self.file_size = file_size
self.seg_size = seg_size = 1.0 * min(MAX_SEGSIZE, file_size)
self.num_segs = num_segs = math.ceil(file_size / seg_size)
- self.num_subblocks = num_subblocks = num_segs
+ self.num_blocks = num_blocks = num_segs
- self.num_blocks = num_blocks = 100
- self.blocks_needed = blocks_needed = 25
+ self.num_shares = num_shares = 100
+ self.shares_needed = shares_needed = 25
- self.subblock_size = subblock_size = seg_size / blocks_needed
- self.block_size = block_size = subblock_size * num_subblocks
+ self.block_size = block_size = seg_size / shares_needed
+ self.share_size = share_size = block_size * num_blocks
- # none of this includes the block-level hash chain yet, since that is
- # only a function of the number of blocks. All overhead numbers
- # assume that the block-level hash chain has already been sent,
- # including the root of the subblock-level hash tree.
+ # none of this includes the share-level hash chain yet, since that is
+ # only a function of the number of shares. All overhead numbers
+ # assume that the share-level hash chain has already been sent,
+ # including the root of the block-level hash tree.
if mode == "alpha":
# no hash tree at all
- self.subblock_arity = 0
- self.subblock_tree_depth = 0
- self.subblock_overhead = 0
- self.bytes_until_some_data = 20 + block_size
- self.block_storage_overhead = 0
- self.block_transmission_overhead = 0
+ self.block_arity = 0
+ self.block_tree_depth = 0
+ self.block_overhead = 0
+ self.bytes_until_some_data = 20 + share_size
+ self.share_storage_overhead = 0
+ self.share_transmission_overhead = 0
elif mode == "beta":
- # k=num_subblocks, d=1
- # each subblock has a 20-byte hash
- self.subblock_arity = num_subblocks
- self.subblock_tree_depth = 1
- self.subblock_overhead = 20
- # the block has a list of hashes, one for each subblock
- self.block_storage_overhead = (self.subblock_overhead *
- num_subblocks)
- # we can get away with not sending the hash of the block that
+ # k=num_blocks, d=1
+ # each block has a 20-byte hash
+ self.block_arity = num_blocks
+ self.block_tree_depth = 1
+ self.block_overhead = 20
+ # the share has a list of hashes, one for each block
+ self.share_storage_overhead = (self.block_overhead *
+ num_blocks)
+ # we can get away with not sending the hash of the share that
# we're sending in full, once
- self.block_transmission_overhead = self.block_storage_overhead - 20
+ self.share_transmission_overhead = self.share_storage_overhead - 20
# we must get the whole list (so it can be validated) before
# any data can be validated
- self.bytes_until_some_data = (self.block_transmission_overhead +
- subblock_size)
+ self.bytes_until_some_data = (self.share_transmission_overhead +
+ block_size)
elif mode == "gamma":
- self.subblock_arity = k = arity
- d = math.ceil(math.log(num_subblocks, k))
- self.subblock_tree_depth = d
+ self.block_arity = k = arity
+ d = math.ceil(math.log(num_blocks, k))
+ self.block_tree_depth = d
num_leaves = k ** d
# to make things easier, we make the pessimistic assumption that
# we have to store hashes for all the empty places in the tree
- # (when the number of blocks is not an exact exponent of k)
- self.subblock_overhead = 20
- # the subblock hashes are organized into a k-ary tree, which
+ # (when the number of shares is not an exact exponent of k)
+ self.block_overhead = 20
+ # the block hashes are organized into a k-ary tree, which
# means storing (and eventually transmitting) more hashes. This
- # count includes all the low-level block hashes and the root.
+ # count includes all the low-level share hashes and the root.
hash_nodes = (num_leaves*k - 1) / (k - 1)
#print "hash_depth", d
#print "num_leaves", num_leaves
#print "hash_nodes", hash_nodes
# the storage overhead is this
- self.block_storage_overhead = 20 * (hash_nodes - 1)
+ self.share_storage_overhead = 20 * (hash_nodes - 1)
# the transmission overhead is smaller: if we actually transmit
- # every subblock, we don't have to transmit 1/k of the
- # lowest-level subblock hashes, and we don't have to transmit the
- # root because it was already sent with the block-level hash tree
- self.block_transmission_overhead = 20 * (hash_nodes
+ # every block, we don't have to transmit 1/k of the
+ # lowest-level block hashes, and we don't have to transmit the
+ # root because it was already sent with the share-level hash tree
+ self.share_transmission_overhead = 20 * (hash_nodes
- 1 # the root
- num_leaves / k)
# we must get a full sibling hash chain before we can validate
# any data
sibling_length = d * (k-1)
- self.bytes_until_some_data = 20 * sibling_length + subblock_size
+ self.bytes_until_some_data = 20 * sibling_length + block_size
else:
raise RuntimeError("unknown mode '%s" % mode)
- self.storage_overhead = self.block_storage_overhead * num_blocks
+ self.storage_overhead = self.share_storage_overhead * num_shares
self.storage_overhead_percentage = 100.0 * self.storage_overhead / file_size
def dump(self):
for k in ("mode", "file_size", "seg_size",
- "num_segs", "num_subblocks", "num_blocks", "blocks_needed",
- "subblock_size", "block_size",
- "subblock_arity", "subblock_tree_depth",
- "subblock_overhead",
- "block_storage_overhead", "block_transmission_overhead",
+ "num_segs", "num_blocks", "num_shares", "shares_needed",
+ "block_size", "share_size",
+ "block_arity", "block_tree_depth",
+ "block_overhead",
+ "share_storage_overhead", "share_transmission_overhead",
"storage_overhead", "storage_overhead_percentage",
"bytes_until_some_data"):
print k, getattr(self, k)
# 0123456789012345678901234567890123456789012345678901234567890123456
print "mode=%s" % mode, " arity=%d" % arity
print " storage storage"
- print "Size blocksize overhead overhead k d alacrity"
+ print "Size sharesize overhead overhead k d alacrity"
print " (bytes) (%)"
print "------- ------- -------- -------- ---- -- --------"
#sizes = [2 ** i for i in range(7, 41)]
s = Sizes(mode, file_size, arity)
out = ""
out += "%7s " % fmt(file_size, trim=True)
- out += "%7s " % fmt(s.block_size)
+ out += "%7s " % fmt(s.share_size)
out += "%8s" % fmt(s.storage_overhead)
out += "%10.2f " % s.storage_overhead_percentage
- out += " %4d" % int(s.subblock_arity)
- out += " %2d" % int(s.subblock_tree_depth)
+ out += " %4d" % int(s.block_arity)
+ out += " %2d" % int(s.block_tree_depth)
out += " %8s" % fmt(s.bytes_until_some_data)
print out