sendfile_linux.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  )
    12  
    13  const supportsSendfile = true
    14  
    15  // sendFile copies the contents of r to c using the sendfile
    16  // system call to minimize copies.
    17  //
    18  // if handled == true, sendFile returns the number (potentially zero) of bytes
    19  // copied and any non-EOF error.
    20  //
    21  // if handled == false, sendFile performed no work.
    22  func sendFile(c *netFD, r io.Reader) (written int64, err error, handled bool) {
    23  	var remain int64 = 1<<63 - 1 // by default, copy until EOF
    24  
    25  	lr, ok := r.(*io.LimitedReader)
    26  	if ok {
    27  		remain, r = lr.N, lr.R
    28  		if remain <= 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  	sc, err := f.SyscallConn()
    38  	if err != nil {
    39  		return 0, nil, false
    40  	}
    41  
    42  	var werr error
    43  	err = sc.Read(func(fd uintptr) bool {
    44  		written, werr, handled = poll.SendFile(&c.pfd, int(fd), remain)
    45  		return true
    46  	})
    47  	if err == nil {
    48  		err = werr
    49  	}
    50  
    51  	if lr != nil {
    52  		lr.N = remain - written
    53  	}
    54  	return written, wrapSyscallError("sendfile", err), handled
    55  }
    56
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