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// Copyright 2022 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 safefilepath
import (
"syscall"
"unicode/utf8"
)
func fromFS(path string) (string, error) {
if !utf8.ValidString(path) {
return "", errInvalidPath
}
for len(path) > 1 && path[0] == '/' && path[1] == '/' {
path = path[1:]
}
containsSlash := false
for p := path; p != ""; {
// Find the next path element.
i := 0
dot := -1
for i < len(p) && p[i] != '/' {
switch p[i] {
case 0, '\\', ':':
return "", errInvalidPath
case '.':
if dot < 0 {
dot = i
}
}
i++
}
part := p[:i]
if i < len(p) {
containsSlash = true
p = p[i+1:]
} else {
p = ""
}
// Trim the extension and look for a reserved name.
base := part
if dot >= 0 {
base = part[:dot]
}
if isReservedName(base) {
if dot < 0 {
return "", errInvalidPath
}
// 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(part); len(p) >= 4 && p[:4] == `\\.\` {
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 {
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'
}
}
return false
}
func toUpper(c byte) byte {
if 'a' <= c && c <= 'z' {
return c - ('a' - 'A')
}
return c
}
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