From b2dbc2dcc05cde0256947fce42a9774a4bac4af8 Mon Sep 17 00:00:00 2001
From: Jean-Paul Calderone <exarkun@twistedmatrix.com>
Date: Tue, 10 Mar 2020 11:11:21 -0400
Subject: [PATCH] Slightly simplify the bucket size reading code
---
src/_zkapauthorizer/_storage_server.py | 25 ++++++++++++++++---------
1 file changed, 16 insertions(+), 9 deletions(-)
diff --git a/src/_zkapauthorizer/_storage_server.py b/src/_zkapauthorizer/_storage_server.py
index d49939d..e7d16a7 100644
--- a/src/_zkapauthorizer/_storage_server.py
+++ b/src/_zkapauthorizer/_storage_server.py
@@ -26,6 +26,7 @@ from __future__ import (
from struct import (
unpack,
+ calcsize,
)
from errno import (
@@ -507,16 +508,22 @@ def get_storage_index_share_size(sharepath):
:return int: The data size of the share in bytes.
"""
+ # Note Tahoe-LAFS immutable/layout.py makes some claims about how the
+ # share data is structured. A lot of this seems to be wrong.
+ # storage/immutable.py appears to have the correct information.
+ fmt = ">LL"
with open(sharepath) as share_file:
- share_data_length_bytes = share_file.read(8)[4:]
- if len(share_data_length_bytes) != 4:
- raise ValueError(
- "Tried to read 4 bytes of share data length from share, got {!r} instead.".format(
- share_data_length_bytes,
- ),
- )
- (share_data_length,) = unpack('>L', share_data_length_bytes)
- return share_data_length
+ header = share_file.read(calcsize(fmt))
+
+ if len(share_data_length_bytes) != calcsize(fmt):
+ raise ValueError(
+ "Tried to read 4 bytes of share data length from share, got {!r} instead.".format(
+ share_data_length_bytes,
+ ),
+ )
+
+ version, share_data_length = unpack(fmt, header)
+ return share_data_length
def get_lease_expiration(get_leases, storage_index_or_slot):
--
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