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Commit b96c3477 authored by Russ Cox's avatar Russ Cox
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exp/regexp/syntax: syntax data structures, parser 

Parser is a work in progress but can populate most of the
interesting parts of the data structure, so a good checkpoint.
All the complicated Perl syntax is missing, as are various
important optimizations made during parsing to the
syntax tree.

The plan is that exp/regexp's API will mimic regexp,
and exp/regexp/syntax provides the parser directly
for programs that need it (and for implementing exp/regexp).

Once finished, exp/regexp will replace regexp.

R=r, sam.thorogood, kevlar, edsrzf
CC=golang-dev
https://golang.org/cl/4538123
parent b4bb970e
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src/pkg/Makefile
View file @ b96c3477
......@@ -81,6 +81,7 @@ DIRS=\
exp/eval\
exp/gui\
exp/gui/x11\
exp/regexp/syntax\
expvar\
flag\
fmt\
......
src/pkg/exp/regexp/syntax/Makefile 0 → 100644
View file @ b96c3477
# Copyright 2011 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.
include ../../../../Make.inc
TARG=exp/regexp/syntax
GOFILES=\
parse.go\
regexp.go\
include ../../../../Make.pkg
src/pkg/exp/regexp/syntax/parse.go 0 → 100644
View file @ b96c3477
// Copyright 2011 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 syntax
import (
"os"
"sort"
"unicode"
"utf8"
)
// An Error describes a failure to parse a regular expression
// and gives the offending expression.
type Error struct {
Code ErrorCode
Expr string
}
func (e *Error) String() string {
return "error parsing regexp: " + e.Code.String() + ": `" + e.Expr + "`"
}
// An ErrorCode describes a failure to parse a regular expression.
type ErrorCode string
const (
// Unexpected error
ErrInternalError ErrorCode = "regexp/syntax: internal error"
// Parse errors
ErrInvalidCharClass ErrorCode = "invalid character class"
ErrInvalidCharRange ErrorCode = "invalid character class range"
ErrInvalidEscape ErrorCode = "invalid escape sequence"
ErrInvalidNamedCapture ErrorCode = "invalid named capture"
ErrInvalidPerlOp ErrorCode = "invalid or unsupported Perl syntax"
ErrInvalidRepeatOp ErrorCode = "invalid nested repetition operator"
ErrInvalidRepeatSize ErrorCode = "invalid repeat count"
ErrInvalidUTF8 ErrorCode = "invalid UTF-8"
ErrMissingBracket ErrorCode = "missing closing ]"
ErrMissingParen ErrorCode = "missing closing )"
ErrMissingRepeatArgument ErrorCode = "missing argument to repetition operator"
ErrTrailingBackslash ErrorCode = "trailing backslash at end of expression"
)
func (e ErrorCode) String() string {
return string(e)
}
// Flags control the behavior of the parser and record information about regexp context.
type Flags uint16
const (
FoldCase Flags = 1 << iota // case-insensitive match
Literal // treat pattern as literal string
ClassNL // allow character classes like [^a-z] and [[:space:]] to match newline
DotNL // allow . to match newline
OneLine // treat ^ and $ as only matching at beginning and end of text
NonGreedy // make repetition operators default to non-greedy
PerlX // allow Perl extensions
UnicodeGroups // allow \p{Han}, \P{Han} for Unicode group and negation
WasDollar // regexp OpEndText was $, not \z
Simple // regexp contains no counted repetition
MatchNL = ClassNL | DotNL
Perl = ClassNL | OneLine | PerlX | UnicodeGroups // as close to Perl as possible
POSIX Flags = 0 // POSIX syntax
)
// Pseudo-ops for parsing stack.
const (
opLeftParen = opPseudo + iota
opVerticalBar
)
type parser struct {
flags Flags // parse mode flags
stack []*Regexp // stack of parsed expressions
numCap int // number of capturing groups seen
wholeRegexp string
}
// Parse stack manipulation.
