sendfile_windows.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  	"internal/poll"
     9  	"io"
    10  	"os"
    11  	"syscall"
    12  )
    13  
    14  const supportsSendfile = true
    15  
    16  // sendFile copies the contents of r to c using the TransmitFile
    17  // system call to minimize copies.
    18  //
    19  // if handled == true, sendFile returns the number of bytes copied and any
    20  // non-EOF error.
    21  //
    22  // if handled == false, sendFile performed no work.
    23  func sendFile(fd *netFD, r io.Reader) (written int64, err error, handled bool) {
    24  	var n int64 = 0 // by default, copy until EOF.
    25  
    26  	lr, ok := r.(*io.LimitedReader)
    27  	if ok {
    28  		n, r = lr.N, lr.R
    29  		if n <= 0 {
    30  			return 0, nil, true
    31  		}
    32  	}
    33  
    34  	f, ok := r.(*os.File)
    35  	if !ok {
    36  		return 0, nil, false
    37  	}
    38  
    39  	written, err = poll.SendFile(&fd.pfd, syscall.Handle(f.Fd()), n)
    40  	if err != nil {
    41  		err = wrapSyscallError("transmitfile", err)
    42  	}
    43  
    44  	// If any byte was copied, regardless of any error
    45  	// encountered mid-way, handled must be set to true.
    46  	handled = written > 0
    47  
    48  	return
    49  }
    50
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