xref: /openbmc/u-boot/test/py/u_boot_spawn.py (revision dffceb4b) 
1# Copyright (c) 2015-2016, NVIDIA CORPORATION. All rights reserved.
2#
3# SPDX-License-Identifier: GPL-2.0
4
5# Logic to spawn a sub-process and interact with its stdio.
6
7import os
8import re
9import pty
10import signal
11import select
12import time
13
14class Timeout(Exception):
15    """An exception sub-class that indicates that a timeout occurred."""
16    pass
17
18class Spawn(object):
19    """Represents the stdio of a freshly created sub-process. Commands may be
20    sent to the process, and responses waited for.
21    """
22
23    def __init__(self, args, cwd=None):
24        """Spawn (fork/exec) the sub-process.
25
26        Args:
27            args: array of processs arguments. argv[0] is the command to
28              execute.
29            cwd: the directory to run the process in, or None for no change.
30
31        Returns:
32            Nothing.
33        """
34
35        self.waited = False
36        self.buf = ''
37        self.logfile_read = None
38        self.before = ''
39        self.after = ''
40        self.timeout = None
41
42        (self.pid, self.fd) = pty.fork()
43        if self.pid == 0:
44            try:
45                # For some reason, SIGHUP is set to SIG_IGN at this point when
46                # run under "go" (www.go.cd). Perhaps this happens under any
47                # background (non-interactive) system?
48                signal.signal(signal.SIGHUP, signal.SIG_DFL)
49                if cwd:
50                    os.chdir(cwd)
51                os.execvp(args[0], args)
52            except:
53                print 'CHILD EXECEPTION:'
54                import traceback
55                traceback.print_exc()
56            finally:
57                os._exit(255)
58
59        self.poll = select.poll()
60        self.poll.register(self.fd, select.POLLIN | select.POLLPRI | select.POLLERR | select.POLLHUP | select.POLLNVAL)
61
62    def kill(self, sig):
63        """Send unix signal "sig" to the child process.
64
65        Args:
66            sig: The signal number to send.
67
68        Returns:
69            Nothing.
70        """
71
72        os.kill(self.pid, sig)
73
74    def isalive(self):
75        """Determine whether the child process is still running.
76
77        Args:
78            None.
79
80        Returns:
81            Boolean indicating whether process is alive.
82        """
83
84        if self.waited:
85            return False
86
87        w = os.waitpid(self.pid, os.WNOHANG)
88        if w[0] == 0:
89            return True
90
91        self.waited = True
92        return False
93
94    def send(self, data):
95        """Send data to the sub-process's stdin.
96
97        Args:
98            data: The data to send to the process.
99
100        Returns:
101            Nothing.
102        """
103
104        os.write(self.fd, data)
105
106    def expect(self, patterns):
107        """Wait for the sub-process to emit specific data.
108
109        This function waits for the process to emit one pattern from the
110        supplied list of patterns, or for a timeout to occur.
111
112        Args:
113            patterns: A list of strings or regex objects that we expect to
114                see in the sub-process' stdout.
115
116        Returns:
117            The index within the patterns array of the pattern the process
118            emitted.
119
120        Notable exceptions:
121            Timeout, if the process did not emit any of the patterns within
122            the expected time.
123        """
124
125        for pi in xrange(len(patterns)):
126            if type(patterns[pi]) == type(''):
127                patterns[pi] = re.compile(patterns[pi])
128
129        tstart_s = time.time()
130        try:
131            while True:
132                earliest_m = None
133                earliest_pi = None
134                for pi in xrange(len(patterns)):
135                    pattern = patterns[pi]
136                    m = pattern.search(self.buf)
137                    if not m:
138                        continue
139                    if earliest_m and m.start() >= earliest_m.start():
140                        continue
141                    earliest_m = m
142                    earliest_pi = pi
143                if earliest_m:
144                    pos = earliest_m.start()
145                    posafter = earliest_m.end() + 1
146                    self.before = self.buf[:pos]
147                    self.after = self.buf[pos:posafter]
148                    self.buf = self.buf[posafter:]
149                    return earliest_pi
150                tnow_s = time.time()
151                tdelta_ms = (tnow_s - tstart_s) * 1000
152                if tdelta_ms > self.timeout:
153                    raise Timeout()
154                events = self.poll.poll(self.timeout - tdelta_ms)
155                if not events:
156                    raise Timeout()
157                c = os.read(self.fd, 1024)
158                if not c:
159                    raise EOFError()
160                if self.logfile_read:
161                    self.logfile_read.write(c)
162                self.buf += c
163        finally:
164            if self.logfile_read:
165                self.logfile_read.flush()
166
167    def close(self):
168        """Close the stdio connection to the sub-process.
169
170        This also waits a reasonable time for the sub-process to stop running.
171
172        Args:
173            None.
174
175        Returns:
176            Nothing.
177        """
178
179        os.close(self.fd)
180        for i in xrange(100):
181            if not self.isalive():
182                break
183            time.sleep(0.1)
184