# vim: tabstop=4 shiftwidth=4 softtabstop=4

# Copyright 2011 OpenStack, LLC
# All Rights Reserved.
#
#    Licensed under the Apache License, Version 2.0 (the "License"); you may
#    not use this swift except in compliance with the License. You may obtain
#    a copy of the License at
#
#         http://www.apache.org/licenses/LICENSE-2.0
#
#    Unless required by applicable law or agreed to in writing, software
#    distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
#    WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
#    License for the specific language governing permissions and limitations
#    under the License.

"""Tests the Swift backend store"""

import hashlib
import httplib
import StringIO
import tempfile
import urllib

import stubout
import swiftclient

from glance.common import exception
from glance.common import utils
from glance.openstack.common import cfg
from glance.store import BackendException
from glance.store.location import get_location_from_uri
import glance.store.swift
from glance.tests.unit import base

CONF = cfg.CONF

FAKE_UUID = utils.generate_uuid

Store = glance.store.swift.Store
FIVE_KB = (5 * 1024)
FIVE_GB = (5 * 1024 * 1024 * 1024)
MAX_SWIFT_OBJECT_SIZE = FIVE_GB
SWIFT_PUT_OBJECT_CALLS = 0
SWIFT_CONF = {'verbose': True,
              'debug': True,
              'known_stores': ['glance.store.swift.Store'],
              'default_store': 'swift',
              'swift_store_user': 'user',
              'swift_store_key': 'key',
              'swift_store_auth_address': 'localhost:8080',
              'swift_store_container': 'glance'}


# We stub out as little as possible to ensure that the code paths
# between glance.store.swift and swiftclient are tested
# thoroughly
def stub_out_swiftclient(stubs, swift_store_auth_version):
    fixture_containers = ['glance']
    fixture_container_headers = {}
    fixture_headers = {'glance/%s' % FAKE_UUID:
                {'content-length': FIVE_KB,
                 'etag': 'c2e5db72bd7fd153f53ede5da5a06de3'}}
    fixture_objects = {'glance/%s' % FAKE_UUID:
                       StringIO.StringIO("*" * FIVE_KB)}

    def fake_head_container(url, token, container, **kwargs):
        if container not in fixture_containers:
            msg = "No container %s found" % container
            raise swiftclient.ClientException(msg,
                        http_status=httplib.NOT_FOUND)
        return fixture_container_headers

    def fake_put_container(url, token, container, **kwargs):
        fixture_containers.append(container)

    def fake_post_container(url, token, container, headers, http_conn=None):
        for key, value in headers.iteritems():
            fixture_container_headers[key] = value

    def fake_put_object(url, token, container, name, contents, **kwargs):
        # PUT returns the ETag header for the newly-added object
        # Large object manifest...
        global SWIFT_PUT_OBJECT_CALLS
        SWIFT_PUT_OBJECT_CALLS += 1
        fixture_key = "%s/%s" % (container, name)
        if not fixture_key in fixture_headers.keys():
            if kwargs.get('headers'):
                etag = kwargs['headers']['ETag']
                fixture_headers[fixture_key] = {'manifest': True,
                                                'etag': etag}
                return etag
            if hasattr(contents, 'read'):
                fixture_object = StringIO.StringIO()
                chunk = contents.read(Store.CHUNKSIZE)
                checksum = hashlib.md5()
                while chunk:
                    fixture_object.write(chunk)
                    checksum.update(chunk)
                    chunk = contents.read(Store.CHUNKSIZE)
                etag = checksum.hexdigest()
            else:
                fixture_object = StringIO.StringIO(contents)
                etag = hashlib.md5(fixture_object.getvalue()).hexdigest()
            read_len = fixture_object.len
            if read_len > MAX_SWIFT_OBJECT_SIZE:
                msg = ('Image size:%d exceeds Swift max:%d' %
                        (read_len, MAX_SWIFT_OBJECT_SIZE))
                raise swiftclient.ClientException(
                        msg, http_status=httplib.REQUEST_ENTITY_TOO_LARGE)
            fixture_objects[fixture_key] = fixture_object
            fixture_headers[fixture_key] = {
                'content-length': read_len,
                'etag': etag}
            return etag
        else:
            msg = ("Object PUT failed - Object with key %s already exists"
                   % fixture_key)
            raise swiftclient.ClientException(msg,
                        http_status=httplib.CONFLICT)

