######################################################################
#
# File: b2sdk/transfer/inbound/downloader/abstract.py
#
# Copyright 2020 Backblaze Inc. All Rights Reserved.
#
# License https://www.backblaze.com/using_b2_code.html
#
######################################################################
from abc import abstractmethod
from io import IOBase
from typing import Optional
from requests.models import Response
from b2sdk.file_version import DownloadVersion
from b2sdk.session import B2Session
from b2sdk.utils import B2TraceMetaAbstract
from b2sdk.utils.range_ import Range
from b2sdk.encryption.setting import EncryptionSetting
[docs]class AbstractDownloader(metaclass=B2TraceMetaAbstract):
REQUIRES_SEEKING = True
[docs] def __init__(
self,
force_chunk_size=None,
min_chunk_size=None,
max_chunk_size=None,
):
assert force_chunk_size is not None or (
min_chunk_size is not None and max_chunk_size is not None and min_chunk_size > 0 and
max_chunk_size >= min_chunk_size
)
self._min_chunk_size = min_chunk_size
self._max_chunk_size = max_chunk_size
self._forced_chunk_size = force_chunk_size
def _get_chunk_size(self, content_length):
if self._forced_chunk_size is not None:
return self._forced_chunk_size
ideal = content_length // 1000
non_aligned = min(max(ideal, self._min_chunk_size), self._max_chunk_size)
aligned = non_aligned // 4096 * 4096
return aligned
@classmethod
def _get_remote_range(cls, response: Response, download_version: DownloadVersion):
"""
Get a range from response or original request (as appropriate).
:param response: requests.Response of initial request
:param download_version: b2sdk.v2.DownloadVersion
:return: a range object
"""
if 'Range' in response.request.headers:
return Range.from_header(response.request.headers['Range'])
return download_version.range_
[docs] def is_suitable(self, download_version: DownloadVersion, allow_seeking: bool):
"""
Analyze download_version (possibly against options passed earlier to constructor
to find out whether the given download request should be handled by this downloader).
"""
if self.REQUIRES_SEEKING and not allow_seeking:
return False
return True
[docs] @abstractmethod
def download(
self,
file: IOBase,
response: Response,
download_version: DownloadVersion,
session: B2Session,
encryption: Optional[EncryptionSetting] = None,
):
"""
@returns (bytes_read, actual_sha1)
"""
pass