// push pushes the regexp re onto the parse stack and returns the regexp.
func (p *parser) push(re *Regexp) *Regexp {
// TODO: automatic concatenation
// TODO: turn character class into literal
// TODO: compute simple
p.stack = append(p.stack, re)
return re
}
// newLiteral returns a new OpLiteral Regexp with the given flags
func newLiteral(r int, flags Flags) *Regexp {
re := &Regexp{
Op: OpLiteral,
Flags: flags,
}
re.Rune0[0] = r
re.Rune = re.Rune0[:1]
return re
}
// literal pushes a literal regexp for the rune r on the stack
// and returns that regexp.
func (p *parser) literal(r int) *Regexp {
return p.push(newLiteral(r, p.flags))
}
// op pushes a regexp with the given op onto the stack
// and returns that regexp.
func (p *parser) op(op Op) *Regexp {
return p.push(&Regexp{Op: op, Flags: p.flags})
}
// repeat replaces the top stack element with itself repeated
// according to op.
func (p *parser) repeat(op Op, opstr string) os.Error {
n := len(p.stack)
if n == 0 {
return &Error{ErrMissingRepeatArgument, opstr}
}
sub := p.stack[n-1]
re := &Regexp{
Op: op,
}
re.Sub = re.Sub0[:1]
re.Sub[0] = sub
p.stack[n-1] = re
return nil
}
// concat replaces the top of the stack (above the topmost '|' or '(') with its concatenation.
func (p *parser) concat() *Regexp {
// TODO: Flatten concats.
// Scan down to find pseudo-operator | or (.
i := len(p.stack)
for i > 0 && p.stack[i-1].Op < opPseudo {
i--
}
sub := p.stack[i:]
p.stack = p.stack[:i]
var re *Regexp
switch len(sub) {
case 0:
re = &Regexp{Op: OpEmptyMatch}
case 1:
re = sub[0]
default:
re = &Regexp{Op: OpConcat}
re.Sub = append(re.Sub0[:0], sub...)
}
return p.push(re)
}
// alternate replaces the top of the stack (above the topmost '(') with its alternation.
func (p *parser) alternate() *Regexp {
// TODO: Flatten alternates.
// Scan down to find pseudo-operator (.
// There are no | above (.
i := len(p.stack)
for i > 0 && p.stack[i-1].Op < opPseudo {
i--
}
sub := p.stack[i:]
p.stack = p.stack[:i]
var re *Regexp
switch len(sub) {
case 0:
re = &Regexp{Op: OpNoMatch}
case 1:
re = sub[0]
default:
re = &Regexp{Op: OpAlternate}
re.Sub = append(re.Sub0[:0], sub...)
}
return p.push(re)
}
// Parsing.
func Parse(s string, flags Flags) (*Regexp, os.Error) {
if flags&Literal != 0 {
// Trivial parser for literal string.
if err := checkUTF8(s); err != nil {
return nil, err
}
re := &Regexp{
Op: OpLiteral,
Flags: flags,
}
re.Rune = re.Rune0[:0] // use local storage for small strings
for _, c := range s {
if len(re.Rune) >= cap(re.Rune) {
// string is too long to fit in Rune0. let Go handle it
re.Rune = []int(s)
break
}
re.Rune = append(re.Rune, c)
}
return re, nil
}
// Otherwise, must do real work.
var (
p parser
err os.Error
c int
op Op
)
p.flags = flags
p.wholeRegexp = s
t := s
for t != "" {
switch t[0] {
default:
if c, t, err = nextRune(t); err != nil {
return nil, err
}
p.literal(c)
case '(':
// TODO: Actual Perl flag parsing.
if len(t) >= 3 && t[1] == '?' && t[2] == ':' {
// non-capturing paren
p.op(opLeftParen)
t = t[3:]
break
}
p.numCap++
p.op(opLeftParen).Cap = p.numCap
t = t[1:]
case '|':
p.concat()
if err = p.parseVerticalBar(); err != nil {
return nil, err
}
t = t[1:]
case ')':
if err = p.parseRightParen(); err != nil {
return nil, err
}
t = t[1:]
case '^':
if p.flags&OneLine != 0 {
p.op(OpBeginText)
} else {
p.op(OpBeginLine)
}
t = t[1:]
case '$':
if p.flags&OneLine != 0 {
p.op(OpEndText).Flags |= WasDollar
} else {
p.op(OpEndLine)
}
t = t[1:]
case '.':
if p.flags&DotNL != 0 {
p.op(OpAnyChar)
} else {
p.op(OpAnyCharNotNL)
}
t = t[1:]
case '[':
if t, err = p.parseClass(t); err != nil {
return nil, err
}
case '*', '+', '?':
switch t[0] {
case '*':
op = OpStar
case '+':
op = OpPlus
case '?':
op = OpQuest
}
// TODO: greedy
if err = p.repeat(op, t[0:1]); err != nil {
return nil, err
}
t = t[1:]
case '{':
return nil, os.NewError("repeat not implemented")
case '\\':
return nil, os.NewError("escape not implemented")
}
}
p.concat()
if p.swapVerticalBar() {
// pop vertical bar
p.stack = p.stack[:len(p.stack)-1]
}
p.alternate()
n := len(p.stack)
if n != 1 {
return nil, &Error{ErrMissingParen, s}
}
return p.stack[0], nil
}
// parseVerticalBar handles a | in the input.
