net: use same sendFile for freebsd/dragonfly and solaris

FreeBSD/Dragonfly and Solaris have identical implementations of
sendFile. Keep one and adjust the comments accordingly.

Change-Id: I77b0f88a4816dd6e40f5cb33919c44606401ac6b
Reviewed-on: https://go-review.googlesource.com/104915
Run-TryBot: Tobias Klauser <tobias.klauser@gmail.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>

src/net/sendfile_solaris.go

-// Copyright 2015 The Go Authors. All rights reserved.
-// Use of this source code is governed by a BSD-style
-// license that can be found in the LICENSE file.
-
-package net
-
-import (
-	"internal/poll"
-	"io"
-	"os"
-)
-
-// sendFile copies the contents of r to c using the sendfile
-// system call to minimize copies.
-//
-// if handled == true, sendFile returns the number of bytes copied and any
-// non-EOF error.
-//
-// if handled == false, sendFile performed no work.
-func sendFile(c *netFD, r io.Reader) (written int64, err error, handled bool) {
-	// Solaris uses 0 as the "until EOF" value. If you pass in more bytes than the
-	// file contains, it will loop back to the beginning ad nauseam until it's sent
-	// exactly the number of bytes told to. As such, we need to know exactly how many
-	// bytes to send.
-	var remain int64 = 0
-
-	lr, ok := r.(*io.LimitedReader)
-	if ok {
-		remain, r = lr.N, lr.R
-		if remain <= 0 {
-			return 0, nil, true
-		}
-	}
-	f, ok := r.(*os.File)
-	if !ok {
-		return 0, nil, false
-	}
-
-	if remain == 0 {
-		fi, err := f.Stat()
-		if err != nil {
-			return 0, err, false
-		}
-
-		remain = fi.Size()
-	}
-
-	// The other quirk with Solaris's sendfile implementation is that it doesn't
-	// use the current position of the file -- if you pass it offset 0, it starts
-	// from offset 0. There's no way to tell it "start from current position", so
-	// we have to manage that explicitly.
-	pos, err := f.Seek(0, io.SeekCurrent)
-	if err != nil {
-		return 0, err, false
-	}
-
-	written, err = poll.SendFile(&c.pfd, int(f.Fd()), pos, remain)
-
-	if lr != nil {
-		lr.N = remain - written
-	}
-	return written, wrapSyscallError("sendfile", err), written > 0
-}

src/net/sendfile_bsd.go → src/net/sendfile_unix_alt.go

@@ -2,7 +2,7 @@
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.
 
-// +build dragonfly freebsd
+// +build dragonfly freebsd solaris
 
 package net
 
@@ -20,7 +20,7 @@ import (
 //
 // if handled == false, sendFile performed no work.
 func sendFile(c *netFD, r io.Reader) (written int64, err error, handled bool) {
-	// FreeBSD and DragonFly use 0 as the "until EOF" value.
+	// FreeBSD, DragonFly and Solaris use 0 as the "until EOF" value.
 	// If you pass in more bytes than the file contains, it will
 	// loop back to the beginning ad nauseam until it's sent
 	// exactly the number of bytes told to. As such, we need to
@@ -48,7 +48,7 @@ func sendFile(c *netFD, r io.Reader) (written int64, err error, handled bool) {
 		remain = fi.Size()
 	}
 
-	// The other quirk with FreeBSD/DragonFly's sendfile
+	// The other quirk with FreeBSD/DragonFly/Solaris's sendfile
 	// implementation is that it doesn't use the current position
 	// of the file -- if you pass it offset 0, it starts from
 	// offset 0. There's no way to tell it "start from current