src/internal/filepathlite/path_windows.go - go - Git at Google

 // Copyright 2010 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 filepathlite

 import (
 	"internal/bytealg"
 	"internal/stringslite"
 	"syscall"
 )

 const (
 	Separator     = '\\' // OS-specific path separator
 	ListSeparator = ';'  // OS-specific path list separator
 )

 func IsPathSeparator(c uint8) bool {
 	return c == '\\' || c == '/'
 }

 func isLocal(path string) bool {
 	if path == "" {
 		return false
 	}
 	if IsPathSeparator(path[0]) {
 		// Path rooted in the current drive.
 		return false
 	}
 	if stringslite.IndexByte(path, ':') >= 0 {
 		// Colons are only valid when marking a drive letter ("C:foo").
 		// Rejecting any path with a colon is conservative but safe.
 		return false
 	}
 	hasDots := false // contains . or .. path elements
 	for p := path; p != ""; {
 		var part string
 		part, p, _ = cutPath(p)
 		if part == "." || part == ".." {
 			hasDots = true
 		}
 		if isReservedName(part) {
 			return false
 		}
 	}
 	if hasDots {
 		path = Clean(path)
 	}
 	if path == ".." || stringslite.HasPrefix(path, `..\`) {
 		return false
 	}
 	return true
 }

 func localize(path string) (string, error) {
 	for i := 0; i < len(path); i++ {
 		switch path[i] {
 		case ':', '\\', 0:
 			return "", errInvalidPath
 		}
 	}
 	containsSlash := false
 	for p := path; p != ""; {
 		// Find the next path element.
 		var element string
 		i := bytealg.IndexByteString(p, '/')
 		if i < 0 {
 			element = p
 			p = ""
 		} else {
 			containsSlash = true
 			element = p[:i]
 			p = p[i+1:]
 		}
 		if isReservedName(element) {
 			return "", errInvalidPath
 		}
 	}
 	if containsSlash {
 		// We can't depend on strings, so substitute \ for / manually.
 		buf := []byte(path)
 		for i, b := range buf {
 			if b == '/' {
 				buf[i] = '\\'
 			}
 		}
 		path = string(buf)
 	}
 	return path, nil
 }

 // isReservedName reports if name is a Windows reserved device name.
 // It does not detect names with an extension, which are also reserved on some Windows versions.
 //
 // For details, search for PRN in
 // https://docs.microsoft.com/en-us/windows/desktop/fileio/naming-a-file.
 func isReservedName(name string) bool {
 	// Device names can have arbitrary trailing characters following a dot or colon.
 	base := name
 	for i := 0; i < len(base); i++ {
 		switch base[i] {
 		case ':', '.':
 			base = base[:i]
 		}
 	}
 	// Trailing spaces in the last path element are ignored.
 	for len(base) > 0 && base[len(base)-1] == ' ' {
 		base = base[:len(base)-1]
 	}
 	if !isReservedBaseName(base) {
 		return false
 	}
 	if len(base) == len(name) {
 		return true
 	}
 	// The path element is a reserved name with an extension.
 	// Some Windows versions consider this a reserved name,
 	// while others do not. Use FullPath to see if the name is
 	// reserved.
 	if p, _ := syscall.FullPath(name); len(p) >= 4 && p[:4] == `\\.\` {
 		return true
 	}
 	return false
 }

 func isReservedBaseName(name string) bool {
 	if len(name) == 3 {
 		switch string([]byte{toUpper(name[0]), toUpper(name[1]), toUpper(name[2])}) {
 		case "CON", "PRN", "AUX", "NUL":
 			return true
 		}
 	}
 	if len(name) >= 4 {
 		switch string([]byte{toUpper(name[0]), toUpper(name[1]), toUpper(name[2])}) {
 		case "COM", "LPT":
 			if len(name) == 4 && '1' <= name[3] && name[3] <= '9' {
 				return true
 			}
 			// Superscript ¹, ², and ³ are considered numbers as well.
 			switch name[3:] {
 			case "\u00b2", "\u00b3", "\u00b9":
 				return true
 			}
 			return false
 		}
 	}

