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      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 // sendFile copies the contents of r to c using the TransmitFile
     14 // system call to minimize copies.
     15 //
     16 // if handled == true, sendFile returns the number of bytes copied and any
     17 // non-EOF error.
     18 //
     19 // if handled == false, sendFile performed no work.
     20 //
     21 // Note that sendfile for windows does not suppport >2GB file.
     22 func sendFile(fd *netFD, r io.Reader) (written int64, err error, handled bool) {
     23 	var n int64 = 0 // by default, copy until EOF
     24 
     25 	lr, ok := r.(*io.LimitedReader)
     26 	if ok {
     27 		n, r = lr.N, lr.R
     28 		if n <= 0 {
     29 			return 0, nil, true
     30 		}
     31 	}
     32 	f, ok := r.(*os.File)
     33 	if !ok {
     34 		return 0, nil, false
     35 	}
     36 
     37 	if err := fd.writeLock(); err != nil {
     38 		return 0, err, true
     39 	}
     40 	defer fd.writeUnlock()
     41 
     42 	o := &fd.wop
     43 	o.qty = uint32(n)
     44 	o.handle = syscall.Handle(f.Fd())
     45 	done, err := wsrv.ExecIO(o, "TransmitFile", func(o *operation) error {
     46 		return syscall.TransmitFile(o.fd.sysfd, o.handle, o.qty, 0, &o.o, nil, syscall.TF_WRITE_BEHIND)
     47 	})
     48 	if err != nil {
     49 		return 0, os.NewSyscallError("transmitfile", err), false
     50 	}
     51 	if lr != nil {
     52 		lr.N -= int64(done)
     53 	}
     54 	return int64(done), nil, true
     55 }
     56