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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 darwin freebsd linux netbsd openbsd

package os

import (

        "runtime"

        "syscall"

)

// File represents an open file descriptor.

type File struct {

        *file

}

// file is the real representation of *File.

// The extra level of indirection ensures that no clients of os

// can overwrite this data, which could cause the finalizer

// to close the wrong file descriptor.

type file struct {

        fd      int

        name    string

        dirinfo *dirInfo // nil unless directory being read

        nepipe  int      // number of consecutive EPIPE in Write

}

// Fd returns the integer Unix file descriptor referencing the open file.

func (f *File) Fd() int {

        if f == nil {

                return -1

        }

        return f.fd

}

// NewFile returns a new File with the given file descriptor and name.

func NewFile(fd int, name string) *File {

        if fd < 0 {

                return nil

        }

        f := &File{&file{fd: fd, name: name}}

        runtime.SetFinalizer(f.file, (*file).close)

        return f

}

// Auxiliary information if the File describes a directory

type dirInfo struct {

        buf []byte       // buffer for directory I/O

        dir *syscall.DIR // from opendir

}

// DevNull is the name of the operating system's ``null device.''

// On Unix-like systems, it is "/dev/null"; on Windows, "NUL".

const DevNull = "/dev/null"

// OpenFile is the generalized open call; most users will use Open

// or Create instead.  It opens the named file with specified flag

// (O_RDONLY etc.) and perm, (0666 etc.) if applicable.  If successful,

// methods on the returned File can be used for I/O.

// It returns the File and an error, if any.

func OpenFile(name string, flag int, perm FileMode) (file *File, err error) {

        r, e := syscall.Open(name, flag|syscall.O_CLOEXEC, syscallMode(perm))

        if e != nil {

                return nil, &PathError{"open", name, e}

        }

        // There's a race here with fork/exec, which we are

        // content to live with.  See ../syscall/exec_unix.go.

        // On OS X 10.6, the O_CLOEXEC flag is not respected.

        // On OS X 10.7, the O_CLOEXEC flag works.

        // Without a cheap & reliable way to detect 10.6 vs 10.7 at

        // runtime, we just always call syscall.CloseOnExec on Darwin.

        // Once >=10.7 is prevalent, this extra call can removed.

        if syscall.O_CLOEXEC == 0 || runtime.GOOS == "darwin" { // O_CLOEXEC not supported

                syscall.CloseOnExec(r)

        }

        return NewFile(r, name), nil

}

// Close closes the File, rendering it unusable for I/O.

// It returns an error, if any.

func (f *File) Close() error {

        return f.file.close()

}

func (file *file) close() error {

        if file == nil || file.fd < 0 {

                return EINVAL

        }

        var err error

        if e := syscall.Close(file.fd); e != nil {

                err = &PathError{"close", file.name, e}

        }

        if file.dirinfo != nil {

                if libc_closedir(file.dirinfo.dir) < 0 && err == nil {

                        err = &PathError{"closedir", file.name, syscall.GetErrno()}

                }

        }

        file.fd = -1 // so it can't be closed again

        // no need for a finalizer anymore

        runtime.SetFinalizer(file, nil)

        return err

}

// Stat returns the FileInfo structure describing file.

// It returns the FileInfo and an error, if any.

func (f *File) Stat() (fi FileInfo, err error) {

        var stat syscall.Stat_t

        err = syscall.Fstat(f.fd, &stat)

        if err != nil {

                return nil, &PathError{"stat", f.name, err}

        }

        return fileInfoFromStat(&stat, f.name), nil

}

// Stat returns a FileInfo describing the named file and an error, if any.

// If name names a valid symbolic link, the returned FileInfo describes

// the file pointed at by the link and has fi.FollowedSymlink set to true.

// If name names an invalid symbolic link, the returned FileInfo describes

// the link itself and has fi.FollowedSymlink set to false.

func Stat(name string) (fi FileInfo, err error) {

        var stat syscall.Stat_t

        err = syscall.Stat(name, &stat)

        if err != nil {

                return nil, &PathError{"stat", name, err}

        }

        return fileInfoFromStat(&stat, name), nil

}

// Lstat returns a FileInfo describing the named file and an

// error, if any.  If the file is a symbolic link, the returned FileInfo

// describes the symbolic link.  Lstat makes no attempt to follow the link.

func Lstat(name string) (fi FileInfo, err error) {

        var stat syscall.Stat_t

        err = syscall.Lstat(name, &stat)

        if err != nil {

                return nil, &PathError{"lstat", name, err}

        }

        return fileInfoFromStat(&stat, name), nil

}

func (f *File) readdir(n int) (fi []FileInfo, err error) {

        dirname := f.name

        if dirname == "" {

                dirname = "."