 	// Passing CONIN$ or CONOUT$ to CreateFile opens a console handle.
 	// https://learn.microsoft.com/en-us/windows/win32/api/fileapi/nf-fileapi-createfilea#consoles
 	//
 	// While CONIN$ and CONOUT$ aren't documented as being files,
 	// they behave the same as CON. For example, ./CONIN$ also opens the console input.
 	if len(name) == 6 && name[5] == '$' && equalFold(name, "CONIN$") {
 		return true
 	}
 	if len(name) == 7 && name[6] == '$' && equalFold(name, "CONOUT$") {
 		return true
 	}
 	return false
 }

 func equalFold(a, b string) bool {
 	if len(a) != len(b) {
 		return false
 	}
 	for i := 0; i < len(a); i++ {
 		if toUpper(a[i]) != toUpper(b[i]) {
 			return false
 		}
 	}
 	return true
 }

 func toUpper(c byte) byte {
 	if 'a' <= c && c <= 'z' {
 		return c - ('a' - 'A')
 	}
 	return c
 }

 // IsAbs reports whether the path is absolute.
 func IsAbs(path string) (b bool) {
 	l := volumeNameLen(path)
 	if l == 0 {
 		return false
 	}
 	// If the volume name starts with a double slash, this is an absolute path.
 	if IsPathSeparator(path[0]) && IsPathSeparator(path[1]) {
 		return true
 	}
 	path = path[l:]
 	if path == "" {
 		return false
 	}
 	return IsPathSeparator(path[0])
 }

 // volumeNameLen returns length of the leading volume name on Windows.
 // It returns 0 elsewhere.
 //
 // See:
 // https://learn.microsoft.com/en-us/dotnet/standard/io/file-path-formats
 // https://googleprojectzero.blogspot.com/2016/02/the-definitive-guide-on-win32-to-nt.html
 func volumeNameLen(path string) int {
 	switch {
 	case len(path) >= 2 && path[1] == ':':
 		// Path starts with a drive letter.
 		//
 		// Not all Windows functions necessarily enforce the requirement that
 		// drive letters be in the set A-Z, and we don't try to here.
 		//
 		// We don't handle the case of a path starting with a non-ASCII character,
 		// in which case the "drive letter" might be multiple bytes long.
 		return 2

 	case len(path) == 0 || !IsPathSeparator(path[0]):
 		// Path does not have a volume component.
 		return 0

 	case pathHasPrefixFold(path, `\\.\UNC`):
 		// We're going to treat the UNC host and share as part of the volume
 		// prefix for historical reasons, but this isn't really principled;
 		// Windows's own GetFullPathName will happily remove the first
 		// component of the path in this space, converting
 		// \\.\unc\a\b\..\c into \\.\unc\a\c.
 		return uncLen(path, len(`\\.\UNC\`))

 	case pathHasPrefixFold(path, `\\.`) ||
 		pathHasPrefixFold(path, `\\?`) || pathHasPrefixFold(path, `\??`):
 		// Path starts with \\.\, and is a Local Device path; or
 		// path starts with \\?\ or \??\ and is a Root Local Device path.
 		//
 		// We treat the next component after the \\.\ prefix as
 		// part of the volume name, which means Clean(`\\?\c:\`)
 		// won't remove the trailing \. (See #64028.)
 		if len(path) == 3 {
 			return 3 // exactly \\.
 		}
 		_, rest, ok := cutPath(path[4:])
 		if !ok {
 			return len(path)
 		}
 		return len(path) - len(rest) - 1

 	case len(path) >= 2 && IsPathSeparator(path[1]):
 		// Path starts with \\, and is a UNC path.
 		return uncLen(path, 2)
 	}
 	return 0
 }

