github.com/code-reading/golang@v0.0.0-20220303082512-ba5bc0e589a3/go/src/net/sendfile_windows.go (about)

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