symlink_windows.go

     1  // Copyright 2012 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 filepath
     6  
     7  import (
     8  	"strings"
     9  	"syscall"
    10  )
    11  
    12  // normVolumeName is like VolumeName, but makes drive letter upper case.
    13  // result of EvalSymlinks must be unique, so we have
    14  // EvalSymlinks(`c:\a`) == EvalSymlinks(`C:\a`).
    15  func normVolumeName(path string) string {
    16  	volume := VolumeName(path)
    17  
    18  	if len(volume) > 2 { // isUNC
    19  		return volume
    20  	}
    21  
    22  	return strings.ToUpper(volume)
    23  }
    24  
    25  // normBase returns the last element of path with correct case.
    26  func normBase(path string) (string, error) {
    27  	p, err := syscall.UTF16PtrFromString(path)
    28  	if err != nil {
    29  		return "", err
    30  	}
    31  
    32  	var data syscall.Win32finddata
    33  
    34  	h, err := syscall.FindFirstFile(p, &data)
    35  	if err != nil {
    36  		return "", err
    37  	}
    38  	syscall.FindClose(h)
    39  
    40  	return syscall.UTF16ToString(data.FileName[:]), nil
    41  }
    42  
    43  // baseIsDotDot reports whether the last element of path is "..".
    44  // The given path should be 'Clean'-ed in advance.
    45  func baseIsDotDot(path string) bool {
    46  	i := strings.LastIndexByte(path, Separator)
    47  	return path[i+1:] == ".."
    48  }
    49  
    50  // toNorm returns the normalized path that is guaranteed to be unique.
    51  // It should accept the following formats:
    52  //   * UNC paths                              (e.g \\server\share\foo\bar)
    53  //   * absolute paths                         (e.g C:\foo\bar)
    54  //   * relative paths begin with drive letter (e.g C:foo\bar, C:..\foo\bar, C:.., C:.)
    55  //   * relative paths begin with '\'          (e.g \foo\bar)
    56  //   * relative paths begin without '\'       (e.g foo\bar, ..\foo\bar, .., .)
    57  // The returned normalized path will be in the same form (of 5 listed above) as the input path.
    58  // If two paths A and B are indicating the same file with the same format, toNorm(A) should be equal to toNorm(B).
    59  // The normBase parameter should be equal to the normBase func, except for in tests.  See docs on the normBase func.
    60  func toNorm(path string, normBase func(string) (string, error)) (string, error) {
    61  	if path == "" {
    62  		return path, nil
    63  	}
    64  
    65  	path = Clean(path)
    66  
    67  	volume := normVolumeName(path)
    68  	path = path[len(volume):]
    69  
    70  	// skip special cases
    71  	if path == "" || path == "." || path == `\` {
    72  		return volume + path, nil
    73  	}
    74  
    75  	var normPath string
    76  
    77  	for {
    78  		if baseIsDotDot(path) {
    79  			normPath = path + `\` + normPath
    80  
    81  			break
    82  		}
    83  
    84  		name, err := normBase(volume + path)
    85  		if err != nil {
    86  			return "", err
    87  		}
    88  
    89  		normPath = name + `\` + normPath
    90  
    91  		i := strings.LastIndexByte(path, Separator)
    92  		if i == -1 {
    93  			break
    94  		}
    95  		if i == 0 { // `\Go` or `C:\Go`
    96  			normPath = `\` + normPath
    97  
    98  			break
    99  		}
   100  
   101  		path = path[:i]
   102  	}
   103  
   104  	normPath = normPath[:len(normPath)-1] // remove trailing '\'
   105  
   106  	return volume + normPath, nil
   107  }
   108  
   109  func evalSymlinks(path string) (string, error) {
   110  	newpath, err := walkSymlinks(path)
   111  	if err != nil {
   112  		return "", err
   113  	}
   114  	newpath, err = toNorm(newpath, normBase)
   115  	if err != nil {
   116  		return "", err
   117  	}
   118  	return newpath, nil
   119  }
   120
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