From: Kevan Carstensen <kevan@isnotajoke.com>
Date: Sat, 13 Aug 2011 18:38:33 +0000 (-0700)
Subject: mutable/retrieve.py: use floor division to calculate segment boundaries, don't fetch... 
X-Git-Tag: trac-5200~1
X-Git-Url: https://git.rkrishnan.org/%5B/%5D%20/uri/index.php?a=commitdiff_plain;h=3423b7d6f78629a15fc4da9705e5e03469b48661;p=tahoe-lafs%2Ftahoe-lafs.git

mutable/retrieve.py: use floor division to calculate segment boundaries, don't fetch more segments than necessary
---

diff --git a/src/allmydata/mutable/retrieve.py b/src/allmydata/mutable/retrieve.py
index d5f17111..cd67f836 100644
--- a/src/allmydata/mutable/retrieve.py
+++ b/src/allmydata/mutable/retrieve.py
@@ -385,11 +385,7 @@ class Retrieve:
             self.log("got offset: %d" % self._offset)
             # our start segment is the first segment containing the
             # offset we were given. 
-            start = mathutil.div_ceil(self._offset,
-                                      self._segment_size)
-            # this gets us the first segment after self._offset. Then
-            # our start segment is the one before it.
-            start -= 1
+            start = self._offset // self._segment_size
 
             assert start < self._num_segments
             self._start_segment = start
@@ -403,9 +399,11 @@ class Retrieve:
             # segment that we were asked to read.
             self.log("got read length %d" % self._read_length)
             end_data = self._offset + self._read_length
-            end = mathutil.div_ceil(end_data,
-                                    self._segment_size)
-            end -= 1
+            # We don't actually need to read the byte at end_data, but
+            # the one before it.
+            end_data = end_data - 1
+            end = end_data // self._segment_size
+
             assert end < self._num_segments
             self._last_segment = end
             self.log("got end segment: %d" % self._last_segment)