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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 (
        "syscall"
        "time"
)

func sameFile(sys1, sys2 interface{}) bool {
        a := sys1.(*Dir)
        b := sys2.(*Dir)
        return a.Qid.Path == b.Qid.Path && a.Type == b.Type && a.Dev == b.Dev
}

func fileInfoFromStat(d *Dir) FileInfo {
        fs := &fileStat{
                name:    d.Name,
                size:    int64(d.Length),
                modTime: time.Unix(int64(d.Mtime), 0),
                sys:     d,
        }
        fs.mode = FileMode(d.Mode & 0777)
        if d.Mode&syscall.DMDIR != 0 {
                fs.mode |= ModeDir
        }
        if d.Mode&syscall.DMAPPEND != 0 {
                fs.mode |= ModeAppend
        }
        if d.Mode&syscall.DMEXCL != 0 {
                fs.mode |= ModeExclusive
        }
        if d.Mode&syscall.DMTMP != 0 {
                fs.mode |= ModeTemporary
        }
        return fs
}

// arg is an open *File or a path string. 
func dirstat(arg interface{}) (d *Dir, err error) {
        var name string

        // This is big enough for most stat messages
        // and rounded to a multiple of 128 bytes.
        size := (syscall.STATFIXLEN + 16*4 + 128) &^ 128

        for i := 0; i < 2; i++ {
                buf := make([]byte, size)

                var n int
                switch a := arg.(type) {
                case *File:
                        name = a.name
                        n, err = syscall.Fstat(a.fd, buf)
                case string:
                        name = a
                        n, err = syscall.Stat(name, buf)
                }
                if err != nil {
                        return nil, &PathError{"stat", name, err}
                }
                if n < syscall.STATFIXLEN {
                        return nil, &PathError{"stat", name, Eshortstat}
                }

                // Pull the real size out of the stat message.
                s, _ := gbit16(buf)
                size = int(s)

                // If the stat message is larger than our buffer we will
                // go around the loop and allocate one that is big enough.
                if size <= n {
                        d, err = UnmarshalDir(buf[:n])
                        if err != nil {
                                return nil, &PathError{"stat", name, err}
                        }
                        return
                }
        }
        return nil, &PathError{"stat", name, Ebadstat}
}

// Stat returns a FileInfo structure describing the named file and an error, if any.
func Stat(name string) (FileInfo, error) {
        d, err := dirstat(name)
        if err != nil {
                return nil, err
        }
        return fileInfoFromStat(d), nil
}

// Lstat returns the FileInfo structure describing the named file and an
// error, if any.  If the file is a symbolic link (though Plan 9 does not have symbolic links), 
// the returned FileInfo describes the symbolic link.  Lstat makes no attempt to follow the link.
func Lstat(name string) (FileInfo, error) {
        return Stat(name)
}

// For testing.
func atime(fi FileInfo) time.Time {
        return time.Unix(int64(fi.Sys().(*Dir).Atime), 0)
}