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1# Copyright (c) 2012 The Chromium Authors. All rights reserved.
2# Use of this source code is governed by a BSD-style license that can be
3# found in the LICENSE file.
4
5# This file is based on gdb_rsp.py file from NaCl repository.
6
7import re
8import socket
9import time
10
11
12def RspChecksum(data):
13  checksum = 0
14  for char in data:
15    checksum = (checksum + ord(char)) % 0x100
16  return checksum
17
18
19class GdbRspConnection(object):
20
21  def __init__(self, addr):
22    self._socket = self._Connect(addr)
23
24  def _Connect(self, addr):
25    # We have to poll because we do not know when sel_ldr has
26    # successfully done bind() on the TCP port.  This is inherently
27    # unreliable.
28    # TODO(mseaborn): Add a more reliable connection mechanism to
29    # sel_ldr's debug stub.
30    timeout_in_seconds = 10
31    poll_time_in_seconds = 0.1
32    for i in xrange(int(timeout_in_seconds / poll_time_in_seconds)):
33      # On Mac OS X, we have to create a new socket FD for each retry.
34      sock = socket.socket()
35      try:
36        sock.connect(addr)
37      except socket.error:
38        # Retry after a delay.
39        time.sleep(poll_time_in_seconds)
40      else:
41        return sock
42    raise Exception('Could not connect to sel_ldr\'s debug stub in %i seconds'
43                    % timeout_in_seconds)
44
45  def _GetReply(self):
46    reply = ''
47    while True:
48      data = self._socket.recv(1024)
49      if len(data) == 0:
50        raise AssertionError('EOF on socket reached with '
51                             'incomplete reply message: %r' % reply)
52      reply += data
53      if '#' in data:
54        break
55    match = re.match('\+\$([^#]*)#([0-9a-fA-F]{2})$', reply)
56    if match is None:
57      raise AssertionError('Unexpected reply message: %r' % reply)
58    reply_body = match.group(1)
59    checksum = match.group(2)
60    expected_checksum = '%02x' % RspChecksum(reply_body)
61    if checksum != expected_checksum:
62      raise AssertionError('Bad RSP checksum: %r != %r' %
63                           (checksum, expected_checksum))
64    # Send acknowledgement.
65    self._socket.send('+')
66    return reply_body
67
68  # Send an rsp message, but don't wait for or expect a reply.
69  def RspSendOnly(self, data):
70    msg = '$%s#%02x' % (data, RspChecksum(data))
71    return self._socket.send(msg)
72
73  def RspRequest(self, data):
74    self.RspSendOnly(data)
75    return self._GetReply()
76
77  def RspInterrupt(self):
78    self._socket.send('\x03')
79    return self._GetReply()
80