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