Python 在IMAP IDLE命令存在后获取电子邮件响应

使用exists响应中的消息总数作为获取uid的方法是否安全

7.3.1。存在响应

内容：无

  The EXISTS response reports the number of messages in the mailbox.
  This response occurs as a result of a SELECT or EXAMINE command,
  and if the size of the mailbox changes (e.g., new messages).

  The update from the EXISTS response MUST be recorded by the
  client.

示例：S:*23存在

应用内输出

2013-02-02 01:24:42-0500 [IMAP4Client (TLSMemoryBIOProtocol),client] C: '0005 IDLE'
2013-02-02 01:24:42-0500 [IMAP4Client (TLSMemoryBIOProtocol),client] S: '+ idling'
2013-02-02 01:25:17-0500 [IMAP4Client (TLSMemoryBIOProtocol),client] S: '* 6 EXISTS'
2013-02-02 01:25:47-0500 [IMAP4Client (TLSMemoryBIOProtocol),client] S: '* 7 EXISTS'

twisted的IMAP客户端协议的修改版本

class IMAP4Client(imap4.IMAP4Client):
    """
        A client with callbacks for greeting messages from an IMAP server and new messages.
        """
    greetDeferred = None

    def __init__(self, *args, **kw):

        # is IDLE active
        self.idle_active = False
        # do we want to support IDLE
        self.idle_enabled = False
        imap4.IMAP4Client.__init__(self, *args, **kw)

    def serverGreeting(self, caps):
        self.serverCapabilities = caps
        if self.greetDeferred is not None:
            d, self.greetDeferred = self.greetDeferred, None
            d.callback(self)

    def enable_IDLE(self):
        print "Enabling Idle...."
        self.idle_enabled = True
        if self.queued == []:# if there is no current command
            # issue the idle command
            cmd = Command("IDLE", continuation = self.idle_continuation)
            d = self.sendCommand(cmd)
            # THEN mark it active NOT BEFORE as, if IDLE is active when a command is sent (such as the above IDLE command) it stops IDLE by sending the DONE line
            self.idle_active = True
            d.addCallback(self.idle_done)
            return d
        else:
            pass # IDLE will be enables when queued commands in waiting are done

    def lineReceived(self, line):
        print "S: %s" % str(repr(line))
        return imap4.IMAP4Client.lineReceived(self, line)

    def sendLine(self, line):
        print "C: %s" % str(repr(line))
        return imap4.IMAP4Client.sendLine(self, line)

    def idle_continuation(self, *args, **kw):
        pass# ignore for now

    def sendCommand(self, cmd):
        cmd.defer = Deferred()

        # checks to see if IDLE command can be enabled when this command is done
        cmd.defer.addCallback(self.command_done)

        if self.idle_active: # if we are waiting for IDLE
            self.sendLine("DONE")
            # append it to the queue and wait for the idle deferred callback
            self.queued.append(cmd)
            return cmd.defer

        if self.waiting:
            self.queued.append(cmd)
            return cmd.defer

        t = self.makeTag()
        self.tags[t] = cmd
        self.sendLine(cmd.format(t))
        self.waiting = t
        self._lastCmd = cmd
        return cmd.defer

    def command_done(self, result):
        print "A command was finished"
        print "Waiting %s" % self.waiting
        print self.queued
        print "IDLE Enabled %s" % self.idle_enabled

        # cannot use if not self.waiting so check if the command queue is empty 
        empty_queue = (self.queued == [])

        if empty_queue and self.idle_enabled: # yay no commands enable IDLE
            print "Enabling idle"
            self.idle_active = True
            # issue the command
            self.idle_active = True
            cmd = Command("IDLE", continuation = self.idle_continuation)
            d = self.sendCommand(cmd)
            d.addCallback(self.idle_done)
            return d
        return result

    def idle_done(self, result):
        print "IDLE Done"
        self.idle_active = False
        # twisted's own handling of the command queue should handle sending the next command
        # so there is no need to grab the next command as when the OK Response after DONE 
        # trigger it

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我认为，使用邮箱中的邮件数量是“足够安全的”，前提是您立即采取行动，并且在需要显示邮箱时，如果邮箱突然不同（可能是另一个客户端删除了一封邮件），您可以返回到搜索。这实际上只适用于非破坏性操作，因此，如果您确实需要使用它，请谨慎使用“删除”。

嗯。。。“安全”？如果你没有控制核电站，那么可能。这里有一条经验法则：当你的软件失败时会有人受伤吗？如果没有，它所做的一切都是安全的

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“正确”怎么样？不，这是不正确的，因为EXISTS响应告诉您邮箱中存在多少邮件。它不会告诉您其中任何一个的UID。

好吧，这就是我的想法，因为它的目标只是获取UID，然后在发送exists命令时获取实际消息。