Mercurial > repos > jpayne > bioproject_to_srr_2

comparison urllib3/util/wait.py @ 7:5eb2d5e3bf22

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planemo upload for repository https://toolrepo.galaxytrakr.org/view/jpayne/bioproject_to_srr_2/556cac4fb538
author jpayne
date Sun, 05 May 2024 23:32:17 -0400
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6:b2745907b1eb 7:5eb2d5e3bf22
1 from __future__ import annotations
2
3 import select
4 import socket
5 from functools import partial
6
7 __all__ = ["wait_for_read", "wait_for_write"]
8
9
10 # How should we wait on sockets?
11 #
12 # There are two types of APIs you can use for waiting on sockets: the fancy
13 # modern stateful APIs like epoll/kqueue, and the older stateless APIs like
14 # select/poll. The stateful APIs are more efficient when you have a lots of
15 # sockets to keep track of, because you can set them up once and then use them
16 # lots of times. But we only ever want to wait on a single socket at a time
17 # and don't want to keep track of state, so the stateless APIs are actually
18 # more efficient. So we want to use select() or poll().
19 #
20 # Now, how do we choose between select() and poll()? On traditional Unixes,
21 # select() has a strange calling convention that makes it slow, or fail
22 # altogether, for high-numbered file descriptors. The point of poll() is to fix
23 # that, so on Unixes, we prefer poll().
24 #
25 # On Windows, there is no poll() (or at least Python doesn't provide a wrapper
26 # for it), but that's OK, because on Windows, select() doesn't have this
27 # strange calling convention; plain select() works fine.
28 #
29 # So: on Windows we use select(), and everywhere else we use poll(). We also
30 # fall back to select() in case poll() is somehow broken or missing.
31
32
33 def select_wait_for_socket(
34 sock: socket.socket,
35 read: bool = False,
36 write: bool = False,
37 timeout: float | None = None,
38 ) -> bool:
39 if not read and not write:
40 raise RuntimeError("must specify at least one of read=True, write=True")
41 rcheck = []
42 wcheck = []
43 if read:
44 rcheck.append(sock)
45 if write:
46 wcheck.append(sock)
47 # When doing a non-blocking connect, most systems signal success by
48 # marking the socket writable. Windows, though, signals success by marked
49 # it as "exceptional". We paper over the difference by checking the write
50 # sockets for both conditions. (The stdlib selectors module does the same
51 # thing.)
52 fn = partial(select.select, rcheck, wcheck, wcheck)
53 rready, wready, xready = fn(timeout)
54 return bool(rready or wready or xready)
55
56
57 def poll_wait_for_socket(
58 sock: socket.socket,
59 read: bool = False,
60 write: bool = False,
61 timeout: float | None = None,
62 ) -> bool:
63 if not read and not write:
64 raise RuntimeError("must specify at least one of read=True, write=True")
65 mask = 0
66 if read:
67 mask |= select.POLLIN
68 if write:
69 mask |= select.POLLOUT
70 poll_obj = select.poll()
71 poll_obj.register(sock, mask)
72
73 # For some reason, poll() takes timeout in milliseconds
74 def do_poll(t: float | None) -> list[tuple[int, int]]:
75 if t is not None:
76 t *= 1000
77 return poll_obj.poll(t)
78
79 return bool(do_poll(timeout))
80
81
82 def _have_working_poll() -> bool:
83 # Apparently some systems have a select.poll that fails as soon as you try
84 # to use it, either due to strange configuration or broken monkeypatching
85 # from libraries like eventlet/greenlet.
86 try:
87 poll_obj = select.poll()
88 poll_obj.poll(0)
89 except (AttributeError, OSError):
90 return False
91 else:
92 return True
93
94
95 def wait_for_socket(
96 sock: socket.socket,
97 read: bool = False,
98 write: bool = False,
99 timeout: float | None = None,
100 ) -> bool:
101 # We delay choosing which implementation to use until the first time we're
102 # called. We could do it at import time, but then we might make the wrong
103 # decision if someone goes wild with monkeypatching select.poll after
104 # we're imported.
105 global wait_for_socket
106 if _have_working_poll():
107 wait_for_socket = poll_wait_for_socket
108 elif hasattr(select, "select"):
109 wait_for_socket = select_wait_for_socket
110 return wait_for_socket(sock, read, write, timeout)
111
112
113 def wait_for_read(sock: socket.socket, timeout: float | None = None) -> bool:
114 """Waits for reading to be available on a given socket.
115 Returns True if the socket is readable, or False if the timeout expired.
116 """
117 return wait_for_socket(sock, read=True, timeout=timeout)
118
119
120 def wait_for_write(sock: socket.socket, timeout: float | None = None) -> bool:
121 """Waits for writing to be available on a given socket.
122 Returns True if the socket is readable, or False if the timeout expired.
123 """
124 return wait_for_socket(sock, write=True, timeout=timeout)