Python errno 模块，EINTR 实例源码

def test_get_messages_retries_on_IOError_EINTR(
        self,
        consumer_instance,
        publish_messages,
        message
    ):
        with consumer_instance as consumer:
            publish_messages(message, count=1)
            real_consumer_group_next = consumer.consumer_group.next
            with mock.patch.object(
                consumer.consumer_group,
                'next',
                side_effect=[
                    IOError(errno.EINTR, 'Interrupted system call'),
                    real_consumer_group_next()
                ]
            ) as mock_consumer_group_next:
                messages = consumer.get_messages(
                    count=1,
                    blocking=True,
                    timeout=TIMEOUT
                )
                assert len(messages) == 1
                assert mock_consumer_group_next.call_count == 2

def _get_next_kafka_message(
            self,
            blocking,
            has_timeout,
            max_time
    ):
        """ Helper function which will retry when encountering an IOError with
        the errno of EINTR. This is now standard behavior in Python3.5. For
        more details see https://www.python.org/dev/peps/pep-0475/
        """
        while not self._break_consume_loop(blocking, has_timeout, max_time):
            try:
                return self.consumer_group.next()
            except IOError as e:
                if e.errno != errno.EINTR:
                    raise
        return None

def _flush_unlocked(self):
        if self.closed:
            raise ValueError("flush of closed file")
        written = 0
        try:
            while self._write_buf:
                try:
                    n = self.raw.write(self._write_buf)
                except IOError as e:
                    if e.errno != EINTR:
                        raise
                    continue
                if n > len(self._write_buf) or n < 0:
                    raise IOError("write() returned incorrect number of bytes")
                del self._write_buf[:n]
                written += n
        except BlockingIOError as e:
            n = e.characters_written
            del self._write_buf[:n]
            written += n
            raise BlockingIOError(e.errno, e.strerror, written)

def _receive_data_on_socket(sock, length):
    msg = b""
    while length:
        try:
            chunk = sock.recv(length)
        except (IOError, OSError) as exc:
            err = None
            if hasattr(exc, 'errno'):
                err = exc.errno
            elif exc.args:
                err = exc.args[0]
            if err == errno.EINTR:
                continue
            raise
        if chunk == b"":
            raise AutoReconnect("connection closed")

        length -= len(chunk)
        msg += chunk

    return msg

def _check_rc(rc, errno=None):
    """internal utility for checking zmq return condition

    and raising the appropriate Exception class
    """
    if rc == -1:
        if errno is None:
            from zmq.backend import zmq_errno
            errno = zmq_errno()
        from zmq import EAGAIN, ETERM
        if errno == EINTR:
            raise InterruptedSystemCall(errno)
        elif errno == EAGAIN:
            raise Again(errno)
        elif errno == ETERM:
            raise ContextTerminated(errno)
        else:
            raise ZMQError(errno)

def _wait_for(fd, readable, writable, error, expiration):
    done = False
    while not done:
        if expiration is None:
            timeout = None
        else:
            timeout = expiration - time.time()
            if timeout <= 0.0:
                raise dns.exception.Timeout
        try:
            if not _polling_backend(fd, readable, writable, error, timeout):
                raise dns.exception.Timeout
        except select_error as e:
            if e.args[0] != errno.EINTR:
                raise e
        done = True

def _read(self, N):
        # Starting with Python 3 open with buffering=0 returns a FileIO object.
        # FileIO.read behaves like read(2) and not like fread(3) and thus we
        # have to handle the case that read returns less data as requested here
        # more carefully.
        data = b("")
        while len(data) < N:
            try:
                d = self.__file.read(N - len(data))
            except IOError, e:
                # read(2) has been interrupted by a signal; redo the read
                if e.errno == errno.EINTR:
                    continue
                raise

            if d is None:
                # __file is in non-blocking mode and no data is available
                return data
            if len(d) == 0:
                # __file is in blocking mode and arrived at EOF
                return data

            data += d
        return data

def writeSomeData(self, data):
        """Connection.writeSomeData(data) -> #of bytes written | CONNECTION_LOST
        This writes as much data as possible to the socket and returns either
        the number of bytes read (which is positive) or a connection error code
        (which is negative)
        """
        try:
            # Limit length of buffer to try to send, because some OSes are too
            # stupid to do so themselves (ahem windows)
            return self.socket.send(buffer(data, 0, self.SEND_LIMIT))
        except socket.error, se:
            if se.args[0] == EINTR:
                return self.writeSomeData(data)
            elif se.args[0] in (EWOULDBLOCK, ENOBUFS):
                return 0
            else:
                return main.CONNECTION_LOST

