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unix: create wrappers for solaris/illumos Event Ports
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This work is in support of a cleanup of fsnotify/fsnotify#263

Change-Id: Ibd7500d20322765bfd50aa18333eb43ee7b659d7
Reviewed-on: https://go-review.googlesource.com/c/sys/+/324630
Run-TryBot: Ian Lance Taylor <iant@golang.org>
TryBot-Result: Go Bot <gobot@golang.org>
Reviewed-by: Ian Lance Taylor <iant@golang.org>
Reviewed-by: Tobias Klauser <tobias.klauser@gmail.com>
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@nshalman @tklauser
nshalman authored and tklauser committed Aug 17, 2021
1 parent 1e6c022 commit 13f9c58
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240 changes: 240 additions & 0 deletions unix/syscall_solaris.go
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Original file line number Diff line number Diff line change
Expand Up @@ -13,7 +13,10 @@
package unix

import (
"fmt"
"os"
"runtime"
"sync"
"syscall"
"unsafe"
)
Expand Down Expand Up @@ -744,3 +747,240 @@ func Mmap(fd int, offset int64, length int, prot int, flags int) (data []byte, e
func Munmap(b []byte) (err error) {
return mapper.Munmap(b)
}

// Event Ports

type fileObjCookie struct {
fobj *fileObj
cookie interface{}
}

// EventPort provides a safe abstraction on top of Solaris/illumos Event Ports.
type EventPort struct {
port int
mu sync.Mutex
fds map[uintptr]interface{}
paths map[string]*fileObjCookie
}

// PortEvent is an abstraction of the port_event C struct.
// Compare Source against PORT_SOURCE_FILE or PORT_SOURCE_FD
// to see if Path or Fd was the event source. The other will be
// uninitialized.
type PortEvent struct {
Cookie interface{}
Events int32
Fd uintptr
Path string
Source uint16
fobj *fileObj
}

// NewEventPort creates a new EventPort including the
// underlying call to port_create(3c).
func NewEventPort() (*EventPort, error) {
port, err := port_create()
if err != nil {
return nil, err
}
e := &EventPort{
port: port,
fds: make(map[uintptr]interface{}),
paths: make(map[string]*fileObjCookie),
}
return e, nil
}

//sys port_create() (n int, err error)
//sys port_associate(port int, source int, object uintptr, events int, user *byte) (n int, err error)
//sys port_dissociate(port int, source int, object uintptr) (n int, err error)
//sys port_get(port int, pe *portEvent, timeout *Timespec) (n int, err error)
//sys port_getn(port int, pe *portEvent, max uint32, nget *uint32, timeout *Timespec) (n int, err error)

// Close closes the event port.
func (e *EventPort) Close() error {
e.mu.Lock()
defer e.mu.Unlock()
e.fds = nil
e.paths = nil
return Close(e.port)
}

// PathIsWatched checks to see if path is associated with this EventPort.
func (e *EventPort) PathIsWatched(path string) bool {
e.mu.Lock()
defer e.mu.Unlock()
_, found := e.paths[path]
return found
}

// FdIsWatched checks to see if fd is associated with this EventPort.
func (e *EventPort) FdIsWatched(fd uintptr) bool {
e.mu.Lock()
defer e.mu.Unlock()
_, found := e.fds[fd]
return found
}

// AssociatePath wraps port_associate(3c) for a filesystem path including
// creating the necessary file_obj from the provided stat information.
func (e *EventPort) AssociatePath(path string, stat os.FileInfo, events int, cookie interface{}) error {
e.mu.Lock()
defer e.mu.Unlock()
if _, found := e.paths[path]; found {
return fmt.Errorf("%v is already associated with this Event Port", path)
}
fobj, err := createFileObj(path, stat)
if err != nil {
return err
}
fCookie := &fileObjCookie{fobj, cookie}
_, err = port_associate(e.port, PORT_SOURCE_FILE, uintptr(unsafe.Pointer(fobj)), events, (*byte)(unsafe.Pointer(&fCookie.cookie)))
if err != nil {
return err
}
e.paths[path] = fCookie
return nil
}

// DissociatePath wraps port_dissociate(3c) for a filesystem path.
func (e *EventPort) DissociatePath(path string) error {
e.mu.Lock()
defer e.mu.Unlock()
f, ok := e.paths[path]
if !ok {
return fmt.Errorf("%v is not associated with this Event Port", path)
}
_, err := port_dissociate(e.port, PORT_SOURCE_FILE, uintptr(unsafe.Pointer(f.fobj)))
if err != nil {
return err
}
delete(e.paths, path)
return nil
}

