1// Copyright 2011 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	"os"
11	"syscall"
12)
13
14const supportsSendfile = true
15
16// sendFile copies the contents of r to c using the TransmitFile
17// system call to minimize copies.
18//
19// if handled == true, sendFile returns the number of bytes copied and any
20// non-EOF error.
21//
22// if handled == false, sendFile performed no work.
23func sendFile(fd *netFD, r io.Reader) (written int64, err error, handled bool) {
24	var n int64 = 0 // by default, copy until EOF.
25
26	lr, ok := r.(*io.LimitedReader)
27	if ok {
28		n, r = lr.N, lr.R
29		if n <= 0 {
30			return 0, nil, true
31		}
32	}
33
34	f, ok := r.(*os.File)
35	if !ok {
36		return 0, nil, false
37	}
38
39	written, err = poll.SendFile(&fd.pfd, syscall.Handle(f.Fd()), n)
40	if err != nil {
41		err = wrapSyscallError("transmitfile", err)
42	}
43
44	// If any byte was copied, regardless of any error
45	// encountered mid-way, handled must be set to true.
46	handled = written > 0
47
48	return
49}
50