        }

        dirname += "/"

        names, err := f.Readdirnames(n)

        fi = make([]FileInfo, len(names))

        for i, filename := range names {

                fip, err := Lstat(dirname + filename)

                if err == nil {

                        fi[i] = fip

                } else {

                        fi[i] = &fileStat{name: filename}

                }

        }

        return fi, err

}

// read reads up to len(b) bytes from the File.

// It returns the number of bytes read and an error, if any.

func (f *File) read(b []byte) (n int, err error) {

        return syscall.Read(f.fd, b)

}

// pread reads len(b) bytes from the File starting at byte offset off.

// It returns the number of bytes read and the error, if any.

// EOF is signaled by a zero count with err set to 0.

func (f *File) pread(b []byte, off int64) (n int, err error) {

        return syscall.Pread(f.fd, b, off)

}

// write writes len(b) bytes to the File.

// It returns the number of bytes written and an error, if any.

func (f *File) write(b []byte) (n int, err error) {

        return syscall.Write(f.fd, b)

}

// pwrite writes len(b) bytes to the File starting at byte offset off.

// It returns the number of bytes written and an error, if any.

func (f *File) pwrite(b []byte, off int64) (n int, err error) {

        return syscall.Pwrite(f.fd, b, off)

}

// seek sets the offset for the next Read or Write on file to offset, interpreted

// according to whence: 0 means relative to the origin of the file, 1 means

// relative to the current offset, and 2 means relative to the end.

// It returns the new offset and an error, if any.

func (f *File) seek(offset int64, whence int) (ret int64, err error) {

        return syscall.Seek(f.fd, offset, whence)

}

// Truncate changes the size of the named file.

// If the file is a symbolic link, it changes the size of the link's target.

func Truncate(name string, size int64) error {

        if e := syscall.Truncate(name, size); e != nil {

                return &PathError{"truncate", name, e}

        }

        return nil

}

// Remove removes the named file or directory.

func Remove(name string) error {

        // System call interface forces us to know

        // whether name is a file or directory.

        // Try both: it is cheaper on average than

        // doing a Stat plus the right one.

        e := syscall.Unlink(name)

        if e == nil {

                return nil

        }

        e1 := syscall.Rmdir(name)

        if e1 == nil {

                return nil

        }

        // Both failed: figure out which error to return.

        // OS X and Linux differ on whether unlink(dir)

        // returns EISDIR, so can't use that.  However,

        // both agree that rmdir(file) returns ENOTDIR,

        // so we can use that to decide which error is real.

        // Rmdir might also return ENOTDIR if given a bad

        // file path, like /etc/passwd/foo, but in that case,

        // both errors will be ENOTDIR, so it's okay to

        // use the error from unlink.

        if e1 != syscall.ENOTDIR {

                e = e1

        }

        return &PathError{"remove", name, e}

}

// basename removes trailing slashes and the leading directory name from path name

func basename(name string) string {

        i := len(name) - 1

        // Remove trailing slashes

        for ; i > 0 && name[i] == '/'; i-- {

                name = name[:i]

        }

        // Remove leading directory name

        for i--; i >= 0; i-- {

                if name[i] == '/' {

                        name = name[i+1:]

                        break

                }

        }

        return name

}

// Pipe returns a connected pair of Files; reads from r return bytes written to w.

// It returns the files and an error, if any.

func Pipe() (r *File, w *File, err error) {

        var p [2]int

        // See ../syscall/exec.go for description of lock.

        syscall.ForkLock.RLock()

        e := syscall.Pipe(p[0:])

        if e != nil {

                syscall.ForkLock.RUnlock()

                return nil, nil, NewSyscallError("pipe", e)

        }

        syscall.CloseOnExec(p[0])

        syscall.CloseOnExec(p[1])

        syscall.ForkLock.RUnlock()

        return NewFile(p[0], "|0"), NewFile(p[1], "|1"), nil

}

// TempDir returns the default directory to use for temporary files.

func TempDir() string {

        dir := Getenv("TMPDIR")

        if dir == "" {

                dir = "/tmp"

        }

        return dir

}