fd.go

     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
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