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"""
Support for downloading objects from the object service, following best
practices for that service.
Downloaded data is written to a "writer" provided by a "writer factory". A
writer has a `write` method which writes the entire passed buffer to storage.
A writer factory is a callable which returns a fresh writer, ready to write the
first byte of the object. When downloads are retried, the writer factory may
be called more than once.
This module provides several pre-defined writers and writer factories for
common cases.
"""
import functools
import six
if six.PY2:
raise ImportError("download is only supported in Python 3")
from .aio import download as aio_download
from .aio.asyncutils import ensureCoro, runAsync
def downloadToBuf(**kwargs):
"""
Convenience method to download data to an in-memory buffer and return the
downloaded data. Arguments are the same as `download`, except that
`writerFactory` should not be supplied. Returns a tuple (buffer, contentType).
"""
return runAsync(aio_download.downloadToBuf(**kwargs))
def downloadToFile(file, **kwargs):
"""
Convenience method to download data to a file object. The file must be
writeable, in binary mode, seekable (`f.seek`), and truncatable
(`f.truncate`) to support retries. Arguments are the same as `download`,
except that `writerFactory` should not be supplied. Returns the content-type.
"""
return runAsync(aio_download.downloadToFile(file=file, **kwargs))
def download(*, writerFactory, **kwargs):
"""
Download the named object from the object service, using a writer returned
from `writerFactory` to write the data. The `maxRetries` parameter has
the same meaning as for service clients. The `objectService` parameter is
an instance of the Object class, configured with credentials for the
upload. Returns the content-type.
"""
wrappedWriterFactory = _wrapSyncWriterFactory(writerFactory)
return runAsync(aio_download.download(writerFactory=wrappedWriterFactory, **kwargs))
def downloadArtifactToBuf(**kwargs):
"""
Convenience method to download an artifact to an in-memory buffer and return the
downloaded data. Arguments are the same as `downloadArtifact`, except that
`writerFactory` should not be supplied. Returns a tuple (buffer, contentType).
"""
return runAsync(aio_download.downloadArtifactToBuf(**kwargs))
def downloadArtifactToFile(file, **kwargs):
"""
Convenience method to download an artifact to a file object. The file must be
writeable, in binary mode, seekable (`f.seek`), and truncatable
(`f.truncate`) to support retries. Arguments are the same as `downloadArtifac`,
except that `writerFactory` should not be supplied. Returns the content-type.
"""
return runAsync(aio_download.downloadArtifactToFile(file=file, **kwargs))
def downloadArtifact(*, writerFactory, **kwargs):
"""
Download the named artifact with the appropriate storageType, using a writer returned
from `writerFactory` to write the data. The `maxRetries` parameter has
the same meaning as for service clients. The `queueService` parameter is
an instance of the Queue class, configured with credentials for the
download. Returns the content-type.
"""
wrappedWriterFactory = _wrapSyncWriterFactory(writerFactory)
return runAsync(aio_download.downloadArtifact(writerFactory=wrappedWriterFactory, **kwargs))
def _wrapSyncWriterFactory(writerFactory):
"""Modify the reader returned by readerFactory to have an async read."""
@functools.wraps(writerFactory)
async def wrappedFactory():
writer = writerFactory()
writer.write = ensureCoro(writer.write)
return writer
return wrappedFactory
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