src/io/fs/fs.go - go - Git at Google

 // Copyright 2020 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 fs defines basic interfaces to a file system.
 // A file system can be provided by the host operating system
 // but also by other packages.
 package fs

 import (
 	"internal/oserror"
 	"time"
 	"unicode/utf8"
 )

 // An FS provides access to a hierarchical file system.
 //
 // The FS interface is the minimum implementation required of the file system.
 // A file system may implement additional interfaces,
 // such as ReadFileFS, to provide additional or optimized functionality.
 type FS interface {
 	// Open opens the named file.
 	//
 	// When Open returns an error, it should be of type *PathError
 	// with the Op field set to "open", the Path field set to name,
 	// and the Err field describing the problem.
 	//
 	// Open should reject attempts to open names that do not satisfy
 	// ValidPath(name), returning a *PathError with Err set to
 	// ErrInvalid or ErrNotExist.
 	Open(name string) (File, error)
 }

 // ValidPath reports whether the given path name
 // is valid for use in a call to Open.
 //
 // Path names passed to open are UTF-8-encoded,
 // unrooted, slash-separated sequences of path elements, like “x/y/z”.
 // Path names must not contain an element that is “.” or “..” or the empty string,
 // except for the special case that the root directory is named “.”.
 // Paths must not start or end with a slash: “/x” and “x/” are invalid.
 //
 // Note that paths are slash-separated on all systems, even Windows.
 // Paths containing other characters such as backslash and colon
 // are accepted as valid, but those characters must never be
 // interpreted by an FS implementation as path element separators.
 func ValidPath(name string) bool {
 	if !utf8.ValidString(name) {
 		return false
 	}

 	if name == "." {
 		// special case
 		return true
 	}

 	// Iterate over elements in name, checking each.
 	for {
 		i := 0
 		for i < len(name) && name[i] != '/' {
 			i++
 		}
 		elem := name[:i]
 		if elem == "" || elem == "." || elem == ".." {
 			return false
 		}
 		if i == len(name) {
 			return true // reached clean ending
 		}
 		name = name[i+1:]
 	}
 }

 // A File provides access to a single file.
 // The File interface is the minimum implementation required of the file.
 // Directory files should also implement ReadDirFile.
 // A file may implement io.ReaderAt or io.Seeker as optimizations.
 type File interface {
 	Stat() (FileInfo, error)
 	Read([]byte) (int, error)
 	Close() error
 }

 // A DirEntry is an entry read from a directory
 // (using the ReadDir function or a ReadDirFile's ReadDir method).
 type DirEntry interface {
 	// Name returns the name of the file (or subdirectory) described by the entry.
 	// This name is only the final element of the path (the base name), not the entire path.
 	// For example, Name would return "hello.go" not "/home/gopher/hello.go".
 	Name() string

 	// IsDir reports whether the entry describes a directory.
 	IsDir() bool

 	// Type returns the type bits for the entry.
 	// The type bits are a subset of the usual FileMode bits, those returned by the FileMode.Type method.
 	Type() FileMode

 	// Info returns the FileInfo for the file or subdirectory described by the entry.
 	// The returned FileInfo may be from the time of the original directory read
 	// or from the time of the call to Info. If the file has been removed or renamed
 	// since the directory read, Info may return an error satisfying errors.Is(err, ErrNotExist).
 	// If the entry denotes a symbolic link, Info reports the information about the link itself,
 	// not the link's target.
 	Info() (FileInfo, error)
 }

 // A ReadDirFile is a directory file whose entries can be read with the ReadDir method.
 // Every directory file should implement this interface.
 // (It is permissible for any file to implement this interface,
 // but if so ReadDir should return an error for non-directories.)
 type ReadDirFile interface {
 	File

 	// ReadDir reads the contents of the directory and returns
 	// a slice of up to n DirEntry values in directory order.
 	// Subsequent calls on the same file will yield further DirEntry values.
 	//
 	// If n > 0, ReadDir returns at most n DirEntry structures.
 	// In this case, if ReadDir returns an empty slice, it will return
 	// a non-nil error explaining why.
 	// At the end of a directory, the error is io.EOF.
 	//
 	// If n <= 0, ReadDir returns all the DirEntry values from the directory
 	// in a single slice. In this case, if ReadDir succeeds (reads all the way
 	// to the end of the directory), it returns the slice and a nil error.
 	// If it encounters an error before the end of the directory,
 	// ReadDir returns the DirEntry list read until that point and a non-nil error.
 	ReadDir(n int) ([]DirEntry, error)
 }

 // Generic file system errors.
 // Errors returned by file systems can be tested against these errors
 // using errors.Is.
 var (
 	ErrInvalid    = errInvalid()    // "invalid argument"
 	ErrPermission = errPermission() // "permission denied"
 	ErrExist      = errExist()      // "file already exists"
 	ErrNotExist   = errNotExist()   // "file does not exist"
 	ErrClosed     = errClosed()     // "file already closed"
 )

 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 }

 // A FileInfo describes a file and is returned by Stat.
 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)
 }

 // 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

 // 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        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

 	// Mask for the type bits. For regular files, none will be set.
 	ModeType = ModeDir | ModeSymlink | ModeNamedPipe | ModeSocket | ModeDevice | ModeCharDevice | ModeIrregular

 	ModePerm FileMode = 0777 // Unix permission bits
 )

