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 aix darwin dragonfly freebsd linux netbsd openbsd solaris
  
  package unix
  
  import (
  	"bytes"
  	"sort"
  	"sync"
  	"syscall"
  	"unsafe"
  )
  
  var (
  	Stdin  = 0
  	Stdout = 1
  	Stderr = 2
  )
  
  // Do the interface allocations only once for common
  // Errno values.
  var (
  	errEAGAIN error = syscall.EAGAIN
  	errEINVAL error = syscall.EINVAL
  	errENOENT error = syscall.ENOENT
  )
  
  // errnoErr returns common boxed Errno values, to prevent
  // allocations at runtime.
  func errnoErr(e syscall.Errno) error {
  	switch e {
  	case 0:
  		return nil
  	case EAGAIN:
  		return errEAGAIN
  	case EINVAL:
  		return errEINVAL
  	case ENOENT:
  		return errENOENT
  	}
  	return e
  }
  
  // ErrnoName returns the error name for error number e.
  func ErrnoName(e syscall.Errno) string {
  	i := sort.Search(len(errorList), func(i int) bool {
  		return errorList[i].num >= e
  	})
  	if i < len(errorList) && errorList[i].num == e {
  		return errorList[i].name
  	}
  	return ""
  }
  
  // SignalName returns the signal name for signal number s.
  func SignalName(s syscall.Signal) string {
  	i := sort.Search(len(signalList), func(i int) bool {
  		return signalList[i].num >= s
  	})
  	if i < len(signalList) && signalList[i].num == s {
  		return signalList[i].name
  	}
  	return ""
  }
  
  // clen returns the index of the first NULL byte in n or len(n) if n contains no NULL byte.
  func clen(n []byte) int {
  	i := bytes.IndexByte(n, 0)
  	if i == -1 {
  		i = len(n)
  	}
  	return i
  }
  
  // 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
  }
  
  func Read(fd int, p []byte) (n int, err error) {
  	n, err = read(fd, p)
  	if raceenabled {
  		if n > 0 {
  			raceWriteRange(unsafe.Pointer(&p[0]), n)
  		}
  		if err == nil {
  			raceAcquire(unsafe.Pointer(&ioSync))
  		}
  	}
  	return
  }
  
  func Write(fd int, p []byte) (n int, err error) {
  	if raceenabled {
  		raceReleaseMerge(unsafe.Pointer(&ioSync))
  	}
  	n, err = write(fd, p)
  	if raceenabled && n > 0 {
  		raceReadRange(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
  
  // Sockaddr represents a socket address.
  type Sockaddr interface {
  	sockaddr() (ptr unsafe.Pointer, len _Socklen, err error) // lowercase; only we can define Sockaddrs
  }
  
  // SockaddrInet4 implements the Sockaddr interface for AF_INET type sockets.
  type SockaddrInet4 struct {
  	Port int
  	Addr [4]byte
  	raw  RawSockaddrInet4
  }
  
  // SockaddrInet6 implements the Sockaddr interface for AF_INET6 type sockets.
  type SockaddrInet6 struct {
  	Port   int
  	ZoneId uint32
  	Addr   [16]byte
  	raw    RawSockaddrInet6
  }
  
  // SockaddrUnix implements the Sockaddr interface for AF_UNIX type sockets.
  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(fd, &rsa)
  }
  
  func GetsockoptByte(fd, level, opt int) (value byte, err error) {
  	var n byte
  	vallen := _Socklen(1)
  	err = getsockopt(fd, level, opt, unsafe.Pointer(&n), &vallen)
  	return n, err
  }
  
  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 GetsockoptInet4Addr(fd, level, opt int) (value [4]byte, err error) {
  	vallen := _Socklen(4)
  	err = getsockopt(fd, level, opt, unsafe.Pointer(&value[0]), &vallen)
  	return value, err
  }
  
  func GetsockoptIPMreq(fd, level, opt int) (*IPMreq, error) {
  	var value IPMreq
  	vallen := _Socklen(SizeofIPMreq)
  	err := getsockopt(fd, level, opt, unsafe.Pointer(&value), &vallen)
  	return &value, err
  }
  
  func GetsockoptIPv6Mreq(fd, level, opt int) (*IPv6Mreq, error) {
  	var value IPv6Mreq
  	vallen := _Socklen(SizeofIPv6Mreq)
  	err := getsockopt(fd, level, opt, unsafe.Pointer(&value), &vallen)
  	return &value, err
  }
  
  func GetsockoptIPv6MTUInfo(fd, level, opt int) (*IPv6MTUInfo, error) {
  	var value IPv6MTUInfo
  	vallen := _Socklen(SizeofIPv6MTUInfo)
  	err := getsockopt(fd, level, opt, unsafe.Pointer(&value), &vallen)
  	return &value, err
  }
  
  func GetsockoptICMPv6Filter(fd, level, opt int) (*ICMPv6Filter, error) {
  	var value ICMPv6Filter
  	vallen := _Socklen(SizeofICMPv6Filter)
  	err := getsockopt(fd, level, opt, unsafe.Pointer(&value), &vallen)
  	return &value, err
  }
  
  func GetsockoptLinger(fd, level, opt int) (*Linger, error) {
  	var linger Linger
  	vallen := _Socklen(SizeofLinger)
  	err := getsockopt(fd, level, opt, unsafe.Pointer(&linger), &vallen)
  	return &linger, err
  }
  
  func GetsockoptTimeval(fd, level, opt int) (*Timeval, error) {
  	var tv Timeval
  	vallen := _Socklen(unsafe.Sizeof(tv))
  	err := getsockopt(fd, level, opt, unsafe.Pointer(&tv), &vallen)
  	return &tv, 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(fd, &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
  }
  
  var ioSync int64
  
  func CloseOnExec(fd int) { fcntl(fd, F_SETFD, FD_CLOEXEC) }
  
  func SetNonblock(fd int, nonblocking bool) (err error) {
  	flag, err := fcntl(fd, F_GETFL, 0)
  	if err != nil {
  		return err
  	}
  	if nonblocking {
  		flag |= O_NONBLOCK
  	} else {
  		flag &= ^O_NONBLOCK
  	}
  	_, err = fcntl(fd, F_SETFL, flag)
  	return err
  }
  
  // Exec calls execve(2), which replaces the calling executable in the process
  // tree. argv0 should be the full path to an executable ("/bin/ls") and the
  // executable name should also be the first argument in argv (["ls", "-l"]).
  // envv are the environment variables that should be passed to the new
  // process (["USER=go", "PWD=/tmp"]).
  func Exec(argv0 string, argv []string, envv []string) error {
  	return syscall.Exec(argv0, argv, envv)
  }
  