def doRead(self):
        """Called when my socket is ready for reading."""
        read = 0
        while read < self.maxThroughput:
            try:
                data, addr = self.socket.recvfrom(self.maxPacketSize)
            except socket.error, se:
                no = se.args[0]
                if no in (EAGAIN, EINTR, EWOULDBLOCK):
                    return
                if (no == ECONNREFUSED) or (platformType == "win32" and no == WSAECONNRESET):
                    if self._connectedAddr:
                        self.protocol.connectionRefused()
                else:
                    raise
            else:
                read += len(data)
                try:
                    self.protocol.datagramReceived(data, addr)
                except:
                    log.err()

def doRead(self):
        """Called when my socket is ready for reading."""
        read = 0
        while read < self.maxThroughput:
            try:
                data, addr = self.socket.recvfrom(self.maxPacketSize)
                read += len(data)
                self.protocol.datagramReceived(data)
            except socket.error, se:
                no = se.args[0]
                if no in (EAGAIN, EINTR, EWOULDBLOCK):
                    return
                if (no == ECONNREFUSED) or (platformType == "win32" and no == WSAECONNRESET):
                    self.protocol.connectionRefused()
                else:
                    raise
            except:
                log.deferr()

def poll(self, flag=os.WNOHANG):
            if self.returncode is None:
                while True:
                    try:
                        pid, sts = os.waitpid(self.pid, flag)
                    except os.error as e:
                        if e.errno == errno.EINTR:
                            continue
                        # Child process not yet created. See #1731717
                        # e.errno == errno.ECHILD == 10
                        return None
                    else:
                        break
                if pid == self.pid:
                    if os.WIFSIGNALED(sts):
                        self.returncode = -os.WTERMSIG(sts)
                    else:
                        assert os.WIFEXITED(sts)
                        self.returncode = os.WEXITSTATUS(sts)
            return self.returncode

def _peek_unlocked(self, n=0):
        want = min(n, self.buffer_size)
        have = len(self._read_buf) - self._read_pos
        if have < want or have <= 0:
            to_read = self.buffer_size - have
            while True:
                try:
                    current = self.raw.read(to_read)
                except IOError as e:
                    if e.errno != EINTR:
                        raise
                    continue
                break
            if current:
                self._read_buf = self._read_buf[self._read_pos:] + current
                self._read_pos = 0
        return self._read_buf[self._read_pos:]

def _flush_unlocked(self):
        if self.closed:
            raise ValueError("flush of closed file")
        while self._write_buf:
            try:
                n = self.raw.write(self._write_buf)
            except BlockingIOError:
                raise RuntimeError("self.raw should implement RawIOBase: it "
                                   "should not raise BlockingIOError")
            except IOError as e:
                if e.errno != EINTR:
                    raise
                continue
            if n is None:
                raise BlockingIOError(
                    errno.EAGAIN,
                    "write could not complete without blocking", 0)
            if n > len(self._write_buf) or n < 0:
                raise IOError("write() returned incorrect number of bytes")
            del self._write_buf[:n]

def _wait_for(fd, readable, writable, error, expiration):
    done = False
    while not done:
        if expiration is None:
            timeout = None
        else:
            timeout = expiration - time.time()
            if timeout <= 0.0:
                raise dns.exception.Timeout
        try:
            if not _polling_backend(fd, readable, writable, error, timeout):
                raise dns.exception.Timeout
        except select.error, e:
            if e.args[0] != errno.EINTR:
                raise e
        done = True

def read(self, get_name=True):
        buf = []
        while True:
            num = self._read(self._inotify_fd, self._buf, len(self._buf))
            if num == 0:
                break
            if num < 0:
                en = ctypes.get_errno()
                if en == errno.EAGAIN:
                    break  # No more data
                if en == errno.EINTR:
                    continue  # Interrupted, try again
                raise OSError(en, self.os.strerror(en))
            buf.append(self._buf.raw[:num])
        raw = b''.join(buf)
        pos = 0
        lraw = len(raw)
        while lraw - pos >= self.hdr.size:
            wd, mask, cookie, name_len = self.hdr.unpack_from(raw, pos)
            pos += self.hdr.size
            name = None
            if get_name:
                name = raw[pos:pos + name_len].rstrip(b'\0')
            pos += name_len
            self.process_event(wd, mask, cookie, name)

