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https://github.com/tahoe-lafs/tahoe-lafs.git
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476 lines
19 KiB
Python
476 lines
19 KiB
Python
import struct
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from zope.interface import implements
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from twisted.internet import defer
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from allmydata.interfaces import IStorageBucketWriter, IStorageBucketReader, \
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FileTooLargeError, HASH_SIZE
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from allmydata.util import mathutil, idlib, observer
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from allmydata.util.assertutil import precondition
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from allmydata import storage
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class LayoutInvalid(Exception):
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""" There is something wrong with these bytes so they can't be interpreted as the kind of
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immutable file that I know how to download. """
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pass
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class RidiculouslyLargeURIExtensionBlock(LayoutInvalid):
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""" When downloading a file, the length of the URI Extension Block was given as >= 2**32.
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This means the share data must have been corrupted, or else the original uploader of the
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file wrote a ridiculous value into the URI Extension Block length. """
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pass
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class ShareVersionIncompatible(LayoutInvalid):
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""" When downloading a share, its format was not one of the formats we know how to
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parse. """
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pass
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"""
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Share data is written in a file. At the start of the file, there is a series of four-byte
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big-endian offset values, which indicate where each section starts. Each offset is measured from
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the beginning of the share data.
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0x00: version number (=00 00 00 01)
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0x04: block size # See Footnote 1 below.
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0x08: share data size # See Footnote 1 below.
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0x0c: offset of data (=00 00 00 24)
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0x10: offset of plaintext_hash_tree UNUSED
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0x14: offset of crypttext_hash_tree
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0x18: offset of block_hashes
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0x1c: offset of share_hashes
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0x20: offset of uri_extension_length + uri_extension
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0x24: start of data
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? : start of plaintext_hash_tree UNUSED
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? : start of crypttext_hash_tree
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? : start of block_hashes
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? : start of share_hashes
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each share_hash is written as a two-byte (big-endian) hashnum
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followed by the 32-byte SHA-256 hash. We store only the hashes
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necessary to validate the share hash root
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? : start of uri_extension_length (four-byte big-endian value)
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? : start of uri_extension
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"""
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"""
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v2 shares: these use 8-byte offsets to remove two of the three ~12GiB size
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limitations described in #346.
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0x00: version number (=00 00 00 02)
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0x04: block size # See Footnote 1 below.
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0x0c: share data size # See Footnote 1 below.
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0x14: offset of data (=00 00 00 00 00 00 00 44)
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0x1c: offset of plaintext_hash_tree UNUSED
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0x24: offset of crypttext_hash_tree
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0x2c: offset of block_hashes
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0x34: offset of share_hashes
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0x3c: offset of uri_extension_length + uri_extension
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0x44: start of data
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: rest of share is the same as v1, above
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... ...
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? : start of uri_extension_length (eight-byte big-endian value)
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? : start of uri_extension
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"""
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# Footnote 1: as of Tahoe v1.3.0 these fields are not used when reading, but
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# they are still provided when writing so that older versions of Tahoe can
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# read them.
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def make_write_bucket_proxy(rref, data_size, block_size, num_segments,
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num_share_hashes, uri_extension_size_max, nodeid):
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# Use layout v1 for small files, so they'll be readable by older versions
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# (<tahoe-1.3.0). Use layout v2 for large files; they'll only be readable
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# by tahoe-1.3.0 or later.
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try:
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wbp = WriteBucketProxy(rref, data_size, block_size, num_segments,
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num_share_hashes, uri_extension_size_max, nodeid)
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except FileTooLargeError:
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wbp = WriteBucketProxy_v2(rref, data_size, block_size, num_segments,
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num_share_hashes, uri_extension_size_max, nodeid)
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return wbp
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class WriteBucketProxy:
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implements(IStorageBucketWriter)
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fieldsize = 4
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fieldstruct = ">L"
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def __init__(self, rref, data_size, block_size, num_segments,
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num_share_hashes, uri_extension_size_max, nodeid):
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self._rref = rref
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self._data_size = data_size
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self._block_size = block_size
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self._num_segments = num_segments
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self._nodeid = nodeid
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effective_segments = mathutil.next_power_of_k(num_segments,2)
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self._segment_hash_size = (2*effective_segments - 1) * HASH_SIZE
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# how many share hashes are included in each share? This will be
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# about ln2(num_shares).
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self._share_hashtree_size = num_share_hashes * (2+HASH_SIZE)
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# we commit to not sending a uri extension larger than this
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self._uri_extension_size_max = uri_extension_size_max
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self._create_offsets(block_size, data_size)
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def get_allocated_size(self):
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return (self._offsets['uri_extension'] + self.fieldsize +
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self._uri_extension_size_max)
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def _create_offsets(self, block_size, data_size):
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if block_size >= 2**32 or data_size >= 2**32:
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raise FileTooLargeError("This file is too large to be uploaded (data_size).")