func (p *parser) parseVerticalBar() os.Error {
p.concat()
// The concatenation we just parsed is on top of the stack.
// If it sits above an opVerticalBar, swap it below
// (things below an opVerticalBar become an alternation).
// Otherwise, push a new vertical bar.
if !p.swapVerticalBar() {
p.op(opVerticalBar)
}
return nil
}
// If the top of the stack is an element followed by an opVerticalBar
// swapVerticalBar swaps the two and returns true.
// Otherwise it returns false.
func (p *parser) swapVerticalBar() bool {
if n := len(p.stack); n >= 2 {
re1 := p.stack[n-1]
re2 := p.stack[n-2]
if re2.Op == opVerticalBar {
p.stack[n-2] = re1
p.stack[n-1] = re2
return true
}
}
return false
}
// parseRightParen handles a ) in the input.
func (p *parser) parseRightParen() os.Error {
p.concat()
if p.swapVerticalBar() {
// pop vertical bar
p.stack = p.stack[:len(p.stack)-1]
}
p.alternate()
n := len(p.stack)
if n < 2 {
return &Error{ErrInternalError, ""}
}
re1 := p.stack[n-1]
re2 := p.stack[n-2]
p.stack = p.stack[:n-2]
if re2.Op != opLeftParen {
return &Error{ErrMissingParen, p.wholeRegexp}
}
if re2.Cap == 0 {
// Just for grouping.
p.push(re1)
} else {
re2.Op = OpCapture
re2.Sub = re2.Sub0[:1]
re2.Sub[0] = re1
p.push(re2)
}
return nil
}
// parseClassChar parses a character class character at the beginning of s
// and returns it.
func (p *parser) parseClassChar(s, wholeClass string) (r int, rest string, err os.Error) {
if s == "" {
return 0, "", &Error{Code: ErrMissingBracket, Expr: wholeClass}
}
// TODO: Escapes
return nextRune(s)
}
// parseClass parses a character class at the beginning of s
// and pushes it onto the parse stack.
func (p *parser) parseClass(s string) (rest string, err os.Error) {
t := s[1:] // chop [
re := &Regexp{Op: OpCharClass, Flags: p.flags}
re.Rune = re.Rune0[:0]
sign := +1
if t != "" && t[0] == '^' {
sign = -1
t = t[1:]
// If character class does not match \n, add it here,
// so that negation later will do the right thing.
if p.flags&ClassNL == 0 {
re.Rune = append(re.Rune, '\n', '\n')
}
}
class := re.Rune
first := true // ] and - are okay as first char in class
for t == "" || t[0] != ']' || first {
// POSIX: - is only okay unescaped as first or last in class.
// Perl: - is okay anywhere.
if t != "" && t[0] == '-' && p.flags&PerlX == 0 && !first && (len(t) == 1 || t[1] != ']') {
_, size := utf8.DecodeRuneInString(t[1:])
return "", &Error{Code: ErrInvalidCharRange, Expr: t[:1+size]}
}
first = false
// TODO: Look for [:alnum:]
// TODO: Look for Unicode group.
// TODO: Look for Perl group.
