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wireprotov2peer: stream decoded responses...
wireprotov2peer: stream decoded responses Previously, wire protocol version 2 would buffer all response data. Only once all data was received did we CBOR decode it and resolve the future associated with the command. This was obviously not desirable. In future commits that introduce large response payloads, this caused significant memory bloat and slowed down client operations due to waiting on the server. This commit refactors the response handling code so that response data can be streamed. Command response objects now contain a buffered CBOR decoder. As new data arrives, it is fed into the decoder. Decoded objects are made available to the generator as they are decoded. Because there is a separate thread processing incoming frames and feeding data into the response object, there is the potential for race conditions when mutating response objects. So a lock has been added to guard access to critical state variables. Because the generator emitting decoded objects needs to wait on those objects to become available, we've added an Event for the generator to wait on so it doesn't busy loop. This does mean there is the potential for deadlocks. And I'm pretty sure they can occur in some scenarios. We already have a handful of TODOs around this. But I've added some more. Fixing this will likely require moving the background thread receiving frames into clienthandler. We likely would have done this anyway when implementing the client bits for the SSH transport. Test output changes because the initial CBOR map holding the overall response state is now always handled internally by the response object. Differential Revision: https://phab.mercurial-scm.org/D4474

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diffhelper.py
78 lines | 2.2 KiB | text/x-python | PythonLexer
# diffhelper.py - helper routines for patch
#
# Copyright 2009 Matt Mackall <mpm@selenic.com> and others
#
# This software may be used and distributed according to the terms of the
# GNU General Public License version 2 or any later version.
from __future__ import absolute_import
from .i18n import _
from . import (
error,
pycompat,
)
def addlines(fp, hunk, lena, lenb, a, b):
"""Read lines from fp into the hunk
The hunk is parsed into two arrays, a and b. a gets the old state of
the text, b gets the new state. The control char from the hunk is saved
when inserting into a, but not b (for performance while deleting files.)
"""
while True:
todoa = lena - len(a)
todob = lenb - len(b)
num = max(todoa, todob)
if num == 0:
break
for i in pycompat.xrange(num):
s = fp.readline()
if not s:
raise error.ParseError(_('incomplete hunk'))
if s == "\\ No newline at end of file\n":
fixnewline(hunk, a, b)
continue
if s == '\n' or s == '\r\n':
# Some patches may be missing the control char
# on empty lines. Supply a leading space.
s = ' ' + s
hunk.append(s)
if s.startswith('+'):
b.append(s[1:])
elif s.startswith('-'):
a.append(s)
else:
b.append(s[1:])
a.append(s)
def fixnewline(hunk, a, b):
"""Fix up the last lines of a and b when the patch has no newline at EOF"""
l = hunk[-1]
# tolerate CRLF in last line
if l.endswith('\r\n'):
hline = l[:-2]
else:
hline = l[:-1]
if hline.startswith((' ', '+')):
b[-1] = hline[1:]
if hline.startswith((' ', '-')):
a[-1] = hline
hunk[-1] = hline
def testhunk(a, b, bstart):
"""Compare the lines in a with the lines in b
a is assumed to have a control char at the start of each line, this char
is ignored in the compare.
"""
alen = len(a)
blen = len(b)
if alen > blen - bstart or bstart < 0:
return False
for i in pycompat.xrange(alen):
if a[i][1:] != b[i + bstart]:
return False
return True