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Source file src/internal/poll/fd.go

Documentation: internal/poll

     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 "errors"
    13  
    14  // ErrNetClosing is returned when a network descriptor is used after
    15  // it has been closed. Keep this string consistent because of issue
    16  // #4373: since historically programs have not been able to detect
    17  // this error, they look for the string.
    18  var ErrNetClosing = errors.New("use of closed network connection")
    19  
    20  // ErrFileClosing is returned when a file descriptor is used after it
    21  // has been closed.
    22  var ErrFileClosing = errors.New("use of closed file")
    23  
    24  // ErrNoDeadline is returned when a request is made to set a deadline
    25  // on a file type that does not use the poller.
    26  var ErrNoDeadline = errors.New("file type does not support deadline")
    27  
    28  // Return the appropriate closing error based on isFile.
    29  func errClosing(isFile bool) error {
    30  	if isFile {
    31  		return ErrFileClosing
    32  	}
    33  	return ErrNetClosing
    34  }
    35  
    36  // ErrTimeout is returned for an expired deadline.
    37  var ErrTimeout error = &TimeoutError{}
    38  
    39  // TimeoutError is returned for an expired deadline.
    40  type TimeoutError struct{}
    41  
    42  // Implement the net.Error interface.
    43  func (e *TimeoutError) Error() string   { return "i/o timeout" }
    44  func (e *TimeoutError) Timeout() bool   { return true }
    45  func (e *TimeoutError) Temporary() bool { return true }
    46  
    47  // consume removes data from a slice of byte slices, for writev.
    48  func consume(v *[][]byte, n int64) {
    49  	for len(*v) > 0 {
    50  		ln0 := int64(len((*v)[0]))
    51  		if ln0 > n {
    52  			(*v)[0] = (*v)[0][n:]
    53  			return
    54  		}
    55  		n -= ln0
    56  		*v = (*v)[1:]
    57  	}
    58  }
    59  
    60  // TestHookDidWritev is a hook for testing writev.
    61  var TestHookDidWritev = func(wrote int) {}
    62  

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