mirror of
https://github.com/golang/go
synced 2024-11-21 19:24:45 -07:00
pipe: implementation #3; this time for sure!
Added goroutine; got simpler. Fixes deadlock when doing Read+Close or Write+Close on same end. R=r, cw CC=golang-dev https://golang.org/cl/994043
This commit is contained in:
Russ Cox
parent
28c6305a0e
commit
cc62bed075
@ -9,114 +9,190 @@ package io
|
||||
|
||||
import (
|
||||
"os"
|
||||
"runtime"
|
||||
"sync"
|
||||
)
|
||||
|
||||
type pipeResult struct {
|
||||
n int
|
||||
err os.Error
|
||||
}
|
||||
|
||||
// Shared pipe structure.
|
||||
type pipe struct {
|
||||
rclosed bool // Read end closed?
|
||||
rerr os.Error // Error supplied to CloseReader
|
||||
wclosed bool // Write end closed?
|
||||
werr os.Error // Error supplied to CloseWriter
|
||||
wpend []byte // Written data waiting to be read.
|
||||
wtot int // Bytes consumed so far in current write.
|
||||
cw chan []byte // Write sends data here...
|
||||
cr chan bool // ... and reads a done notification from here.
|
||||
// Reader sends on cr1, receives on cr2.
|
||||
// Writer does the same on cw1, cw2.
|
||||
r1, w1 chan []byte
|
||||
r2, w2 chan pipeResult
|
||||
|
||||
rclose chan os.Error // read close; error to return to writers
|
||||
wclose chan os.Error // write close; error to return to readers
|
||||
|
||||
done chan int // read or write half is done
|
||||
}
|
||||
|
||||
func (p *pipe) Read(data []byte) (n int, err os.Error) {
|
||||
if p.rclosed {
|
||||
return 0, os.EINVAL
|
||||
}
|
||||
func (p *pipe) run() {
|
||||
var (
|
||||
rb []byte // pending Read
|
||||
wb []byte // pending Write
|
||||
wn int // amount written so far from wb
|
||||
rerr os.Error // if read end is closed, error to send to writers
|
||||
werr os.Error // if write end is closed, error to send to readers
|
||||
r1 chan []byte // p.cr1 or nil depending on whether Read is ok
|
||||
w1 chan []byte // p.cw1 or nil depending on whether Write is ok
|
||||
ndone int
|
||||
)
|
||||
|
||||
// Wait for next write block if necessary.
|
||||
if p.wpend == nil {
|
||||
if !closed(p.cw) {
|
||||
p.wpend = <-p.cw
|
||||
// Read and Write are enabled at the start.
|
||||
r1 = p.r1
|
||||
w1 = p.w1
|
||||
|
||||
for {
|
||||
select {
|
||||
case <-p.done:
|
||||
if ndone++; ndone == 2 {
|
||||
// both reader and writer are gone
|
||||
return
|
||||
}
|
||||
continue
|
||||
case rerr = <-p.rclose:
|
||||
if w1 == nil {
|
||||
// finish pending Write
|
||||
p.w2 <- pipeResult{wn, rerr}
|
||||
wn = 0
|
||||
w1 = p.w1 // allow another Write
|
||||
}
|
||||
if r1 == nil {
|
||||
// Close of read side during Read.
|
||||
// finish pending Read with os.EINVAL.
|
||||
p.r2 <- pipeResult{0, os.EINVAL}
|
||||
r1 = p.r1 // allow another Read
|
||||
}
|
||||
continue
|
||||
case werr = <-p.wclose:
|
||||
if r1 == nil {
|
||||
// finish pending Read
|
||||
p.r2 <- pipeResult{0, werr}
|
||||
r1 = p.r1 // allow another Read
|
||||
}
|
||||
if w1 == nil {
|
||||
// Close of write side during Write.
|
||||
// finish pending Write with os.EINVAL.
