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// 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)
}