    def fake_get_object(url, token, container, name, **kwargs):
        # GET returns the tuple (list of headers, file object)
        fixture_key = "%s/%s" % (container, name)
        if not fixture_key in fixture_headers:
            msg = "Object GET failed"
            raise swiftclient.ClientException(msg,
                        http_status=httplib.NOT_FOUND)

        fixture = fixture_headers[fixture_key]
        if 'manifest' in fixture:
            # Large object manifest... we return a file containing
            # all objects with prefix of this fixture key
            chunk_keys = sorted([k for k in fixture_headers.keys()
                                 if k.startswith(fixture_key) and
                                 k != fixture_key])
            result = StringIO.StringIO()
            for key in chunk_keys:
                result.write(fixture_objects[key].getvalue())
            return fixture_headers[fixture_key], result

        else:
            return fixture_headers[fixture_key], fixture_objects[fixture_key]

    def fake_head_object(url, token, container, name, **kwargs):
        # HEAD returns the list of headers for an object
        try:
            fixture_key = "%s/%s" % (container, name)
            return fixture_headers[fixture_key]
        except KeyError:
            msg = "Object HEAD failed - Object does not exist"
            raise swiftclient.ClientException(msg,
                        http_status=httplib.NOT_FOUND)

    def fake_delete_object(url, token, container, name, **kwargs):
        # DELETE returns nothing
        fixture_key = "%s/%s" % (container, name)
        if fixture_key not in fixture_headers.keys():
            msg = "Object DELETE failed - Object does not exist"
            raise swiftclient.ClientException(msg,
                        http_status=httplib.NOT_FOUND)
        else:
            del fixture_headers[fixture_key]
            del fixture_objects[fixture_key]

    def fake_http_connection(*args, **kwargs):
        return None

    def fake_get_auth(url, user, key, snet, auth_version, **kwargs):
        if url is None:
            return None, None
        if 'http' in url and '://' not in url:
            raise ValueError('Invalid url %s' % url)
        # Check the auth version against the configured value
        if swift_store_auth_version != auth_version:
            msg = 'AUTHENTICATION failed (version mismatch)'
            raise swiftclient.ClientException(msg)
        return None, None

    stubs.Set(swiftclient.client,
              'head_container', fake_head_container)
    stubs.Set(swiftclient.client,
              'put_container', fake_put_container)
    stubs.Set(swiftclient.client,
              'post_container', fake_post_container)
    stubs.Set(swiftclient.client,
              'put_object', fake_put_object)
    stubs.Set(swiftclient.client,
              'delete_object', fake_delete_object)
    stubs.Set(swiftclient.client,
              'head_object', fake_head_object)
    stubs.Set(swiftclient.client,
              'get_object', fake_get_object)
    stubs.Set(swiftclient.client,
              'get_auth', fake_get_auth)
    stubs.Set(swiftclient.client,
              'http_connection', fake_http_connection)


class SwiftTests(object):

    @property
    def swift_store_user(self):
        return urllib.quote(CONF.swift_store_user)

    def test_get_size(self):
        """
        Test that we can get the size of an object in the swift store
        """
        uri = "swift://%s:key@auth_address/glance/%s" % (
            self.swift_store_user, FAKE_UUID)
        loc = get_location_from_uri(uri)
        image_size = self.store.get_size(loc)
        self.assertEqual(image_size, 5120)

    def test_get(self):
        """Test a "normal" retrieval of an image in chunks"""
        uri = "swift://%s:key@auth_address/glance/%s" % (
            self.swift_store_user, FAKE_UUID)
        loc = get_location_from_uri(uri)
        (image_swift, image_size) = self.store.get(loc)
        self.assertEqual(image_size, 5120)

        expected_data = "*" * FIVE_KB
        data = ""

        for chunk in image_swift:
            data += chunk
        self.assertEqual(expected_data, data)

    def test_get_with_http_auth(self):
        """
        Test a retrieval from Swift with an HTTP authurl. This is
        specified either via a Location header with swift+http:// or using
        http:// in the swift_store_auth_address config value
        """
        loc = get_location_from_uri("swift+http://%s:key@auth_address/"
                                    "glance/%s" %
                                    (self.swift_store_user, FAKE_UUID))
        (image_swift, image_size) = self.store.get(loc)
        self.assertEqual(image_size, 5120)

