github.com/miolini/go@v0.0.0-20160405192216-fca68c8cb408/src/net/sendfile_solaris.go (about)

     1  // Copyright 2015 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  // Not strictly needed, but very helpful for debugging, see issue #10221.
    14  //go:cgo_import_dynamic _ _ "libsendfile.so"
    15  //go:cgo_import_dynamic _ _ "libsocket.so"
    16  
    17  // maxSendfileSize is the largest chunk size we ask the kernel to copy
    18  // at a time.
    19  const maxSendfileSize int = 4 << 20
    20  
    21  // sendFile copies the contents of r to c using the sendfile
    22  // system call to minimize copies.
    23  //
    24  // if handled == true, sendFile returns the number of bytes copied and any
    25  // non-EOF error.
    26  //
    27  // if handled == false, sendFile performed no work.
    28  func sendFile(c *netFD, r io.Reader) (written int64, err error, handled bool) {
    29  	return // Solaris sendfile is disabled until Issue 13892 is understood and fixed
    30  
    31  	// Solaris uses 0 as the "until EOF" value. If you pass in more bytes than the
    32  	// file contains, it will loop back to the beginning ad nauseam until it's sent
    33  	// exactly the number of bytes told to. As such, we need to know exactly how many
    34  	// bytes to send.
    35  	var remain int64 = 0
    36  
    37  	lr, ok := r.(*io.LimitedReader)
    38  	if ok {
    39  		remain, r = lr.N, lr.R
    40  		if remain <= 0 {
    41  			return 0, nil, true
    42  		}
    43  	}
    44  	f, ok := r.(*os.File)
    45  	if !ok {
    46  		return 0, nil, false
    47  	}
    48  
    49  	if remain == 0 {
    50  		fi, err := f.Stat()
    51  		if err != nil {
    52  			return 0, err, false
    53  		}
    54  
    55  		remain = fi.Size()
    56  	}
    57  
    58  	// The other quirk with Solaris's sendfile implementation is that it doesn't
    59  	// use the current position of the file -- if you pass it offset 0, it starts
    60  	// from offset 0. There's no way to tell it "start from current position", so
    61  	// we have to manage that explicitly.
    62  	pos, err := f.Seek(0, os.SEEK_CUR)
    63  	if err != nil {
    64  		return 0, err, false
    65  	}
    66  
    67  	if err := c.writeLock(); err != nil {
    68  		return 0, err, true
    69  	}
    70  	defer c.writeUnlock()
    71  
    72  	dst := c.sysfd
    73  	src := int(f.Fd())
    74  	for remain > 0 {
    75  		n := maxSendfileSize
    76  		if int64(n) > remain {
    77  			n = int(remain)
    78  		}
    79  		pos1 := pos
    80  		n, err1 := syscall.Sendfile(dst, src, &pos1, n)
    81  		if n > 0 {
    82  			pos += int64(n)
    83  			written += int64(n)
    84  			remain -= int64(n)
    85  		}
    86  		if n == 0 && err1 == nil {
    87  			break
    88  		}
    89  		if err1 == syscall.EAGAIN {
    90  			if err1 = c.pd.waitWrite(); err1 == nil {
    91  				continue
    92  			}
    93  		}
    94  		if err1 == syscall.EINTR {
    95  			continue
    96  		}
    97  		if err1 != nil {
    98  			// This includes syscall.ENOSYS (no kernel
    99  			// support) and syscall.EINVAL (fd types which
   100  			// don't implement sendfile)
   101  			err = err1
   102  			break
   103  		}
   104  	}
   105  	if lr != nil {
   106  		lr.N = remain
   107  	}
   108  	if err != nil {
   109  		err = os.NewSyscallError("sendfile", err)
   110  	}
   111  	return written, err, written > 0
   112  }