|
||||
p.w2 <- pipeResult{wn, os.EINVAL}
|
||||
wn = 0
|
||||
w1 = p.w1 // allow another Write
|
||||
}
|
||||
continue
|
||||
case rb = <-r1:
|
||||
if werr != nil {
|
||||
// write end is closed
|
||||
p.r2 <- pipeResult{0, werr}
|
||||
continue
|
||||
}
|
||||
r1 = nil // disable Read until this one is done
|
||||
case wb = <-w1:
|
||||
if rerr != nil {
|
||||
// read end is closed
|
||||
p.w2 <- pipeResult{0, rerr}
|
||||
continue
|
||||
}
|
||||
w1 = nil // disable Write until this one is done
|
||||
}
|
||||
if closed(p.cw) {
|
||||
return 0, p.werr
|
||||
|
||||
if r1 == nil && w1 == nil {
|
||||
// Have rb and wb. Execute.
|
||||
n := copy(rb, wb)
|
||||
wn += n
|
||||
wb = wb[n:]
|
||||
|
||||
// Finish Read.
|
||||
p.r2 <- pipeResult{n, nil}
|
||||
r1 = p.r1 // allow another Read
|
||||
|
||||
// Maybe finish Write.
|
||||
if len(wb) == 0 {
|
||||
p.w2 <- pipeResult{wn, nil}
|
||||
wn = 0
|
||||
w1 = p.w1 // allow another Write
|
||||
}
|
||||
}
|
||||
p.wtot = 0
|
||||
}
|
||||
|
||||
// Read from current write block.
|
||||
n = copy(data, p.wpend)
|
||||
p.wtot += n
|
||||
p.wpend = p.wpend[n:]
|
||||
|
||||
// If write block is done, finish the write.
|
||||
if len(p.wpend) == 0 {
|
||||
p.wpend = nil
|
||||
p.cr <- true
|
||||
p.wtot = 0
|
||||
}
|
||||
|
||||
return n, nil
|
||||
}
|
||||
|
||||
func (p *pipe) Write(data []byte) (n int, err os.Error) {
|
||||
if p.wclosed {
|
||||
return 0, os.EINVAL
|
||||
}
|
||||
if closed(p.cr) {
|
||||
return 0, p.rerr
|
||||
}
|
||||
|
||||
// Send write to reader.
|
||||
p.cw <- data
|
||||
|
||||
// Wait for reader to finish copying it.
|
||||
<-p.cr
|
||||
if closed(p.cr) {
|
||||
_, _ = <-p.cw // undo send if reader is gone
|
||||
return 0, p.rerr
|
||||
}
|
||||
return len(data), nil
|
||||
}
|
||||
|
||||
func (p *pipe) CloseReader(rerr os.Error) os.Error {
|
||||
if p.rclosed {
|
||||
return os.EINVAL
|
||||
}
|
||||
p.rclosed = true
|
||||
|
||||
// Wake up writes.
|
||||
if rerr == nil {
|
||||
rerr = os.EPIPE
|
||||
}
|
||||
p.rerr = rerr
|
||||
close(p.cr)
|
||||
return nil
|
||||
}
|
||||
|
||||
func (p *pipe) CloseWriter(werr os.Error) os.Error {
|
||||
if p.wclosed {
|
||||
return os.EINVAL
|
||||
}
|
||||
p.wclosed = true
|
||||
|
||||
// Wake up reads.
|
||||
if werr == nil {
|
||||
werr = os.EOF
|
||||
}
|
||||
p.werr = werr
|
||||
close(p.cw)
|
||||
return nil
|
||||
}
|
||||
|
||||
// Read/write halves of the pipe.
|
||||
// They are separate structures for two reasons:
|
||||
// 1. If one end becomes garbage without being Closed,
|
||||
// its finisher can Close so that the other end
|
||||
// its finalizer can Close so that the other end
|
||||
// does not hang indefinitely.
|
||||
// 2. Clients cannot use interface conversions on the
|
||||
// read end to find the Write method, and vice versa.
|
||||
|
||||
type pipeHalf struct {
|
||||
c1 chan []byte
|
||||
c2 chan pipeResult
|
||||
cclose chan os.Error
|
||||
done chan int
|
||||
|
||||
lock sync.Mutex
|
||||
closed bool
|
||||
|
||||
io sync.Mutex
|
||||
ioclosed bool
|
||||
}
|
||||
|
||||
func (p *pipeHalf) rw(data []byte) (n int, err os.Error) {
|
||||
// Run i/o operation.
|
||||
// Check ioclosed flag under lock to make sure we're still allowed to do i/o.
