add plugin http handler (#7289)

plugin/rpcplugin/io.go

@@ -1,7 +1,10 @@
 package rpcplugin
 
 import (
+	"bufio"
+	"encoding/binary"
 	"io"
+	"os"
 )
 
 type rwc struct {
@@ -9,15 +12,56 @@ type rwc struct {
 	io.WriteCloser
 }
 
-func (rwc *rwc) Close() error {
-	rerr := rwc.ReadCloser.Close()
-	werr := rwc.WriteCloser.Close()
-	if rerr != nil {
-		return rerr
+func (rwc *rwc) Close() (err error) {
+	if f, ok := rwc.ReadCloser.(*os.File); ok {
+		// https://groups.google.com/d/topic/golang-nuts/i4w58KJ5-J8/discussion
+		err = os.NewFile(f.Fd(), "").Close()
+	} else {
+		err = rwc.ReadCloser.Close()
 	}
-	return werr
+	werr := rwc.WriteCloser.Close()
+	if err == nil {
+		err = werr
+	}
+	return
 }
 
 func NewReadWriteCloser(r io.ReadCloser, w io.WriteCloser) io.ReadWriteCloser {
 	return &rwc{r, w}
 }
+
+type RemoteIOReader struct {
+	conn io.ReadWriteCloser
+}
+
+func (r *RemoteIOReader) Read(b []byte) (int, error) {
+	var buf [10]byte
+	n := binary.PutVarint(buf[:], int64(len(b)))
+	if _, err := r.conn.Write(buf[:n]); err != nil {
+		return 0, err
+	}
+	return r.conn.Read(b)
+}
+
+func (r *RemoteIOReader) Close() error {
+	return r.conn.Close()
+}
+
+func ConnectIOReader(conn io.ReadWriteCloser) io.ReadCloser {
+	return &RemoteIOReader{conn}
+}
+
+func ServeIOReader(r io.Reader, conn io.ReadWriteCloser) {
+	cr := bufio.NewReader(conn)
+	defer conn.Close()
+	buf := make([]byte, 32*1024)
+	for {
+		n, err := binary.ReadVarint(cr)
+		if err != nil {
+			break
+		}
+		if written, err := io.CopyBuffer(conn, io.LimitReader(r, n), buf); err != nil || written < n {
+			break
+		}
+	}
+}