1// Copyright 2009 The Go Authors. All rights reserved.
2// Use of this source code is governed by a BSD-style
3// license that can be found in the LICENSE file.
4
5//go:build unix || (js && wasm) || wasip1 || windows
6
7package poll
8
9import (
10	"io"
11	"syscall"
12)
13
14// eofError returns io.EOF when fd is available for reading end of
15// file.
16func (fd *FD) eofError(n int, err error) error {
17	if n == 0 && err == nil && fd.ZeroReadIsEOF {
18		return io.EOF
19	}
20	return err
21}
22
23// Shutdown wraps syscall.Shutdown.
24func (fd *FD) Shutdown(how int) error {
25	if err := fd.incref(); err != nil {
26		return err
27	}
28	defer fd.decref()
29	return syscall.Shutdown(fd.Sysfd, how)
30}
31
32// Fchown wraps syscall.Fchown.
33func (fd *FD) Fchown(uid, gid int) error {
34	if err := fd.incref(); err != nil {
35		return err
36	}
37	defer fd.decref()
38	return ignoringEINTR(func() error {
39		return syscall.Fchown(fd.Sysfd, uid, gid)
40	})
41}
42
43// Ftruncate wraps syscall.Ftruncate.
44func (fd *FD) Ftruncate(size int64) error {
45	if err := fd.incref(); err != nil {
46		return err
47	}
48	defer fd.decref()
49	return ignoringEINTR(func() error {
50		return syscall.Ftruncate(fd.Sysfd, size)
51	})
52}
53
54// RawControl invokes the user-defined function f for a non-IO
55// operation.
56func (fd *FD) RawControl(f func(uintptr)) error {
57	if err := fd.incref(); err != nil {
58		return err
59	}
60	defer fd.decref()
61	f(uintptr(fd.Sysfd))
62	return nil
63}
64
65// ignoringEINTR makes a function call and repeats it if it returns
66// an EINTR error. This appears to be required even though we install all
67// signal handlers with SA_RESTART: see #22838, #38033, #38836, #40846.
68// Also #20400 and #36644 are issues in which a signal handler is
69// installed without setting SA_RESTART. None of these are the common case,
70// but there are enough of them that it seems that we can't avoid
71// an EINTR loop.
72func ignoringEINTR(fn func() error) error {
73	for {
74		err := fn()
75		if err != syscall.EINTR {
76			return err
77		}
78	}
79}
80