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# Copyright (c) 2012 Amazon.com, Inc. or its affiliates. All Rights Reserved
#
# Permission is hereby granted, free of charge, to any person obtaining a
# copy of this software and associated documentation files (the
# "Software"), to deal in the Software without restriction, including
# without limitation the rights to use, copy, modify, merge, publish, dis-
# tribute, sublicense, and/or sell copies of the Software, and to permit
# persons to whom the Software is furnished to do so, subject to the fol-
# lowing conditions:
#
# The above copyright notice and this permission notice shall be included
# in all copies or substantial portions of the Software.
#
# THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS
# OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABIL-
# ITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT
# SHALL THE AUTHOR BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY,
# WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
# OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS
# IN THE SOFTWARE.
#
import hashlib
import math
import binascii
_MEGABYTE = 1024 * 1024
DEFAULT_PART_SIZE = 4 * _MEGABYTE
MAXIMUM_NUMBER_OF_PARTS = 10000
def minimum_part_size(size_in_bytes, default_part_size=DEFAULT_PART_SIZE):
"""Calculate the minimum part size needed for a multipart upload.
Glacier allows a maximum of 10,000 parts per upload. It also
states that the maximum archive size is 10,000 * 4 GB, which means
the part size can range from 1MB to 4GB (provided it is one 1MB
multiplied by a power of 2).
This function will compute what the minimum part size must be in
order to upload a file of size ``size_in_bytes``.
It will first check if ``default_part_size`` is sufficient for
a part size given the ``size_in_bytes``. If this is not the case,
then the smallest part size than can accomodate a file of size
``size_in_bytes`` will be returned.
If the file size is greater than the maximum allowed archive
size of 10,000 * 4GB, a ``ValueError`` will be raised.
"""
# The default part size (4 MB) will be too small for a very large
# archive, as there is a limit of 10,000 parts in a multipart upload.
# This puts the maximum allowed archive size with the default part size
# at 40,000 MB. We need to do a sanity check on the part size, and find
# one that works if the default is too small.
part_size = _MEGABYTE
if (default_part_size * MAXIMUM_NUMBER_OF_PARTS) < size_in_bytes:
if size_in_bytes > (4096 * _MEGABYTE * 10000):
raise ValueError("File size too large: %s" % size_in_bytes)
min_part_size = size_in_bytes / 10000
power = 3
while part_size < min_part_size:
part_size = math.ldexp(_MEGABYTE, power)
power += 1
part_size = int(part_size)
else:
part_size = default_part_size
return part_size
def chunk_hashes(bytestring, chunk_size=_MEGABYTE):
chunk_count = int(math.ceil(len(bytestring) / float(chunk_size)))
hashes = []
for i in range(chunk_count):
start = i * chunk_size
end = (i + 1) * chunk_size
hashes.append(hashlib.sha256(bytestring[start:end]).digest())
if not hashes:
return [hashlib.sha256(b'').digest()]
return hashes
def tree_hash(fo):
"""
Given a hash of each 1MB chunk (from chunk_hashes) this will hash
together adjacent hashes until it ends up with one big one. So a
tree of hashes.
"""
hashes = []
hashes.extend(fo)
while len(hashes) > 1:
new_hashes = []
while True:
if len(hashes) > 1:
first = hashes.pop(0)
second = hashes.pop(0)
new_hashes.append(hashlib.sha256(first + second).digest())
elif len(hashes) == 1:
only = hashes.pop(0)
new_hashes.append(only)
else:
break
hashes.extend(new_hashes)
return hashes[0]
def compute_hashes_from_fileobj(fileobj, chunk_size=1024 * 1024):
"""Compute the linear and tree hash from a fileobj.
This function will compute the linear/tree hash of a fileobj
in a single pass through the fileobj.
:param fileobj: A file like object.
:param chunk_size: The size of the chunks to use for the tree
hash. This is also the buffer size used to read from
`fileobj`.
:rtype: tuple
:return: A tuple of (linear_hash, tree_hash). Both hashes
are returned in hex.
"""
linear_hash = hashlib.sha256()
chunks = []
chunk = fileobj.read(chunk_size).encode('utf-8')
while chunk:
linear_hash.update(chunk)
chunks.append(hashlib.sha256(chunk).digest())
chunk = fileobj.read(chunk_size)
if not chunks:
chunks = [hashlib.sha256(b'').digest()]
return linear_hash.hexdigest(), bytes_to_hex(tree_hash(chunks))
def bytes_to_hex(str_as_bytes):
return binascii.hexlify(str_as_bytes)
def tree_hash_from_str(str_as_bytes):
"""
:type str_as_bytes: str
:param str_as_bytes: The string for which to compute the tree hash.
:rtype: str
:return: The computed tree hash, returned as hex.
"""
return bytes_to_hex(tree_hash(chunk_hashes(str_as_bytes)))
class ResettingFileSender(object):
def __init__(self, archive):
self._archive = archive
self._starting_offset = archive.tell()
def __call__(self, connection, method, path, body, headers):
try:
connection.request(method, path, self._archive, headers)
return connection.getresponse()
finally:
self._archive.seek(self._starting_offset)
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