        expected_data = "*" * FIVE_KB
        data = ""

        for chunk in image_swift:
            data += chunk
        self.assertEqual(expected_data, data)

    def test_get_non_existing(self):
        """
        Test that trying to retrieve a swift that doesn't exist
        raises an error
        """
        loc = get_location_from_uri("swift://%s:key@authurl/glance/noexist" % (
                    self.swift_store_user))
        self.assertRaises(exception.NotFound,
                          self.store.get,
                          loc)

    def test_add(self):
        """Test that we can add an image via the swift backend"""
        expected_swift_size = FIVE_KB
        expected_swift_contents = "*" * expected_swift_size
        expected_checksum = hashlib.md5(expected_swift_contents).hexdigest()
        expected_image_id = utils.generate_uuid()
        loc = 'swift+https://%s:key@localhost:8080/glance/%s'
        expected_location = loc % (self.swift_store_user,
                                   expected_image_id)
        image_swift = StringIO.StringIO(expected_swift_contents)

        global SWIFT_PUT_OBJECT_CALLS
        SWIFT_PUT_OBJECT_CALLS = 0

        location, size, checksum = self.store.add(expected_image_id,
                                                  image_swift,
                                                  expected_swift_size)

        self.assertEquals(expected_location, location)
        self.assertEquals(expected_swift_size, size)
        self.assertEquals(expected_checksum, checksum)
        # Expecting a single object to be created on Swift i.e. no chunking.
        self.assertEquals(SWIFT_PUT_OBJECT_CALLS, 1)

        loc = get_location_from_uri(expected_location)
        (new_image_swift, new_image_size) = self.store.get(loc)
        new_image_contents = new_image_swift.getvalue()
        new_image_swift_size = len(new_image_swift)

        self.assertEquals(expected_swift_contents, new_image_contents)
        self.assertEquals(expected_swift_size, new_image_swift_size)

    def test_add_auth_url_variations(self):
        """
        Test that we can add an image via the swift backend with
        a variety of different auth_address values
        """
        variations = {
            'http://localhost:80': 'swift+http://%s:key@localhost:80'
                                   '/glance/%s',
            'http://localhost': 'swift+http://%s:key@localhost/glance/%s',
            'http://localhost/v1': 'swift+http://%s:key@localhost'
                                   '/v1/glance/%s',
            'http://localhost/v1/': 'swift+http://%s:key@localhost'
                                    '/v1/glance/%s',
            'https://localhost': 'swift+https://%s:key@localhost/glance/%s',
            'https://localhost:8080': 'swift+https://%s:key@localhost:8080'
                                      '/glance/%s',
            'https://localhost/v1': 'swift+https://%s:key@localhost'
                                    '/v1/glance/%s',
            'https://localhost/v1/': 'swift+https://%s:key@localhost'
                                     '/v1/glance/%s',
            'localhost': 'swift+https://%s:key@localhost/glance/%s',
            'localhost:8080/v1': 'swift+https://%s:key@localhost:8080'
                                 '/v1/glance/%s',
        }

        for variation, expected_location in variations.items():
            image_id = utils.generate_uuid()
            expected_location = expected_location % (
                self.swift_store_user, image_id)
            expected_swift_size = FIVE_KB
            expected_swift_contents = "*" * expected_swift_size
            expected_checksum = \
                    hashlib.md5(expected_swift_contents).hexdigest()

            image_swift = StringIO.StringIO(expected_swift_contents)

            global SWIFT_PUT_OBJECT_CALLS
            SWIFT_PUT_OBJECT_CALLS = 0

            self.config(swift_store_auth_address=variation)
            self.store = Store()
            location, size, checksum = self.store.add(image_id, image_swift,
                                                      expected_swift_size)

            self.assertEquals(expected_location, location)
            self.assertEquals(expected_swift_size, size)
            self.assertEquals(expected_checksum, checksum)
            self.assertEquals(SWIFT_PUT_OBJECT_CALLS, 1)

            loc = get_location_from_uri(expected_location)
            (new_image_swift, new_image_size) = self.store.get(loc)
            new_image_contents = new_image_swift.getvalue()
            new_image_swift_size = len(new_image_swift)

