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
5// +build dragonfly freebsd
6
7package poll
8
9import "syscall"
10
11// maxSendfileSize is the largest chunk size we ask the kernel to copy
12// at a time.
13const maxSendfileSize int = 4 << 20
14
15// SendFile wraps the sendfile system call.
16func SendFile(dstFD *FD, src int, pos, remain int64) (int64, error) {
17	if err := dstFD.writeLock(); err != nil {
18		return 0, err
19	}
20	defer dstFD.writeUnlock()
21	dst := int(dstFD.Sysfd)
22	var written int64
23	var err error
24	for remain > 0 {
25		n := maxSendfileSize
26		if int64(n) > remain {
27			n = int(remain)
28		}
29		pos1 := pos
30		n, err1 := syscall.Sendfile(dst, src, &pos1, n)
31		if n > 0 {
32			pos += int64(n)
33			written += int64(n)
34			remain -= int64(n)
35		} else if n == 0 && err1 == nil {
36			break
37		}
38		if err1 == syscall.EAGAIN {
39			if err1 = dstFD.pd.waitWrite(dstFD.isFile); err1 == nil {
40				continue
41			}
42		}
43		if err1 != nil {
44			// This includes syscall.ENOSYS (no kernel
45			// support) and syscall.EINVAL (fd types which
46			// don't implement sendfile)
47			err = err1
48			break
49		}
50	}
51	return written, err
52}
53