libgo/go/net/sendfile_solaris.go

   1 // Copyright 2015 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 // Not strictly needed, but very helpful for debugging, see issue #10221.
  14 //go:cgo_import_dynamic _ _ "libsendfile.so"
  15 //go:cgo_import_dynamic _ _ "libsocket.so"
  16
  17 // maxSendfileSize is the largest chunk size we ask the kernel to copy
  18 // at a time.
  19 const maxSendfileSize int = 4 << 20
  20
  21 // sendFile copies the contents of r to c using the sendfile
  22 // system call to minimize copies.
  23 //
  24 // if handled == true, sendFile returns the number of bytes copied and any
  25 // non-EOF error.
  26 //
  27 // if handled == false, sendFile performed no work.
  28 func sendFile(c *netFD, r io.Reader) (written int64, err error, handled bool) {
  29         // Solaris uses 0 as the "until EOF" value. If you pass in more bytes than the
  30         // file contains, it will loop back to the beginning ad nauseam until it's sent
  31         // exactly the number of bytes told to. As such, we need to know exactly how many
  32         // bytes to send.
  33         var remain int64 = 0
  34
  35         lr, ok := r.(*io.LimitedReader)
  36         if ok {
  37                 remain, r = lr.N, lr.R
  38                 if remain <= 0 {
  39                         return 0, nil, true
  40                 }
  41         }
  42         f, ok := r.(*os.File)
  43         if !ok {
  44                 return 0, nil, false
  45         }
  46
  47         if remain == 0 {
  48                 fi, err := f.Stat()
  49                 if err != nil {
  50                         return 0, err, false
  51                 }
  52
  53                 remain = fi.Size()
  54         }
  55
  56         // The other quirk with Solaris's sendfile implementation is that it doesn't
  57         // use the current position of the file -- if you pass it offset 0, it starts
  58         // from offset 0. There's no way to tell it "start from current position", so
  59         // we have to manage that explicitly.
  60         pos, err := f.Seek(0, io.SeekCurrent)
  61         if err != nil {
  62                 return 0, err, false
  63         }
  64
  65         if err := c.writeLock(); err != nil {
  66                 return 0, err, true
  67         }
  68         defer c.writeUnlock()
  69
  70         dst := c.sysfd
  71         src := int(f.Fd())
  72         for remain > 0 {
  73                 n := maxSendfileSize
  74                 if int64(n) > remain {
  75                         n = int(remain)
  76                 }
  77                 pos1 := pos
  78                 n, err1 := syscall.Sendfile(dst, src, &pos1, n)
  79                 if err1 == syscall.EAGAIN || err1 == syscall.EINTR {
  80                         // partial write may have occurred
  81                         if n = int(pos1 - pos); n == 0 {
  82                                 // nothing more to write
  83                                 err1 = nil
  84                         }
  85                 }
  86                 if n > 0 {
  87                         pos += int64(n)
  88                         written += int64(n)
  89                         remain -= int64(n)
  90                 }
  91                 if n == 0 && err1 == nil {
  92                         break
  93                 }
  94                 if err1 == syscall.EAGAIN {
  95                         if err1 = c.pd.waitWrite(); err1 == nil {
  96                                 continue
  97                         }
  98                 }
  99                 if err1 == syscall.EINTR {
 100                         continue
 101                 }
 102                 if err1 != nil {
 103                         // This includes syscall.ENOSYS (no kernel
 104                         // support) and syscall.EINVAL (fd types which
 105                         // don't implement sendfile)
 106                         err = err1
 107                         break
 108                 }
 109         }
 110         if lr != nil {
 111                 lr.N = remain
 112         }
 113         if err != nil {
 114                 err = os.NewSyscallError("sendfile", err)
 115         }
 116         return written, err, written > 0
 117 }