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
5package net
6
7import (
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.
17func 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}
45