|
||||
p.io.Lock()
|
||||
defer p.io.Unlock()
|
||||
if p.ioclosed {
|
||||
return 0, os.EINVAL
|
||||
}
|
||||
p.c1 <- data
|
||||
res := <-p.c2
|
||||
return res.n, res.err
|
||||
}
|
||||
|
||||
func (p *pipeHalf) close(err os.Error) os.Error {
|
||||
// Close pipe half.
|
||||
// Only first call to close does anything.
|
||||
p.lock.Lock()
|
||||
if p.closed {
|
||||
p.lock.Unlock()
|
||||
return os.EINVAL
|
||||
}
|
||||
p.closed = true
|
||||
p.lock.Unlock()
|
||||
|
||||
// First, send the close notification.
|
||||
p.cclose <- err
|
||||
|
||||
// Runner is now responding to rw operations
|
||||
// with os.EINVAL. Cut off future rw operations
|
||||
// by setting ioclosed flag.
|
||||
p.io.Lock()
|
||||
p.ioclosed = true
|
||||
p.io.Unlock()
|
||||
|
||||
// With ioclosed set, there will be no more rw operations
|
||||
// working on the channels.
|
||||
// Tell the runner we won't be bothering it anymore.
|
||||
p.done <- 1
|
||||
|
||||
// Successfully torn down; can disable finalizer.
|
||||
runtime.SetFinalizer(p, nil)
|
||||
|
||||
return nil
|
||||
}
|
||||
|
||||
func (p *pipeHalf) finalizer() {
|
||||
p.close(os.EINVAL)
|
||||
}
|
||||
|
||||
|
||||
// A PipeReader is the read half of a pipe.
|
||||
type PipeReader struct {
|
||||
lock sync.Mutex
|
||||
p *pipe
|
||||
pipeHalf
|
||||
}
|
||||
|
||||
// Read implements the standard Read interface:
|
||||
@ -125,36 +201,27 @@ type PipeReader struct {
|
||||
// If the write end is closed with an error, that error is
|
||||
// returned as err; otherwise err is nil.
|
||||
func (r *PipeReader) Read(data []byte) (n int, err os.Error) {
|
||||
r.lock.Lock()
|
||||
defer r.lock.Unlock()
|
||||
|
||||
return r.p.Read(data)
|
||||
return r.rw(data)
|
||||
}
|
||||
|
||||
// Close closes the reader; subsequent writes to the
|
||||
// write half of the pipe will return the error os.EPIPE.
|
||||
func (r *PipeReader) Close() os.Error {
|
||||
r.lock.Lock()
|
||||
defer r.lock.Unlock()
|
||||
|
||||
return r.p.CloseReader(nil)
|
||||
return r.CloseWithError(nil)
|
||||
}
|
||||
|
||||
// CloseWithError closes the reader; subsequent writes
|
||||
// to the write half of the pipe will return the error rerr.
|
||||
func (r *PipeReader) CloseWithError(rerr os.Error) os.Error {
|
||||
r.lock.Lock()
|
||||
defer r.lock.Unlock()
|
||||
|
||||
return r.p.CloseReader(rerr)
|
||||
// to the write half of the pipe will return the error err.
|
||||
func (r *PipeReader) CloseWithError(err os.Error) os.Error {
|
||||
if err == nil {
|
||||
err = os.EPIPE
|
||||
}
|
||||
return r.close(err)
|
||||
}
|
||||
|
||||
func (r *PipeReader) finish() { r.Close() }
|
||||
|
||||
// Write half of pipe.
|
||||
// A PipeWriter is the write half of a pipe.
|
||||
type PipeWriter struct {
|
||||
lock sync.Mutex
|
||||
p *pipe
|
||||
pipeHalf
|
||||
}
|
||||
|
||||
// Write implements the standard Write interface:
|
||||
@ -163,32 +230,24 @@ type PipeWriter struct {
|
||||
// If the read end is closed with an error, that err is
|
||||
// returned as err; otherwise err is os.EPIPE.
|
||||
func (w *PipeWriter) Write(data []byte) (n int, err os.Error) {
|
||||
w.lock.Lock()
|
||||
defer w.lock.Unlock()
|
||||
|
||||
return w.p.Write(data)
|
||||
return w.rw(data)
|
||||
}
|
||||
|
||||
// Close closes the writer; subsequent reads from the
|
||||
// read half of the pipe will return no bytes and a nil error.
|
||||
// read half of the pipe will return no bytes and os.EOF.