// AssociateFd wraps calls to port_associate(3c) on file descriptors.
func (e *EventPort) AssociateFd(fd uintptr, events int, cookie interface{}) error {
e.mu.Lock()
defer e.mu.Unlock()
if _, found := e.fds[fd]; found {
return fmt.Errorf("%v is already associated with this Event Port", fd)
}
pcookie := &cookie
_, err := port_associate(e.port, PORT_SOURCE_FD, fd, events, (*byte)(unsafe.Pointer(pcookie)))
if err != nil {
return err
}
e.fds[fd] = pcookie
return nil
}

// DissociateFd wraps calls to port_dissociate(3c) on file descriptors.
func (e *EventPort) DissociateFd(fd uintptr) error {
e.mu.Lock()
defer e.mu.Unlock()
_, ok := e.fds[fd]
if !ok {
return fmt.Errorf("%v is not associated with this Event Port", fd)
}
_, err := port_dissociate(e.port, PORT_SOURCE_FD, fd)
if err != nil {
return err
}
delete(e.fds, fd)
return nil
}

func createFileObj(name string, stat os.FileInfo) (*fileObj, error) {
fobj := new(fileObj)
bs, err := ByteSliceFromString(name)
if err != nil {
return nil, err
}
fobj.Name = (*int8)(unsafe.Pointer(&bs[0]))
s := stat.Sys().(*syscall.Stat_t)
fobj.Atim.Sec = s.Atim.Sec
fobj.Atim.Nsec = s.Atim.Nsec
fobj.Mtim.Sec = s.Mtim.Sec
fobj.Mtim.Nsec = s.Mtim.Nsec
fobj.Ctim.Sec = s.Ctim.Sec
fobj.Ctim.Nsec = s.Ctim.Nsec
return fobj, nil
}

// GetOne wraps port_get(3c) and returns a single PortEvent.
func (e *EventPort) GetOne(t *Timespec) (*PortEvent, error) {
pe := new(portEvent)
_, err := port_get(e.port, pe, t)
if err != nil {
return nil, err
}
p := new(PortEvent)
p.Events = pe.Events
p.Source = pe.Source
e.mu.Lock()
defer e.mu.Unlock()
switch pe.Source {
case PORT_SOURCE_FD:
p.Fd = uintptr(pe.Object)
cookie := (*interface{})(unsafe.Pointer(pe.User))
p.Cookie = *cookie
delete(e.fds, p.Fd)
case PORT_SOURCE_FILE:
p.fobj = (*fileObj)(unsafe.Pointer(uintptr(pe.Object)))
p.Path = BytePtrToString((*byte)(unsafe.Pointer(p.fobj.Name)))
cookie := (*interface{})(unsafe.Pointer(pe.User))
p.Cookie = *cookie
delete(e.paths, p.Path)
}
return p, nil
}

// Pending wraps port_getn(3c) and returns how many events are pending.
func (e *EventPort) Pending() (int, error) {
var n uint32 = 0
_, err := port_getn(e.port, nil, 0, &n, nil)
return int(n), err
}

// Get wraps port_getn(3c) and fills a slice of PortEvent.
// It will block until either min events have been received
// or the timeout has been exceeded. It will return how many
// events were actually received along with any error information.
func (e *EventPort) Get(s []PortEvent, min int, timeout *Timespec) (int, error) {
if min == 0 {
return 0, fmt.Errorf("need to request at least one event or use Pending() instead")
}
if len(s) < min {
return 0, fmt.Errorf("len(s) (%d) is less than min events requested (%d)", len(s), min)
}
got := uint32(min)
max := uint32(len(s))
var err error
ps := make([]portEvent, max, max)
_, err = port_getn(e.port, &ps[0], max, &got, timeout)
// got will be trustworthy with ETIME, but not any other error.
if err != nil && err != ETIME {
return 0, err
}
e.mu.Lock()
defer e.mu.Unlock()
for i := 0; i < int(got); i++ {
s[i].Events = ps[i].Events
s[i].Source = ps[i].Source
switch ps[i].Source {
case PORT_SOURCE_FD:
s[i].Fd = uintptr(ps[i].Object)
cookie := (*interface{})(unsafe.Pointer(ps[i].User))
s[i].Cookie = *cookie
delete(e.fds, s[i].Fd)
case PORT_SOURCE_FILE:
s[i].fobj = (*fileObj)(unsafe.Pointer(uintptr(ps[i].Object)))
s[i].Path = BytePtrToString((*byte)(unsafe.Pointer(s[i].fobj.Name)))
cookie := (*interface{})(unsafe.Pointer(ps[i].User))
s[i].Cookie = *cookie
delete(e.paths, s[i].Path)
}
}
return int(got), err
}

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