text: // Copyright 2009 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.
  
  // +build darwin dragonfly freebsd linux netbsd openbsd solaris
  
  package syscall
  
  import (
  	"internal/race"
  	"runtime"
  	"sync"
  	"unsafe"
  )
  
  var (
  	Stdin  = 0
  	Stdout = 1
  	Stderr = 2
  )
  
  const (
  	darwin64Bit    = runtime.GOOS == "darwin" && sizeofPtr == 8
  	dragonfly64Bit = runtime.GOOS == "dragonfly" && sizeofPtr == 8
  	netbsd32Bit    = runtime.GOOS == "netbsd" && sizeofPtr == 4
  	solaris64Bit   = runtime.GOOS == "solaris" && sizeofPtr == 8
  )
  
  func Syscall(trap, a1, a2, a3 uintptr) (r1, r2 uintptr, err Errno)
  func Syscall6(trap, a1, a2, a3, a4, a5, a6 uintptr) (r1, r2 uintptr, err Errno)
  func RawSyscall(trap, a1, a2, a3 uintptr) (r1, r2 uintptr, err Errno)
  func RawSyscall6(trap, a1, a2, a3, a4, a5, a6 uintptr) (r1, r2 uintptr, err Errno)
  
  // Mmap manager, for use by operating system-specific implementations.
  
  type mmapper struct {
  	sync.Mutex
  	active map[*byte][]byte // active mappings; key is last byte in mapping
  	mmap   func(addr, length uintptr, prot, flags, fd int, offset int64) (uintptr, error)
  	munmap func(addr uintptr, length uintptr) error
  }
  
  func (m *mmapper) Mmap(fd int, offset int64, length int, prot int, flags int) (data []byte, err error) {
  	if length <= 0 {
  		return nil, EINVAL
  	}
  
  	// Map the requested memory.
  	addr, errno := m.mmap(0, uintptr(length), prot, flags, fd, offset)
  	if errno != nil {
  		return nil, errno
  	}
  
  	// Slice memory layout
  	var sl = struct {
  		addr uintptr
  		len  int
  		cap  int
  	}{addr, length, length}
  
  	// Use unsafe to turn sl into a []byte.
  	b := *(*[]byte)(unsafe.Pointer(&sl))
  
  	// Register mapping in m and return it.
  	p := &b[cap(b)-1]
  	m.Lock()
  	defer m.Unlock()
  	m.active[p] = b
  	return b, nil
  }
  
  func (m *mmapper) Munmap(data []byte) (err error) {
  	if len(data) == 0 || len(data) != cap(data) {
  		return EINVAL
  	}
  
  	// Find the base of the mapping.
  	p := &data[cap(data)-1]
  	m.Lock()
  	defer m.Unlock()
  	b := m.active[p]
  	if b == nil || &b[0] != &data[0] {
  		return EINVAL
  	}
  
  	// Unmap the memory and update m.
  	if errno := m.munmap(uintptr(unsafe.Pointer(&b[0])), uintptr(len(b))); errno != nil {
  		return errno
  	}
  	delete(m.active, p)
  	return nil
  }
  
  // An Errno is an unsigned number describing an error condition.
  // It implements the error interface. The zero Errno is by convention
  // a non-error, so code to convert from Errno to error should use:
  //	err = nil
  //	if errno != 0 {
  //		err = errno
  //	}
  type Errno uintptr
  
  func (e Errno) Error() string {
  	if 0 <= int(e) && int(e) < len(errors) {
  		s := errors[e]
  		if s != "" {
  			return s
  		}
  	}
  	return "errno " + itoa(int(e))
  }
  
  func (e Errno) Temporary() bool {
  	return e == EINTR || e == EMFILE || e == ECONNRESET || e == ECONNABORTED || e.Timeout()
  }
  
  func (e Errno) Timeout() bool {
  	return e == EAGAIN || e == EWOULDBLOCK || e == ETIMEDOUT
  }
  
  // Do the interface allocations only once for common
  // Errno values.
  var (
  	errEAGAIN error = EAGAIN
  	errEINVAL error = EINVAL
  	errENOENT error = ENOENT
  )
  
  // errnoErr returns common boxed Errno values, to prevent
  // allocations at runtime.
  func errnoErr(e Errno) error {
  	switch e {
  	case 0:
  		return nil
  	case EAGAIN:
  		return errEAGAIN
  	case EINVAL:
  		return errEINVAL
  	case ENOENT:
  		return errENOENT
  	}
  	return e
  }
  
  // A Signal is a number describing a process signal.
  // It implements the os.Signal interface.
  type Signal int
  
  func (s Signal) Signal() {}
  
  func (s Signal) String() string {
  	if 0 <= s && int(s) < len(signals) {
  		str := signals[s]
  		if str != "" {
  			return str
  		}
  	}
  	return "signal " + itoa(int(s))
  }
  
  func Read(fd int, p []byte) (n int, err error) {
  	n, err = read(fd, p)
  	if race.Enabled {
  		if n > 0 {
  			race.WriteRange(unsafe.Pointer(&p[0]), n)
  		}
  		if err == nil {
  			race.Acquire(unsafe.Pointer(&ioSync))
  		}
  	}
  	if msanenabled && n > 0 {
  		msanWrite(unsafe.Pointer(&p[0]), n)
  	}
  	return
  }
  
  func Write(fd int, p []byte) (n int, err error) {
  	if race.Enabled {
  		race.ReleaseMerge(unsafe.Pointer(&ioSync))
  	}
  	n, err = write(fd, p)
  	if race.Enabled && n > 0 {
  		race.ReadRange(unsafe.Pointer(&p[0]), n)
  	}
  	if msanenabled && n > 0 {
  		msanRead(unsafe.Pointer(&p[0]), n)
  	}
  	return
  }
  
