src/path/filepath/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 filepath

 import (
 	"strings"
 	"syscall"
 )

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

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

 // isReservedName reports if name is a Windows reserved device name or a console handle.
 // 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 {
 	if 3 <= len(name) && len(name) <= 4 {
 		switch string([]byte{toUpper(name[0]), toUpper(name[1]), toUpper(name[2])}) {
 		case "CON", "PRN", "AUX", "NUL":
 			return len(name) == 3
 		case "COM", "LPT":
 			return len(name) == 4 && '1' <= name[3] && name[3] <= '9'
 		}
 	}
 	// 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] == '$' && strings.EqualFold(name, "CONIN$") {
 		return true
 	}
 	if len(name) == 7 && name[6] == '$' && strings.EqualFold(name, "CONOUT$") {
 		return true
 	}
 	return false
 }

 func isLocal(path string) bool {
 	if path == "" {
 		return false
 	}
 	if isSlash(path[0]) {
 		// Path rooted in the current drive.
 		return false
 	}
 	if strings.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
 		}
 		// Trim the extension and look for a reserved name.
 		base, _, hasExt := strings.Cut(part, ".")
 		if isReservedName(base) {
 			if !hasExt {
 				return false
 			}
 			// 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.
 			//
 			// FullPath will convert references to reserved device names to their
 			// canonical form: \\.\${DEVICE_NAME}
 			//
 			// FullPath does not perform this conversion for paths which contain
 			// a reserved device name anywhere other than in the last element,
 			// so check the part rather than the full path.
 			if p, _ := syscall.FullPath(part); len(p) >= 4 && p[:4] == `\\.\` {
 				return false
 			}
 		}
 	}
 	if hasDots {
 		path = Clean(path)
 	}
 	if path == ".." || strings.HasPrefix(path, `..\`) {
 		return false
 	}
 	return true
 }

 // 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 isSlash(path[0]) && isSlash(path[1]) {
 		return true
 	}
 	path = path[l:]
 	if path == "" {
 		return false
 	}
 	return isSlash(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
 func volumeNameLen(path string) int {
 	if len(path) < 2 {
 		return 0
 	}
 	// with drive letter
 	c := path[0]
 	if path[1] == ':' && ('a' <= c && c <= 'z' || 'A' <= c && c <= 'Z') {
 		return 2
 	}
 	// UNC and DOS device paths start with two slashes.
 	if !isSlash(path[0]) || !isSlash(path[1]) {
 		return 0
 	}
 	rest := path[2:]
 	p1, rest, _ := cutPath(rest)
 	p2, rest, ok := cutPath(rest)
 	if !ok {
 		return len(path)
 	}
 	if p1 != "." && p1 != "?" {
 		// This is a UNC path: \\${HOST}\${SHARE}\
 		return len(path) - len(rest) - 1
 	}
 	// This is a DOS device path.
 	if len(p2) == 3 && toUpper(p2[0]) == 'U' && toUpper(p2[1]) == 'N' && toUpper(p2[2]) == 'C' {
 		// This is a DOS device path that links to a UNC: \\.\UNC\${HOST}\${SHARE}\
 		_, rest, _ = cutPath(rest)  // host
 		_, rest, ok = cutPath(rest) // share
 		if !ok {
 			return len(path)
 		}
 	}
 	return len(path) - len(rest) - 1
 }

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

 // HasPrefix exists for historical compatibility and should not be used.
 //
 // Deprecated: HasPrefix does not respect path boundaries and
 // does not ignore case when required.
 func HasPrefix(p, prefix string) bool {
 	if strings.HasPrefix(p, prefix) {
 		return true
 	}
 	return strings.HasPrefix(strings.ToLower(p), strings.ToLower(prefix))
 }

 func splitList(path string) []string {
 	// The same implementation is used in LookPath in os/exec;
 	// consider changing os/exec when changing this.

 	if path == "" {
 		return []string{}
 	}

 	// Split path, respecting but preserving quotes.
 	list := []string{}
 	start := 0
 	quo := false
 	for i := 0; i < len(path); i++ {
 		switch c := path[i]; {
 		case c == '"':
 			quo = !quo
 		case c == ListSeparator && !quo:
 			list = append(list, path[start:i])
 			start = i + 1
 		}
 	}
 	list = append(list, path[start:])

