--- /dev/null
+// Copyright 2015 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// +build linux
+
+package fsnotify
+
+import (
+ "errors"
+
+ "golang.org/x/sys/unix"
+)
+
+type fdPoller struct {
+ fd int // File descriptor (as returned by the inotify_init() syscall)
+ epfd int // Epoll file descriptor
+ pipe [2]int // Pipe for waking up
+}
+
+func emptyPoller(fd int) *fdPoller {
+ poller := new(fdPoller)
+ poller.fd = fd
+ poller.epfd = -1
+ poller.pipe[0] = -1
+ poller.pipe[1] = -1
+ return poller
+}
+
+// Create a new inotify poller.
+// This creates an inotify handler, and an epoll handler.
+func newFdPoller(fd int) (*fdPoller, error) {
+ var errno error
+ poller := emptyPoller(fd)
+ defer func() {
+ if errno != nil {
+ poller.close()
+ }
+ }()
+ poller.fd = fd
+
+ // Create epoll fd
+ poller.epfd, errno = unix.EpollCreate1(0)
+ if poller.epfd == -1 {
+ return nil, errno
+ }
+ // Create pipe; pipe[0] is the read end, pipe[1] the write end.
+ errno = unix.Pipe2(poller.pipe[:], unix.O_NONBLOCK)
+ if errno != nil {
+ return nil, errno
+ }
+
+ // Register inotify fd with epoll
+ event := unix.EpollEvent{
+ Fd: int32(poller.fd),
+ Events: unix.EPOLLIN,
+ }
+ errno = unix.EpollCtl(poller.epfd, unix.EPOLL_CTL_ADD, poller.fd, &event)
+ if errno != nil {
+ return nil, errno
+ }
+
+ // Register pipe fd with epoll
+ event = unix.EpollEvent{
+ Fd: int32(poller.pipe[0]),
+ Events: unix.EPOLLIN,
+ }
+ errno = unix.EpollCtl(poller.epfd, unix.EPOLL_CTL_ADD, poller.pipe[0], &event)
+ if errno != nil {
+ return nil, errno
+ }
+
+ return poller, nil
+}
+
+// Wait using epoll.
+// Returns true if something is ready to be read,
+// false if there is not.
+func (poller *fdPoller) wait() (bool, error) {
+ // 3 possible events per fd, and 2 fds, makes a maximum of 6 events.
+ // I don't know whether epoll_wait returns the number of events returned,
+ // or the total number of events ready.
+ // I decided to catch both by making the buffer one larger than the maximum.
+ events := make([]unix.EpollEvent, 7)
+ for {
+ n, errno := unix.EpollWait(poller.epfd, events, -1)
+ if n == -1 {
+ if errno == unix.EINTR {
+ continue
+ }
+ return false, errno
+ }
+ if n == 0 {
+ // If there are no events, try again.
+ continue
+ }
+ if n > 6 {
+ // This should never happen. More events were returned than should be possible.
+ return false, errors.New("epoll_wait returned more events than I know what to do with")
+ }
+ ready := events[:n]
+ epollhup := false
+ epollerr := false
+ epollin := false
+ for _, event := range ready {
+ if event.Fd == int32(poller.fd) {
+ if event.Events&unix.EPOLLHUP != 0 {
+ // This should not happen, but if it does, treat it as a wakeup.
+ epollhup = true
+ }
+ if event.Events&unix.EPOLLERR != 0 {
+ // If an error is waiting on the file descriptor, we should pretend
+ // something is ready to read, and let unix.Read pick up the error.
+ epollerr = true
+ }
+ if event.Events&unix.EPOLLIN != 0 {
+ // There is data to read.
+ epollin = true
+ }
+ }
+ if event.Fd == int32(poller.pipe[0]) {
+ if event.Events&unix.EPOLLHUP != 0 {
+ // Write pipe descriptor was closed, by us. This means we're closing down the
+ // watcher, and we should wake up.
+ }
+ if event.Events&unix.EPOLLERR != 0 {
+ // If an error is waiting on the pipe file descriptor.
+ // This is an absolute mystery, and should never ever happen.
+ return false, errors.New("Error on the pipe descriptor.")
+ }
+ if event.Events&unix.EPOLLIN != 0 {
+ // This is a regular wakeup, so we have to clear the buffer.
+ err := poller.clearWake()
+ if err != nil {
+ return false, err
+ }
+ }
+ }
+ }
+
+ if epollhup || epollerr || epollin {
+ return true, nil
+ }
+ return false, nil
+ }
+}
+
+// Close the write end of the poller.
+func (poller *fdPoller) wake() error {
+ buf := make([]byte, 1)
+ n, errno := unix.Write(poller.pipe[1], buf)
+ if n == -1 {
+ if errno == unix.EAGAIN {
+ // Buffer is full, poller will wake.
+ return nil
+ }
+ return errno
+ }
+ return nil
+}
+
+func (poller *fdPoller) clearWake() error {
+ // You have to be woken up a LOT in order to get to 100!
+ buf := make([]byte, 100)
+ n, errno := unix.Read(poller.pipe[0], buf)
+ if n == -1 {
+ if errno == unix.EAGAIN {
+ // Buffer is empty, someone else cleared our wake.
+ return nil
+ }
+ return errno
+ }
+ return nil
+}
+
+// Close all poller file descriptors, but not the one passed to it.
+func (poller *fdPoller) close() {
+ if poller.pipe[1] != -1 {
+ unix.Close(poller.pipe[1])
+ }
+ if poller.pipe[0] != -1 {
+ unix.Close(poller.pipe[0])
+ }
+ if poller.epfd != -1 {
+ unix.Close(poller.epfd)
+ }
+}
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