            self.assertEquals(expected_swift_contents, new_image_contents)
            self.assertEquals(expected_swift_size, new_image_swift_size)

    def test_add_no_container_no_create(self):
        """
        Tests that adding an image with a non-existing container
        raises an appropriate exception
        """
        self.config(swift_store_create_container_on_put=False,
                    swift_store_container='noexist')
        self.store = Store()

        image_swift = StringIO.StringIO("nevergonnamakeit")

        global SWIFT_PUT_OBJECT_CALLS
        SWIFT_PUT_OBJECT_CALLS = 0

        # We check the exception text to ensure the container
        # missing text is found in it, otherwise, we would have
        # simply used self.assertRaises here
        exception_caught = False
        try:
            self.store.add(utils.generate_uuid(), image_swift, 0)
        except BackendException, e:
            exception_caught = True
            self.assertTrue("container noexist does not exist "
                            "in Swift" in str(e))
        self.assertTrue(exception_caught)
        self.assertEquals(SWIFT_PUT_OBJECT_CALLS, 0)

    def test_add_no_container_and_create(self):
        """
        Tests that adding an image with a non-existing container
        creates the container automatically if flag is set
        """
        expected_swift_size = FIVE_KB
        expected_swift_contents = "*" * expected_swift_size
        expected_checksum = hashlib.md5(expected_swift_contents).hexdigest()
        expected_image_id = utils.generate_uuid()
        loc = 'swift+https://%s:key@localhost:8080/noexist/%s'
        expected_location = loc % (self.swift_store_user,
                                   expected_image_id)
        image_swift = StringIO.StringIO(expected_swift_contents)

        global SWIFT_PUT_OBJECT_CALLS
        SWIFT_PUT_OBJECT_CALLS = 0

        self.config(swift_store_create_container_on_put=True,
                    swift_store_container='noexist')
        self.store = Store()
        location, size, checksum = self.store.add(expected_image_id,
                                                  image_swift,
                                                  expected_swift_size)

        self.assertEquals(expected_location, location)
        self.assertEquals(expected_swift_size, size)
        self.assertEquals(expected_checksum, checksum)
        self.assertEquals(SWIFT_PUT_OBJECT_CALLS, 1)

        loc = get_location_from_uri(expected_location)
        (new_image_swift, new_image_size) = self.store.get(loc)
        new_image_contents = new_image_swift.getvalue()
        new_image_swift_size = len(new_image_swift)

        self.assertEquals(expected_swift_contents, new_image_contents)
        self.assertEquals(expected_swift_size, new_image_swift_size)

    def test_add_large_object(self):
        """
        Tests that adding a very large image. We simulate the large
        object by setting store.large_object_size to a small number
        and then verify that there have been a number of calls to
        put_object()...
        """
        expected_swift_size = FIVE_KB
        expected_swift_contents = "*" * expected_swift_size
        expected_checksum = hashlib.md5(expected_swift_contents).hexdigest()
        expected_image_id = utils.generate_uuid()
        loc = 'swift+https://%s:key@localhost:8080/glance/%s'
        expected_location = loc % (self.swift_store_user,
                                   expected_image_id)
        image_swift = StringIO.StringIO(expected_swift_contents)

        global SWIFT_PUT_OBJECT_CALLS
        SWIFT_PUT_OBJECT_CALLS = 0

        self.config(swift_store_container='glance')
        self.store = Store()
        orig_max_size = self.store.large_object_size
        orig_temp_size = self.store.large_object_chunk_size
        try:
            self.store.large_object_size = 1024
            self.store.large_object_chunk_size = 1024
            location, size, checksum = self.store.add(expected_image_id,
                                                      image_swift,
                                                      expected_swift_size)
        finally:
            self.store.large_object_chunk_size = orig_temp_size
            self.store.large_object_size = orig_max_size

        self.assertEquals(expected_location, location)
        self.assertEquals(expected_swift_size, size)
        self.assertEquals(expected_checksum, checksum)
        # Expecting 6 objects to be created on Swift -- 5 chunks and 1
        # manifest.
        self.assertEquals(SWIFT_PUT_OBJECT_CALLS, 6)

        loc = get_location_from_uri(expected_location)
        (new_image_swift, new_image_size) = self.store.get(loc)
        new_image_contents = new_image_swift.getvalue()
        new_image_swift_size = len(new_image_swift)

        self.assertEquals(expected_swift_contents, new_image_contents)
        self.assertEquals(expected_swift_size, new_image_swift_size)

    def test_add_large_object_zero_size(self):
        """
        Tests that adding an image to Swift which has both an unknown size and
        exceeds Swift's maximum limit of 5GB is correctly uploaded.