def get_event(self, block=1):
        while self.event_queue.empty():
            while 1:
                # All hail Unix!
                try:
                    self.push_char(os.read(self.input_fd, 1))
                except (IOError, OSError) as err:
                    if err.errno == errno.EINTR:
                        if not self.event_queue.empty():
                            return self.event_queue.get()
                        else:
                            continue
                    else:
                        raise
                else:
                    break
            if not block:
                break
        return self.event_queue.get()

def _read(self, N):
        # Starting with Python 3 open with buffering=0 returns a FileIO object.
        # FileIO.read behaves like read(2) and not like fread(3) and thus we
        # have to handle the case that read returns less data as requested here
        # more carefully.
        data = b("")
        while len(data) < N:
            try:
                d = self.__file.read(N - len(data))
            except IOError, e:
                # read(2) has been interrupted by a signal; redo the read
                if e.errno == errno.EINTR:
                    continue
                raise

            if d is None:
                # __file is in non-blocking mode and no data is available
                return data
            if len(d) == 0:
                # __file is in blocking mode and arrived at EOF
                return data

            data += d
        return data

def _read_timeout(self, timeout):
        if PY22:
            return self._py22_read_timeout(timeout)
        start = time.time()
        while True:
            try:
                x = self.__socket.recv(128)
                if len(x) == 0:
                    raise EOFError()
                break
            except socket.timeout:
                pass
            except EnvironmentError, e:
                if ((type(e.args) is tuple) and (len(e.args) > 0) and
                    (e.args[0] == errno.EINTR)):
                    pass
                else:
                    raise
            if self.__closed:
                raise EOFError()
            now = time.time()
            if now - start >= timeout:
                raise socket.timeout()
        return x

def _read_bytes(self, num_bytes):
        self._sock.settimeout(self._read_timeout)
        while True:
            try:
                data = self._rfile.read(num_bytes)
                break
            except (IOError, OSError) as e:
                if e.errno == errno.EINTR:
                    continue
                self._force_close()
                raise err.OperationalError(
                    CR.CR_SERVER_LOST,
                    "Lost connection to MySQL server during query (%s)" % (e,))
        if len(data) < num_bytes:
            self._force_close()
            raise err.OperationalError(
                CR.CR_SERVER_LOST, "Lost connection to MySQL server during query")
        return data

def readinto(self, b):
        """Read up to len(b) bytes into the writable buffer *b* and return
        the number of bytes read.  If the socket is non-blocking and no bytes
        are available, None is returned.

        If *b* is non-empty, a 0 return value indicates that the connection
        was shutdown at the other end.
        """
        self._checkClosed()
        self._checkReadable()
        if self._timeout_occurred:
            raise IOError("cannot read from timed out object")
        while True:
            try:
                return self._sock.recv_into(b)
            except timeout:
                self._timeout_occurred = True
                raise
            except error as e:
                n = e.args[0]
                if n == EINTR:
                    continue
                if n in _blocking_errnos:
                    return None
                raise

def _wait_for(fd, readable, writable, error, expiration):
    done = False
    while not done:
        if expiration is None:
            timeout = None
        else:
            timeout = expiration - time.time()
            if timeout <= 0.0:
                raise dns.exception.Timeout
        try:
            if not _polling_backend(fd, readable, writable, error, timeout):
                raise dns.exception.Timeout
        except select.error, e:
            if e.args[0] != errno.EINTR:
                raise e
        done = True

def _read_bytes(self, num_bytes):
        self._sock.settimeout(self._read_timeout)
        while True:
            try:
                data = self._rfile.read(num_bytes)
                break
            except (IOError, OSError) as e:
                if e.errno == errno.EINTR:
                    continue
                raise err.OperationalError(
                    2013,
                    "Lost connection to MySQL server during query (%s)" % (e,))
        if len(data) < num_bytes:
            raise err.OperationalError(
                2013, "Lost connection to MySQL server during query")
        return data

def readinto(self, b):
        """Read up to len(b) bytes into the writable buffer *b* and return
        the number of bytes read.  If the socket is non-blocking and no bytes
        are available, None is returned.