 // pathHasPrefixFold tests whether the path s begins with prefix,
 // ignoring case and treating all path separators as equivalent.
 // If s is longer than prefix, then s[len(prefix)] must be a path separator.
 func pathHasPrefixFold(s, prefix string) bool {
 	if len(s) < len(prefix) {
 		return false
 	}
 	for i := 0; i < len(prefix); i++ {
 		if IsPathSeparator(prefix[i]) {
 			if !IsPathSeparator(s[i]) {
 				return false
 			}
 		} else if toUpper(prefix[i]) != toUpper(s[i]) {
 			return false
 		}
 	}
 	if len(s) > len(prefix) && !IsPathSeparator(s[len(prefix)]) {
 		return false
 	}
 	return true
 }

 // uncLen returns the length of the volume prefix of a UNC path.
 // prefixLen is the prefix prior to the start of the UNC host;
 // for example, for "//host/share", the prefixLen is len("//")==2.
 func uncLen(path string, prefixLen int) int {
 	count := 0
 	for i := prefixLen; i < len(path); i++ {
 		if IsPathSeparator(path[i]) {
 			count++
 			if count == 2 {
 				return i
 			}
 		}
 	}
 	return len(path)
 }

 // cutPath slices path around the first path separator.
 func cutPath(path string) (before, after string, found bool) {
 	for i := range path {
 		if IsPathSeparator(path[i]) {
 			return path[:i], path[i+1:], true
 		}
 	}
 	return path, "", false
 }

 // isUNC reports whether path is a UNC path.
 func isUNC(path string) bool {
 	return len(path) > 1 && IsPathSeparator(path[0]) && IsPathSeparator(path[1])
 }

 // postClean adjusts the results of Clean to avoid turning a relative path
 // into an absolute or rooted one.
 func postClean(out *lazybuf) {
 	if out.volLen != 0 || out.buf == nil {
 		return
 	}
 	// If a ':' appears in the path element at the start of a path,
 	// insert a .\ at the beginning to avoid converting relative paths
 	// like a/../c: into c:.
 	for _, c := range out.buf {
 		if IsPathSeparator(c) {
 			break
 		}
 		if c == ':' {
 			out.prepend('.', Separator)
 			return
 		}
 	}
 	// If a path begins with \??\, insert a \. at the beginning
 	// to avoid converting paths like \a\..\??\c:\x into \??\c:\x
 	// (equivalent to c:\x).
 	if len(out.buf) >= 3 && IsPathSeparator(out.buf[0]) && out.buf[1] == '?' && out.buf[2] == '?' {
 		out.prepend(Separator, '.')
 	}
 }
	// Copyright 2010 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 filepathlite

	import (
	"internal/bytealg"
	"internal/stringslite"
	"syscall"
	)

	const (
	Separator = '\\' // OS-specific path separator
	ListSeparator = ';' // OS-specific path list separator
	)

	func IsPathSeparator(c uint8) bool {
	return c == '\\' \|\| c == '/'
	}

	func isLocal(path string) bool {
	if path == "" {
	return false
	}
	if IsPathSeparator(path[0]) {
	// Path rooted in the current drive.
	return false
	}
	if stringslite.IndexByte(path, ':') >= 0 {
	// Colons are only valid when marking a drive letter ("C:foo").
	// Rejecting any path with a colon is conservative but safe.
	return false
	}
	hasDots := false // contains . or .. path elements
	for p := path; p != ""; {
	var part string
	part, p, _ = cutPath(p)
	if part == "." \|\| part == ".." {
	hasDots = true
	}
	if isReservedName(part) {
	return false
	}
	}
	if hasDots {
	path = Clean(path)
	}
	if path == ".." \|\| stringslite.HasPrefix(path, `..\`) {
	return false
	}
	return true
	}

	func localize(path string) (string, error) {
	for i := 0; i < len(path); i++ {
	switch path[i] {
	case ':', '\\', 0:
	return "", errInvalidPath
	}
	}
	containsSlash := false
	for p := path; p != ""; {
	// Find the next path element.
	var element string
	i := bytealg.IndexByteString(p, '/')
	if i < 0 {
	element = p
	p = ""
	} else {
	containsSlash = true
	element = p[:i]
	p = p[i+1:]
	}
	if isReservedName(element) {
	return "", errInvalidPath
	}
	}
	if containsSlash {
	// We can't depend on strings, so substitute \ for / manually.
	buf := []byte(path)
	for i, b := range buf {
	if b == '/' {
	buf[i] = '\\'
	}
	}
	path = string(buf)
	}
	return path, nil
	}

