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// Copyright 2009 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.
// Pipe adapter to connect code expecting an io.Read
// with code expecting an io.Write.
package io
import (
"io";
"os";
"sync";
)
type pipeReturn struct {
n int;
err *os.Error;
}
// Shared pipe structure.
type pipe struct {
rclosed bool; // Read end closed?
wclosed bool; // Write end closed?
wpend []byte; // Written data waiting to be read.
wtot int; // Bytes consumed so far in current write.
cr chan []byte; // Write sends data here...
cw chan pipeReturn; // ... and reads the n, err back from here.
}
func (p *pipe) Read(data []byte) (n int, err *os.Error) {
if p == nil || p.rclosed {
return 0, os.EINVAL;
}
// Wait for next write block if necessary.
if p.wpend == nil {
if !p.wclosed {
p.wpend = <-p.cr;
}
if p.wpend == nil {
return 0, nil;
}
p.wtot = 0;
}
// Read from current write block.
n = len(data);
if n > len(p.wpend) {
n = len(p.wpend);
}
for i := 0; i < n; i++ {
data[i] = p.wpend[i];
}
p.wtot += n;
p.wpend = p.wpend[n:len(p.wpend)];
// If write block is done, finish the write.
if len(p.wpend) == 0 {
p.wpend = nil;
p.cw <- pipeReturn(p.wtot, nil);
p.wtot = 0;
}
return n, nil;
}
func (p *pipe) Write(data []byte) (n int, err *os.Error) {
if p == nil || p.wclosed {
return 0, os.EINVAL;
}
if p.rclosed {
return 0, os.EPIPE;
}
// Send data to reader.
p.cr <- data;
// Wait for reader to finish copying it.
res := <-p.cw;
return res.n, res.err;
}
func (p *pipe) CloseReader() *os.Error {
if p == nil || p.rclosed {
return os.EINVAL;
}
// Stop any future writes.
p.rclosed = true;
// Stop the current write.
if !p.wclosed {
p.cw <- pipeReturn(p.wtot, os.EPIPE);
}
return nil;
}
func (p *pipe) CloseWriter() *os.Error {
if p == nil || p.wclosed {
return os.EINVAL;
}
// Stop any future reads.
p.wclosed = true;
// Stop the current read.
if !p.rclosed {
p.cr <- nil;
}
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
// does not hang indefinitely.
// 2. Clients cannot use interface conversions on the
// read end to find the Write method, and vice versa.
// Read half of pipe.
type pipeRead struct {
lock sync.Mutex;
p *pipe;
}
func (r *pipeRead) Read(data []byte) (n int, err *os.Error) {
r.lock.Lock();
defer r.lock.Unlock();
return r.p.Read(data);
}
func (r *pipeRead) Close() *os.Error {
r.lock.Lock();
defer r.lock.Unlock();
return r.p.CloseReader();
}
func (r *pipeRead) finish() {
r.Close();
}
// Write half of pipe.
type pipeWrite struct {
lock sync.Mutex;
p *pipe;
}
func (w *pipeWrite) Write(data []byte) (n int, err *os.Error) {
w.lock.Lock();
defer w.lock.Unlock();
return w.p.Write(data);
}
func (w *pipeWrite) Close() *os.Error {
w.lock.Lock();
defer w.lock.Unlock();
return w.p.CloseWriter();
}
func (w *pipeWrite) finish() {
w.Close();
}
// Create a synchronous in-memory pipe.
// Reads on one end are matched by writes on the other.
// Writes don't complete until all the data has been
// written or the read end is closed. Reads return
// any available data or block until the next write
// or the write end is closed.
func Pipe() (io.ReadClose, io.WriteClose) {
p := new(pipe);
p.cr = make(chan []byte, 1);
p.cw = make(chan pipeReturn, 1);
r := new(pipeRead);
r.p = p;
w := new(pipeWrite);
w.p = p;
return r, w;
}
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