        If *b* is non-empty, a 0 return value indicates that the connection
        was shutdown at the other end.
        """
        self._checkClosed()
        self._checkReadable()
        if self._timeout_occurred:
            raise IOError("cannot read from timed out object")
        while True:
            try:
                return self._sock.recv_into(b)
            except timeout:
                self._timeout_occurred = True
                raise
            except error as e:
                n = e.args[0]
                if n == EINTR:
                    continue
                if n in _blocking_errnos:
                    return None
                raise

def non_polling_read(self, read_length, timeout):
        data = ''
        bytes_left = read_length

        while bytes_left > 0:
            try:
                ready, _, _ = select.select([self._sock.fileno()], [], [], timeout)

                if not ready:
                    raise NetBIOSTimeout

                received = self._sock.recv(bytes_left)
                if len(received) == 0:
                    raise NetBIOSError, ('Error while reading from remote', ERRCLASS_OS, None)

                data = data + received
                bytes_left = read_length - len(data)
            except select.error, ex:
                if ex[0] != errno.EINTR and ex[0] != errno.EAGAIN:
                    raise NetBIOSError, ('Error occurs while reading from remote', ERRCLASS_OS, ex[0])

        return data

def _wait_for(ir, iw, ix, expiration):
    done = False
    while not done:
        if expiration is None:
            timeout = None
        else:
            timeout = expiration - time.time()
            if timeout <= 0.0:
                raise dns.exception.Timeout
        try:
            if timeout is None:
                (r, w, x) = select.select(ir, iw, ix)
            else:
                (r, w, x) = select.select(ir, iw, ix, timeout)
        except select.error, e:
            if e.args[0] != errno.EINTR:
                raise e
        done = True
        if len(r) == 0 and len(w) == 0 and len(x) == 0:
            raise dns.exception.Timeout

def _read(self, N):
        # Starting with Python 3 open with buffering=0 returns a FileIO object.
        # FileIO.read behaves like read(2) and not like fread(3) and thus we
        # have to handle the case that read returns less data as requested here
        # more carefully.
        data = b("")
        while len(data) < N:
            try:
                d = self.__file.read(N - len(data))
            except IOError, e:
                # read(2) has been interrupted by a signal; redo the read
                if e.errno == errno.EINTR:
                    continue
                raise

            if d is None:
                # __file is in non-blocking mode and no data is available
                return data
            if len(d) == 0:
                # __file is in blocking mode and arrived at EOF
                return data

            data += d
        return data

def run(command):
    child_pid = os.fork()
    if child_pid == 0:
        os.execlp(command[0], *command)
    else:
        while True:
            try:
                os.waitpid(child_pid, 0)
            except OSError as error:
                if error.errno == errno.ECHILD:
                    # No child processes.
                    # It has exited already.
                    break
                elif error.errno == errno.EINTR:
                    # Interrupted system call.
                    # This happens when resizing the terminal.
                    pass
                else:
                    # An actual error occurred.
                    raise

def _read(self, N):
        # Starting with Python 3 open with buffering=0 returns a FileIO object.
        # FileIO.read behaves like read(2) and not like fread(3) and thus we
        # have to handle the case that read returns less data as requested here
        # more carefully.
        data = b("")
        while len(data) < N:
            try:
                d = self.__file.read(N - len(data))
            except IOError, e:
                # read(2) has been interrupted by a signal; redo the read
                if e.errno == errno.EINTR:
                    continue
                raise

            if d is None:
                # __file is in non-blocking mode and no data is available
                return data
            if len(d) == 0:
                # __file is in blocking mode and arrived at EOF
                return data

            data += d
        return data

def sleep(self):
        """\
        Sleep until PIPE is readable or we timeout.
        A readable PIPE means a signal occurred.
        """
        try:
            ready = select.select([self.PIPE[0]], [], [], 1.0)
            if not ready[0]:
                return
            while os.read(self.PIPE[0], 1):
                pass
        except select.error as e:
            if e.args[0] not in [errno.EAGAIN, errno.EINTR]:
                raise
        except OSError as e:
            if e.errno not in [errno.EAGAIN, errno.EINTR]:
                raise
        except KeyboardInterrupt:
            sys.exit()

def wait(self, timeout):
        try:
            self.notify()
            ret = select.select(self.sockets, [], self.PIPE, timeout)
            if ret[0]:
                return ret[0]