	// isReservedName reports if name is a Windows reserved device name.
	// It does not detect names with an extension, which are also reserved on some Windows versions.
	//
	// For details, search for PRN in
	// https://docs.microsoft.com/en-us/windows/desktop/fileio/naming-a-file.
	func isReservedName(name string) bool {
	// Device names can have arbitrary trailing characters following a dot or colon.
	base := name
	for i := 0; i < len(base); i++ {
	switch base[i] {
	case ':', '.':
	base = base[:i]
	}
	}
	// Trailing spaces in the last path element are ignored.
	for len(base) > 0 && base[len(base)-1] == ' ' {
	base = base[:len(base)-1]
	}
	if !isReservedBaseName(base) {
	return false
	}
	if len(base) == len(name) {
	return true
	}
	// The path element is a reserved name with an extension.
	// Some Windows versions consider this a reserved name,
	// while others do not. Use FullPath to see if the name is
	// reserved.
	if p, _ := syscall.FullPath(name); len(p) >= 4 && p[:4] == `\\.\` {
	return true
	}
	return false
	}

	func isReservedBaseName(name string) bool {
	if len(name) == 3 {
	switch string([]byte{toUpper(name[0]), toUpper(name[1]), toUpper(name[2])}) {
	case "CON", "PRN", "AUX", "NUL":
	return true
	}
	}
	if len(name) >= 4 {
	switch string([]byte{toUpper(name[0]), toUpper(name[1]), toUpper(name[2])}) {
	case "COM", "LPT":
	if len(name) == 4 && '1' <= name[3] && name[3] <= '9' {
	return true
	}
	// Superscript ¹, ², and ³ are considered numbers as well.
	switch name[3:] {
	case "\u00b2", "\u00b3", "\u00b9":
	return true
	}
	return false
	}
	}

	// Passing CONIN$ or CONOUT$ to CreateFile opens a console handle.
	// https://learn.microsoft.com/en-us/windows/win32/api/fileapi/nf-fileapi-createfilea#consoles
	//
	// While CONIN$ and CONOUT$ aren't documented as being files,
	// they behave the same as CON. For example, ./CONIN$ also opens the console input.
	if len(name) == 6 && name[5] == '$' && equalFold(name, "CONIN$") {
	return true
	}
	if len(name) == 7 && name[6] == '$' && equalFold(name, "CONOUT$") {
	return true
	}
	return false
	}

	func equalFold(a, b string) bool {
	if len(a) != len(b) {
	return false
	}
	for i := 0; i < len(a); i++ {
	if toUpper(a[i]) != toUpper(b[i]) {
	return false
	}
	}
	return true
	}

	func toUpper(c byte) byte {
	if 'a' <= c && c <= 'z' {
	return c - ('a' - 'A')
	}
	return c
	}

	// IsAbs reports whether the path is absolute.
	func IsAbs(path string) (b bool) {
	l := volumeNameLen(path)
	if l == 0 {
	return false
	}
	// If the volume name starts with a double slash, this is an absolute path.
	if IsPathSeparator(path[0]) && IsPathSeparator(path[1]) {
	return true
	}
	path = path[l:]
	if path == "" {
	return false
	}
	return IsPathSeparator(path[0])
	}