// Single character or simple range.
rng := t
var lo, hi int
if lo, t, err = p.parseClassChar(t, s); err != nil {
return "", err
}
hi = lo
// [a-] means (a|-) so check for final ].
if len(t) >= 2 && t[0] == '-' && t[1] != ']' {
t = t[1:]
if hi, t, err = p.parseClassChar(t, s); err != nil {
return "", err
}
if hi < lo {
rng = rng[:len(rng)-len(t)]
return "", &Error{Code: ErrInvalidCharRange, Expr: rng}
}
}
// Expand last range if overlaps or abuts.
if n := len(class); n > 0 {
clo, chi := class[n-2], class[n-1]
if lo <= chi+1 && clo <= hi+1 {
if lo < clo {
class[n-2] = lo
}
if hi > chi {
class[n-1] = hi
}
continue
}
}
class = append(class, lo, hi)
}
t = t[1:] // chop ]
// Use &re.Rune instead of &class to avoid allocation.
re.Rune = class
class = cleanClass(&re.Rune)
if sign < 0 {
class = negateClass(class)
}
re.Rune = class
p.push(re)
return t, nil
}
// cleanClass sorts the ranges (pairs of elements of r),
// merges them, and eliminates duplicates.
func cleanClass(rp *[]int) []int {
// Sort by lo increasing, hi decreasing to break ties.
sort.Sort(ranges{rp})
r := *rp
// Merge abutting, overlapping.
w := 2 // write index
for i := 2; i < len(r); i += 2 {
lo, hi := r[i], r[i+1]
if lo <= r[w-1]+1 {
// merge with previous range
if hi > r[w-1] {
r[w-1] = hi
}
continue
}
// new disjoint range
r[w] = lo
r[w+1] = hi
w += 2
}
return r[:w]
}
// negateClass overwrites r and returns r's negation.
// It assumes the class r is already clean.
func negateClass(r []int) []int {
nextLo := 0 // lo end of next class to add
w := 0 // write index
for i := 0; i < len(r); i += 2 {
lo, hi := r[i], r[i+1]
if nextLo <= lo-1 {
r[w] = nextLo
r[w+1] = lo - 1
w += 2
}
nextLo = hi + 1
}
if nextLo <= unicode.MaxRune {
// It's possible for the negation to have one more
// range - this one - than the original class, so use append.
r = append(r[:w], nextLo, unicode.MaxRune)
}
return r
}
// ranges implements sort.Interface on a []rune.
// The choice of receiver type definition is strange
// but avoids an allocation since we already have
// a *[]int.
type ranges struct {
p *[]int
}
func (ra ranges) Less(i, j int) bool {
p := *ra.p
i *= 2
j *= 2
return p[i] < p[j] || p[i] == p[j] && p[i+1] > p[j+1]
}
func (ra ranges) Len() int {
return len(*ra.p) / 2
}
func (ra ranges) Swap(i, j int) {
p := *ra.p
i *= 2
j *= 2
p[i], p[i+1], p[j], p[j+1] = p[j], p[j+1], p[i], p[i+1]
}
func checkUTF8(s string) os.Error {
for s != "" {
rune, size := utf8.DecodeRuneInString(s)
if rune == utf8.RuneError && size == 1 {
return &Error{Code: ErrInvalidUTF8, Expr: s}
}
s = s[size:]
}
return nil
}
func nextRune(s string) (c int, t string, err os.Error) {
c, size := utf8.DecodeRuneInString(s)
if c == utf8.RuneError && size == 1 {
return 0, "", &Error{Code: ErrInvalidUTF8, Expr: s}
}
return c, s[size:], nil
}
