1 // Copyright 2017 The Go Authors. All rights reserved.
2 // Use of this source code is governed by a BSD-style
3 // license that can be found in the LICENSE file.
4 5 // Package poll supports non-blocking I/O on file descriptors with polling.
6 // This supports I/O operations that block only a goroutine, not a thread.
7 // This is used by the net and os packages.
8 // It uses a poller built into the runtime, with support from the
9 // runtime scheduler.
10 package poll
11 12 import (
13 "errors"
14 )
15 16 // errNetClosing is the type of the variable ErrNetClosing.
17 // This is used to implement the net.Error interface.
18 type errNetClosing struct{}
19 20 // Error returns the error message for ErrNetClosing.
21 // Keep this string consistent because of issue #4373:
22 // since historically programs have not been able to detect
23 // this error, they look for the string.
24 func (e errNetClosing) Error() string { return "use of closed network connection" }
25 26 func (e errNetClosing) Timeout() bool { return false }
27 func (e errNetClosing) Temporary() bool { return false }
28 29 // ErrNetClosing is returned when a network descriptor is used after
30 // it has been closed.
31 var ErrNetClosing = errNetClosing{}
32 33 // ErrFileClosing is returned when a file descriptor is used after it
34 // has been closed.
35 var ErrFileClosing = errors.New("use of closed file")
36 37 // ErrNoDeadline is returned when a request is made to set a deadline
38 // on a file type that does not use the poller.
39 var ErrNoDeadline = errors.New("file type does not support deadline")
40 41 // Return the appropriate closing error based on isFile.
42 func errClosing(isFile bool) error {
43 if isFile {
44 return ErrFileClosing
45 }
46 return ErrNetClosing
47 }
48 49 // ErrDeadlineExceeded is returned for an expired deadline.
50 // This is exported by the os package as os.ErrDeadlineExceeded.
51 var ErrDeadlineExceeded error = &DeadlineExceededError{}
52 53 // DeadlineExceededError is returned for an expired deadline.
54 type DeadlineExceededError struct{}
55 56 // Implement the net.Error interface.
57 // The string is "i/o timeout" because that is what was returned
58 // by earlier Go versions. Changing it may break programs that
59 // match on error strings.
60 func (e *DeadlineExceededError) Error() string { return "i/o timeout" }
61 func (e *DeadlineExceededError) Timeout() bool { return true }
62 func (e *DeadlineExceededError) Temporary() bool { return true }
63 64 // ErrNotPollable is returned when the file or socket is not suitable
65 // for event notification.
66 var ErrNotPollable = errors.New("not pollable")
67 68 // consume removes data from a slice of byte slices, for writev.
69 func consume(v *[][]byte, n int64) {
70 for len(*v) > 0 {
71 ln0 := int64(len((*v)[0]))
72 if ln0 > n {
73 (*v)[0] = (*v)[0][n:]
74 return
75 }
76 n -= ln0
77 (*v)[0] = nil
78 *v = (*v)[1:]
79 }
80 }
81 82 // TestHookDidWritev is a hook for testing writev.
83 var TestHookDidWritev = func(wrote int) {}
84 85 // String is an internal string definition for methods/functions
86 // that is not intended for use outside the standard libraries.
87 //
88 // Other packages in std that import internal/poll and have some
89 // exported APIs (now we've got some in net.rawConn) which are only used
90 // internally and are not intended to be used outside the standard libraries,
91 // Therefore, we make those APIs use internal types like poll.FD or poll.String
92 // in their function signatures to disable the usability of these APIs from
93 // external codebase.
94 type String []byte
95