github.com/epfl-dcsl/gotee@v0.0.0-20200909122901-014b35f5e5e9/src/net/sendfile_linux.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  )
    12  
    13  // sendFile copies the contents of r to c using the sendfile
    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  func sendFile(c *netFD, r io.Reader) (written int64, err error, handled bool) {
    21  	var remain int64 = 1 << 62 // by default, copy until EOF
    22  
    23  	lr, ok := r.(*io.LimitedReader)
    24  	if ok {
    25  		remain, r = lr.N, lr.R
    26  		if remain <= 0 {
    27  			return 0, nil, true
    28  		}
    29  	}
    30  	f, ok := r.(*os.File)
    31  	if !ok {
    32  		return 0, nil, false
    33  	}
    34  
    35  	written, err = poll.SendFile(&c.pfd, int(f.Fd()), remain)
    36  
    37  	if lr != nil {
    38  		lr.N = remain - written
    39  	}
    40  	return written, wrapSyscallError("sendfile", err), written > 0
    41  }