syscall: Create syscall_bsd.go for code used by Darwin and other *BSDs

In this change I'd like to combine the common code that is
present in syscall_darwin.go and syscall_freebsd.go.  I
have three reasons for wanting to do this now:

1. reducing code duplication is nearly always good :-)
2. the duplication will get worse if I duplicate this code
   a third time for the NetBSD port I'm working on, which
   I need to do almost immediately
3. by making this change all in one lump and ignoring any
   commonality with the syscall_linux*.go files the diff
   is long but, I think, readable

In future it may be possible to cherry pick functions that
also apply to Linux and put them in (say) syscall_unix.go,
and of course some functions may diverge in future and have
to move out to OS or architecture specific files, but today
I want just the low hanging fruit.

Tested and passed on:

  Darwin (Snow Leopard, 10.6): amd64 and 386
  FreeBSD (8.0-RELEASE):       386 only(*)

(*) All my virtualisation software has stopped playing nice
with FreeBSD for the moment, so I don't have facilities to
test the amd64 port.  As the OS X port is OK and the diff
looks all right to my eyes I shall keep my fingers crossed.
If someone with a FreeBSD/amd64 system cares to test and
report I would be appreciative.

2010-03-27 update: I have replaced my virtualisation software, and have working FreeBSD/i386 and FreeBSD/amd64 virtual machines again.

As I hoped (and expected -- programmers are optimists :-) the code built and passed all but the two currently known to fail tests on FreeBSD/amd64. I rechecked FreeBSD/i386 too: same results.

R=rsc
CC=golang-dev
https://golang.org/cl/751041
diff --git a/src/pkg/syscall/syscall_freebsd.go b/src/pkg/syscall/syscall_freebsd.go
index a1a34b2..acf6367 100644
--- a/src/pkg/syscall/syscall_freebsd.go
+++ b/src/pkg/syscall/syscall_freebsd.go
@@ -1,4 +1,4 @@
-// Copyright 2009 The Go Authors. All rights reserved.
+// Copyright 2009,2010 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.
 
@@ -6,474 +6,15 @@
 // This file is compiled as ordinary Go code,
 // but it is also input to mksyscall,
 // which parses the //sys lines and generates system call stubs.
-// Note that sometimes we use a lowercase //sys name and
-// wrap it in our own nicer implementation.
+// Note that sometimes we use a lowercase //sys name and wrap
+// it in our own nicer implementation, either here or in
+// syscall_bsd.go or syscall_unix.go.
 
 package syscall
 
-import "unsafe"
-
 const OS = "freebsd"
 
