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 net 6 7 import ( 8 "io" 9 "os" 10 "syscall" 11 ) 12 13 // maxSendfileSize is the largest chunk size we ask the kernel to copy 14 // at a time. 15 const maxSendfileSize int = 4 << 20 16 17 // sendFile copies the contents of r to c using the sendfile 18 // system call to minimize copies. 19 // 20 // if handled == true, sendFile returns the number of bytes copied and any 21 // non-EOF error. 22 // 23 // if handled == false, sendFile performed no work. 24 func sendFile(c *netFD, r io.Reader) (written int64, err error, handled bool) { 25 var remain int64 = 1 << 62 // by default, copy until EOF 26 27 lr, ok := r.(*io.LimitedReader) 28 if ok { 29 remain, r = lr.N, lr.R 30 if remain <= 0 { 31 return 0, nil, true 32 } 33 } 34 f, ok := r.(*os.File) 35 if !ok { 36 return 0, nil, false 37 } 38 39 if err := c.writeLock(); err != nil { 40 return 0, err, true 41 } 42 defer c.writeUnlock() 43 44 dst := c.sysfd 45 src := int(f.Fd()) 46 for remain > 0 { 47 n := maxSendfileSize 48 if int64(n) > remain { 49 n = int(remain) 50 } 51 n, err1 := syscall.Sendfile(dst, src, nil, n) 52 if n > 0 { 53 written += int64(n) 54 remain -= int64(n) 55 } 56 if n == 0 && err1 == nil { 57 break 58 } 59 if err1 == syscall.EAGAIN { 60 if err1 = c.pd.WaitWrite(); err1 == nil { 61 continue 62 } 63 } 64 if err1 != nil { 65 // This includes syscall.ENOSYS (no kernel 66 // support) and syscall.EINVAL (fd types which 67 // don't implement sendfile) 68 err = err1 69 break 70 } 71 } 72 if lr != nil { 73 lr.N = remain 74 } 75 if err != nil { 76 err = os.NewSyscallError("sendfile", err) 77 } 78 return written, err, written > 0 79 } 80