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offsets = self._offsets = {}
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x = 0x24
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offsets['data'] = x
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x += data_size
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offsets['plaintext_hash_tree'] = x # UNUSED
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x += self._segment_hash_size
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offsets['crypttext_hash_tree'] = x
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x += self._segment_hash_size
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offsets['block_hashes'] = x
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x += self._segment_hash_size
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offsets['share_hashes'] = x
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x += self._share_hashtree_size
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offsets['uri_extension'] = x
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if x >= 2**32:
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raise FileTooLargeError("This file is too large to be uploaded (offsets).")
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offset_data = struct.pack(">LLLLLLLLL",
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1, # version number
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block_size,
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data_size,
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offsets['data'],
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offsets['plaintext_hash_tree'], # UNUSED
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offsets['crypttext_hash_tree'],
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offsets['block_hashes'],
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offsets['share_hashes'],
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offsets['uri_extension'],
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)
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assert len(offset_data) == 0x24
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self._offset_data = offset_data
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def __repr__(self):
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if self._nodeid:
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nodeid_s = idlib.nodeid_b2a(self._nodeid)
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else:
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nodeid_s = "[None]"
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return "<allmydata.storage.WriteBucketProxy for node %s>" % nodeid_s
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def put_header(self):
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return self._write(0, self._offset_data)
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def put_block(self, segmentnum, data):
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offset = self._offsets['data'] + segmentnum * self._block_size
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assert offset + len(data) <= self._offsets['uri_extension']
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assert isinstance(data, str)
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if segmentnum < self._num_segments-1:
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precondition(len(data) == self._block_size,
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len(data), self._block_size)
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else:
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precondition(len(data) == (self._data_size -
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(self._block_size *
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(self._num_segments - 1))),
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len(data), self._block_size)
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return self._write(offset, data)
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def put_crypttext_hashes(self, hashes):
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offset = self._offsets['crypttext_hash_tree']
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assert isinstance(hashes, list)
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data = "".join(hashes)
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precondition(len(data) == self._segment_hash_size,
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len(data), self._segment_hash_size)
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precondition(offset + len(data) <= self._offsets['block_hashes'],
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offset, len(data), offset+len(data),
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self._offsets['block_hashes'])
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return self._write(offset, data)
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def put_block_hashes(self, blockhashes):
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offset = self._offsets['block_hashes']
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assert isinstance(blockhashes, list)
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data = "".join(blockhashes)
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precondition(len(data) == self._segment_hash_size,
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len(data), self._segment_hash_size)
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precondition(offset + len(data) <= self._offsets['share_hashes'],
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offset, len(data), offset+len(data),
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self._offsets['share_hashes'])
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return self._write(offset, data)
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def put_share_hashes(self, sharehashes):
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# sharehashes is a list of (index, hash) tuples, so they get stored
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# as 2+32=34 bytes each
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offset = self._offsets['share_hashes']
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assert isinstance(sharehashes, list)
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data = "".join([struct.pack(">H", hashnum) + hashvalue
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for hashnum,hashvalue in sharehashes])
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precondition(len(data) == self._share_hashtree_size,
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len(data), self._share_hashtree_size)
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precondition(offset + len(data) <= self._offsets['uri_extension'],
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offset, len(data), offset+len(data),
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self._offsets['uri_extension'])
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return self._write(offset, data)
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def put_uri_extension(self, data):
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offset = self._offsets['uri_extension']
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assert isinstance(data, str)
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precondition(len(data) <= self._uri_extension_size_max,
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len(data), self._uri_extension_size_max)
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length = struct.pack(self.fieldstruct, len(data))
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return self._write(offset, length+data)
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def _write(self, offset, data):
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# TODO: for small shares, buffer the writes and do just a single call
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return self._rref.callRemote("write", offset, data)
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def close(self):
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return self._rref.callRemote("close")
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def abort(self):
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return self._rref.callRemoteOnly("abort")
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class WriteBucketProxy_v2(WriteBucketProxy):
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fieldsize = 8
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fieldstruct = ">Q"
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def _create_offsets(self, block_size, data_size):
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if block_size >= 2**64 or data_size >= 2**64:
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raise FileTooLargeError("This file is too large to be uploaded (data_size).")
