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Source file src/path/match.go

Documentation: path

  // Copyright 2010 The Go Authors. All rights reserved.
  // Use of this source code is governed by a BSD-style
  // license that can be found in the LICENSE file.
  
  package path
  
  import (
  	"errors"
  	"strings"
  	"unicode/utf8"
  )
  
  // ErrBadPattern indicates a globbing pattern was malformed.
  var ErrBadPattern = errors.New("syntax error in pattern")
  
  // Match reports whether name matches the shell file name pattern.
  // The pattern syntax is:
  //
  //	pattern:
  //		{ term }
  //	term:
  //		'*'         matches any sequence of non-/ characters
  //		'?'         matches any single non-/ character
  //		'[' [ '^' ] { character-range } ']'
  //		            character class (must be non-empty)
  //		c           matches character c (c != '*', '?', '\\', '[')
  //		'\\' c      matches character c
  //
  //	character-range:
  //		c           matches character c (c != '\\', '-', ']')
  //		'\\' c      matches character c
  //		lo '-' hi   matches character c for lo <= c <= hi
  //
  // Match requires pattern to match all of name, not just a substring.
  // The only possible returned error is ErrBadPattern, when pattern
  // is malformed.
  //
  func Match(pattern, name string) (matched bool, err error) {
  Pattern:
  	for len(pattern) > 0 {
  		var star bool
  		var chunk string
  		star, chunk, pattern = scanChunk(pattern)
  		if star && chunk == "" {
  			// Trailing * matches rest of string unless it has a /.
  			return !strings.Contains(name, "/"), nil
  		}
  		// Look for match at current position.
  		t, ok, err := matchChunk(chunk, name)
  		// if we're the last chunk, make sure we've exhausted the name
  		// otherwise we'll give a false result even if we could still match
  		// using the star
  		if ok && (len(t) == 0 || len(pattern) > 0) {
  			name = t
  			continue
  		}
  		if err != nil {
  			return false, err
  		}
  		if star {
  			// Look for match skipping i+1 bytes.
  			// Cannot skip /.
  			for i := 0; i < len(name) && name[i] != '/'; i++ {
  				t, ok, err := matchChunk(chunk, name[i+1:])
  				if ok {
  					// if we're the last chunk, make sure we exhausted the name
  					if len(pattern) == 0 && len(t) > 0 {
  						continue
  					}
  					name = t
  					continue Pattern
  				}
  				if err != nil {
  					return false, err
  				}
  			}
  		}
  		return false, nil
  	}
  	return len(name) == 0, nil
  }
  
  // scanChunk gets the next segment of pattern, which is a non-star string
  // possibly preceded by a star.
  func scanChunk(pattern string) (star bool, chunk, rest string) {
  	for len(pattern) > 0 && pattern[0] == '*' {
  		pattern = pattern[1:]
  		star = true
  	}
  	inrange := false
  	var i int
  Scan:
  	for i = 0; i < len(pattern); i++ {
  		switch pattern[i] {
  		case '\\':
  			// error check handled in matchChunk: bad pattern.
  			if i+1 < len(pattern) {
  				i++
  			}
  		case '[':
  			inrange = true
  		case ']':
  			inrange = false
  		case '*':
  			if !inrange {
  				break Scan
  			}
  		}
  	}
  	return star, pattern[0:i], pattern[i:]
  }
  
  // matchChunk checks whether chunk matches the beginning of s.
  // If so, it returns the remainder of s (after the match).
  // Chunk is all single-character operators: literals, char classes, and ?.
  func matchChunk(chunk, s string) (rest string, ok bool, err error) {
  	for len(chunk) > 0 {
  		if len(s) == 0 {
  			return
  		}
  		switch chunk[0] {
  		case '[':
  			// character class
  			r, n := utf8.DecodeRuneInString(s)
  			s = s[n:]
  			chunk = chunk[1:]
  			// possibly negated
  			notNegated := true
  			if len(chunk) > 0 && chunk[0] == '^' {
  				notNegated = false
  				chunk = chunk[1:]
  			}
  			// parse all ranges
  			match := false
  			nrange := 0
  			for {
  				if len(chunk) > 0 && chunk[0] == ']' && nrange > 0 {
  					chunk = chunk[1:]
  					break
  				}
  				var lo, hi rune
  				if lo, chunk, err = getEsc(chunk); err != nil {
  					return
  				}
  				hi = lo
  				if chunk[0] == '-' {
  					if hi, chunk, err = getEsc(chunk[1:]); err != nil {
  						return
  					}
  				}
  				if lo <= r && r <= hi {
  					match = true
  				}
  				nrange++
  			}
  			if match != notNegated {
  				return
  			}
  
  		case '?':
  			if s[0] == '/' {
  				return
  			}
  			_, n := utf8.DecodeRuneInString(s)
  			s = s[n:]
  			chunk = chunk[1:]
  
  		case '\\':
  			chunk = chunk[1:]
  			if len(chunk) == 0 {
  				err = ErrBadPattern
  				return
  			}
  			fallthrough
  
  		default:
  			if chunk[0] != s[0] {
  				return
  			}
  			s = s[1:]
  			chunk = chunk[1:]
  		}
  	}
  	return s, true, nil
  }
  
  // getEsc gets a possibly-escaped character from chunk, for a character class.
  func getEsc(chunk string) (r rune, nchunk string, err error) {
  	if len(chunk) == 0 || chunk[0] == '-' || chunk[0] == ']' {
  		err = ErrBadPattern
  		return
  	}
  	if chunk[0] == '\\' {
  		chunk = chunk[1:]
  		if len(chunk) == 0 {
  			err = ErrBadPattern
  			return
  		}
  	}
  	r, n := utf8.DecodeRuneInString(chunk)
  	if r == utf8.RuneError && n == 1 {
  		err = ErrBadPattern
  	}
  	nchunk = chunk[n:]
  	if len(nchunk) == 0 {
  		err = ErrBadPattern
  	}
  	return
  }
  

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