        except select.error as e:
            if e.args[0] == errno.EINTR:
                return self.sockets
            if e.args[0] == errno.EBADF:
                if self.nr < 0:
                    return self.sockets
                else:
                    raise StopWaiting
            raise

def test_selector_raises_timeout_error_on_interrupt_over_time(self):
        selectors2._DEFAULT_SELECTOR = None

        mock_socket = mock.Mock()
        mock_socket.fileno.return_value = 1

        def slow_interrupting_select(*args, **kwargs):
            time.sleep(0.2)
            error = OSError()
            error.errno = errno.EINTR
            raise error

        patch_select_module(self, select=slow_interrupting_select)

        selector = self.make_selector()
        selector.register(mock_socket, selectors2.EVENT_READ)

        try:
            selector.select(timeout=0.1)
        except OSError as e:
            self.assertEqual(e.errno, errno.ETIMEDOUT)
        else:
            self.fail('Didn\'t raise an OSError')

def _wait_for(fd, readable, writable, error, expiration):
    done = False
    while not done:
        if expiration is None:
            timeout = None
        else:
            timeout = expiration - time.time()
            if timeout <= 0.0:
                raise dns.exception.Timeout
        try:
            if not _polling_backend(fd, readable, writable, error, timeout):
                raise dns.exception.Timeout
        except select_error as e:
            if e.args[0] != errno.EINTR:
                raise e
        done = True

def _read(self, N):
        # Starting with Python 3 open with buffering=0 returns a FileIO object.
        # FileIO.read behaves like read(2) and not like fread(3) and thus we
        # have to handle the case that read returns less data as requested here
        # more carefully.
        data = b("")
        while len(data) < N:
            try:
                d = self.__file.read(N - len(data))
            except IOError, e:
                # read(2) has been interrupted by a signal; redo the read
                if e.errno == errno.EINTR:
                    continue
                raise

            if d is None:
                # __file is in non-blocking mode and no data is available
                return data
            if len(d) == 0:
                # __file is in blocking mode and arrived at EOF
                return data

            data += d
        return data

def _peek_unlocked(self, n=0):
        want = min(n, self.buffer_size)
        have = len(self._read_buf) - self._read_pos
        if have < want or have <= 0:
            to_read = self.buffer_size - have
            while True:
                try:
                    current = self.raw.read(to_read)
                except IOError as e:
                    if e.errno != EINTR:
                        raise
                    continue
                break
            if current:
                self._read_buf = self._read_buf[self._read_pos:] + current
                self._read_pos = 0
        return self._read_buf[self._read_pos:]

def _flush_unlocked(self):
        if self.closed:
            raise ValueError("flush of closed file")
        while self._write_buf:
            try:
                n = self.raw.write(self._write_buf)
            except BlockingIOError:
                raise RuntimeError("self.raw should implement RawIOBase: it "
                                   "should not raise BlockingIOError")
            except IOError as e:
                if e.errno != EINTR:
                    raise
                continue
            if n is None:
                raise BlockingIOError(
                    errno.EAGAIN,
                    "write could not complete without blocking", 0)
            if n > len(self._write_buf) or n < 0:
                raise IOError("write() returned incorrect number of bytes")
            del self._write_buf[:n]

def reset_input_buffer(self):
        """Clear input buffer, discarding all that is in the buffer."""
        if not self.is_open:
            raise portNotOpenError

        # just use recv to remove input, while there is some
        ready = True
        while ready:
            ready, _, _ = select.select([self._socket], [], [], 0)
            try:
                self._socket.recv(4096)
            except OSError as e:
                # this is for Python 3.x where select.error is a subclass of
                # OSError ignore BlockingIOErrors and EINTR. other errors are shown
                # https://www.python.org/dev/peps/pep-0475.
                if e.errno not in (errno.EAGAIN, errno.EALREADY, errno.EWOULDBLOCK, errno.EINPROGRESS, errno.EINTR):
                    raise SerialException('read failed: {}'.format(e))
            except (select.error, socket.error) as e:
                # this is for Python 2.x
                # ignore BlockingIOErrors and EINTR. all errors are shown
                # see also http://www.python.org/dev/peps/pep-3151/#select
                if e[0] not in (errno.EAGAIN, errno.EALREADY, errno.EWOULDBLOCK, errno.EINPROGRESS, errno.EINTR):
                    raise SerialException('read failed: {}'.format(e))

def wait_on_children(self):
        """Wait on children exit."""