 	// Remove quotes.
 	for i, s := range list {
 		list[i] = strings.ReplaceAll(s, `"`, ``)
 	}

 	return list
 }

 func abs(path string) (string, error) {
 	if path == "" {
 		// syscall.FullPath returns an error on empty path, because it's not a valid path.
 		// To implement Abs behavior of returning working directory on empty string input,
 		// special-case empty path by changing it to "." path. See golang.org/issue/24441.
 		path = "."
 	}
 	fullPath, err := syscall.FullPath(path)
 	if err != nil {
 		return "", err
 	}
 	return Clean(fullPath), nil
 }

 func join(elem []string) string {
 	var b strings.Builder
 	appendSep := false
 	for _, e := range elem {
 		// Strip leading slashes from everything after the first element,
 		// to avoid creating a UNC path (any path starting with "\\") from
 		// non-UNC elements.
 		//
 		// The correct behavior for Join when the first element is an incomplete UNC
 		// path (for example, "\\") is underspecified. We currently join subsequent
 		// elements so Join("\\", "host", "share") produces "\\host\share".
 		for b.Len() > 0 && len(e) > 0 && isSlash(e[0]) {
 			e = e[1:]
 		}
 		if e == "" {
 			continue
 		}
 		if appendSep {
 			b.WriteByte('\\')
 		}
 		b.WriteString(e)
 		appendSep = !isSlash(e[len(e)-1])
 		if b.Len() == 2 && volumeNameLen(b.String()) == 2 {
 			// If the string is two characters long and consists of nothing but
 			// a volume name, this is either a drive ("C:") or the start of an
 			// incomplete UNC path ("\\"). In either case, don't append a separator.
 			appendSep = false
 		}
 	}
 	if b.Len() == 0 {
 		return ""
 	}
 	return Clean(b.String())
 }

 // joinNonEmpty is like join, but it assumes that the first element is non-empty.
 func joinNonEmpty(elem []string) string {
 	if len(elem[0]) == 2 && elem[0][1] == ':' {
 		// First element is drive letter without terminating slash.
 		// Keep path relative to current directory on that drive.
 		// Skip empty elements.
 		i := 1
 		for ; i < len(elem); i++ {
 			if elem[i] != "" {
 				break
 			}
 		}
 		return Clean(elem[0] + strings.Join(elem[i:], string(Separator)))
 	}
 	// The following logic prevents Join from inadvertently creating a
 	// UNC path on Windows. Unless the first element is a UNC path, Join
 	// shouldn't create a UNC path. See golang.org/issue/9167.
 	p := Clean(strings.Join(elem, string(Separator)))
 	if !isUNC(p) {
 		return p
 	}
 	// p == UNC only allowed when the first element is a UNC path.
 	head := Clean(elem[0])
 	if isUNC(head) {
 		return p
 	}
 	// head + tail == UNC, but joining two non-UNC paths should not result
 	// in a UNC path. Undo creation of UNC path.
 	tail := Clean(strings.Join(elem[1:], string(Separator)))
 	if head[len(head)-1] == Separator {
 		return head + tail
 	}
 	return head + string(Separator) + tail
 }

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

 func sameWord(a, b string) bool {
 	return strings.EqualFold(a, b)
 }
	// 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 filepath

	import (
	"strings"
	"syscall"
	)

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

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

	// isReservedName reports if name is a Windows reserved device name or a console handle.
	// 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 {
	if 3 <= len(name) && len(name) <= 4 {
	switch string([]byte{toUpper(name[0]), toUpper(name[1]), toUpper(name[2])}) {
	case "CON", "PRN", "AUX", "NUL":
	return len(name) == 3
	case "COM", "LPT":
	return len(name) == 4 && '1' <= name[3] && name[3] <= '9'
	}
	}
	// 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] == '$' && strings.EqualFold(name, "CONIN$") {
	return true
	}
	if len(name) == 7 && name[6] == '$' && strings.EqualFold(name, "CONOUT$") {
	return true
	}
	return false
	}

	func isLocal(path string) bool {
	if path == "" {
	return false
	}
	if isSlash(path[0]) {
	// Path rooted in the current drive.
	return false
	}
	if strings.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
	}
	// Trim the extension and look for a reserved name.
	base, _, hasExt := strings.Cut(part, ".")
	if isReservedName(base) {
	if !hasExt {
	return false
	}
	// 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.
	//
	// FullPath will convert references to reserved device names to their
	// canonical form: \\.\${DEVICE_NAME}
	//
	// FullPath does not perform this conversion for paths which contain
	// a reserved device name anywhere other than in the last element,
	// so check the part rather than the full path.
	if p, _ := syscall.FullPath(part); len(p) >= 4 && p[:4] == `\\.\` {
	return false
	}
	}
	}
	if hasDots {
	path = Clean(path)
	}
	if path == ".." \|\| strings.HasPrefix(path, `..\`) {
	return false
	}
	return true
	}

