1package doublestar
 2
 3import "path/filepath"
 4
 5// Validate a pattern. Patterns are validated while they run in Match(),
 6// PathMatch(), and Glob(), so, you normally wouldn't need to call this.
 7// However, there are cases where this might be useful: for example, if your
 8// program allows a user to enter a pattern that you'll run at a later time,
 9// you might want to validate it.
10//
11// ValidatePattern assumes your pattern uses '/' as the path separator.
12//
13func ValidatePattern(s string) bool {
14	return doValidatePattern(s, '/')
15}
16
17// Like ValidatePattern, only uses your OS path separator. In other words, use
18// ValidatePattern if you would normally use Match() or Glob(). Use
19// ValidatePathPattern if you would normally use PathMatch(). Keep in mind,
20// Glob() requires '/' separators, even if your OS uses something else.
21//
22func ValidatePathPattern(s string) bool {
23	return doValidatePattern(s, filepath.Separator)
24}
25
26func doValidatePattern(s string, separator rune) bool {
27	altDepth := 0
28	l := len(s)
29VALIDATE:
30	for i := 0; i < l; i++ {
31		switch s[i] {
32		case '\\':
33			if separator != '\\' {
34				// skip the next byte - return false if there is no next byte
35				if i++; i >= l {
36					return false
37				}
38			}
39			continue
40
41		case '[':
42			if i++; i >= l {
43				// class didn't end
44				return false
45			}
46			if s[i] == '^' || s[i] == '!' {
47				i++
48			}
49			if i >= l || s[i] == ']' {
50				// class didn't end or empty character class
51				return false
52			}
53
54			for ; i < l; i++ {
55				if separator != '\\' && s[i] == '\\' {
56					i++
57				} else if s[i] == ']' {
58					// looks good
59					continue VALIDATE
60				}
61			}
62
63			// class didn't end
64			return false
65
66		case '{':
67			altDepth++
68			continue
69
70		case '}':
71			if altDepth == 0 {
72				// alt end without a corresponding start
73				return false
74			}
75			altDepth--
76			continue
77		}
78	}
79
80	// valid as long as all alts are closed
81	return altDepth == 0
82}