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offsets = self._offsets = {}
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x = 0x44
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offsets['data'] = x
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x += data_size
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offsets['plaintext_hash_tree'] = x # UNUSED
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x += self._segment_hash_size
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offsets['crypttext_hash_tree'] = x
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x += self._segment_hash_size
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offsets['block_hashes'] = x
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x += self._segment_hash_size
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offsets['share_hashes'] = x
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x += self._share_hashtree_size
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offsets['uri_extension'] = x
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if x >= 2**64:
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raise FileTooLargeError("This file is too large to be uploaded (offsets).")
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offset_data = struct.pack(">LQQQQQQQQ",
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2, # version number
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block_size,
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data_size,
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offsets['data'],
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offsets['plaintext_hash_tree'], # UNUSED
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offsets['crypttext_hash_tree'],
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offsets['block_hashes'],
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offsets['share_hashes'],
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offsets['uri_extension'],
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)
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assert len(offset_data) == 0x44, len(offset_data)
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self._offset_data = offset_data
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class ReadBucketProxy:
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implements(IStorageBucketReader)
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MAX_UEB_SIZE = 2000 # actual size is closer to 419, but varies by a few bytes
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def __init__(self, rref, peerid, storage_index):
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self._rref = rref
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self._peerid = peerid
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peer_id_s = idlib.shortnodeid_b2a(peerid)
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storage_index_s = storage.si_b2a(storage_index)
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self._reprstr = "<ReadBucketProxy %s to peer [%s] SI %s>" % (id(self), peer_id_s, storage_index_s)
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self._started = False # sent request to server
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self._ready = observer.OneShotObserverList() # got response from server
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def get_peerid(self):
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return self._peerid
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def __repr__(self):
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return self._reprstr
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def _start_if_needed(self):
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""" Returns a deferred that will be fired when I'm ready to return data, or errbacks if
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the starting (header reading and parsing) process fails."""
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if not self._started:
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self._start()
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return self._ready.when_fired()
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def _start(self):
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self._started = True
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# TODO: for small shares, read the whole bucket in _start()
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d = self._fetch_header()
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d.addCallback(self._parse_offsets)
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# XXX The following two callbacks implement a slightly faster/nicer way to get the ueb
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# and sharehashtree, but it requires that the storage server be >= v1.3.0.
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# d.addCallback(self._fetch_sharehashtree_and_ueb)
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# d.addCallback(self._parse_sharehashtree_and_ueb)
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def _fail_waiters(f):
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self._ready.fire(f)
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def _notify_waiters(result):
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self._ready.fire(result)
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d.addCallbacks(_notify_waiters, _fail_waiters)
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return d
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def _fetch_header(self):
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return self._read(0, 0x44)
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def _parse_offsets(self, data):
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precondition(len(data) >= 0x4)
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self._offsets = {}
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(version,) = struct.unpack(">L", data[0:4])
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if version != 1 and version != 2:
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raise ShareVersionIncompatible(version)
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if version == 1:
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precondition(len(data) >= 0x24)
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x = 0x0c
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fieldsize = 0x4
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fieldstruct = ">L"
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else:
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precondition(len(data) >= 0x44)
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x = 0x14
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fieldsize = 0x8
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fieldstruct = ">Q"
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self._version = version
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self._fieldsize = fieldsize
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self._fieldstruct = fieldstruct
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for field in ( 'data',
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'plaintext_hash_tree', # UNUSED
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'crypttext_hash_tree',
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'block_hashes',
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'share_hashes',
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'uri_extension',
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):
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offset = struct.unpack(fieldstruct, data[x:x+fieldsize])[0]
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x += fieldsize
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self._offsets[field] = offset
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return self._offsets
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def _fetch_sharehashtree_and_ueb(self, offsets):
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sharehashtree_size = offsets['uri_extension'] - offsets['share_hashes']
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return self._read(offsets['share_hashes'], self.MAX_UEB_SIZE+sharehashtree_size)
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def _parse_sharehashtree_and_ueb(self, data):
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sharehashtree_size = self._offsets['uri_extension'] - self._offsets['share_hashes']
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if len(data) < sharehashtree_size:
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raise LayoutInvalid("share hash tree truncated -- should have at least %d bytes -- not %d" % (sharehashtree_size, len(data)))
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if sharehashtree_size % (2+HASH_SIZE) != 0:
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raise LayoutInvalid("share hash tree malformed -- should have an even multiple of %d bytes -- not %d" % (2+HASH_SIZE, sharehashtree_size))
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self._share_hashes = []
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for i in range(0, sharehashtree_size, 2+HASH_SIZE):
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hashnum = struct.unpack(">H", data[i:i+2])[0]
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hashvalue = data[i+2:i+2+HASH_SIZE]
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self._share_hashes.append( (hashnum, hashvalue) )
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i = self._offsets['uri_extension']-self._offsets['share_hashes']
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if len(data) < i+self._fieldsize:
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raise LayoutInvalid("not enough bytes to encode URI length -- should be at least %d bytes long, not %d " % (i+self._fieldsize, len(data),))
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length = struct.unpack(self._fieldstruct, data[i:i+self._fieldsize])[0]
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self._ueb_data = data[i+self._fieldsize:i+self._fieldsize+length]
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def _get_block_data(self, unused, blocknum, blocksize, thisblocksize):
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offset = self._offsets['data'] + blocknum * blocksize
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return self._read(offset, thisblocksize)
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def get_block_data(self, blocknum, blocksize, thisblocksize):
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d = self._start_if_needed()
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d.addCallback(self._get_block_data, blocknum, blocksize, thisblocksize)
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return d
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def _str2l(self, s):
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""" split string (pulled from storage) into a list of blockids """
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return [ s[i:i+HASH_SIZE]
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for i in range(0, len(s), HASH_SIZE) ]
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def _get_crypttext_hashes(self, unused=None):
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offset = self._offsets['crypttext_hash_tree']
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size = self._offsets['block_hashes'] - offset
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d = self._read(offset, size)
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d.addCallback(self._str2l)
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return d
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def get_crypttext_hashes(self):
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d = self._start_if_needed()
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d.addCallback(self._get_crypttext_hashes)
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return d
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def _get_block_hashes(self, unused=None, at_least_these=()):
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# TODO: fetch only at_least_these instead of all of them.
