109 lines
2.1 KiB
Go
109 lines
2.1 KiB
Go
package eventfd
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/*
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* eventfd wrapper for go
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* Provides a ReadWriteCloser interface for handling eventfd()'s
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* Eventfd provides a simple filedescriptor with very low overhead.
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* It stores a bitfield of 64 bits which are added when written to
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* the fd.
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*
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* For more information on eventfd() see `man eventfd`.
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*/
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import (
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"fmt"
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"syscall"
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"github.com/gxed/GoEndian"
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)
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type EventFD struct {
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fd int
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valid bool
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}
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/* Create a new EventFD. */
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func New() (*EventFD, error) {
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fd, _, err := syscall.Syscall(syscall.SYS_EVENTFD2, 0, uintptr(syscall.O_CLOEXEC), 0)
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if err != 0 {
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return nil, err
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}
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e := &EventFD{
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fd: int(fd),
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valid: true,
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}
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return e, nil
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}
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/* Read events from Eventfd. p should be at max 8 bytes.
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* Returns the number of read bytes or 0 and error is set.
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*/
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func (e *EventFD) Read(p []byte) (int, error) {
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n, err := syscall.Read(e.fd, p[:])
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if err != nil {
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return 0, err
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}
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return n, nil
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}
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/* Read events into a uint64 and return it. Returns 0 and error
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* if an error occured
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*/
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func (e *EventFD) ReadEvents() (uint64, error) {
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buf := make([]byte, 8)
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n, err := syscall.Read(e.fd, buf[:])
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if err != nil {
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return 0, err
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}
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if n != 8 {
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return 0, fmt.Errorf("could not read for eventfd")
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}
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val := endian.Endian.Uint64(buf)
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return val, nil
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}
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/* Write bytes to eventfd. Will be added to the current
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* value of the internal uint64 of the eventfd().
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*/
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func (e *EventFD) Write(p []byte) (int, error) {
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n, err := syscall.Write(e.fd, p[:])
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if err != nil {
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return 0, err
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}
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return n, nil
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}
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/* Write a uint64 to eventfd. Value will be added to current value
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* of the eventfd
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*/
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func (e *EventFD) WriteEvents(val uint64) error {
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buf := make([]byte, 8)
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endian.Endian.PutUint64(buf, val)
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n, err := syscall.Write(e.fd, buf[:])
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if err != nil {
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return err
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}
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if n != 8 {
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return fmt.Errorf("could not write to eventfd")
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}
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return nil
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}
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/* Returns the filedescriptor which is internally used */
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func (e *EventFD) Fd() int {
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return e.fd
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}
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/* Close the eventfd */
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func (e *EventFD) Close() error {
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if e.valid == false {
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return nil
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}
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e.valid = false
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return syscall.Close(e.fd)
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}
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