src/pkg/exp/regexp/syntax/parse_test.go 0 → 100644
View file @ b96c3477
// Copyright 2011 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 syntax
import (
"bytes"
"fmt"
"testing"
"unicode"
)
var parseTests = []struct {
Regexp string
Dump string
}{
// Base cases
{"a", "lit{a}"},
{"a.", "cat{lit{a}dot{}}"},
{"a.b", "cat{lit{a}dot{}lit{b}}"},
// { "ab", "str{ab}" },
{"ab", "cat{lit{a}lit{b}}"},
{"a.b.c", "cat{lit{a}dot{}lit{b}dot{}lit{c}}"},
// { "abc", "str{abc}" },
{"abc", "cat{lit{a}lit{b}lit{c}}"},
{"a|^", "alt{lit{a}bol{}}"},
// { "a|b", "cc{0x61-0x62}" },
{"a|b", "alt{lit{a}lit{b}}"},
{"(a)", "cap{lit{a}}"},
{"(a)|b", "alt{cap{lit{a}}lit{b}}"},
{"a*", "star{lit{a}}"},
{"a+", "plus{lit{a}}"},
{"a?", "que{lit{a}}"},
// { "a{2}", "rep{2,2 lit{a}}" },
// { "a{2,3}", "rep{2,3 lit{a}}" },
// { "a{2,}", "rep{2,-1 lit{a}}" },
// { "a*?", "nstar{lit{a}}" },
// { "a+?", "nplus{lit{a}}" },
// { "a??", "nque{lit{a}}" },
// { "a{2}?", "nrep{2,2 lit{a}}" },
// { "a{2,3}?", "nrep{2,3 lit{a}}" },
// { "a{2,}?", "nrep{2,-1 lit{a}}" },
{"", "emp{}"},
// { "|", "emp{}" }, // alt{emp{}emp{}} but got factored
// { "|", "alt{emp{}emp{}}" },
{"|x|", "alt{emp{}lit{x}emp{}}"},
{".", "dot{}"},
{"^", "bol{}"},
{"$", "eol{}"},
// { "\\|", "lit{|}" },
// { "\\(", "lit{(}" },
// { "\\)", "lit{)}" },
// { "\\*", "lit{*}" },
// { "\\+", "lit{+}" },
// { "\\?", "lit{?}" },
// { "{", "lit{{}" },
{"}", "lit{}}"},
// { "\\.", "lit{.}" },
// { "\\^", "lit{^}" },
// { "\\$", "lit{$}" },
// { "\\\\", "lit{\\}" },
{"[ace]", "cc{0x61 0x63 0x65}"},
{"[abc]", "cc{0x61-0x63}"},
{"[a-z]", "cc{0x61-0x7a}"},
// { "[a]", "lit{a}" },
{"[a]", "cc{0x61}"},
// { "\\-", "lit{-}" },
{"-", "lit{-}"},
// { "\\_", "lit{_}" },
// Posix and Perl extensions
// { "[[:lower:]]", "cc{0x61-0x7a}" },
// { "[a-z]", "cc{0x61-0x7a}" },
// { "[^[:lower:]]", "cc{0x0-0x60 0x7b-0x10ffff}" },
// { "[[:^lower:]]", "cc{0x0-0x60 0x7b-0x10ffff}" },
// { "(?i)[[:lower:]]", "cc{0x41-0x5a 0x61-0x7a 0x17f 0x212a}" },
// { "(?i)[a-z]", "cc{0x41-0x5a 0x61-0x7a 0x17f 0x212a}" },
// { "(?i)[^[:lower:]]", "cc{0x0-0x40 0x5b-0x60 0x7b-0x17e 0x180-0x2129 0x212b-0x10ffff}" },
// { "(?i)[[:^lower:]]", "cc{0x0-0x40 0x5b-0x60 0x7b-0x17e 0x180-0x2129 0x212b-0x10ffff}" },
// { "\\d", "cc{0x30-0x39}" },
// { "\\D", "cc{0x0-0x2f 0x3a-0x10ffff}" },
// { "\\s", "cc{0x9-0xa 0xc-0xd 0x20}" },
// { "\\S", "cc{0x0-0x8 0xb 0xe-0x1f 0x21-0x10ffff}" },
// { "\\w", "cc{0x30-0x39 0x41-0x5a 0x5f 0x61-0x7a}" },
// { "\\W", "cc{0x0-0x2f 0x3a-0x40 0x5b-0x5e 0x60 0x7b-0x10ffff}" },
// { "(?i)\\w", "cc{0x30-0x39 0x41-0x5a 0x5f 0x61-0x7a 0x17f 0x212a}" },
// { "(?i)\\W", "cc{0x0-0x2f 0x3a-0x40 0x5b-0x5e 0x60 0x7b-0x17e 0x180-0x2129 0x212b-0x10ffff}" },
// { "[^\\\\]", "cc{0x0-0x5b 0x5d-0x10ffff}" },
// { "\\C", "byte{}" },
// Unicode, negatives, and a double negative.
