79 lines
2.3 KiB
Python
79 lines
2.3 KiB
Python
import os
|
|
import tarfile
|
|
|
|
class TarLayerReadException(Exception):
|
|
""" Exception raised when reading a layer has failed. """
|
|
pass
|
|
|
|
|
|
class TarLayerFormat(object):
|
|
""" Class which creates a generator of the combined TAR data. """
|
|
def __init__(self, tar_iterator):
|
|
self.tar_iterator = tar_iterator
|
|
|
|
def get_generator(self):
|
|
for current_tar in self.tar_iterator():
|
|
# Read the current TAR. If it is empty, we just continue
|
|
# to the next one.
|
|
tar_file = None
|
|
try:
|
|
tar_file = tarfile.open(mode='r|*', fileobj=current_tar)
|
|
except tarfile.ReadError as re:
|
|
if re.message != 'empty file':
|
|
raise TarLayerReadException('Could not read layer')
|
|
|
|
if not tar_file:
|
|
continue
|
|
|
|
# For each of the tar entries, yield them IF and ONLY IF we have not
|
|
# encountered the path before.
|
|
|
|
# 9MB (+ padding below) so that it matches the 10MB expected by Gzip.
|
|
chunk_size = 1024 * 1024 * 9
|
|
|
|
for tar_info in tar_file:
|
|
if not self.check_tar_info(tar_info):
|
|
continue
|
|
|
|
# Yield the tar header.
|
|
yield tar_info.tobuf()
|
|
|
|
# Try to extract any file contents for the tar. If found, we yield them as well.
|
|
if tar_info.isreg():
|
|
file_stream = tar_file.extractfile(tar_info)
|
|
if file_stream is not None:
|
|
length = 0
|
|
while True:
|
|
current_block = file_stream.read(chunk_size)
|
|
if not len(current_block):
|
|
break
|
|
|
|
yield current_block
|
|
length += len(current_block)
|
|
|
|
file_stream.close()
|
|
|
|
# Files must be padding to 512 byte multiples.
|
|
if length % 512 != 0:
|
|
yield '\0' * (512 - (length % 512))
|
|
|
|
# Close the layer stream now that we're done with it.
|
|
tar_file.close()
|
|
|
|
# Conduct any post-tar work.
|
|
self.after_tar_layer(current_tar)
|
|
|
|
# Last two records are empty in TAR spec.
|
|
yield '\0' * 512
|
|
yield '\0' * 512
|
|
|
|
|
|
def check_tar_info(self, tar_info):
|
|
""" Returns true if the current tar_info should be added to the combined tar. False
|
|
otherwise.
|
|
"""
|
|
raise NotImplementedError()
|
|
|
|
def after_tar_layer(self, current_tar):
|
|
""" Invoked after a TAR layer is added, to do any post-add work. """
|
|
raise NotImplementedError()
|