status-go/vendor/github.com/gxed/eventfd/eventfd.go

109 lines
2.1 KiB
Go

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