io/fs: move FileInfo, FileMode, PathError, ErrInvalid, ... from os to io/fs

First step of creating the new io/fs package.

For #41190.

Change-Id: I1339b1abdd533b0f1deab283628088b2f706fb5b
Reviewed-on: https://go-review.googlesource.com/c/go/+/243906
Trust: Russ Cox <rsc@golang.org>
Run-TryBot: Russ Cox <rsc@golang.org>
Run-TryBot: Emmanuel Odeke <emm.odeke@gmail.com>
TryBot-Result: Go Bot <gobot@golang.org>
Reviewed-by: Rob Pike <r@golang.org>
Reviewed-by: Emmanuel Odeke <emm.odeke@gmail.com>

2 files changed, 26 insertions, 97 deletions

diff --git a/src/os/error.go b/src/os/error.go
index 875cc9711f..7cd9f22bfb 100644
--- a/src/os/error.go
+++ b/src/os/error.go
@@ -7,6 +7,7 @@ package os
 import (
 	"internal/oserror"
 	"internal/poll"
+	"io/fs"
 )
 
 // Portable analogs of some common system call errors.
@@ -16,20 +17,17 @@ import (
 var (
 	// ErrInvalid indicates an invalid argument.
 	// Methods on File will return this error when the receiver is nil.
-	ErrInvalid = errInvalid() // "invalid argument"
+	ErrInvalid = fs.ErrInvalid // "invalid argument"
+
+	ErrPermission = fs.ErrPermission // "permission denied"
+	ErrExist      = fs.ErrExist      // "file already exists"
+	ErrNotExist   = fs.ErrNotExist   // "file does not exist"
+	ErrClosed     = fs.ErrClosed     // "file already closed"
 
-	ErrPermission       = errPermission()       // "permission denied"
-	ErrExist            = errExist()            // "file already exists"
-	ErrNotExist         = errNotExist()         // "file does not exist"
-	ErrClosed           = errClosed()           // "file already closed"
 	ErrNoDeadline       = errNoDeadline()       // "file type does not support deadline"
 	ErrDeadlineExceeded = errDeadlineExceeded() // "i/o timeout"
 )
 
-func errInvalid() error    { return oserror.ErrInvalid }
-func errPermission() error { return oserror.ErrPermission }
-func errExist() error      { return oserror.ErrExist }
-func errNotExist() error   { return oserror.ErrNotExist }
 func errClosed() error     { return oserror.ErrClosed }
 func errNoDeadline() error { return poll.ErrNoDeadline }
 
@@ -47,21 +45,7 @@ type timeout interface {
 }
 
 // PathError records an error and the operation and file path that caused it.
-type PathError struct {
-	Op   string
-	Path string
-	Err  error
-}
-
-func (e *PathError) Error() string { return e.Op + " " + e.Path + ": " + e.Err.Error() }
-
-func (e *PathError) Unwrap() error { return e.Err }
-
-// Timeout reports whether this error represents a timeout.
-func (e *PathError) Timeout() bool {
-	t, ok := e.Err.(timeout)
-	return ok && t.Timeout()
-}
+type PathError = fs.PathError
 
 // SyscallError records an error from a specific system call.
 type SyscallError struct {
diff --git a/src/os/types.go b/src/os/types.go
index 0f51a48286..d8edd98b68 100644
--- a/src/os/types.go
+++ b/src/os/types.go
@@ -5,8 +5,8 @@
 package os
 
 import (
+	"io/fs"
 	"syscall"
-	"time"
 )
 
 // Getpagesize returns the underlying system's memory page size.
@@ -18,21 +18,14 @@ type File struct {
 }
 
 // A FileInfo describes a file and is returned by Stat and Lstat.
-type FileInfo interface {
-	Name() string       // base name of the file
-	Size() int64        // length in bytes for regular files; system-dependent for others
-	Mode() FileMode     // file mode bits
-	ModTime() time.Time // modification time
-	IsDir() bool        // abbreviation for Mode().IsDir()
-	Sys() interface{}   // underlying data source (can return nil)
-}
+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 uint32
+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.
@@ -42,74 +35,26 @@ type FileMode uint32
 const (
 	// The single letters are the abbreviations
 	// used by the String method's formatting.
-	ModeDir        FileMode = 1 << (32 - 1 - iota) // d: is a directory
-	ModeAppend                                     // a: append-only
-	ModeExclusive                                  // l: exclusive use
-	ModeTemporary                                  // T: temporary file; Plan 9 only
-	ModeSymlink                                    // L: symbolic link
-	ModeDevice                                     // D: device file
-	ModeNamedPipe                                  // p: named pipe (FIFO)
-	ModeSocket                                     // S: Unix domain socket
-	ModeSetuid                                     // u: setuid
-	ModeSetgid                                     // g: setgid
-	ModeCharDevice                                 // c: Unix character device, when ModeDevice is set
-	ModeSticky                                     // t: sticky
-	ModeIrregular                                  // ?: non-regular file; nothing else is known about this file
+	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 = ModeDir | ModeSymlink | ModeNamedPipe | ModeSocket | ModeDevice | ModeCharDevice | ModeIrregular
+	ModeType = fs.ModeType
 
-	ModePerm FileMode = 0777 // Unix permission bits
+	ModePerm = fs.ModePerm // Unix permission bits, 0o777
 )
 
-func (m FileMode) String() string {
-	const str = "dalTLDpSugct?"
-	var buf [32]byte // Mode is uint32.
-	w := 0
-	for i, c := range str {
-		if m&(1<<uint(32-1-i)) != 0 {
-			buf[w] = byte(c)
-			w++
-		}
-	}
-	if w == 0 {
-		buf[w] = '-'
-		w++
-	}
-	const rwx = "rwxrwxrwx"
-	for i, c := range rwx {
-		if m&(1<<uint(9-1-i)) != 0 {
-			buf[w] = byte(c)
-		} else {
-			buf[w] = '-'
-		}
-		w++
-	}
-	return string(buf[:w])
-}
-
-// IsDir reports whether m describes a directory.
-// That is, it tests for the ModeDir bit being set in m.
-func (m FileMode) IsDir() bool {
-	return m&ModeDir != 0
-}
-
-// IsRegular reports whether m describes a regular file.
-// That is, it tests that no mode type bits are set.
-func (m FileMode) IsRegular() bool {
-	return m&ModeType == 0
-}
-
-// Perm returns the Unix permission bits in m (m & ModePerm).
-func (m FileMode) Perm() FileMode {
-	return m & ModePerm
-}
-
-// Type returns type bits in m (m & ModeType).
-func (m FileMode) Type() FileMode {
-	return m & ModeType
-}
-
 func (fs *fileStat) Name() string { return fs.name }
 func (fs *fileStat) IsDir() bool  { return fs.Mode().IsDir() }