[MERGE][1.1][#115781] Limit smart protocol reads to 64k to avoid 'no buffer space available' errors on Windows.

[Andrew Bennetts]

Josh Jensen reported that the previous fix to #115781 didn't totally eradicate
the problem for him.  It turns out that reading large amounts from a socket also
has the same problem as writing large amounts, i.e. on Windows it can cause
error 10053 or 10055.

This change limits reads by the smart protocol implementation to 64k, which
seems to be a safe maximum.  Hopefully it shouldn't make a significant impact on
performance.

-Andrew.

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# Bazaar merge directive format 2 (Bazaar 0.90)
# revision_id: andrew.bennetts at canonical.com-20080108053931-\
#   ezafty4oqtnl8j4z
# target_branch: http://bazaar-vcs.org/bzr/bzr.dev
# testament_sha1: d2f071b2b8ee30dafd528c1adf1e47ccd56b754f
# timestamp: 2008-01-08 16:44:27 +1100
# source_branch: http://people.ubuntu.com/~andrew/bzr/windows-recv-\
#   limit
# base_revision_id: pqm at pqm.ubuntu.com-20080107174938-hvwo399dzshh3cod
# 
# Begin patch
=== modified file 'bzrlib/smart/protocol.py'
--- bzrlib/smart/protocol.py	2007-11-09 20:49:54 +0000
+++ bzrlib/smart/protocol.py	2008-01-08 05:39:31 +0000
@@ -543,8 +543,11 @@
             return self._body_buffer.read(count)
         _body_decoder = LengthPrefixedBodyDecoder()
 
+        # Read no more than 64k at a time so that we don't risk error 10055 (no
+        # buffer space available) on Windows.
+        max_read = 64 * 1024
         while not _body_decoder.finished_reading:
-            bytes_wanted = _body_decoder.next_read_size()
+            bytes_wanted = min(_body_decoder.next_read_size(), max_read)
             bytes = self._request.read_bytes(bytes_wanted)
             _body_decoder.accept_bytes(bytes)
         self._request.finished_reading()
@@ -627,9 +630,12 @@
     def read_streamed_body(self):
         """Read bytes from the body, decoding into a byte stream.
         """
+        # Read no more than 64k at a time so that we don't risk error 10055 (no
+        # buffer space available) on Windows.
+        max_read = 64 * 1024
         _body_decoder = ChunkedBodyDecoder()
         while not _body_decoder.finished_reading:
-            bytes_wanted = _body_decoder.next_read_size()
+            bytes_wanted = min(_body_decoder.next_read_size(), max_read)
             bytes = self._request.read_bytes(bytes_wanted)
             _body_decoder.accept_bytes(bytes)
             for body_bytes in iter(_body_decoder.read_next_chunk, None):

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