github.com/JimmyHuang454/JLS-go@v0.0.0-20230831150107-90d536585ba0/internal/safefilepath/path_windows.go (about)

     1  // Copyright 2022 The Go Authors. All rights reserved.
     2  // Use of this source code is governed by a BSD-style
     3  // license that can be found in the LICENSE file.
     4  
     5  package safefilepath
     6  
     7  import (
     8  	"syscall"
     9  	"unicode/utf8"
    10  )
    11  
    12  func fromFS(path string) (string, error) {
    13  	if !utf8.ValidString(path) {
    14  		return "", errInvalidPath
    15  	}
    16  	for len(path) > 1 && path[0] == '/' && path[1] == '/' {
    17  		path = path[1:]
    18  	}
    19  	containsSlash := false
    20  	for p := path; p != ""; {
    21  		// Find the next path element.
    22  		i := 0
    23  		dot := -1
    24  		for i < len(p) && p[i] != '/' {
    25  			switch p[i] {
    26  			case 0, '\\', ':':
    27  				return "", errInvalidPath
    28  			case '.':
    29  				if dot < 0 {
    30  					dot = i
    31  				}
    32  			}
    33  			i++
    34  		}
    35  		part := p[:i]
    36  		if i < len(p) {
    37  			containsSlash = true
    38  			p = p[i+1:]
    39  		} else {
    40  			p = ""
    41  		}
    42  		// Trim the extension and look for a reserved name.
    43  		base := part
    44  		if dot >= 0 {
    45  			base = part[:dot]
    46  		}
    47  		if isReservedName(base) {
    48  			if dot < 0 {
    49  				return "", errInvalidPath
    50  			}
    51  			// The path element is a reserved name with an extension.
    52  			// Some Windows versions consider this a reserved name,
    53  			// while others do not. Use FullPath to see if the name is
    54  			// reserved.
    55  			if p, _ := syscall.FullPath(part); len(p) >= 4 && p[:4] == `\\.\` {
    56  				return "", errInvalidPath
    57  			}
    58  		}
    59  	}
    60  	if containsSlash {
    61  		// We can't depend on strings, so substitute \ for / manually.
    62  		buf := []byte(path)
    63  		for i, b := range buf {
    64  			if b == '/' {
    65  				buf[i] = '\\'
    66  			}
    67  		}
    68  		path = string(buf)
    69  	}
    70  	return path, nil
    71  }
    72  
    73  // isReservedName reports if name is a Windows reserved device name.
    74  // It does not detect names with an extension, which are also reserved on some Windows versions.
    75  //
    76  // For details, search for PRN in
    77  // https://docs.microsoft.com/en-us/windows/desktop/fileio/naming-a-file.
    78  func isReservedName(name string) bool {
    79  	if 3 <= len(name) && len(name) <= 4 {
    80  		switch string([]byte{toUpper(name[0]), toUpper(name[1]), toUpper(name[2])}) {
    81  		case "CON", "PRN", "AUX", "NUL":
    82  			return len(name) == 3
    83  		case "COM", "LPT":
    84  			return len(name) == 4 && '1' <= name[3] && name[3] <= '9'
    85  		}
    86  	}
    87  	return false
    88  }
    89  
    90  func toUpper(c byte) byte {
    91  	if 'a' <= c && c <= 'z' {
    92  		return c - ('a' - 'A')
    93  	}
    94  	return c
    95  }