|
||||
func (w *PipeWriter) Close() os.Error {
|
||||
w.lock.Lock()
|
||||
defer w.lock.Unlock()
|
||||
|
||||
return w.p.CloseWriter(nil)
|
||||
return w.CloseWithError(nil)
|
||||
}
|
||||
|
||||
// CloseWithError closes the writer; subsequent reads from the
|
||||
// read half of the pipe will return no bytes and the error werr.
|
||||
func (w *PipeWriter) CloseWithError(werr os.Error) os.Error {
|
||||
w.lock.Lock()
|
||||
defer w.lock.Unlock()
|
||||
|
||||
return w.p.CloseWriter(werr)
|
||||
// read half of the pipe will return no bytes and the error err.
|
||||
func (w *PipeWriter) CloseWithError(err os.Error) os.Error {
|
||||
if err == nil {
|
||||
err = os.EOF
|
||||
}
|
||||
return w.close(err)
|
||||
}
|
||||
|
||||
func (w *PipeWriter) finish() { w.Close() }
|
||||
|
||||
// Pipe creates a synchronous in-memory pipe.
|
||||
// It can be used to connect code expecting an io.Reader
|
||||
// with code expecting an io.Writer.
|
||||
@ -196,8 +255,39 @@ func (w *PipeWriter) finish() { w.Close() }
|
||||
// copying data directly between the two; there is no internal buffering.
|
||||
func Pipe() (*PipeReader, *PipeWriter) {
|
||||
p := &pipe{
|
||||
cw: make(chan []byte, 1),
|
||||
cr: make(chan bool, 1),
|
||||
r1: make(chan []byte),
|
||||
r2: make(chan pipeResult),
|
||||
w1: make(chan []byte),
|
||||
w2: make(chan pipeResult),
|
||||
rclose: make(chan os.Error),
|
||||
wclose: make(chan os.Error),
|
||||
done: make(chan int),
|
||||
}
|
||||
return &PipeReader{p: p}, &PipeWriter{p: p}
|
||||
go p.run()
|
||||
|
||||
// NOTE: Cannot use composite literal here:
|
||||
// pipeHalf{c1: p.cr1, c2: p.cr2, cclose: p.crclose, cdone: p.cdone}
|
||||
// because this implicitly copies the pipeHalf, which copies the inner mutex.
|
||||
|
||||
r := new(PipeReader)
|
||||
r.c1 = p.r1
|
||||
r.c2 = p.r2
|
||||
r.cclose = p.rclose
|
||||
r.done = p.done
|
||||
// TODO(rsc): Should be able to write
|
||||
// runtime.SetFinalizer(r, (*PipeReader).finalizer)
|
||||
// but 6g doesn't see the finalizer method.
|
||||
runtime.SetFinalizer(&r.pipeHalf, (*pipeHalf).finalizer)
|
||||
|
||||
w := new(PipeWriter)
|
||||
w.c1 = p.w1
|
||||
w.c2 = p.w2
|
||||
w.cclose = p.wclose
|
||||
w.done = p.done
|
||||
// TODO(rsc): Should be able to write
|
||||
// runtime.SetFinalizer(w, (*PipeWriter).finalizer)
|
||||
// but 6g doesn't see the finalizer method.
|
||||
runtime.SetFinalizer(&w.pipeHalf, (*pipeHalf).finalizer)
|
||||
|
||||
return r, w
|
||||
}
|
||||
|
||||
@ -207,6 +207,18 @@ func TestPipeReadClose(t *testing.T) {
|
||||
}
|
||||
}
|
||||
|
||||
// Test close on Read side during Read.
|
||||
func TestPipeReadClose2(t *testing.T) {
|
||||
c := make(chan int, 1)
|
||||
r, _ := Pipe()
|
||||
go delayClose(t, r, c, pipeTest{})
|
||||
n, err := r.Read(make([]byte, 64))
|
||||
<-c
|
||||
if n != 0 || err != os.EINVAL {
|
||||
t.Errorf("read from closed pipe: %v, %v want %v, %v", n, err, 0, os.EINVAL)
|
||||
}
|
||||
}
|
||||
|
||||
// Test write after/before reader close.
|
||||
|
||||
func TestPipeWriteClose(t *testing.T) {
|
||||
|
||||
Loading…
Reference in New Issue
Block a user