	// 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 isSlash(path[0]) && isSlash(path[1]) {
	return true
	}
	path = path[l:]
	if path == "" {
	return false
	}
	return isSlash(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
	func volumeNameLen(path string) int {
	if len(path) < 2 {
	return 0
	}
	// with drive letter
	c := path[0]
	if path[1] == ':' && ('a' <= c && c <= 'z' \|\| 'A' <= c && c <= 'Z') {
	return 2
	}
	// UNC and DOS device paths start with two slashes.
	if !isSlash(path[0]) \|\| !isSlash(path[1]) {
	return 0
	}
	rest := path[2:]
	p1, rest, _ := cutPath(rest)
	p2, rest, ok := cutPath(rest)
	if !ok {
	return len(path)
	}
	if p1 != "." && p1 != "?" {
	// This is a UNC path: \\${HOST}\${SHARE}\
	return len(path) - len(rest) - 1
	}
	// This is a DOS device path.
	if len(p2) == 3 && toUpper(p2[0]) == 'U' && toUpper(p2[1]) == 'N' && toUpper(p2[2]) == 'C' {
	// This is a DOS device path that links to a UNC: \\.\UNC\${HOST}\${SHARE}\
	_, rest, _ = cutPath(rest) // host
	_, rest, ok = cutPath(rest) // share
	if !ok {
	return len(path)
	}
	}
	return len(path) - len(rest) - 1
	}

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

	// HasPrefix exists for historical compatibility and should not be used.
	//
	// Deprecated: HasPrefix does not respect path boundaries and
	// does not ignore case when required.
	func HasPrefix(p, prefix string) bool {
	if strings.HasPrefix(p, prefix) {
	return true
	}
	return strings.HasPrefix(strings.ToLower(p), strings.ToLower(prefix))
	}

	func splitList(path string) []string {
	// The same implementation is used in LookPath in os/exec;
	// consider changing os/exec when changing this.

	if path == "" {
	return []string{}
	}

	// Split path, respecting but preserving quotes.
	list := []string{}
	start := 0
	quo := false
	for i := 0; i < len(path); i++ {
	switch c := path[i]; {
	case c == '"':
	quo = !quo
	case c == ListSeparator && !quo:
	list = append(list, path[start:i])
	start = i + 1
	}
	}
	list = append(list, path[start:])

	// Remove quotes.
	for i, s := range list {
	list[i] = strings.ReplaceAll(s, `"`, ``)
	}

	return list
	}

	func abs(path string) (string, error) {
	if path == "" {
	// syscall.FullPath returns an error on empty path, because it's not a valid path.
	// To implement Abs behavior of returning working directory on empty string input,
	// special-case empty path by changing it to "." path. See golang.org/issue/24441.
	path = "."
	}
	fullPath, err := syscall.FullPath(path)
	if err != nil {
	return "", err
	}
	return Clean(fullPath), nil
	}

	func join(elem []string) string {
	var b strings.Builder
	appendSep := false
	for _, e := range elem {
	// Strip leading slashes from everything after the first element,
	// to avoid creating a UNC path (any path starting with "\\") from
	// non-UNC elements.
	//
	// The correct behavior for Join when the first element is an incomplete UNC
	// path (for example, "\\") is underspecified. We currently join subsequent
	// elements so Join("\\", "host", "share") produces "\\host\share".
	for b.Len() > 0 && len(e) > 0 && isSlash(e[0]) {
	e = e[1:]
	}
	if e == "" {
	continue
	}
	if appendSep {
	b.WriteByte('\\')
	}
	b.WriteString(e)
	appendSep = !isSlash(e[len(e)-1])
	if b.Len() == 2 && volumeNameLen(b.String()) == 2 {
	// If the string is two characters long and consists of nothing but
	// a volume name, this is either a drive ("C:") or the start of an
	// incomplete UNC path ("\\"). In either case, don't append a separator.
	appendSep = false
	}
	}
	if b.Len() == 0 {
	return ""
	}
	return Clean(b.String())
	}

	// joinNonEmpty is like join, but it assumes that the first element is non-empty.
	func joinNonEmpty(elem []string) string {
	if len(elem[0]) == 2 && elem[0][1] == ':' {
	// First element is drive letter without terminating slash.
	// Keep path relative to current directory on that drive.
	// Skip empty elements.
	i := 1
	for ; i < len(elem); i++ {
	if elem[i] != "" {
	break
	}
	}
	return Clean(elem[0] + strings.Join(elem[i:], string(Separator)))
	}
	// The following logic prevents Join from inadvertently creating a
	// UNC path on Windows. Unless the first element is a UNC path, Join
	// shouldn't create a UNC path. See golang.org/issue/9167.
	p := Clean(strings.Join(elem, string(Separator)))
	if !isUNC(p) {
	return p
	}
	// p == UNC only allowed when the first element is a UNC path.
	head := Clean(elem[0])
	if isUNC(head) {
	return p
	}
	// head + tail == UNC, but joining two non-UNC paths should not result
	// in a UNC path. Undo creation of UNC path.
	tail := Clean(strings.Join(elem[1:], string(Separator)))
	if head[len(head)-1] == Separator {
	return head + tail
	}
	return head + string(Separator) + tail
	}

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

	func sameWord(a, b string) bool {
	return strings.EqualFold(a, b)
	}