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 hurd linux
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, remain int64) (int64, error) {
17	if err := dstFD.writeLock(); err != nil {
18		return 0, err
19	}
20	defer dstFD.writeUnlock()
21	if err := dstFD.pd.prepareWrite(dstFD.isFile); err != nil {
22		return 0, err
23	}
24
25	dst := int(dstFD.Sysfd)
26	var written int64
27	var err error
28	for remain > 0 {
29		n := maxSendfileSize
30		if int64(n) > remain {
31			n = int(remain)
32		}
33		n, err1 := syscall.Sendfile(dst, src, nil, n)
34		if n > 0 {
35			written += int64(n)
36			remain -= int64(n)
37		} else if n == 0 && err1 == nil {
38			break
39		}
40		if err1 == syscall.EINTR {
41			continue
42		}
43		if err1 == syscall.EAGAIN {
44			if err1 = dstFD.pd.waitWrite(dstFD.isFile); err1 == nil {
45				continue
46			}
47		}
48		if err1 != nil {
49			// This includes syscall.ENOSYS (no kernel
50			// support) and syscall.EINVAL (fd types which
51			// don't implement sendfile)
52			err = err1
53			break
54		}
55	}
56	return written, err
57}
58