libgo/go/net/splice_linux.go

   1 // Copyright 2018 The Go Authors. All rights reserved.
   2 // Use of this source code is governed by a BSD-style
   3 // license that can be found in the LICENSE file.
   4
   5 package net
   6
   7 import (
   8         "internal/poll"
   9         "io"
  10 )
  11
  12 // splice transfers data from r to c using the splice system call to minimize
  13 // copies from and to userspace. c must be a TCP connection. Currently, splice
  14 // is only enabled if r is a TCP or a stream-oriented Unix connection.
  15 //
  16 // If splice returns handled == false, it has performed no work.
  17 func splice(c *netFD, r io.Reader) (written int64, err error, handled bool) {
  18         var remain int64 = 1 << 62 // by default, copy until EOF
  19         lr, ok := r.(*io.LimitedReader)
  20         if ok {
  21                 remain, r = lr.N, lr.R
  22                 if remain <= 0 {
  23                         return 0, nil, true
  24                 }
  25         }
  26
  27         var s *netFD
  28         if tc, ok := r.(*TCPConn); ok {
  29                 s = tc.fd
  30         } else if uc, ok := r.(*UnixConn); ok {
  31                 if uc.fd.net != "unix" {
  32                         return 0, nil, false
  33                 }
  34                 s = uc.fd
  35         } else {
  36                 return 0, nil, false
  37         }
  38
  39         written, handled, sc, err := poll.Splice(&c.pfd, &s.pfd, remain)
  40         if lr != nil {
  41                 lr.N -= written
  42         }
  43         return written, wrapSyscallError(sc, err), handled
  44 }