使用golang实现 IO copy，测试程序如下：
package main
import (
"fmt"
"io"
"os"
"syscall"
)
func main() {
var errCh chan error
errCh = Go(func() error {
return test_stdout()
})
if err := <-errCh; err != nil {
fmt.Printf("End io_copy: %s\n", err)
//return err
}
}
//异步执行
func Go(f func() error) chan error {
ch := make(chan error, 1)
go func() {
ch <- f()
}()
return ch
}
//输入流复制到文件里面
func test_stdin() error {
var out io.Writer
var in io.Reader
in = os.NewFile(uintptr(syscall.Stdin), "/dev/stdin")
out, _ = os.OpenFile("D:/golang/project/docker/env.txt", os.O_RDWR, 0666)
n, err := io.Copy(out, in)
fmt.Printf("\n write %d err %v \n", n, err)
return err
}
//文件里面复制到输出流
func test_stdout() error {
var out io.Writer
var in io.Reader
out = os.NewFile(uintptr(syscall.Stdout), "/dev/stdout")
in, _ = os.OpenFile("D:/golang/project/docker/env.txt", os.O_RDWR, 0666)
n, err := io.Copy(out, in)
fmt.Printf("\n write %d err %v \n", n, err)
return err
}
再看看io.Copy的代码：
func Copy(dst Writer, src Reader) (written int64, err error) {
// If the reader has a WriteTo method, use it to do the copy.
// Avoids an allocation and a copy.
if wt, ok := src.(WriterTo); ok {
return wt.WriteTo(dst)
}
// Similarly, if the writer has a ReadFrom method, use it to do the copy.
if rt, ok := dst.(ReaderFrom); ok {
return rt.ReadFrom(src)
}
buf := make([]byte, 32*1024)
for {
nr, er := src.Read(buf)
if nr > 0 {
nw, ew := dst.Write(buf[0:nr])
if nw > 0 {
written += int64(nw)
}
if ew != nil {
err = ew
break
}
if nr != nw {
err = ErrShortWrite
break
}
}
if er == EOF {
break
}
if er != nil {
err = er
break
}
}
return written, err
}
阻塞式的从src输入流读数据到dst输出流
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