1 files changed, 329 insertions, 0 deletions
diff --git a/src/internal/filepathlite/path_windows.go b/src/internal/filepathlite/path_windows.go
new file mode 100644
index 0000000000..8f34838a98
--- /dev/null
+++ b/src/internal/filepathlite/path_windows.go
@@ -0,0 +1,329 @@
+// 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, '.')
+	}
+}