How to use the s3transfer.utils.ReadFileChunk.from_filename function in s3transfer

def test_read_past_end_of_file(self):
        filename = os.path.join(self.tempdir, 'foo')
        with open(filename, 'wb') as f:
            f.write(b'onetwothreefourfivesixseveneightnineten')
        chunk = ReadFileChunk.from_filename(
            filename, start_byte=36, chunk_size=100000)
        self.assertEqual(chunk.read(), b'ten')
        self.assertEqual(chunk.read(), b'')
        self.assertEqual(len(chunk), 3)

def test_read_with_amount_size(self):
        filename = os.path.join(self.tempdir, 'foo')
        with open(filename, 'wb') as f:
            f.write(b'onetwothreefourfivesixseveneightnineten')
        chunk = ReadFileChunk.from_filename(
            filename, start_byte=11, chunk_size=4)
        self.assertEqual(chunk.read(1), b'f')
        self.assertEqual(chunk.read(1), b'o')
        self.assertEqual(chunk.read(1), b'u')
        self.assertEqual(chunk.read(1), b'r')
        self.assertEqual(chunk.read(1), b'')

def test_callback_will_also_be_triggered_by_seek(self):
        chunk = ReadFileChunk.from_filename(
            self.filename, start_byte=0, chunk_size=3,
            callbacks=[self.callback])
        chunk.read(2)
        chunk.seek(0)
        chunk.read(2)
        chunk.seek(1)
        chunk.read(2)
        self.assertEqual(self.amounts_seen, [2, -2, 2, -1, 2])

def test_reset_stream_emulation(self):
        filename = os.path.join(self.tempdir, 'foo')
        with open(filename, 'wb') as f:
            f.write(b'onetwothreefourfivesixseveneightnineten')
        chunk = ReadFileChunk.from_filename(
            filename, start_byte=11, chunk_size=4)
        self.assertEqual(chunk.read(), b'four')
        chunk.seek(0)
        self.assertEqual(chunk.read(), b'four')

def test_callback_can_be_disabled(self):
        chunk = ReadFileChunk.from_filename(
            self.filename, start_byte=0, chunk_size=3,
            callbacks=[self.callback])
        chunk.disable_callback()
        # Now reading from the ReadFileChunk should not invoke
        # the callback.
        chunk.read()
        self.assertEqual(self.amounts_seen, [])

def test_tell_and_seek(self):
        filename = os.path.join(self.tempdir, 'foo')
        with open(filename, 'wb') as f:
            f.write(b'onetwothreefourfivesixseveneightnineten')
        chunk = ReadFileChunk.from_filename(
            filename, start_byte=36, chunk_size=100000)
        self.assertEqual(chunk.tell(), 0)
        self.assertEqual(chunk.read(), b'ten')
        self.assertEqual(chunk.tell(), 3)
        chunk.seek(0)
        self.assertEqual(chunk.tell(), 0)

def test_iter_is_always_empty(self):
        # This tests the workaround for the httplib bug (see
        # the source for more info).
        filename = os.path.join(self.tempdir, 'foo')
        open(filename, 'wb').close()
        chunk = ReadFileChunk.from_filename(
            filename, start_byte=0, chunk_size=10)
        self.assertEqual(list(chunk), [])

def test_signal_transferring(self):
        chunk = ReadFileChunk.from_filename(
            self.filename, start_byte=0, chunk_size=3,
            callbacks=[self.callback])
        chunk.signal_not_transferring()
        chunk.read(1)
        self.assertEqual(self.amounts_seen, [])
        chunk.signal_transferring()
        chunk.read(1)
        self.assertEqual(self.amounts_seen, [1])

def open_file_chunk_reader(self, filename, start_byte, size, callbacks):
        return ReadFileChunk.from_filename(filename, start_byte,
                                           size, callbacks,
                                           enable_callbacks=False)