  // For testing: clients can set this flag to force
  // creation of IPv6 sockets to return EAFNOSUPPORT.
  var SocketDisableIPv6 bool
  
  type Sockaddr interface {
  	sockaddr() (ptr unsafe.Pointer, len _Socklen, err error) // lowercase; only we can define Sockaddrs
  }
  
  type SockaddrInet4 struct {
  	Port int
  	Addr [4]byte
  	raw  RawSockaddrInet4
  }
  
  type SockaddrInet6 struct {
  	Port   int
  	ZoneId uint32
  	Addr   [16]byte
  	raw    RawSockaddrInet6
  }
  
  type SockaddrUnix struct {
  	Name string
  	raw  RawSockaddrUnix
  }
  
  func Bind(fd int, sa Sockaddr) (err error) {
  	ptr, n, err := sa.sockaddr()
  	if err != nil {
  		return err
  	}
  	return bind(fd, ptr, n)
  }
  
  func Connect(fd int, sa Sockaddr) (err error) {
  	ptr, n, err := sa.sockaddr()
  	if err != nil {
  		return err
  	}
  	return connect(fd, ptr, n)
  }
  
  func Getpeername(fd int) (sa Sockaddr, err error) {
  	var rsa RawSockaddrAny
  	var len _Socklen = SizeofSockaddrAny
  	if err = getpeername(fd, &rsa, &len); err != nil {
  		return
  	}
  	return anyToSockaddr(&rsa)
  }
  
  func GetsockoptInt(fd, level, opt int) (value int, err error) {
  	var n int32
  	vallen := _Socklen(4)
  	err = getsockopt(fd, level, opt, unsafe.Pointer(&n), &vallen)
  	return int(n), err
  }
  
  func Recvfrom(fd int, p []byte, flags int) (n int, from Sockaddr, err error) {
  	var rsa RawSockaddrAny
  	var len _Socklen = SizeofSockaddrAny
  	if n, err = recvfrom(fd, p, flags, &rsa, &len); err != nil {
  		return
  	}
  	if rsa.Addr.Family != AF_UNSPEC {
  		from, err = anyToSockaddr(&rsa)
  	}
  	return
  }
  
  func Sendto(fd int, p []byte, flags int, to Sockaddr) (err error) {
  	ptr, n, err := to.sockaddr()
  	if err != nil {
  		return err
  	}
  	return sendto(fd, p, flags, ptr, n)
  }
  
  func SetsockoptByte(fd, level, opt int, value byte) (err error) {
  	return setsockopt(fd, level, opt, unsafe.Pointer(&value), 1)
  }
  
  func SetsockoptInt(fd, level, opt int, value int) (err error) {
  	var n = int32(value)
  	return setsockopt(fd, level, opt, unsafe.Pointer(&n), 4)
  }
  
  func SetsockoptInet4Addr(fd, level, opt int, value [4]byte) (err error) {
  	return setsockopt(fd, level, opt, unsafe.Pointer(&value[0]), 4)
  }
  
  func SetsockoptIPMreq(fd, level, opt int, mreq *IPMreq) (err error) {
  	return setsockopt(fd, level, opt, unsafe.Pointer(mreq), SizeofIPMreq)
  }
  
  func SetsockoptIPv6Mreq(fd, level, opt int, mreq *IPv6Mreq) (err error) {
  	return setsockopt(fd, level, opt, unsafe.Pointer(mreq), SizeofIPv6Mreq)
  }
  
  func SetsockoptICMPv6Filter(fd, level, opt int, filter *ICMPv6Filter) error {
  	return setsockopt(fd, level, opt, unsafe.Pointer(filter), SizeofICMPv6Filter)
  }
  
  func SetsockoptLinger(fd, level, opt int, l *Linger) (err error) {
  	return setsockopt(fd, level, opt, unsafe.Pointer(l), SizeofLinger)
  }
  
  func SetsockoptString(fd, level, opt int, s string) (err error) {
  	return setsockopt(fd, level, opt, unsafe.Pointer(&[]byte(s)[0]), uintptr(len(s)))
  }
  
  func SetsockoptTimeval(fd, level, opt int, tv *Timeval) (err error) {
  	return setsockopt(fd, level, opt, unsafe.Pointer(tv), unsafe.Sizeof(*tv))
  }
  
  func Socket(domain, typ, proto int) (fd int, err error) {
  	if domain == AF_INET6 && SocketDisableIPv6 {
  		return -1, EAFNOSUPPORT
  	}
  	fd, err = socket(domain, typ, proto)
  	return
  }
  
  func Socketpair(domain, typ, proto int) (fd [2]int, err error) {
  	var fdx [2]int32
  	err = socketpair(domain, typ, proto, &fdx)
  	if err == nil {
  		fd[0] = int(fdx[0])
  		fd[1] = int(fdx[1])
  	}
  	return
  }
  
  func Sendfile(outfd int, infd int, offset *int64, count int) (written int, err error) {
  	if race.Enabled {
  		race.ReleaseMerge(unsafe.Pointer(&ioSync))
  	}
  	return sendfile(outfd, infd, offset, count)
  }
  
  var ioSync int64
  