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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,132 @@ | ||
| /* SPDX-License-Identifier: GPL-2.0 | ||
| * | ||
| * Copyright (C) 2017-2018 Jason A. Donenfeld <[email protected]>. All Rights Reserved. | ||
| */ | ||
|
|
||
| package rwcancel | ||
|
|
||
| import ( | ||
| "errors" | ||
| "golang.org/x/sys/unix" | ||
| "os" | ||
| "runtime" | ||
| "syscall" | ||
| ) | ||
|
|
||
| type RWCancel struct { | ||
| fd int | ||
| closingReader *os.File | ||
| closingWriter *os.File | ||
| } | ||
|
|
||
| type fdSet struct { | ||
| fdset unix.FdSet | ||
| } | ||
|
|
||
| func (fdset *fdSet) set(i int) { | ||
| bits := 32 << (^uint(0) >> 63) | ||
| fdset.fdset.Bits[i/bits] |= 1 << uint(i%bits) | ||
| } | ||
|
|
||
| func (fdset *fdSet) check(i int) bool { | ||
| bits := 32 << (^uint(0) >> 63) | ||
| return (fdset.fdset.Bits[i/bits] & (1 << uint(i%bits))) != 0 | ||
| } | ||
|
|
||
| func max(a, b int) int { | ||
| if a > b { | ||
| return a | ||
| } | ||
| return b | ||
| } | ||
|
|
||
| func NewRWCancel(fd int) (*RWCancel, error) { | ||
| err := unix.SetNonblock(fd, true) | ||
| if err != nil { | ||
| return nil, err | ||
| } | ||
| rwcancel := RWCancel{fd: fd} | ||
|
|
||
| rwcancel.closingReader, rwcancel.closingWriter, err = os.Pipe() | ||
| if err != nil { | ||
| return nil, err | ||
| } | ||
|
|
||
| runtime.SetFinalizer(&rwcancel, func(rw *RWCancel) { | ||
| rw.Cancel() | ||
| }) | ||
|
|
||
| return &rwcancel, nil | ||
| } | ||
|
|
||
| /* https://golang.org/src/crypto/rand/eagain.go */ | ||
| func ErrorIsEAGAIN(err error) bool { | ||
| if pe, ok := err.(*os.PathError); ok { | ||
| if errno, ok := pe.Err.(syscall.Errno); ok && errno == syscall.EAGAIN { | ||
| return true | ||
| } | ||
| } | ||
| if errno, ok := err.(syscall.Errno); ok && errno == syscall.EAGAIN { | ||
| return true | ||
| } | ||
| return false | ||
| } | ||
|
|
||
| func (rw *RWCancel) ReadyRead() bool { | ||
| closeFd := int(rw.closingReader.Fd()) | ||
| fdset := fdSet{} | ||
| fdset.set(rw.fd) | ||
| fdset.set(closeFd) | ||
| _, err := unix.Select(max(rw.fd, closeFd)+1, &fdset.fdset, nil, nil, nil) | ||
| if err != nil { | ||
| return false | ||
| } | ||
| if fdset.check(closeFd) { | ||
| return false | ||
| } | ||
| return fdset.check(rw.fd) | ||
| } | ||
|
|
||
| func (rw *RWCancel) ReadyWrite() bool { | ||
| closeFd := int(rw.closingReader.Fd()) | ||
| fdset := fdSet{} | ||
| fdset.set(rw.fd) | ||
| fdset.set(closeFd) | ||
| _, err := unix.Select(max(rw.fd, closeFd)+1, nil, &fdset.fdset, nil, nil) | ||
| if err != nil { | ||
| return false | ||
| } | ||
| if fdset.check(closeFd) { | ||
| return false | ||
| } | ||
| return fdset.check(rw.fd) | ||
| } | ||
|
|
||
| func (rw *RWCancel) Read(p []byte) (n int, err error) { | ||
| for { | ||
| n, err := unix.Read(rw.fd, p) | ||
| if err == nil || !ErrorIsEAGAIN(err) { | ||
| return n, err | ||
| } | ||
| if !rw.ReadyRead() { | ||
| return 0, errors.New("fd closed") | ||
| } | ||
| } | ||
| } | ||
|
|
||
| func (rw *RWCancel) Write(p []byte) (n int, err error) { | ||
| for { | ||
| n, err := unix.Write(rw.fd, p) | ||
| if err == nil || !ErrorIsEAGAIN(err) { | ||
| return n, err | ||
| } | ||
| if !rw.ReadyWrite() { | ||
| return 0, errors.New("fd closed") | ||
| } | ||
| } | ||
| } | ||
|
|
||
| func (rw *RWCancel) Cancel() (err error) { | ||
| _, err = rw.closingWriter.Write([]byte{0}) | ||
| return | ||
| } |
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