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// Copyright 2011 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.

package os

import (

        "runtime"

        "syscall"

        "time"

)

// 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

}

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

func (file *File) Fd() int {

        if file == nil {

                return -1

        }

        return file.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  [syscall.STATMAX]byte // buffer for directory I/O

        nbuf int                   // length of buf; return value from Read

        bufp int                   // location of next record in buf.

}

func epipecheck(file *File, e error) {

}

// 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"

// syscallMode returns the syscall-specific mode bits from Go's portable mode bits.

func syscallMode(i FileMode) (o uint32) {

        o |= uint32(i.Perm())

        if i&ModeAppend != 0 {

                o |= syscall.DMAPPEND

        }

        if i&ModeExclusive != 0 {

                o |= syscall.DMEXCL

        }

        if i&ModeTemporary != 0 {

                o |= syscall.DMTMP

        }

        return

}

// 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) {

        var (

                fd     int

                e      error

                create bool

                excl   bool

                trunc  bool

                append bool

        )

        if flag&O_CREATE == O_CREATE {

                flag = flag & ^O_CREATE

                create = true

        }

        if flag&O_EXCL == O_EXCL {

                excl = true

        }

        if flag&O_TRUNC == O_TRUNC {

                trunc = true

        }

        // O_APPEND is emulated on Plan 9

        if flag&O_APPEND == O_APPEND {

                flag = flag &^ O_APPEND

                append = true

        }

        syscall.ForkLock.RLock()

        if (create && trunc) || excl {

                fd, e = syscall.Create(name, flag, syscallMode(perm))

        } else {

                fd, e = syscall.Open(name, flag)

                if e != nil && create {

                        var e1 error

                        fd, e1 = syscall.Create(name, flag, syscallMode(perm))

                        if e1 == nil {

                                e = nil

                        }

                }

        }

        syscall.ForkLock.RUnlock()

        if e != nil {

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

        }

        if append {

                if _, e = syscall.Seek(fd, 0, SEEK_END); e != nil {

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

                }

        }

        return NewFile(fd, name), nil

}

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

// It returns an error, if any.

func (file *File) Close() error {

        return file.file.close()

}

func (file *file) close() error {

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

                return Ebadfd

        }

        var err error

        syscall.ForkLock.RLock()

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

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

        }

        syscall.ForkLock.RUnlock()

        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() (FileInfo, error) {

        d, err := dirstat(f)

        if err != nil {

                return nil, err

        }

        return fileInfoFromStat(d), nil

}

// Truncate changes the size of the file.

// It does not change the I/O offset.

func (f *File) Truncate(size int64) error {

        var d Dir

        d.Null()

        d.Length = uint64(size)

        if e := syscall.Fwstat(f.fd, pdir(nil, &d)); e != nil {

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

        }

        return nil

}

const chmodMask = uint32(syscall.DMAPPEND | syscall.DMEXCL | syscall.DMTMP | ModePerm)

// Chmod changes the mode of the file to mode.

func (f *File) Chmod(mode FileMode) error {

        var d Dir

        odir, e := dirstat(f)

        if e != nil {

                return &PathError{"chmod", f.name, e}

        }

        d.Null()

        d.Mode = odir.Mode&^chmodMask | syscallMode(mode)&chmodMask

        if e := syscall.Fwstat(f.fd, pdir(nil, &d)); e != nil {

                return &PathError{"chmod", f.name, e}

        }

        return nil

}

// Sync commits the current contents of the file to stable storage.

// Typically, this means flushing the file system's in-memory copy

// of recently written data to disk.

func (f *File) Sync() (err error) {

        if f == nil {

                return EINVAL

        }

        var d Dir

        d.Null()

        if e := syscall.Fwstat(f.fd, pdir(nil, &d)); e != nil {

                return NewSyscallError("fsync", e)

        }

        return nil

}

// 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 nil.

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 {

        var d Dir

        d.Null()

        d.Length = uint64(size)

        if e := syscall.Wstat(name, pdir(nil, &d)); e != nil {

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

        }

        return nil

}

// Remove removes the named file or directory.

func Remove(name string) error {

        if e := syscall.Remove(name); e != nil {

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

        }

        return nil

}

// Rename renames a file.

func Rename(oldname, newname string) error {

        var d Dir

        d.Null()

        d.Name = newname

        if e := syscall.Wstat(oldname, pdir(nil, &d)); e != nil {

                return &PathError{"rename", oldname, e}

        }

        return nil

}

// Chmod changes the mode of the named file to mode.

func Chmod(name string, mode FileMode) error {

        var d Dir

        odir, e := dirstat(name)

        if e != nil {

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

        }

        d.Null()

        d.Mode = odir.Mode&^chmodMask | syscallMode(mode)&chmodMask

        if e := syscall.Wstat(name, pdir(nil, &d)); e != nil {

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

        }

        return nil

}

// Chtimes changes the access and modification times of the named

// file, similar to the Unix utime() or utimes() functions.

//

// The underlying filesystem may truncate or round the values to a

// less precise time unit.

func Chtimes(name string, atime time.Time, mtime time.Time) error {

        var d Dir

        d.Null()

        d.Atime = uint32(atime.Unix())

        d.Mtime = uint32(mtime.Unix())

        if e := syscall.Wstat(name, pdir(nil, &d)); e != nil {

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

        }

        return nil

}

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

        var p [2]int

        syscall.ForkLock.RLock()

        if e := syscall.Pipe(p[0:]); e != nil {

                syscall.ForkLock.RUnlock()

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

        }

        syscall.ForkLock.RUnlock()

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

}

// not supported on Plan 9

// Link creates a hard link.

func Link(oldname, newname string) error {

        return EPLAN9

}

func Symlink(oldname, newname string) error {

        return EPLAN9

}

func Readlink(name string) (string, error) {

        return "", EPLAN9

}

func Chown(name string, uid, gid int) error {

        return EPLAN9

}

func Lchown(name string, uid, gid int) error {

        return EPLAN9

}

func (f *File) Chown(uid, gid int) error {

        return EPLAN9

}

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

func TempDir() string {

        return "/tmp"

}