path.go

     1  // Copyright 2018 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 str
     6  
     7  import (
     8  	"os"
     9  	"path/filepath"
    10  	"runtime"
    11  	"strings"
    12  )
    13  
    14  // HasPathPrefix reports whether the slash-separated path s
    15  // begins with the elements in prefix.
    16  func HasPathPrefix(s, prefix string) bool {
    17  	if len(s) == len(prefix) {
    18  		return s == prefix
    19  	}
    20  	if prefix == "" {
    21  		return true
    22  	}
    23  	if len(s) > len(prefix) {
    24  		if prefix[len(prefix)-1] == '/' || s[len(prefix)] == '/' {
    25  			return s[:len(prefix)] == prefix
    26  		}
    27  	}
    28  	return false
    29  }
    30  
    31  // HasFilePathPrefix reports whether the filesystem path s
    32  // begins with the elements in prefix.
    33  //
    34  // HasFilePathPrefix is case-sensitive (except for volume names) even if the
    35  // filesystem is not, does not apply Unicode normalization even if the
    36  // filesystem does, and assumes that all path separators are canonicalized to
    37  // filepath.Separator (as returned by filepath.Clean).
    38  func HasFilePathPrefix(s, prefix string) bool {
    39  	sv := filepath.VolumeName(s)
    40  	pv := filepath.VolumeName(prefix)
    41  
    42  	// Strip the volume from both paths before canonicalizing sv and pv:
    43  	// it's unlikely that strings.ToUpper will change the length of the string,
    44  	// but doesn't seem impossible.
    45  	s = s[len(sv):]
    46  	prefix = prefix[len(pv):]
    47  
    48  	// Always treat Windows volume names as case-insensitive, even though
    49  	// we don't treat the rest of the path as such.
    50  	//
    51  	// TODO(bcmills): Why do we care about case only for the volume name? It's
    52  	// been this way since https://go.dev/cl/11316, but I don't understand why
    53  	// that problem doesn't apply to case differences in the entire path.
    54  	if sv != pv {
    55  		sv = strings.ToUpper(sv)
    56  		pv = strings.ToUpper(pv)
    57  	}
    58  
    59  	switch {
    60  	default:
    61  		return false
    62  	case sv != pv:
    63  		return false
    64  	case len(s) == len(prefix):
    65  		return s == prefix
    66  	case prefix == "":
    67  		return true
    68  	case len(s) > len(prefix):
    69  		if prefix[len(prefix)-1] == filepath.Separator {
    70  			return strings.HasPrefix(s, prefix)
    71  		}
    72  		return s[len(prefix)] == filepath.Separator && s[:len(prefix)] == prefix
    73  	}
    74  }
    75  
    76  // TrimFilePathPrefix returns s without the leading path elements in prefix,
    77  // such that joining the string to prefix produces s.
    78  //
    79  // If s does not start with prefix (HasFilePathPrefix with the same arguments
    80  // returns false), TrimFilePathPrefix returns s. If s equals prefix,
    81  // TrimFilePathPrefix returns "".
    82  func TrimFilePathPrefix(s, prefix string) string {
    83  	if prefix == "" {
    84  		// Trimming the empty string from a path should join to produce that path.
    85  		// (Trim("/tmp/foo", "") should give "/tmp/foo", not "tmp/foo".)
    86  		return s
    87  	}
    88  	if !HasFilePathPrefix(s, prefix) {
    89  		return s
    90  	}
    91  
    92  	trimmed := s[len(prefix):]
    93  	if len(trimmed) > 0 && os.IsPathSeparator(trimmed[0]) {
    94  		if runtime.GOOS == "windows" && prefix == filepath.VolumeName(prefix) && len(prefix) == 2 && prefix[1] == ':' {
    95  			// Joining a relative path to a bare Windows drive letter produces a path
    96  			// relative to the working directory on that drive, but the original path
    97  			// was absolute, not relative. Keep the leading path separator so that it
    98  			// remains absolute when joined to prefix.
    99  		} else {
   100  			// Prefix ends in a regular path element, so strip the path separator that
   101  			// follows it.
   102  			trimmed = trimmed[1:]
   103  		}
   104  	}
   105  	return trimmed
   106  }
   107  
   108  // WithFilePathSeparator returns s with a trailing path separator, or the empty
   109  // string if s is empty.
   110  func WithFilePathSeparator(s string) string {
   111  	if s == "" || os.IsPathSeparator(s[len(s)-1]) {
   112  		return s
   113  	}
   114  	return s + string(filepath.Separator)
   115  }
   116  
   117  // QuoteGlob returns s with all Glob metacharacters quoted.
   118  // We don't try to handle backslash here, as that can appear in a
   119  // file path on Windows.
   120  func QuoteGlob(s string) string {
   121  	if !strings.ContainsAny(s, `*?[]`) {
   122  		return s
   123  	}
   124  	var sb strings.Builder
   125  	for _, c := range s {
   126  		switch c {
   127  		case '*', '?', '[', ']':
   128  			sb.WriteByte('\\')
   129  		}
   130  		sb.WriteRune(c)
   131  	}
   132  	return sb.String()
   133  }
   134
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