glob.go

     1  // Copyright 2020 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 fs
     6  
     7  import (
     8  	"path"
     9  )
    10  
    11  // A GlobFS is a file system with a Glob method.
    12  type GlobFS interface {
    13  	FS
    14  
    15  	// Glob returns the names of all files matching pattern,
    16  	// providing an implementation of the top-level
    17  	// Glob function.
    18  	Glob(pattern string) ([]string, error)
    19  }
    20  
    21  // Glob returns the names of all files matching pattern or nil
    22  // if there is no matching file. The syntax of patterns is the same
    23  // as in path.Match. The pattern may describe hierarchical names such as
    24  // usr/*/bin/ed.
    25  //
    26  // Glob ignores file system errors such as I/O errors reading directories.
    27  // The only possible returned error is path.ErrBadPattern, reporting that
    28  // the pattern is malformed.
    29  //
    30  // If fs implements GlobFS, Glob calls fs.Glob.
    31  // Otherwise, Glob uses ReadDir to traverse the directory tree
    32  // and look for matches for the pattern.
    33  func Glob(fsys FS, pattern string) (matches []string, err error) {
    34  	if fsys, ok := fsys.(GlobFS); ok {
    35  		return fsys.Glob(pattern)
    36  	}
    37  
    38  	// Check pattern is well-formed.
    39  	if _, err := path.Match(pattern, ""); err != nil {
    40  		return nil, err
    41  	}
    42  	if !hasMeta(pattern) {
    43  		if _, err = Stat(fsys, pattern); err != nil {
    44  			return nil, nil
    45  		}
    46  		return []string{pattern}, nil
    47  	}
    48  
    49  	dir, file := path.Split(pattern)
    50  	dir = cleanGlobPath(dir)
    51  
    52  	if !hasMeta(dir) {
    53  		return glob(fsys, dir, file, nil)
    54  	}
    55  
    56  	// Prevent infinite recursion. See issue 15879.
    57  	if dir == pattern {
    58  		return nil, path.ErrBadPattern
    59  	}
    60  
    61  	var m []string
    62  	m, err = Glob(fsys, dir)
    63  	if err != nil {
    64  		return
    65  	}
    66  	for _, d := range m {
    67  		matches, err = glob(fsys, d, file, matches)
    68  		if err != nil {
    69  			return
    70  		}
    71  	}
    72  	return
    73  }
    74  
    75  // cleanGlobPath prepares path for glob matching.
    76  func cleanGlobPath(path string) string {
    77  	switch path {
    78  	case "":
    79  		return "."
    80  	default:
    81  		return path[0 : len(path)-1] // chop off trailing separator
    82  	}
    83  }
    84  
    85  // glob searches for files matching pattern in the directory dir
    86  // and appends them to matches, returning the updated slice.
    87  // If the directory cannot be opened, glob returns the existing matches.
    88  // New matches are added in lexicographical order.
    89  func glob(fs FS, dir, pattern string, matches []string) (m []string, e error) {
    90  	m = matches
    91  	infos, err := ReadDir(fs, dir)
    92  	if err != nil {
    93  		return // ignore I/O error
    94  	}
    95  
    96  	for _, info := range infos {
    97  		n := info.Name()
    98  		matched, err := path.Match(pattern, n)
    99  		if err != nil {
   100  			return m, err
   101  		}
   102  		if matched {
   103  			m = append(m, path.Join(dir, n))
   104  		}
   105  	}
   106  	return
   107  }
   108  
   109  // hasMeta reports whether path contains any of the magic characters
   110  // recognized by path.Match.
   111  func hasMeta(path string) bool {
   112  	for i := 0; i < len(path); i++ {
   113  		switch path[i] {
   114  		case '*', '?', '[', '\\':
   115  			return true
   116  		}
   117  	}
   118  	return false
   119  }
   120
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