        We avoid the overhead of creating a 5GB object for this test by
        temporarily setting MAX_SWIFT_OBJECT_SIZE to 1KB, and then adding
        an object of 5KB.

        Bug lp:891738
        """
        # Set up a 'large' image of 5KB
        expected_swift_size = FIVE_KB
        expected_swift_contents = "*" * expected_swift_size
        expected_checksum = hashlib.md5(expected_swift_contents).hexdigest()
        expected_image_id = utils.generate_uuid()
        loc = 'swift+https://%s:key@localhost:8080/glance/%s'
        expected_location = loc % (self.swift_store_user,
                                   expected_image_id)
        image_swift = StringIO.StringIO(expected_swift_contents)

        global SWIFT_PUT_OBJECT_CALLS
        SWIFT_PUT_OBJECT_CALLS = 0

        # Temporarily set Swift MAX_SWIFT_OBJECT_SIZE to 1KB and add our image,
        # explicitly setting the image_length to 0
        self.config(swift_store_container='glance')
        self.store = Store()
        orig_max_size = self.store.large_object_size
        orig_temp_size = self.store.large_object_chunk_size
        global MAX_SWIFT_OBJECT_SIZE
        orig_max_swift_object_size = MAX_SWIFT_OBJECT_SIZE
        try:
            MAX_SWIFT_OBJECT_SIZE = 1024
            self.store.large_object_size = 1024
            self.store.large_object_chunk_size = 1024
            location, size, checksum = self.store.add(expected_image_id,
                                                      image_swift, 0)
        finally:
            self.store.large_object_chunk_size = orig_temp_size
            self.store.large_object_size = orig_max_size
            MAX_SWIFT_OBJECT_SIZE = orig_max_swift_object_size

        self.assertEquals(expected_location, location)
        self.assertEquals(expected_swift_size, size)
        self.assertEquals(expected_checksum, checksum)
        # Expecting 7 calls to put_object -- 5 chunks, a zero chunk which is
        # then deleted, and the manifest.  Note the difference with above
        # where the image_size is specified in advance (there's no zero chunk
        # in that case).
        self.assertEquals(SWIFT_PUT_OBJECT_CALLS, 7)

        loc = get_location_from_uri(expected_location)
        (new_image_swift, new_image_size) = self.store.get(loc)
        new_image_contents = new_image_swift.getvalue()
        new_image_swift_size = len(new_image_swift)

        self.assertEquals(expected_swift_contents, new_image_contents)
        self.assertEquals(expected_swift_size, new_image_swift_size)

    def test_add_already_existing(self):
        """
        Tests that adding an image with an existing identifier
        raises an appropriate exception
        """
        image_swift = StringIO.StringIO("nevergonnamakeit")
        self.assertRaises(exception.Duplicate,
                          self.store.add,
                          FAKE_UUID, image_swift, 0)

    def _option_required(self, key):
        conf = self.getConfig()
        conf[key] = None

        try:
            self.config(**conf)
            self.store = Store()
            return self.store.add == self.store.add_disabled
        except:
            return False
        return False

    def test_no_user(self):
        """
        Tests that options without user disables the add method
        """
        self.assertTrue(self._option_required('swift_store_user'))

    def test_no_key(self):
        """
        Tests that options without key disables the add method
        """
        self.assertTrue(self._option_required('swift_store_key'))

    def test_no_auth_address(self):
        """
        Tests that options without auth address disables the add method
        """
        self.assertTrue(self._option_required('swift_store_auth_address'))

    def test_delete(self):
        """
        Test we can delete an existing image in the swift store
        """
        uri = "swift://%s:key@authurl/glance/%s" % (
            self.swift_store_user, FAKE_UUID)
        loc = get_location_from_uri(uri)
        self.store.delete(loc)

        self.assertRaises(exception.NotFound, self.store.get, loc)