	// volumeNameLen returns length of the leading volume name on Windows.
	// It returns 0 elsewhere.
	//
	// See:
	// https://learn.microsoft.com/en-us/dotnet/standard/io/file-path-formats
	// https://googleprojectzero.blogspot.com/2016/02/the-definitive-guide-on-win32-to-nt.html
	func volumeNameLen(path string) int {
	switch {
	case len(path) >= 2 && path[1] == ':':
	// Path starts with a drive letter.
	//
	// Not all Windows functions necessarily enforce the requirement that
	// drive letters be in the set A-Z, and we don't try to here.
	//
	// We don't handle the case of a path starting with a non-ASCII character,
	// in which case the "drive letter" might be multiple bytes long.
	return 2

	case len(path) == 0 \|\| !IsPathSeparator(path[0]):
	// Path does not have a volume component.
	return 0

	case pathHasPrefixFold(path, `\\.\UNC`):
	// We're going to treat the UNC host and share as part of the volume
	// prefix for historical reasons, but this isn't really principled;
	// Windows's own GetFullPathName will happily remove the first
	// component of the path in this space, converting
	// \\.\unc\a\b\..\c into \\.\unc\a\c.
	return uncLen(path, len(`\\.\UNC\`))

	case pathHasPrefixFold(path, `\\.`) \|\|
	pathHasPrefixFold(path, `\\?`) \|\| pathHasPrefixFold(path, `\??`):
	// Path starts with \\.\, and is a Local Device path; or
	// path starts with \\?\ or \??\ and is a Root Local Device path.
	//
	// We treat the next component after the \\.\ prefix as
	// part of the volume name, which means Clean(`\\?\c:\`)
	// won't remove the trailing \. (See #64028.)
	if len(path) == 3 {
	return 3 // exactly \\.
	}
	_, rest, ok := cutPath(path[4:])
	if !ok {
	return len(path)
	}
	return len(path) - len(rest) - 1

	case len(path) >= 2 && IsPathSeparator(path[1]):
	// Path starts with \\, and is a UNC path.
	return uncLen(path, 2)
	}
	return 0
	}

	// pathHasPrefixFold tests whether the path s begins with prefix,
	// ignoring case and treating all path separators as equivalent.
	// If s is longer than prefix, then s[len(prefix)] must be a path separator.
	func pathHasPrefixFold(s, prefix string) bool {
	if len(s) < len(prefix) {
	return false
	}
	for i := 0; i < len(prefix); i++ {
	if IsPathSeparator(prefix[i]) {
	if !IsPathSeparator(s[i]) {
	return false
	}
	} else if toUpper(prefix[i]) != toUpper(s[i]) {
	return false
	}
	}
	if len(s) > len(prefix) && !IsPathSeparator(s[len(prefix)]) {
	return false
	}
	return true
	}

	// uncLen returns the length of the volume prefix of a UNC path.
	// prefixLen is the prefix prior to the start of the UNC host;
	// for example, for "//host/share", the prefixLen is len("//")==2.
	func uncLen(path string, prefixLen int) int {
	count := 0
	for i := prefixLen; i < len(path); i++ {
	if IsPathSeparator(path[i]) {
	count++
	if count == 2 {
	return i
	}
	}
	}
	return len(path)
	}

	// cutPath slices path around the first path separator.
	func cutPath(path string) (before, after string, found bool) {
	for i := range path {
	if IsPathSeparator(path[i]) {
	return path[:i], path[i+1:], true
	}
	}
	return path, "", false
	}

	// isUNC reports whether path is a UNC path.
	func isUNC(path string) bool {
	return len(path) > 1 && IsPathSeparator(path[0]) && IsPathSeparator(path[1])
	}

	// postClean adjusts the results of Clean to avoid turning a relative path
	// into an absolute or rooted one.
	func postClean(out *lazybuf) {
	if out.volLen != 0 \|\| out.buf == nil {
	return
	}
	// If a ':' appears in the path element at the start of a path,
	// insert a .\ at the beginning to avoid converting relative paths
	// like a/../c: into c:.
	for _, c := range out.buf {
	if IsPathSeparator(c) {
	break
	}
	if c == ':' {
	out.prepend('.', Separator)
	return
	}
	}
	// If a path begins with \??\, insert a \. at the beginning
	// to avoid converting paths like \a\..\??\c:\x into \??\c:\x
	// (equivalent to c:\x).
	if len(out.buf) >= 3 && IsPathSeparator(out.buf[0]) && out.buf[1] == '?' && out.buf[2] == '?' {
	out.prepend(Separator, '.')
	}
	}