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offset = self._offsets['block_hashes']
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size = self._offsets['share_hashes'] - offset
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d = self._read(offset, size)
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d.addCallback(self._str2l)
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return d
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def get_block_hashes(self, at_least_these=()):
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if at_least_these:
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d = self._start_if_needed()
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d.addCallback(self._get_block_hashes, at_least_these)
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return d
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else:
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return defer.succeed([])
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def _get_share_hashes(self, unused=None):
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if hasattr(self, '_share_hashes'):
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return self._share_hashes
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else:
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return self._get_share_hashes_the_old_way()
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return self._share_hashes
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def get_share_hashes(self):
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d = self._start_if_needed()
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d.addCallback(self._get_share_hashes)
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return d
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def _get_share_hashes_the_old_way(self):
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""" Tahoe storage servers < v1.3.0 would return an error if you tried to read past the
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end of the share, so we need to use the offset and read just that much."""
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offset = self._offsets['share_hashes']
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size = self._offsets['uri_extension'] - offset
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if size % (2+HASH_SIZE) != 0:
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raise LayoutInvalid("share hash tree corrupted -- should occupy a multiple of %d bytes, not %d bytes" % ((2+HASH_SIZE), size))
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d = self._read(offset, size)
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def _unpack_share_hashes(data):
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if len(data) != size:
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raise LayoutInvalid("share hash tree corrupted -- got a short read of the share data -- should have gotten %d, not %d bytes" % (size, len(data)))
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hashes = []
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for i in range(0, size, 2+HASH_SIZE):
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hashnum = struct.unpack(">H", data[i:i+2])[0]
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hashvalue = data[i+2:i+2+HASH_SIZE]
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hashes.append( (hashnum, hashvalue) )
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return hashes
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d.addCallback(_unpack_share_hashes)
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return d
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def _get_uri_extension_the_old_way(self, unused=None):
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""" Tahoe storage servers < v1.3.0 would return an error if you tried to read past the
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end of the share, so we need to fetch the UEB size and then read just that much."""
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offset = self._offsets['uri_extension']
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d = self._read(offset, self._fieldsize)
|
|
def _got_length(data):
|
|
if len(data) != self._fieldsize:
|
|
raise LayoutInvalid("not enough bytes to encode URI length -- should be %d bytes long, not %d " % (self._fieldsize, len(data),))
|
|
length = struct.unpack(self._fieldstruct, data)[0]
|
|
if length >= 2**31:
|
|
# URI extension blocks are around 419 bytes long, so this must be corrupted.
|
|
# Anyway, the foolscap interface schema for "read" will not allow >= 2**31 bytes
|
|
# length.
|
|
raise RidiculouslyLargeURIExtensionBlock(length)
|
|
|
|
return self._read(offset+self._fieldsize, length)
|
|
d.addCallback(_got_length)
|
|
return d
|
|
|
|
def _get_uri_extension(self, unused=None):
|
|
if hasattr(self, '_ueb_data'):
|
|
return self._ueb_data
|
|
else:
|
|
return self._get_uri_extension_the_old_way()
|
|
|
|
def get_uri_extension(self):
|
|
d = self._start_if_needed()
|
|
d.addCallback(self._get_uri_extension)
|
|
return d
|
|
|
|
def _read(self, offset, length):
|
|
return self._rref.callRemote("read", offset, length)
|