// 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.

package os

import (
	"io/fs"
	"syscall"
)

// Getpagesize returns the underlying system's memory page size.
func Getpagesize() int { return syscall.Getpagesize() }

// File represents an open file descriptor.
//
// The methods of File are safe for concurrent use.
type File struct {
	*file // os specific
}

// A FileInfo describes a file and is returned by [Stat] and [Lstat].
type FileInfo = fs.FileInfo

// A FileMode represents a file's mode and permission bits.
// The bits have the same definition on all systems, so that
// information about files can be moved from one system
// to another portably. Not all bits apply to all systems.
// The only required bit is [ModeDir] for directories.
type FileMode = fs.FileMode

// The defined file mode bits are the most significant bits of the [FileMode].
// The nine least-significant bits are the standard Unix rwxrwxrwx permissions.
// The values of these bits should be considered part of the public API and
// may be used in wire protocols or disk representations: they must not be
// changed, although new bits might be added.
const (
	// The single letters are the abbreviations
	// used by the String method's formatting.
	ModeDir        = fs.ModeDir        // d: is a directory
	ModeAppend     = fs.ModeAppend     // a: append-only
	ModeExclusive  = fs.ModeExclusive  // l: exclusive use
	ModeTemporary  = fs.ModeTemporary  // T: temporary file; Plan 9 only
	ModeSymlink    = fs.ModeSymlink    // L: symbolic link
	ModeDevice     = fs.ModeDevice     // D: device file
	ModeNamedPipe  = fs.ModeNamedPipe  // p: named pipe (FIFO)
	ModeSocket     = fs.ModeSocket     // S: Unix domain socket
	ModeSetuid     = fs.ModeSetuid     // u: setuid
	ModeSetgid     = fs.ModeSetgid     // g: setgid
	ModeCharDevice = fs.ModeCharDevice // c: Unix character device, when ModeDevice is set
	ModeSticky     = fs.ModeSticky     // t: sticky
	ModeIrregular  = fs.ModeIrregular  // ?: non-regular file; nothing else is known about this file

	// Mask for the type bits. For regular files, none will be set.
	ModeType = fs.ModeType

	ModePerm = fs.ModePerm // Unix permission bits, 0o777
)

func (fs *fileStat) Name() string { return fs.name }
func (fs *fileStat) IsDir() bool  { return fs.Mode().IsDir() }

// SameFile reports whether fi1 and fi2 describe the same file.
// For example, on Unix this means that the device and inode fields
// of the two underlying structures are identical; on other systems
// the decision may be based on the path names.
// SameFile only applies to results returned by this package's [Stat].
// It returns false in other cases.
func SameFile(fi1, fi2 FileInfo) bool {
	fs1, ok1 := fi1.(*fileStat)
	fs2, ok2 := fi2.(*fileStat)
	if !ok1 || !ok2 {
		return false
	}
	return sameFile(fs1, fs2)
}