// { "\\p{Braille}", "cc{0x2800-0x28ff}" },
// { "\\P{Braille}", "cc{0x0-0x27ff 0x2900-0x10ffff}" },
// { "\\p{^Braille}", "cc{0x0-0x27ff 0x2900-0x10ffff}" },
// { "\\P{^Braille}", "cc{0x2800-0x28ff}" },
// More interesting regular expressions.
// { "a{,2}", "str{a{,2}}" },
// { "\\.\\^\\$\\\\", "str{.^$\\}" },
{"[a-zABC]", "cc{0x41-0x43 0x61-0x7a}"},
{"[^a]", "cc{0x0-0x60 0x62-0x10ffff}"},
{"[\xce\xb1-\xce\xb5\xe2\x98\xba]", "cc{0x3b1-0x3b5 0x263a}"}, // utf-8
// { "a*{", "cat{star{lit{a}}lit{{}}" },
// Test precedences
// { "(?:ab)*", "star{str{ab}}" },
// { "(ab)*", "star{cap{str{ab}}}" },
// { "ab|cd", "alt{str{ab}str{cd}}" },
// { "a(b|c)d", "cat{lit{a}cap{cc{0x62-0x63}}lit{d}}" },
{"(?:ab)*", "star{cat{lit{a}lit{b}}}"},
{"(ab)*", "star{cap{cat{lit{a}lit{b}}}}"},
{"ab|cd", "alt{cat{lit{a}lit{b}}cat{lit{c}lit{d}}}"},
{"a(b|c)d", "cat{lit{a}cap{alt{lit{b}lit{c}}}lit{d}}"},
// Test flattening.
// { "(?:a)", "lit{a}" },
// { "(?:ab)(?:cd)", "str{abcd}" },
// { "(?:a|b)|(?:c|d)", "cc{0x61-0x64}" },
// { "a|.", "dot{}" },
// { ".|a", "dot{}" },
// Test Perl quoted literals
// { "\\Q+|*?{[\\E", "str{+|*?{[}" },
// { "\\Q+\\E+", "plus{lit{+}}" },
// { "\\Q\\\\E", "lit{\\}" },
// { "\\Q\\\\\\E", "str{\\\\}" },
// Test Perl \A and \z
// { "(?m)^", "bol{}" },
// { "(?m)$", "eol{}" },
// { "(?-m)^", "bot{}" },
// { "(?-m)$", "eot{}" },
// { "(?m)\\A", "bot{}" },
// { "(?m)\\z", "eot{\\z}" },
// { "(?-m)\\A", "bot{}" },
// { "(?-m)\\z", "eot{\\z}" },
// Test named captures
// { "(?P<name>a)", "cap{name:lit{a}}" },
// Case-folded literals
// { "[Aa]", "litfold{a}" },
// Strings
// { "abcde", "str{abcde}" },
// { "[Aa][Bb]cd", "cat{strfold{ab}str{cd}}" },
}
const testFlags = MatchNL | PerlX | UnicodeGroups
// Test Parse -> Dump.
func TestParseDump(t *testing.T) {
for _, tt := range parseTests {
re, err := Parse(tt.Regexp, testFlags)
if err != nil {
t.Errorf("Parse(%#q): %v", tt.Regexp, err)
continue
}
d := dump(re)
if d != tt.Dump {
t.Errorf("Parse(%#q).Dump() = %#q want %#q", tt.Regexp, d, tt.Dump)
}
}
}
// dump prints a string representation of the regexp showing
// the structure explicitly.
func dump(re *Regexp) string {
var b bytes.Buffer
dumpRegexp(&b, re)
return b.String()
}
var opNames = []string{
OpNoMatch: "no",
OpEmptyMatch: "emp",
OpLiteral: "lit",
OpCharClass: "cc",
OpAnyCharNotNL: "dnl",
OpAnyChar: "dot",
OpBeginLine: "bol",
OpEndLine: "eol",
OpBeginText: "bot",
OpEndText: "eot",
OpWordBoundary: "wb",
OpNoWordBoundary: "nwb",
OpCapture: "cap",
OpStar: "star",
OpPlus: "plus",
OpQuest: "que",
OpRepeat: "rep",
OpConcat: "cat",
OpAlternate: "alt",
}
// dumpRegexp writes an encoding of the syntax tree for the regexp re to b.
