path: add Match

R=eridius, r, rog
CC=golang-dev
https://golang.org/cl/217088

src/pkg/path/Makefile

@@ -6,6 +6,7 @@ include ../../Make.$(GOARCH)
 
 TARG=path
 GOFILES=\
+	match.go\
 	path.go\
 
 include ../../Make.pkg

src/pkg/path/match.go

@@ -0,0 +1,197 @@
+package path
+
+import (
+	"os"
+	"strings"
+	"utf8"
+)
+
+var ErrBadPattern = os.NewError("syntax error in pattern")
+
+// Match returns true if name matches the shell file name pattern.
+// The syntax used by pattern 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 error return is when pattern is malformed.
+//
+func Match(pattern, name string) (matched bool, err os.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.Index(name, "/") < 0, nil
+		}
+		// Look for match at current position.
+		t, ok, err := matchChunk(chunk, name)
+		if ok {
+			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 {
+					name = t
+					continue Pattern
+				}
+				if err != nil {
+					return false, err
+				}
+			}
+		}
+		return false, nil
+	}
+	return len(name) == 0, nil
+}
+
+// scanChunk gets the next section 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++
+			}
+			continue
+		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 os.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 int
+				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 int, nchunk string, err os.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
+}

src/pkg/path/match_test.go

@@ -0,0 +1,76 @@
+// Copyright 2009 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 (
+	"os"
+	"testing"
+)
+
+type MatchTest struct {
+	pattern, s string
+	match      bool
+	err        os.Error
+}
+
+var matchTests = []MatchTest{
+	MatchTest{"abc", "abc", true, nil},
+	MatchTest{"*", "abc", true, nil},
+	MatchTest{"*c", "abc", true, nil},
+	MatchTest{"a*", "a", true, nil},
+	MatchTest{"a*", "abc", true, nil},
+	MatchTest{"a*", "ab/c", false, nil},
+	MatchTest{"a*/b", "abc/b", true, nil},
+	MatchTest{"a*/b", "a/c/b", false, nil},
+	MatchTest{"a*b*c*d*e*/f", "axbxcxdxe/f", true, nil},
+	MatchTest{"a*b*c*d*e*/f", "axbxcxdxexxx/f", true, nil},
+	MatchTest{"a*b*c*d*e*/f", "axbxcxdxe/xxx/f", false, nil},
+	MatchTest{"a*b*c*d*e*/f", "axbxcxdxexxx/fff", false, nil},
+	MatchTest{"a*b?c*x", "abxbbxdbxebxczzx", true, nil},
+	MatchTest{"a*b?c*x", "abxbbxdbxebxczzy", false, nil},
+	MatchTest{"ab[c]", "abc", true, nil},
+	MatchTest{"ab[b-d]", "abc", true, nil},
+	MatchTest{"ab[e-g]", "abc", false, nil},
+	MatchTest{"ab[^c]", "abc", false, nil},
+	MatchTest{"ab[^b-d]", "abc", false, nil},
+	MatchTest{"ab[^e-g]", "abc", true, nil},
+	MatchTest{"a\\*b", "a*b", true, nil},
+	MatchTest{"a\\*b", "ab", false, nil},
+	MatchTest{"a?b", "a☺b", true, nil},
+	MatchTest{"a[^a]b", "a☺b", true, nil},
+	MatchTest{"a???b", "a☺b", false, nil},
+	MatchTest{"a[^a][^a][^a]b", "a☺b", false, nil},
+	MatchTest{"[a-ζ]*", "α", true, nil},
+	MatchTest{"*[a-ζ]", "A", false, nil},
+	MatchTest{"a?b", "a/b", false, nil},
+	MatchTest{"a*b", "a/b", false, nil},
+	MatchTest{"[\\]a]", "]", true, nil},
+	MatchTest{"[\\-]", "-", true, nil},
+	MatchTest{"[x\\-]", "x", true, nil},
+	MatchTest{"[x\\-]", "-", true, nil},
+	MatchTest{"[x\\-]", "z", false, nil},
+	MatchTest{"[\\-x]", "x", true, nil},
+	MatchTest{"[\\-x]", "-", true, nil},
+	MatchTest{"[\\-x]", "a", false, nil},
+	MatchTest{"[]a]", "]", false, ErrBadPattern},
+	MatchTest{"[-]", "-", false, ErrBadPattern},
+	MatchTest{"[x-]", "x", false, ErrBadPattern},
+	MatchTest{"[x-]", "-", false, ErrBadPattern},
+	MatchTest{"[x-]", "z", false, ErrBadPattern},
+	MatchTest{"[-x]", "x", false, ErrBadPattern},
+	MatchTest{"[-x]", "-", false, ErrBadPattern},
+	MatchTest{"[-x]", "a", false, ErrBadPattern},
+	MatchTest{"\\", "a", false, ErrBadPattern},
+	MatchTest{"[a-b-c]", "a", false, ErrBadPattern},
+}
+
+func TestMatch(t *testing.T) {
+	for _, tt := range matchTests {
+		ok, err := Match(tt.pattern, tt.s)
+		if ok != tt.match || err != tt.err {
+			t.Errorf("Match(%#q, %#q) = %v, %v want %v, nil\n", tt.pattern, tt.s, ok, err, tt.match)
+		}
+	}
+}