    def test_delete_non_existing(self):
        """
        Test that trying to delete a swift that doesn't exist
        raises an error
        """
        loc = get_location_from_uri("swift://%s:key@authurl/glance/noexist" % (
                self.swift_store_user))
        self.assertRaises(exception.NotFound, self.store.delete, loc)

    def test_read_acl_public(self):
        """
        Test that we can set a public read acl.
        """
        self.config(swift_store_multi_tenant=True)
        uri = "swift+http://storeurl/glance/%s" % FAKE_UUID
        loc = get_location_from_uri(uri)
        self.store.multi_tenant = True
        self.store.set_acls(loc, public=True)
        container_headers = swiftclient.client.head_container('x', 'y',
                                                              'glance')
        self.assertEqual(container_headers['X-Container-Read'], ".r:*")

    def test_read_acl_tenants(self):
        """
        Test that we can set read acl for tenants.
        """
        self.config(swift_store_multi_tenant=True)
        uri = "swift+http://storeurl/glance/%s" % FAKE_UUID
        loc = get_location_from_uri(uri)
        self.store.multi_tenant = True
        read_tenants = ['matt', 'mark']
        self.store.set_acls(loc, read_tenants=read_tenants)
        container_headers = swiftclient.client.head_container('x', 'y',
                                                              'glance')
        self.assertEqual(container_headers['X-Container-Read'],
                         ','.join(read_tenants))

    def test_read_write_public(self):
        """
        Test that we can set write acl for tenants.
        """
        self.config(swift_store_multi_tenant=True)
        uri = "swift+http://storeurl/glance/%s" % FAKE_UUID
        loc = get_location_from_uri(uri)
        self.store.multi_tenant = True
        read_tenants = ['frank', 'jim']
        self.store.set_acls(loc, write_tenants=read_tenants)
        container_headers = swiftclient.client.head_container('x', 'y',
                                                              'glance')
        self.assertEqual(container_headers['X-Container-Write'],
                         ','.join(read_tenants))


class TestStoreAuthV1(base.StoreClearingUnitTest, SwiftTests):

    def getConfig(self):
        conf = SWIFT_CONF.copy()
        conf['swift_store_auth_version'] = '1'
        conf['swift_store_user'] = 'user'
        return conf

    def setUp(self):
        """Establish a clean test environment"""
        conf = self.getConfig()
        self.config(**conf)
        super(TestStoreAuthV1, self).setUp()
        self.stubs = stubout.StubOutForTesting()
        stub_out_swiftclient(self.stubs,
                                     conf['swift_store_auth_version'])
        self.store = Store()

    def tearDown(self):
        """Clear the test environment"""
        super(TestStoreAuthV1, self).tearDown()
        self.stubs.UnsetAll()


class TestStoreAuthV2(TestStoreAuthV1):

    def getConfig(self):
        conf = super(TestStoreAuthV2, self).getConfig()
        conf['swift_store_user'] = 'tenant:user'
        conf['swift_store_auth_version'] = '2'
        return conf

    def test_v2_with_no_tenant(self):
        conf = self.getConfig()
        conf['swift_store_user'] = 'failme'
        uri = "swift://%s:key@auth_address/glance/%s" % (
            conf['swift_store_user'], FAKE_UUID)
        loc = get_location_from_uri(uri)
        self.assertRaises(exception.BadStoreUri,
                          self.store.get,
                          loc)

    def test_v2_multi_tenant_location(self):
        conf = self.getConfig()
        conf['swift_store_multi_tenant'] = True
        uri = "swift://auth_address/glance/%s" % (FAKE_UUID)
        loc = get_location_from_uri(uri)
        self.assertEqual('swift', loc.store_name)


class TestChunkReader(base.StoreClearingUnitTest):

    def test_read_all_data(self):
        """
        Replicate what goes on in the Swift driver with the
        repeated creation of the ChunkReader object
        """
        CHUNKSIZE = 100
        checksum = hashlib.md5()
        data_file = tempfile.NamedTemporaryFile()
        data_file.write('*' * 1024)
        data_file.flush()
        infile = open(data_file.name, 'rb')
        bytes_read = 0
        while True:
            cr = glance.store.swift.ChunkReader(infile, checksum, CHUNKSIZE)
            chunk = cr.read(CHUNKSIZE)
            bytes_read += len(chunk)
            if len(chunk) == 0:
                break
        self.assertEqual(1024, bytes_read)
        data_file.close()