        while self.running:
            try:
                pid, status = os.wait()
                if os.WIFEXITED(status) or os.WIFSIGNALED(status):
                    self._remove_children(pid)
                    self._verify_and_respawn_children(pid, status)
            except OSError as err:
                if err.errno not in (errno.EINTR, errno.ECHILD):
                    raise
            except KeyboardInterrupt:
                LOG.info(_LI('Caught keyboard interrupt. Exiting.'))
                os.killpg(0, signal.SIGTERM)
                break
            except exception.SIGHUPInterrupt:
                self.reload()
                continue

        eventlet.greenio.shutdown_safe(self.sock)
        self.sock.close()
        LOG.debug('Exited')

def poll(self, timeout):
        try:
            fds = self._poller.poll(timeout * 1000)
        except select.error as err:
            if err[0] == errno.EINTR:
                display.vvv(u"EINTR encountered in poll")
                return [], []
            raise
        readables = []
        for fd, eventmask in fds:
            if eventmask & select.POLLNVAL:
                # POLLNVAL means `fd` value is invalid, not open.
                self._poller.unregister(fd)
            elif eventmask & self.READ:
                if fd in self.readables_fd_map:
                    readables.append(self.readables_fd_map[fd])
        return readables, []

def sleep(self):
        """\
        Sleep until PIPE is readable or we timeout.
        A readable PIPE means a signal occurred.
        """
        try:
            ready = select.select([self.PIPE[0]], [], [], 1.0)
            if not ready[0]:
                return
            while os.read(self.PIPE[0], 1):
                pass
        except select.error as e:
            if e.args[0] not in [errno.EAGAIN, errno.EINTR]:
                raise
        except OSError as e:
            if e.errno not in [errno.EAGAIN, errno.EINTR]:
                raise
        except KeyboardInterrupt:
            sys.exit()

def wait(self, timeout):
        try:
            self.notify()
            ret = select.select(self.wait_fds, [], [], timeout)
            if ret[0]:
                return ret[0]

        except select.error as e:
            if e.args[0] == errno.EINTR:
                return self.sockets
            if e.args[0] == errno.EBADF:
                if self.nr < 0:
                    return self.sockets
                else:
                    raise StopWaiting
            raise

def sleep(self):
        """\
        Sleep until PIPE is readable or we timeout.
        A readable PIPE means a signal occurred.
        """
        try:
            ready = select.select([self.PIPE[0]], [], [], 1.0)
            if not ready[0]:
                return
            while os.read(self.PIPE[0], 1):
                pass
        except select.error as e:
            if e.args[0] not in [errno.EAGAIN, errno.EINTR]:
                raise
        except OSError as e:
            if e.errno not in [errno.EAGAIN, errno.EINTR]:
                raise
        except KeyboardInterrupt:
            sys.exit()

def wait(self, timeout):
        try:
            self.notify()
            ret = select.select(self.wait_fds, [], [], timeout)
            if ret[0]:
                if self.PIPE[0] in ret[0]:
                    os.read(self.PIPE[0], 1)
                return ret[0]

        except select.error as e:
            if e.args[0] == errno.EINTR:
                return self.sockets
            if e.args[0] == errno.EBADF:
                if self.nr < 0:
                    return self.sockets
                else:
                    raise StopWaiting
            raise

def _read_bytes(self, num_bytes):
        self._sock.settimeout(self._read_timeout)
        while True:
            try:
                data = self._rfile.read(num_bytes)
                break
            except (IOError, OSError) as e:
                if e.errno == errno.EINTR:
                    continue
                raise err.OperationalError(
                    2013,
                    "Lost connection to MySQL server during query (%s)" % (e,))
        if len(data) < num_bytes:
            raise err.OperationalError(
                2013, "Lost connection to MySQL server during query")
        return data

def readinto(self, b):
        """Read up to len(b) bytes into the writable buffer *b* and return
        the number of bytes read.  If the socket is non-blocking and no bytes
        are available, None is returned.

