libgo/go/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 {
  62                         if err1 = c.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 }