bpo-32373: Add socket.getblocking() method. (#4926)

Author: 1st1

Doc/library/socket.rst

@@ -1087,6 +1087,16 @@ to sockets.
  to decode C structures encoded as byte strings).
 
 
+.. method:: socket.getblocking()
+
+ Return ``True`` if socket is in blocking mode, ``False`` if in
+ non-blocking.
+
+ This is equivalent to checking ``socket.gettimeout() == 0``.
+
+ .. versionadded:: 3.7
+
+
 .. method:: socket.gettimeout()
 
  Return the timeout in seconds (float) associated with socket operations,

Lib/test/test_socket.py

@@ -98,6 +98,12 @@ def _have_socket_vsock():
  ret = get_cid() is not None
  return ret
 
+
+def _is_fd_in_blocking_mode(sock):
+ return not bool(
+ fcntl.fcntl(sock, fcntl.F_GETFL, os.O_NONBLOCK) & os.O_NONBLOCK)
+
+
 HAVE_SOCKET_CAN = _have_socket_can()
 
 HAVE_SOCKET_CAN_ISOTP = _have_socket_can_isotp()
@@ -4079,8 +4085,44 @@ def testSetBlocking(self):
  # Testing whether set blocking works
  self.serv.setblocking(True)
  self.assertIsNone(self.serv.gettimeout())
+ self.assertTrue(self.serv.getblocking())
+ if fcntl:
+ self.assertTrue(_is_fd_in_blocking_mode(self.serv))
+
  self.serv.setblocking(False)
  self.assertEqual(self.serv.gettimeout(), 0.0)
+ self.assertFalse(self.serv.getblocking())
+ if fcntl:
+ self.assertFalse(_is_fd_in_blocking_mode(self.serv))
+
+ self.serv.settimeout(None)
+ self.assertTrue(self.serv.getblocking())
+ if fcntl:
+ self.assertTrue(_is_fd_in_blocking_mode(self.serv))
+
+ self.serv.settimeout(0)
+ self.assertFalse(self.serv.getblocking())
+ self.assertEqual(self.serv.gettimeout(), 0)
+ if fcntl:
+ self.assertFalse(_is_fd_in_blocking_mode(self.serv))
+
+ self.serv.settimeout(10)
+ self.assertTrue(self.serv.getblocking())
+ self.assertEqual(self.serv.gettimeout(), 10)
+ if fcntl:
+ # When a Python socket has a non-zero timeout, it's
+ # switched internally to a non-blocking mode.
+ # Later, sock.sendall(), sock.recv(), and other socket
+ # operations use a `select()` call and handle EWOULDBLOCK/EGAIN
+ # on all socket operations. That's how timeouts are
+ # enforced.
+ self.assertFalse(_is_fd_in_blocking_mode(self.serv))
+
+ self.serv.settimeout(0)
+ self.assertFalse(self.serv.getblocking())
+ if fcntl:
+ self.assertFalse(_is_fd_in_blocking_mode(self.serv))
+
  start = time.time()
  try:
  self.serv.accept()
@@ -4113,6 +4155,8 @@ def testInitNonBlocking(self):
  self.serv.close()
  self.serv = socket.socket(socket.AF_INET, socket.SOCK_STREAM |
  socket.SOCK_NONBLOCK)
+ self.assertFalse(self.serv.getblocking())
+ self.assertEqual(self.serv.gettimeout(), 0)
  self.port = support.bind_port(self.serv)
  self.serv.listen()
  # actual testing
@@ -5190,11 +5234,24 @@ def checkNonblock(self, s, nonblock=True, timeout=0.0):
  self.assertEqual(s.gettimeout(), timeout)
  self.assertTrue(
  fcntl.fcntl(s, fcntl.F_GETFL, os.O_NONBLOCK) & os.O_NONBLOCK)
+ if timeout == 0:
+ # timeout == 0: means that getblocking() must be False.
+ self.assertFalse(s.getblocking())
+ else:
+ # If timeout > 0, the socket will be in a "blocking" mode
+ # from the standpoint of the Python API. For Python socket
+ # object, "blocking" means that operations like 'sock.recv()'
+ # will block. Internally, file descriptors for
+ # "blocking" Python sockets *with timeouts* are in a
+ # *non-blocking* mode, and 'sock.recv()' uses 'select()'
+ # and handles EWOULDBLOCK/EAGAIN to enforce the timeout.
+ self.assertTrue(s.getblocking())
  else:
  self.assertEqual(s.type, socket.SOCK_STREAM)
  self.assertEqual(s.gettimeout(), None)
  self.assertFalse(
  fcntl.fcntl(s, fcntl.F_GETFL, os.O_NONBLOCK) & os.O_NONBLOCK)
+ self.assertTrue(s.getblocking())
 