 /*
- * Pseudo-system calls
- */
-// The const provides a compile-time constant so clients
-// can adjust to whether there is a working Getwd and avoid
-// even linking this function into the binary.  See ../os/getwd.go.
-const ImplementsGetwd = false
-
-func Getwd() (string, int) { return "", ENOTSUP }
-
-
-/*
- * Wrapped
- */
-
-//sys	getgroups(ngid int, gid *_Gid_t) (n int, errno int)
-//sys	setgroups(ngid int, gid *_Gid_t) (errno int)
-
-func Getgroups() (gids []int, errno int) {
-	n, err := getgroups(0, nil)
-	if err != 0 {
-		return nil, errno
-	}
-	if n == 0 {
-		return nil, 0
-	}
-
-	// Sanity check group count.  Max is 16 on BSD.
-	if n < 0 || n > 1000 {
-		return nil, EINVAL
-	}
-
-	a := make([]_Gid_t, n)
-	n, err = getgroups(n, &a[0])
-	if err != 0 {
-		return nil, errno
-	}
-	gids = make([]int, n)
-	for i, v := range a[0:n] {
-		gids[i] = int(v)
-	}
-	return
-}
-
-func Setgroups(gids []int) (errno int) {
-	if len(gids) == 0 {
-		return setgroups(0, nil)
-	}
-
-	a := make([]_Gid_t, len(gids))
-	for i, v := range gids {
-		a[i] = _Gid_t(v)
-	}
-	return setgroups(len(a), &a[0])
-}
-
-// Wait status is 7 bits at bottom, either 0 (exited),
-// 0x7F (stopped), or a signal number that caused an exit.
-// The 0x80 bit is whether there was a core dump.
-// An extra number (exit code, signal causing a stop)
-// is in the high bits.
-
-type WaitStatus uint32
-
-const (
-	mask  = 0x7F
-	core  = 0x80
-	shift = 8
-
-	exited  = 0
-	stopped = 0x7F
-)
-
-func (w WaitStatus) Exited() bool { return w&mask == exited }
-
-func (w WaitStatus) ExitStatus() int {
-	if w&mask != exited {
-		return -1
-	}
-	return int(w >> shift)
-}
-
-func (w WaitStatus) Signaled() bool { return w&mask != stopped && w&mask != 0 }
-
-func (w WaitStatus) Signal() int {
-	sig := int(w & mask)
-	if sig == stopped || sig == 0 {
-		return -1
-	}
-	return sig
-}
-
-func (w WaitStatus) CoreDump() bool { return w.Signaled() && w&core != 0 }
-
-func (w WaitStatus) Stopped() bool { return w&mask == stopped && w>>shift != SIGSTOP }
-
-func (w WaitStatus) Continued() bool { return w&mask == stopped && w>>shift == SIGSTOP }
-
-func (w WaitStatus) StopSignal() int {
-	if !w.Stopped() {
-		return -1
-	}
-	return int(w>>shift) & 0xFF
-}
-
-func (w WaitStatus) TrapCause() int {
-	// Darwin doesn't have trap causes
-	return -1
-}
-
-//sys	wait4(pid int, wstatus *_C_int, options int, rusage *Rusage) (wpid int, errno int)
-
-func Wait4(pid int, wstatus *WaitStatus, options int, rusage *Rusage) (wpid int, errno int) {
-	var status _C_int
-	wpid, errno = wait4(pid, &status, options, rusage)
-	if wstatus != nil {
-		*wstatus = WaitStatus(status)
-	}
-	return
-}
-
-//sys	pipe() (r int, w int, errno int)
-
-func Pipe(p []int) (errno int) {
-	if len(p) != 2 {
-		return EINVAL
-	}
-	p[0], p[1], errno = pipe()
-	return
-}
-
-func Sleep(ns int64) (errno int) {
-	tv := NsecToTimeval(ns)
-	return Select(0, nil, nil, nil, &tv)
-}
-
-//sys	accept(s int, rsa *RawSockaddrAny, addrlen *_Socklen) (fd int, errno int)
-//sys	bind(s int, addr uintptr, addrlen _Socklen) (errno int)
