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mutable.py: sketch out data-structure packing/unpacking methods

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This commit is contained in:
Brian Warner 2007-11-02 00:03:28 -07:00
parent d772ea850d
commit 6510510ea7
1 changed files with 59 additions and 0 deletions
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59
src/allmydata/mutable.py
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@ -1,4 +1,5 @@
import struct
from zope.interface import implements
from twisted.internet import defer
from allmydata.interfaces import IMutableFileNode, IMutableFileURI
@ -68,4 +69,62 @@ class MutableFileNode:
def replace(self, newdata):
return defer.succeed(None)
def unpack_data(self, data):
offsets = {}
(version,
seqnum,
root_hash,
k, N, segsize, datalen,
offsets['signature'],
offsets['share_hash_chain'],
offsets['block_hash_tree'],
offsets['IV'],
offsets['share_data'],
offsets['enc_privkey']) = struct.unpack(">BQ32s" + "BBQQ" + "LLLLLQ")
assert version == 0
signature = data[offsets['signature']:offsets['share_hash_chain']]
share_hash_chain = data[offsets['share_hash_chain']:offsets['block_hash_tree']]
block_hash_tree = data[offsets['block_hash_tree']:offsets['IV']]
IV = data[offsets['IV']:offsets['share_data']]
share_data = data[offsets['share_data']:offsets['share_data']+datalen]
enc_privkey = data[offsets['enc_privkey']:]
def pack_data(self):
# dummy values to satisfy pyflakes until we wire this all up
seqnum, root_hash, k, N, segsize, datalen = 0,0,0,0,0,0
(verification_key, signature, share_hash_chain, block_hash_tree,
IV, share_data, enc_privkey) = ["0"*16] * 7
seqnum += 1
newbuf = [struct.pack(">BQ32s" + "BBQQ",
0, # version byte
seqnum,
root_hash,
k, N, segsize, datalen)]
post_offset = struct.calcsize(">BQ32s" + "BBQQ" + "LLLLLQ")
offsets = {}
o1 = offsets['signature'] = post_offset + len(verification_key)
o2 = offsets['share_hash_chain'] = o1 + len(signature)
o3 = offsets['block_hash_tree'] = o2 + len(share_hash_chain)
assert len(IV) == 16
o4 = offsets['IV'] = o3 + len(block_hash_tree)
o5 = offsets['share_data'] = o4 + len(IV)
o6 = offsets['enc_privkey'] = o5 + len(share_data)
newbuf.append(struct.pack(">LLLLLQ",
offsets['signature'],
offsets['share_hash_chain'],
offsets['block_hash_tree'],
offsets['IV'],
offsets['share_data'],
offsets['enc_privkey']))
newbuf.extend([verification_key,
signature,
share_hash_chain,
block_hash_tree,
IV,
share_data,
enc_privkey])
return "".join(newbuf)
# use client.create_mutable_file() to make one of these