syscall, net: sendfile for FreeBSD

R=golang-dev, rsc, bradfitz, devon.odell
CC=golang-dev
https://golang.org/cl/6221054

src/pkg/net/sendfile_freebsd.go

+// Copyright 2011 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 (
+	"io"
+	"os"
+	"syscall"
+)
+
+// maxSendfileSize is the largest chunk size we ask the kernel to copy
+// at a time.
+const maxSendfileSize int = 4 << 20
+
+// 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) {
+	// FreeBSD 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 nauseum 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 FreeBSD'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, os.SEEK_CUR)
+	if err != nil {
+		return 0, err, false
+	}
+
+	c.wio.Lock()
+	defer c.wio.Unlock()
+	if err := c.incref(false); err != nil {
+		return 0, err, true
+	}
+	defer c.decref()
+
+	dst := c.sysfd
+	src := int(f.Fd())
+	for remain > 0 {
+		n := maxSendfileSize
+		if int64(n) > remain {
+			n = int(remain)
+		}
+		n, err1 := syscall.Sendfile(dst, src, pos, n)
+		if n > 0 {
+			pos += int64(n)
+			written += int64(n)
+			remain -= int64(n)
+		}
+		if n == 0 && err1 == nil {
+			break
+		}
+		if err1 == syscall.EAGAIN && c.wdeadline >= 0 {
+			if err1 = pollserver.WaitWrite(c); err1 == nil {
+				continue
+			}
+		}
+		if err1 == syscall.EINTR {
+			continue
+		}
+		if err1 != nil {
+			// This includes syscall.ENOSYS (no kernel
+			// support) and syscall.EINVAL (fd types which
+			// don't implement sendfile together)
+			err = &OpError{"sendfile", c.net, c.raddr, err1}
+			break
+		}
+	}
+	if lr != nil {
+		lr.N = remain
+	}
+	return written, err, written > 0
+}

src/pkg/net/sendfile_stub.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 darwin freebsd netbsd openbsd
+// +build darwin netbsd openbsd
 
 package net
 

src/pkg/syscall/asm_freebsd_amd64.s

@@ -8,6 +8,7 @@
 
 // func Syscall(trap int64, a1, a2, a3 int64) (r1, r2, err int64);
 // func Syscall6(trap int64, a1, a2, a3, a4, a5, a6 int64) (r1, r2, err int64);
+// func Syscall9(trap int64, a1, a2, a3, a4, a5, a6, a7, a8, a9 int64) (r1, r2, err int64)
 // Trap # in AX, args in DI SI DX, return in AX DX
 
 TEXT	·Syscall(SB),7,$0
@@ -56,6 +57,39 @@ ok6:
 	CALL	runtime·exitsyscall(SB)
 	RET
 
+TEXT	·Syscall9(SB),7,$0
+	CALL	runtime·entersyscall(SB)
+	MOVQ	8(SP), AX
+	MOVQ	16(SP), DI
+	MOVQ	24(SP), SI
+	MOVQ	32(SP), DX
+	MOVQ	40(SP),	R10
+	MOVQ	48(SP), R8
+	MOVQ	56(SP), R9
+
+	// shift around the last three arguments so they're at the
+	// top of the stack when the syscall is called.
+	MOVQ	64(SP), R11 // arg 7
+	MOVQ	R11, 8(SP)
+	MOVQ	72(SP), R11 // arg 8
+	MOVQ	R11, 16(SP)
+	MOVQ	80(SP), R11 // arg 9
+	MOVQ	R11, 24(SP)
+
+	SYSCALL
+	JCC	ok9
+	MOVQ	$-1, 88(SP)	// r1
+	MOVQ	$0, 96(SP)	// r2
+	MOVQ	AX, 104(SP)  // errno
+	CALL	runtime·exitsyscall(SB)
+	RET
+ok9:
+	MOVQ	AX, 88(SP)	// r1
+	MOVQ	DX, 96(SP)	// r2
+	MOVQ	$0, 104(SP)	// errno
+	CALL	runtime·exitsyscall(SB)
+	RET
+
 TEXT ·RawSyscall(SB),7,$0
 	MOVQ	16(SP), DI
 	MOVQ	24(SP), SI

src/pkg/syscall/syscall_freebsd.go

@@ -89,9 +89,16 @@ func Pipe(p []int) (err error) {
 	return
 }
 
-// TODO
-func Sendfile(outfd int, infd int, offset *int64, count int) (written int, err error) {
-	return -1, ENOSYS
+func Sendfile(outfd int, infd int, offset int64, count int) (written int, err error) {
+	var writtenOut uint64 = 0
+	_, _, e1 := Syscall9(SYS_SENDFILE, uintptr(infd), uintptr(outfd), uintptr(offset), uintptr(count), 0, uintptr(unsafe.Pointer(&writtenOut)), 0, 0, 0)
+
+	written = int(writtenOut)
+
+	if e1 != 0 {
+		err = e1
+	}
+	return
 }
 
 func GetsockoptIPMreqn(fd, level, opt int) (*IPMreqn, error) {

src/pkg/syscall/syscall_freebsd_amd64.go

@@ -40,3 +40,5 @@ func (msghdr *Msghdr) SetControllen(length int) {
 func (cmsg *Cmsghdr) SetLen(length int) {
 	cmsg.Len = uint32(length)
 }
+
+func Syscall9(num, a1, a2, a3, a4, a5, a6, a7, a8, a9 uintptr) (r1, r2 uintptr, err Errno)