 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
 }

 // 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.(interface{ Timeout() bool })
 	return ok && t.Timeout()
 }
	// Copyright 2020 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 fs defines basic interfaces to a file system.
	// A file system can be provided by the host operating system
	// but also by other packages.
	package fs

	import (
	"internal/oserror"
	"time"
	"unicode/utf8"
	)

	// An FS provides access to a hierarchical file system.
	//
	// The FS interface is the minimum implementation required of the file system.
	// A file system may implement additional interfaces,
	// such as ReadFileFS, to provide additional or optimized functionality.
	type FS interface {
	// Open opens the named file.
	//
	// When Open returns an error, it should be of type *PathError
	// with the Op field set to "open", the Path field set to name,
	// and the Err field describing the problem.
	//
	// Open should reject attempts to open names that do not satisfy
	// ValidPath(name), returning a *PathError with Err set to
	// ErrInvalid or ErrNotExist.
	Open(name string) (File, error)
	}

	// ValidPath reports whether the given path name
	// is valid for use in a call to Open.
	//
	// Path names passed to open are UTF-8-encoded,
	// unrooted, slash-separated sequences of path elements, like “x/y/z”.
	// Path names must not contain an element that is “.” or “..” or the empty string,
	// except for the special case that the root directory is named “.”.
	// Paths must not start or end with a slash: “/x” and “x/” are invalid.
	//
	// Note that paths are slash-separated on all systems, even Windows.
	// Paths containing other characters such as backslash and colon
	// are accepted as valid, but those characters must never be
	// interpreted by an FS implementation as path element separators.
	func ValidPath(name string) bool {
	if !utf8.ValidString(name) {
	return false
	}

	if name == "." {
	// special case
	return true
	}

	// Iterate over elements in name, checking each.
	for {
	i := 0
	for i < len(name) && name[i] != '/' {
	i++
	}
	elem := name[:i]
	if elem == "" \|\| elem == "." \|\| elem == ".." {
	return false
	}
	if i == len(name) {
	return true // reached clean ending
	}
	name = name[i+1:]
	}
	}

	// A File provides access to a single file.
	// The File interface is the minimum implementation required of the file.
	// Directory files should also implement ReadDirFile.
	// A file may implement io.ReaderAt or io.Seeker as optimizations.
	type File interface {
	Stat() (FileInfo, error)
	Read([]byte) (int, error)
	Close() error
	}

	// A DirEntry is an entry read from a directory
	// (using the ReadDir function or a ReadDirFile's ReadDir method).
	type DirEntry interface {
	// Name returns the name of the file (or subdirectory) described by the entry.
	// This name is only the final element of the path (the base name), not the entire path.
	// For example, Name would return "hello.go" not "/home/gopher/hello.go".
	Name() string

	// IsDir reports whether the entry describes a directory.
	IsDir() bool

	// Type returns the type bits for the entry.
	// The type bits are a subset of the usual FileMode bits, those returned by the FileMode.Type method.
	Type() FileMode

	// Info returns the FileInfo for the file or subdirectory described by the entry.
	// The returned FileInfo may be from the time of the original directory read
	// or from the time of the call to Info. If the file has been removed or renamed
	// since the directory read, Info may return an error satisfying errors.Is(err, ErrNotExist).
	// If the entry denotes a symbolic link, Info reports the information about the link itself,
	// not the link's target.
	Info() (FileInfo, error)
	}

	// A ReadDirFile is a directory file whose entries can be read with the ReadDir method.
	// Every directory file should implement this interface.
	// (It is permissible for any file to implement this interface,
	// but if so ReadDir should return an error for non-directories.)
	type ReadDirFile interface {
	File

	// ReadDir reads the contents of the directory and returns
	// a slice of up to n DirEntry values in directory order.
	// Subsequent calls on the same file will yield further DirEntry values.
	//
	// If n > 0, ReadDir returns at most n DirEntry structures.
	// In this case, if ReadDir returns an empty slice, it will return
	// a non-nil error explaining why.
	// At the end of a directory, the error is io.EOF.
	//
	// If n <= 0, ReadDir returns all the DirEntry values from the directory
	// in a single slice. In this case, if ReadDir succeeds (reads all the way
	// to the end of the directory), it returns the slice and a nil error.
	// If it encounters an error before the end of the directory,
	// ReadDir returns the DirEntry list read until that point and a non-nil error.
	ReadDir(n int) ([]DirEntry, error)
	}

	// Generic file system errors.
	// Errors returned by file systems can be tested against these errors
	// using errors.Is.
	var (
	ErrInvalid = errInvalid() // "invalid argument"
	ErrPermission = errPermission() // "permission denied"
	ErrExist = errExist() // "file already exists"
	ErrNotExist = errNotExist() // "file does not exist"
	ErrClosed = errClosed() // "file already closed"
	)

	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 }

	// A FileInfo describes a file and is returned by Stat.
	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)
	}

	// 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

	// 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 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

	// Mask for the type bits. For regular files, none will be set.
	ModeType = ModeDir \| ModeSymlink \| ModeNamedPipe \| ModeSocket \| ModeDevice \| ModeCharDevice \| ModeIrregular

	ModePerm FileMode = 0777 // Unix permission bits
	)

	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
	}

	// 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.(interface{ Timeout() bool })
	return ok && t.Timeout()
	}