tobias/docker-offlineimap
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Simplify & document savemessage_getnewheader

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savemessage_getnewheader was an undocmented, cryptic and overengineered
function. It generates a new unique value that can be used as a mail
header to be inserted. For this it used LOTS of randomness sources: hash
of the mail content, hash of the folder name, hash of the repository
name, the current time, a random() value, and the offlineimap version string.
All we need is something random. So reduce this to hash of content
appended by a random integer. Sufficient and somewhat faster to calculate.

Rename the function to actually describe accurately what it does or
would you have guessed that savemessage_getnewheader() did nothing more
than returning ('X-OfflineIMAP', <randomstring> )? Rename to
generate_randomheader() to make it clearer what this is all about.

Also document the function, describing what it does, and what it returns.

Signed-off-by: Sebastian Spaeth <Sebastian@SSpaeth.de>
Signed-off-by: Nicolas Sebrecht <nicolas.s-dev@laposte.net>
This commit is contained in:
Sebastian Spaeth 2011-03-04 17:34:20 +01:00 committed by Nicolas Sebrecht
parent a271f90271
commit 419f27418e
1 changed files with 26 additions and 10 deletions
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36
offlineimap/folder/IMAP.py
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@ -25,7 +25,7 @@ import time
from StringIO import StringIO
from copy import copy
from Base import BaseFolder
from offlineimap import imaputil, imaplibutil, __version__
from offlineimap import imaputil, imaplibutil
class IMAPFolder(BaseFolder):
def __init__(self, imapserver, name, visiblename, accountname, repository):
@ -226,14 +226,30 @@ class IMAPFolder(BaseFolder):
def getmessageflags(self, uid):
return self.messagelist[uid]['flags']
def savemessage_getnewheader(self, content):
def generate_randomheader(self, content):
"""Returns a unique X-OfflineIMAP header
Generate an 'X-OfflineIMAP' mail header which contains a random
unique value (which is based on the mail content, and a random
number). This header allows us to fetch a mail after APPENDing
it to an IMAP server and thus find out the UID that the server
assigned it.
:returns: (headername, headervalue) tuple, consisting of strings
headername == 'X-OfflineIMAP' and headervalue will be a
random string
"""
headername = 'X-OfflineIMAP'
headervalue = '%s-' % str(binascii.crc32(content)).replace('-', 'x')
headervalue += binascii.hexlify(self.repository.getname()) + '-'
headervalue += binascii.hexlify(self.getname())
headervalue += '-%d-' % long(time.time())
headervalue += str(self.randomgenerator.random()).replace('.', '')
headervalue += '-v' + __version__
# We need a random component too. If we ever upload the same
# mail twice (e.g. in different folders), we would still need to
# get the UID for the correct one. As we won't have too many
# mails with identical content, the randomness requirements are
# not extremly critial though.
# compute unsigned crc32 of 'content' as unique hash
# NB: crc32 returns unsigned only starting with python 3.0
headervalue = str( binascii.crc32(content) & 0xffffffff ) + '-'
headervalue += str(self.randomgenerator.randint(0,9999999999))
return (headername, headervalue)
def savemessage_addheader(self, content, headername, headervalue):
@ -332,8 +348,8 @@ class IMAPFolder(BaseFolder):
content = re.sub("(?<!\r)\n", "\r\n", content)
self.ui.debug('imap', 'savemessage: initial content is: ' + repr(content))
(headername, headervalue) = self.savemessage_getnewheader(content)
self.ui.debug('imap', 'savemessage: new headers are: %s: %s' % \
(headername, headervalue) = self.generate_randomheader(content)
ui.debug('imap', 'savemessage: new headers are: %s: %s' % \
(headername, headervalue))
content = self.savemessage_addheader(content, headername,
headervalue)