github.com/jlmucb/cloudproxy@v0.0.0-20170830161738-b5aa0b619bc4/go/util/unix_single_rwc.go (about)

     1  // Copyright (c) 2014, Google Inc.  All rights reserved.
     2  //
     3  // Licensed under the Apache License, Version 2.0 (the "License");
     4  // you may not use this file except in compliance with the License.
     5  // You may obtain a copy of the License at
     6  //
     7  //     http://www.apache.org/licenses/LICENSE-2.0
     8  //
     9  // Unless required by applicable law or agreed to in writing, software
    10  // distributed under the License is distributed on an "AS IS" BASIS,
    11  // WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
    12  // See the License for the specific language governing permissions and
    13  // limitations under the License.
    14  
    15  package util
    16  
    17  import (
    18  	"fmt"
    19  	"io"
    20  	"net"
    21  	"os"
    22  )
    23  
    24  // A UnixSingleReadWriteCloser accepts a single connection and reads and writes
    25  // to this connection
    26  type UnixSingleReadWriteCloser struct {
    27  	l net.Listener
    28  	c net.Conn
    29  }
    30  
    31  // NewUnixSingleReadWriteCloser listens on a given Unix socket path and returns
    32  // a UnixSingleReadWriteCloser that will accept a single connection on this
    33  // socket and communicate only with it.
    34  func NewUnixSingleReadWriteCloser(path string) io.ReadWriteCloser {
    35  	l, err := net.Listen("unix", path)
    36  	if err != nil {
    37  		fmt.Fprintf(os.Stderr, "Failed to listen on the channel: %s\n", err)
    38  		return nil
    39  	}
    40  
    41  	return &UnixSingleReadWriteCloser{l, nil}
    42  }
    43  
    44  // Read accepts a connection if there isn't one already and reads from the
    45  // connection.
    46  func (usrwc *UnixSingleReadWriteCloser) Read(p []byte) (int, error) {
    47  	var err error
    48  	if usrwc.c == nil {
    49  		usrwc.c, err = usrwc.l.Accept()
    50  		if err != nil {
    51  			return 0, err
    52  		}
    53  	}
    54  
    55  	return usrwc.c.Read(p)
    56  }
    57  
    58  // Write accepts a connection if there isn't one already and writes to the
    59  // connection.
    60  func (usrwc *UnixSingleReadWriteCloser) Write(p []byte) (int, error) {
    61  	var err error
    62  	if usrwc.c == nil {
    63  		usrwc.c, err = usrwc.l.Accept()
    64  		if err != nil {
    65  			return 0, err
    66  		}
    67  	}
    68  
    69  	return usrwc.c.Write(p)
    70  }
    71  
    72  // Close closes the connection if there is one and closes the listener.
    73  func (usrwc *UnixSingleReadWriteCloser) Close() error {
    74  	if usrwc.c != nil {
    75  		usrwc.c.Close()
    76  	}
    77  
    78  	return usrwc.l.Close()
    79  }