Source: fd.go in package internal/poll

Package poll supports non-blocking I/O on file descriptors with polling. This supports I/O operations that block only a goroutine, not a thread. This is used by the net and os packages. It uses a poller built into the runtime, with support from the runtime scheduler.

package poll

import (
	"errors"
)

ErrNetClosing is returned when a network descriptor is used after it has been closed. Keep this string consistent because of issue #4373: since historically programs have not been able to detect this error, they look for the string.

var ErrNetClosing = errors.New("use of closed network connection")

ErrFileClosing is returned when a file descriptor is used after it has been closed.

var ErrFileClosing = errors.New("use of closed file")

ErrNoDeadline is returned when a request is made to set a deadline on a file type that does not use the poller.

var ErrNoDeadline = errors.New("file type does not support deadline")

Return the appropriate closing error based on isFile.

func errClosing(isFile bool) error {
	if isFile {
		return ErrFileClosing
	}
	return ErrNetClosing
}

ErrDeadlineExceeded is returned for an expired deadline. This is exported by the os package as os.ErrDeadlineExceeded.

var ErrDeadlineExceeded error = &DeadlineExceededError{}

DeadlineExceededError is returned for an expired deadline.

type DeadlineExceededError struct{}

Implement the net.Error interface. The string is "i/o timeout" because that is what was returned by earlier Go versions. Changing it may break programs that match on error strings.

func (e *DeadlineExceededError) Error() string   { return "i/o timeout" }
func (e *DeadlineExceededError) Timeout() bool   { return true }
func (e *DeadlineExceededError) Temporary() bool { return true }

ErrNotPollable is returned when the file or socket is not suitable for event notification.

var ErrNotPollable = errors.New("not pollable")

consume removes data from a slice of byte slices, for writev.

func consume(v *[][]byte, n int64) {
	for len(*v) > 0 {
		ln0 := int64(len((*v)[0]))
		if ln0 > n {
			(*v)[0] = (*v)[0][n:]
			return
		}
		n -= ln0
		*v = (*v)[1:]
	}
}

TestHookDidWritev is a hook for testing writev.