  @support.requires_linux_version(2, 6, 28)
  def test_SOCK_NONBLOCK(self):
@@ -5204,15 +5261,15 @@ def test_SOCK_NONBLOCK(self):
  socket.SOCK_STREAM | socket.SOCK_NONBLOCK) as s:
  self.checkNonblock(s)
  s.setblocking(1)
- self.checkNonblock(s, False)
+ self.checkNonblock(s, nonblock=False)
  s.setblocking(0)
  self.checkNonblock(s)
  s.settimeout(None)
- self.checkNonblock(s, False)
+ self.checkNonblock(s, nonblock=False)
  s.settimeout(2.0)
  self.checkNonblock(s, timeout=2.0)
  s.setblocking(1)
- self.checkNonblock(s, False)
+ self.checkNonblock(s, nonblock=False)
  # defaulttimeout
  t = socket.getdefaulttimeout()
  socket.setdefaulttimeout(0.0)

Misc/NEWS.d/next/Library/2017-12-19-09-23-46.bpo-32373.8qAkoW.rst

@@ -0,0 +1 @@
+Add socket.getblocking() method.

Modules/socketmodule.c

@@ -136,6 +136,7 @@ sendall(data[, flags]) -- send all data\n\
 send(data[, flags]) -- send data, may not send all of it\n\
 sendto(data[, flags], addr) -- send data to a given address\n\
 setblocking(0 | 1) -- set or clear the blocking I/O flag\n\
+getblocking() -- return True if socket is blocking, False if non-blocking\n\
 setsockopt(level, optname, value[, optlen]) -- set socket options\n\
 settimeout(None | float) -- set or clear the timeout\n\
 shutdown(how) -- shut down traffic in one or both directions\n\
@@ -2525,6 +2526,27 @@ Set the socket to blocking (flag is true) or non-blocking (false).\n\
 setblocking(True) is equivalent to settimeout(None);\n\
 setblocking(False) is equivalent to settimeout(0.0).");
 
+/* s.getblocking() method.
+ Returns True if socket is in blocking mode,
+ False if it is in non-blocking mode.
+*/
+static PyObject *
+sock_getblocking(PySocketSockObject *s)
+{
+ if (s->sock_timeout) {
+ Py_RETURN_TRUE;
+ }
+ else {
+ Py_RETURN_FALSE;
+ }
+}
+
+PyDoc_STRVAR(getblocking_doc,
+"getblocking()\n\
+\n\
+Returns True if socket is in blocking mode, or False if it\n\
+is in non-blocking mode.");
+
 static int
 socket_parse_timeout(_PyTime_t *timeout, PyObject *timeout_obj)
 {
@@ -2581,7 +2603,30 @@ sock_settimeout(PySocketSockObject *s, PyObject *arg)
  return NULL;
 
  s->sock_timeout = timeout;
- if (internal_setblocking(s, timeout < 0) == -1) {
+
+ int block = timeout < 0;
+ /* Blocking mode for a Python socket object means that operations
+ like :meth:`recv` or :meth:`sendall` will block the execution of
+ the current thread until they are complete or aborted with a
+ `socket.timeout` or `socket.error` errors. When timeout is `None`,
+ the underlying FD is in a blocking mode. When timeout is a positive
+ number, the FD is in a non-blocking mode, and socket ops are
+ implemented with a `select()` call.
+
+ When timeout is 0.0, the FD is in a non-blocking mode.
+
+ This table summarizes all states in which the socket object and
+ its underlying FD can be:
+
+ ==================== ===================== ==============
+ `gettimeout()` `getblocking()` FD
+ ==================== ===================== ==============
+ ``None`` ``True`` blocking
+ ``0.0`` ``False`` non-blocking
+ ``> 0`` ``True`` non-blocking
+ */
+
+ if (internal_setblocking(s, block) == -1) {
  return NULL;
  }
  Py_RETURN_NONE;
@@ -4601,6 +4646,8 @@ static PyMethodDef sock_methods[] = {
  sendto_doc},
  {"setblocking", (PyCFunction)sock_setblocking, METH_O,
  setblocking_doc},
+ {"getblocking", (PyCFunction)sock_getblocking, METH_NOARGS,
+ getblocking_doc},
  {"settimeout", (PyCFunction)sock_settimeout, METH_O,
  settimeout_doc},
  {"gettimeout", (PyCFunction)sock_gettimeout, METH_NOARGS,