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 string 95