-//sys	connect(s int, addr uintptr, addrlen _Socklen) (errno int)
-//sys	socket(domain int, typ int, proto int) (fd int, errno int)
-//sys	setsockopt(s int, level int, name int, val uintptr, vallen int) (errno int)
-//sys	getpeername(fd int, rsa *RawSockaddrAny, addrlen *_Socklen) (errno int)
-//sys	getsockname(fd int, rsa *RawSockaddrAny, addrlen *_Socklen) (errno int)
-//sys	Shutdown(s int, how int) (errno int)
-
-// For testing: clients can set this flag to force
-// creation of IPv6 sockets to return EAFNOSUPPORT.
-var SocketDisableIPv6 bool
-
-type Sockaddr interface {
-	sockaddr() (ptr uintptr, len _Socklen, errno int) // lowercase; only we can define Sockaddrs
-}
-
-type SockaddrInet4 struct {
-	Port int
-	Addr [4]byte
-	raw  RawSockaddrInet4
-}
-
-func (sa *SockaddrInet4) sockaddr() (uintptr, _Socklen, int) {
-	if sa.Port < 0 || sa.Port > 0xFFFF {
-		return 0, 0, EINVAL
-	}
-	sa.raw.Len = SizeofSockaddrInet4
-	sa.raw.Family = AF_INET
-	p := (*[2]byte)(unsafe.Pointer(&sa.raw.Port))
-	p[0] = byte(sa.Port >> 8)
-	p[1] = byte(sa.Port)
-	for i := 0; i < len(sa.Addr); i++ {
-		sa.raw.Addr[i] = sa.Addr[i]
-	}
-	return uintptr(unsafe.Pointer(&sa.raw)), _Socklen(sa.raw.Len), 0
-}
-
-type SockaddrInet6 struct {
-	Port int
-	Addr [16]byte
-	raw  RawSockaddrInet6
-}
-
-func (sa *SockaddrInet6) sockaddr() (uintptr, _Socklen, int) {
-	if sa.Port < 0 || sa.Port > 0xFFFF {
-		return 0, 0, EINVAL
-	}
-	sa.raw.Len = SizeofSockaddrInet6
-	sa.raw.Family = AF_INET6
-	p := (*[2]byte)(unsafe.Pointer(&sa.raw.Port))
-	p[0] = byte(sa.Port >> 8)
-	p[1] = byte(sa.Port)
-	for i := 0; i < len(sa.Addr); i++ {
-		sa.raw.Addr[i] = sa.Addr[i]
-	}
-	return uintptr(unsafe.Pointer(&sa.raw)), _Socklen(sa.raw.Len), 0
-}
-
-type SockaddrUnix struct {
-	Name string
-	raw  RawSockaddrUnix
-}
-
-func (sa *SockaddrUnix) sockaddr() (uintptr, _Socklen, int) {
-	name := sa.Name
-	n := len(name)
-	if n >= len(sa.raw.Path) || n == 0 {
-		return 0, 0, EINVAL
-	}
-	sa.raw.Len = byte(3 + n) // 2 for Family, Len; 1 for NUL
-	sa.raw.Family = AF_UNIX
-	for i := 0; i < n; i++ {
-		sa.raw.Path[i] = int8(name[i])
-	}
-	return uintptr(unsafe.Pointer(&sa.raw)), _Socklen(sa.raw.Len), 0
-}
-
-func anyToSockaddr(rsa *RawSockaddrAny) (Sockaddr, int) {
-	switch rsa.Addr.Family {
-	case AF_UNIX:
-		pp := (*RawSockaddrUnix)(unsafe.Pointer(rsa))
-		if pp.Len < 3 || pp.Len > SizeofSockaddrUnix {
-			return nil, EINVAL
-		}
-		sa := new(SockaddrUnix)
-		n := int(pp.Len) - 3 // subtract leading Family, Len, terminating NUL
-		for i := 0; i < n; i++ {
-			if pp.Path[i] == 0 {
-				// found early NUL; assume Len is overestimating
-				n = i
-				break
-			}
-		}
-		bytes := (*[len(pp.Path)]byte)(unsafe.Pointer(&pp.Path[0]))
-		sa.Name = string(bytes[0:n])
-		return sa, 0
-
-	case AF_INET:
-		pp := (*RawSockaddrInet4)(unsafe.Pointer(rsa))
-		sa := new(SockaddrInet4)
-		p := (*[2]byte)(unsafe.Pointer(&pp.Port))
-		sa.Port = int(p[0])<<8 + int(p[1])
-		for i := 0; i < len(sa.Addr); i++ {
-			sa.Addr[i] = pp.Addr[i]
-		}
-		return sa, 0
-
-	case AF_INET6:
-		pp := (*RawSockaddrInet6)(unsafe.Pointer(rsa))
