '1MB',
                '16m': '2MB',
                '32m': '4MB',
                '16m-c1': '2MB-c1',
                '32m-c1': '4MB-c1',
            }[values[0]]
            print("WARNING: Flash size arguments in megabits like '%s' are deprecated." % (values[0]))
            print("Please use the equivalent size '%s'." % (value))
            print("Megabit arguments may be removed in a future release.")
        except KeyError:
            value = values[0]

        known_sizes = dict(ESP8266ROM.FLASH_SIZES)
        known_sizes.update(ESP32ROM.FLASH_SIZES)
        if self._auto_detect:
            known_sizes['detect'] = 'detect'
        if value not in known_sizes:
            raise argparse.ArgumentError(self, '%s is not a known flash size. Known sizes: %s' % (value, ", ".join(known_sizes.keys())))
        setattr(namespace, self.dest, value)

end = 0
        for address, argfile in sorted(pairs):
            argfile.seek(0,2)  # seek to end
            size = argfile.tell()
            argfile.seek(0)
            sector_start = address & ~(ESPLoader.FLASH_SECTOR_SIZE - 1)
            sector_end = ((address + size + ESPLoader.FLASH_SECTOR_SIZE - 1) & ~(ESPLoader.FLASH_SECTOR_SIZE - 1)) - 1
            if sector_start < end:
                message = 'Detected overlap at address: 0x%x for file: %s' % (address, argfile.name)
                raise argparse.ArgumentError(self, message)
            end = sector_end
        setattr(namespace, self.dest, pairs)


# Binary stub code (see flasher_stub dir for source & details)
ESP8266ROM.STUB_CODE = eval(zlib.decompress(base64.b64decode(b"""
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value = {
                '2m': '256KB',
                '4m': '512KB',
                '8m': '1MB',
                '16m': '2MB',
                '32m': '4MB',
                '16m-c1': '2MB-c1',
                '32m-c1': '4MB-c1',
            }[values[0]]
            print("WARNING: Flash size arguments in megabits like '%s' are deprecated." % (values[0]))
            print("Please use the equivalent size '%s'." % (value))
            print("Megabit arguments may be removed in a future release.")
        except KeyError:
            value = values[0]

        known_sizes = dict(ESP8266ROM.FLASH_SIZES)
        known_sizes.update(ESP32ROM.FLASH_SIZES)
        if self._auto_detect:
            known_sizes['detect'] = 'detect'
        if value not in known_sizes:
            raise argparse.ArgumentError(self, '%s is not a known flash size. Known sizes: %s' % (value, ", ".join(known_sizes.keys())))
        setattr(namespace, self.dest, value)