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storage.py : replace 4294967295 with 2**32-1: python does constant folding, I measured this statement as taking 50ns, versus the 400ns for the call to min(), or the 9us required for the 'assert not os.path.exists' syscall

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This commit is contained in:
Brian Warner 2009-01-09 19:52:22 -07:00
parent c7cd3f38e7
commit 167742c2b3
1 changed files with 10 additions and 9 deletions
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19
src/allmydata/storage.py
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@ -112,15 +112,16 @@ class ShareFile:
assert not os.path.exists(self.home)
fileutil.make_dirs(os.path.dirname(self.home))
f = open(self.home, 'wb')
# The second field -- share data length -- is no longer used as of Tahoe v1.3.0, but
# we continue to write it in there in case someone downgrades a storage server from
# >= Tahoe-1.3.0 to < Tahoe-1.3.0, or moves a share file from one server to another,
# etc. We do saturation -- a share data length larger than what can fit into the
# field is marked as the largest length that can fit into the field. That way, even
# if this does happen, the old < v1.3.0 server will still allow clients to read the
# first part of the share. The largest size that will fit in this 4-byte field is
# 2**32-1, or 4294967295.
f.write(struct.pack(">LLL", 1, min(4294967295, max_size), 0))
# The second field -- the four-byte share data length -- is no
# longer used as of Tahoe v1.3.0, but we continue to write it in
# there in case someone downgrades a storage server from >=
# Tahoe-1.3.0 to < Tahoe-1.3.0, or moves a share file from one
# server to another, etc. We do saturation -- a share data length
# larger than 2**32-1 (what can fit into the field) is marked as
# the largest length that can fit into the field. That way, even
# if this does happen, the old < v1.3.0 server will still allow
# clients to read the first part of the share.
f.write(struct.pack(">LLL", 1, min(2**32-1, max_size), 0))
f.close()
self._lease_offset = max_size + 0x0c
self._num_leases = 0