-		sa := new(SockaddrInet6)
-		p := (*[2]byte)(unsafe.Pointer(&pp.Port))
-		sa.Port = int(p[0])<<8 + int(p[1])
-		for i := 0; i < len(sa.Addr); i++ {
-			sa.Addr[i] = pp.Addr[i]
-		}
-		return sa, 0
-	}
-	return nil, EAFNOSUPPORT
-}
-
-func Accept(fd int) (nfd int, sa Sockaddr, errno int) {
-	var rsa RawSockaddrAny
-	var len _Socklen = SizeofSockaddrAny
-	nfd, errno = accept(fd, &rsa, &len)
-	if errno != 0 {
-		return
-	}
-	sa, errno = anyToSockaddr(&rsa)
-	if errno != 0 {
-		Close(nfd)
-		nfd = 0
-	}
-	return
-}
-
-func Getsockname(fd int) (sa Sockaddr, errno int) {
-	var rsa RawSockaddrAny
-	var len _Socklen = SizeofSockaddrAny
-	if errno = getsockname(fd, &rsa, &len); errno != 0 {
-		return
-	}
-	return anyToSockaddr(&rsa)
-}
-
-func Getpeername(fd int) (sa Sockaddr, errno int) {
-	var rsa RawSockaddrAny
-	var len _Socklen = SizeofSockaddrAny
-	if errno = getpeername(fd, &rsa, &len); errno != 0 {
-		return
-	}
-	return anyToSockaddr(&rsa)
-}
-
-func Bind(fd int, sa Sockaddr) (errno int) {
-	ptr, n, err := sa.sockaddr()
-	if err != 0 {
-		return err
-	}
-	return bind(fd, ptr, n)
-}
-
-func Connect(fd int, sa Sockaddr) (errno int) {
-	ptr, n, err := sa.sockaddr()
-	if err != 0 {
-		return err
-	}
-	return connect(fd, ptr, n)
-}
-
-func Socket(domain, typ, proto int) (fd, errno int) {
-	if domain == AF_INET6 && SocketDisableIPv6 {
-		return -1, EAFNOSUPPORT
-	}
-	fd, errno = socket(domain, typ, proto)
-	return
-}
-
-func SetsockoptInt(fd, level, opt int, value int) (errno int) {
-	var n = int32(value)
-	return setsockopt(fd, level, opt, uintptr(unsafe.Pointer(&n)), 4)
-}
-
-func SetsockoptTimeval(fd, level, opt int, tv *Timeval) (errno int) {
-	return setsockopt(fd, level, opt, uintptr(unsafe.Pointer(tv)), unsafe.Sizeof(*tv))
-}
-
-func SetsockoptLinger(fd, level, opt int, l *Linger) (errno int) {
-	return setsockopt(fd, level, opt, uintptr(unsafe.Pointer(l)), unsafe.Sizeof(*l))
-}
-
-func SetsockoptString(fd, level, opt int, s string) (errno int) {
-	return setsockopt(fd, level, opt, uintptr(unsafe.Pointer(&[]byte(s)[0])), len(s))
-}
-
-//sys recvfrom(fd int, p []byte, flags int, from *RawSockaddrAny, fromlen *_Socklen) (n int, errno int)
-
-func Recvfrom(fd int, p []byte, flags int) (n int, from Sockaddr, errno int) {
-	var rsa RawSockaddrAny
-	var len _Socklen = SizeofSockaddrAny
-	if n, errno = recvfrom(fd, p, flags, &rsa, &len); errno != 0 {
-		return
-	}
-	from, errno = anyToSockaddr(&rsa)
-	return
-}
-
-//sys sendto(s int, buf []byte, flags int, to uintptr, addrlen _Socklen) (errno int)
-
-func Sendto(fd int, p []byte, flags int, to Sockaddr) (errno int) {
-	ptr, n, err := to.sockaddr()
-	if err != 0 {
-		return err
-	}
-	return sendto(fd, p, flags, ptr, n)
-}
-
-//sys	kevent(kq int, change uintptr, nchange int, event uintptr, nevent int, timeout *Timespec) (n int, errno int)
-
-func Kevent(kq int, changes, events []Kevent_t, timeout *Timespec) (n int, errno int) {
-	var change, event uintptr
-	if len(changes) > 0 {
-		change = uintptr(unsafe.Pointer(&changes[0]))
-	}
-	if len(events) > 0 {
-		event = uintptr(unsafe.Pointer(&events[0]))