        If *b* is non-empty, a 0 return value indicates that the connection
        was shutdown at the other end.
        """
        self._checkClosed()
        self._checkReadable()
        if self._timeout_occurred:
            raise IOError("cannot read from timed out object")
        while True:
            try:
                return self._sock.recv_into(b)
            except timeout:
                self._timeout_occurred = True
                raise
            except error as e:
                n = e.args[0]
                if n == EINTR:
                    continue
                if n in _blocking_errnos:
                    return None
                raise

def serve_forever():
    listen_socket = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
    listen_socket.setsockopt(socket.SOL_SOCKET, socket.SO_REUSEADDR, 1)
    listen_socket.bind(SERVER_ADDRESS)
    listen_socket.listen(REQUEST_QUEUE_SIZE)
    print('Serving HTTP on port {port} ...'.format(port=PORT))

    signal.signal(signal.SIGTSTP, grim_reaper)

    while True:
        try:
            client_connection, client_address = listen_socket.accept()
        except IOError as e:
            code, msg = e.args
            # restart 'accept' if it was interrupted
            if code == errno.EINTR:
                continue
            else:
                raise

        pid = os.fork()
        if pid == 0:  # child
            listen_socket.close()  # close child copy
            handle_request(client_connection)
            client_connection.close()
            os._exit(0)
        else:  # parent
            client_connection.close()  # close parent copy and loop over

def Popen(*args, **kwargs):
    """
    Wrapper for subprocess.Popen() that provides thread-safety and works around
    other known bugs.
    """
    _popen_lock.acquire()
    try:
        # Python's subprocess module has a bug where it propagates the
        # exception to the caller when it gets interrupted trying to read the
        # status back from the child process, leaving the child process
        # effectively orphaned and registering a false failure. To work around
        # it, we temporarily replace os.read with a retrying version that
        # allows Popen to succeed in this case.
        class RetryFunc(object):
            def __init__ (self, func):
                import os
                self.func = func

            def __call__ (self, *args, **kwargs):
                while True:
                    try:
                        return self.func(*args, **kwargs)
                    except OSError, e:
                        if e.errno != errno.EINTR:
                            raise

        reader = RetryFunc(os.read)
        os.read = reader
        return subprocess.Popen(*args, **kwargs)
    finally:
        os.read = reader.func
        _popen_lock.release()

def _eintr_retry(func, *args):
    """restart a system call interrupted by EINTR"""
    while True:
        try:
            return func(*args)
        except OSError as e:
            if e.args[0] != errno.EINTR:
                raise

def _eintr_retry_call(func, *args):
    while True:
        try:
            return func(*args)
        except OSError, e:
            if e.errno == errno.EINTR:
                continue
            raise

def wait(self, timeout=None):
        """
        Wait through 'timeout' (in seconds) for a notification, or forever
        if it is None.  Return True if a notification was received or
        False otherwise.
        """

        if timeout is not None:
            timeout = float(timeout)

        while True:
            try:
                selected = select.select([self.pg], [], [], timeout)
                break
            except select.error as ex:
                err_no, message = ex
                if err_no == errno.EINTR:
                    # TODO: This needs to adjust the time remaining
                    continue
                raise ex

        if selected == ([], [], []):
            return False

        self.pg.poll()
        self.__capture_notifications()
        return len(self.pending_notifications) > 0

def read_socket_input(connection, socket_obj):
    """Read from the network layer and processes all data read.  Can
    support both blocking and non-blocking sockets.
    Returns the number of input bytes processed, or EOS if input processing
    is done.  Any exceptions raised by the socket are re-raised.
    """
    count = connection.needs_input
    if count <= 0:
        return count  # 0 or EOS

    while True:
        try:
            sock_data = socket_obj.recv(count)
            break
        except socket.timeout as e:
            LOG.debug("Socket timeout exception %s", str(e))
            raise  # caller must handle
        except socket.error as e:
            err = e.errno
            if err in [errno.EAGAIN,
                       errno.EWOULDBLOCK,
                       errno.EINTR]:
                # try again later
                return 0
            # otherwise, unrecoverable, caller must handle
            LOG.debug("Socket error exception %s", str(e))
            raise
        except Exception as e:  # beats me... assume fatal
            LOG.debug("unknown socket exception %s", str(e))
            raise  # caller must handle

    if len(sock_data) > 0:
        count = connection.process_input(sock_data)
    else:
        LOG.debug("Socket closed")
        count = Connection.EOS
        connection.close_input()
        connection.close_output()
    return count