Source file src/pkg/net/sendfile_linux.go
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 c.wio.Lock() 40 defer c.wio.Unlock() 41 if err := c.incref(false); err != nil { 42 return 0, err, true 43 } 44 defer c.decref() 45 46 dst := c.sysfd 47 src := int(f.Fd()) 48 for remain > 0 { 49 n := maxSendfileSize 50 if int64(n) > remain { 51 n = int(remain) 52 } 53 n, err1 := syscall.Sendfile(dst, src, nil, n) 54 if n > 0 { 55 written += int64(n) 56 remain -= int64(n) 57 } 58 if n == 0 && err1 == nil { 59 break 60 } 61 if err1 == syscall.EAGAIN && c.wdeadline >= 0 { 62 if err1 = pollserver.WaitWrite(c); err1 == nil { 63 continue 64 } 65 } 66 if err1 != nil { 67 // This includes syscall.ENOSYS (no kernel 68 // support) and syscall.EINVAL (fd types which 69 // don't implement sendfile together) 70 err = &OpError{"sendfile", c.net, c.raddr, err1} 71 break 72 } 73 } 74 if lr != nil { 75 lr.N = remain 76 } 77 return written, err, written > 0 78 }