-	}
-	return kevent(kq, change, len(changes), event, len(events), timeout)
-}
-
-//sys	sysctl(mib []_C_int, old *byte, oldlen *uintptr, new *byte, newlen uintptr) (errno int) = SYS___SYSCTL
-
-// Translate "kern.hostname" to []_C_int{0,1,2,3}.
-func nametomib(name string) (mib []_C_int, errno int) {
-	const CTL_MAXNAME = 12
-	const siz = uintptr(unsafe.Sizeof(mib[0]))
-
-	// NOTE(rsc): It seems strange to set the buffer to have
-	// size CTL_MAXNAME+2 but use only CTL_MAXNAME
-	// as the size.  I don't know why the +2 is here, but the
-	// kernel uses +2 for its own implementation of this function.
-	// I am scared that if we don't include the +2 here, the kernel
-	// will silently write 2 words farther than we specify
-	// and we'll get memory corruption.
-	var buf [CTL_MAXNAME + 2]_C_int
-	n := uintptr(CTL_MAXNAME) * siz
-
-	p := (*byte)(unsafe.Pointer(&buf[0]))
-	bytes := StringByteSlice(name)
-
-	// Magic sysctl: "setting" 0.3 to a string name
-	// lets you read back the array of integers form.
-	if errno = sysctl([]_C_int{0, 3}, p, &n, &bytes[0], uintptr(len(name))); errno != 0 {
-		return nil, errno
-	}
-	return buf[0 : n/siz], 0
-}
-
-func Sysctl(name string) (value string, errno int) {
-	// Translate name to mib number.
-	mib, errno := nametomib(name)
-	if errno != 0 {
-		return "", errno
-	}
-
-	// Find size.
-	n := uintptr(0)
-	if errno = sysctl(mib, nil, &n, nil, 0); errno != 0 {
-		return "", errno
-	}
-	if n == 0 {
-		return "", 0
-	}
-
-	// Read into buffer of that size.
-	buf := make([]byte, n)
-	if errno = sysctl(mib, &buf[0], &n, nil, 0); errno != 0 {
-		return "", errno
-	}
-
-	// Throw away terminating NUL.
-	if n > 0 && buf[n-1] == '\x00' {
-		n--
-	}
-	return string(buf[0:n]), 0
-}
-
-func SysctlUint32(name string) (value uint32, errno int) {
-	// Translate name to mib number.
-	mib, errno := nametomib(name)
-	if errno != 0 {
-		return 0, errno
-	}
-
-	// Read into buffer of that size.
-	n := uintptr(4)
-	buf := make([]byte, 4)
-	if errno = sysctl(mib, &buf[0], &n, nil, 0); errno != 0 {
-		return 0, errno
-	}
-	if n != 4 {
-		return 0, EIO
-	}
-	return *(*uint32)(unsafe.Pointer(&buf[0])), 0
-}
-
-// TODO: wrap
-//	Acct(name nil-string) (errno int)
-//	Futimes(fd int, timeval *Timeval) (errno int)	// Pointer to 2 timevals!
-//	Gethostuuid(uuid *byte, timeout *Timespec) (errno int)
-//	Getsockopt(s int, level int, name int, val *byte, vallen *int) (errno int)
-//	Madvise(addr *byte, len int, behav int) (errno int)
-//	Mprotect(addr *byte, len int, prot int) (errno int)
-//	Msync(addr *byte, len int, flags int) (errno int)
-//	Munmap(addr *byte, len int) (errno int)
-//	Ptrace(req int, pid int, addr uintptr, data int) (ret uintptr, errno int)
-//	Recvmsg(s int, msg *Msghdr, flags int) (n int, errno int)
-//	Sendmsg(s int, msg *Msghdr, flags int) (n int, errno int)
-//	Utimes(path string, timeval *Timeval) (errno int)	// Pointer to 2 timevals!
-//sys	fcntl(fd int, cmd int, arg int) (val int, errno int)
-
-
-/*
  * Exposed directly
  */
 //sys	Access(path string, flags int) (errno int)