// It is used during testing to distinguish between parses that might print
// the same using re's String method.
func dumpRegexp(b *bytes.Buffer, re *Regexp) {
if int(re.Op) >= len(opNames) || opNames[re.Op] == "" {
fmt.Fprintf(b, "op%d", re.Op)
} else {
switch re.Op {
default:
b.WriteString(opNames[re.Op])
case OpStar, OpPlus, OpQuest, OpRepeat:
if re.Flags&NonGreedy != 0 {
b.WriteByte('n')
}
b.WriteString(opNames[re.Op])
case OpLiteral:
if len(re.Rune) > 1 {
b.WriteString("str")
} else {
b.WriteString("lit")
}
if re.Flags&FoldCase != 0 {
for _, r := range re.Rune {
if unicode.ToUpper(r) != r {
b.WriteString("fold")
}
}
}
}
}
b.WriteByte('{')
switch re.Op {
case OpEndText:
if re.Flags&WasDollar == 0 {
b.WriteString(`\z`)
}
case OpLiteral:
for _, r := range re.Rune {
b.WriteRune(r)
}
case OpConcat, OpAlternate:
for _, sub := range re.Sub {
dumpRegexp(b, sub)
}
case OpStar, OpPlus, OpQuest:
dumpRegexp(b, re.Sub[0])
case OpRepeat:
fmt.Fprintf(b, "%d,%d ", re.Min, re.Max)
dumpRegexp(b, re.Sub[0])
case OpCapture:
if re.Name != "" {
b.WriteString(re.Name)
b.WriteByte(':')
}
dumpRegexp(b, re.Sub[0])
case OpCharClass:
sep := ""
for i := 0; i < len(re.Rune); i += 2 {
b.WriteString(sep)
sep = " "
lo, hi := re.Rune[i], re.Rune[i+1]
if lo == hi {
fmt.Fprintf(b, "%#x", lo)
} else {
fmt.Fprintf(b, "%#x-%#x", lo, hi)
}
}
}
b.WriteByte('}')
}
src/pkg/exp/regexp/syntax/regexp.go 0 → 100644
View file @ b96c3477
// Copyright 2011 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 syntax parses regular expressions into syntax trees.
// WORK IN PROGRESS.
package syntax
// Note to implementers:
// In this package, re is always a *Regexp and r is always a rune.
import (
"bytes"
"strconv"
"strings"
"unicode"
)
// A Regexp is a node in a regular expression syntax tree.
type Regexp struct {
Op Op // operator
Flags Flags
Sub []*Regexp // subexpressions, if any
Sub0 [1]*Regexp // storage for short Sub
Rune []int // matched runes, for OpLiteral, OpCharClass
Rune0 [2]int // storage for short Rune
Min, Max int // min, max for OpRepeat
Cap int // capturing index, for OpCapture
Name string // capturing name, for OpCapture
}
// An Op is a single regular expression operator.
type Op uint8
// Operators are listed in precedence order, tightest binding to weakest.
const (
OpNoMatch Op = 1 + iota // matches no strings
OpEmptyMatch // matches empty string
OpLiteral // matches Runes sequence
OpCharClass // matches Runes interpreted as range pair list
OpAnyCharNotNL // matches any character
OpAnyChar // matches any character
OpBeginLine // matches empty string at beginning of line
OpEndLine // matches empty string at end of line
OpBeginText // matches empty string at beginning of text
OpEndText // matches empty string at end of text
OpWordBoundary // matches word boundary `\b`
OpNoWordBoundary // matches word non-boundary `\B`
OpCapture // capturing subexpression with index Cap, optional name Name
OpStar // matches Sub[0] zero or more times
OpPlus // matches Sub[0] one or more times
OpQuest // matches Sub[0] zero or one times
OpRepeat // matches Sub[0] at least Min times, at most Max (Max == -1 is no limit)
OpConcat // matches concatenation of Subs
OpAlternate // matches alternation of Subs
)
const opPseudo Op = 128 // where pseudo-ops start
// writeRegexp writes the Perl syntax for the regular expression re to b.
func writeRegexp(b *bytes.Buffer, re *Regexp) {
switch re.Op {
default:
b.WriteString("<invalid op" + strconv.Itoa(int(re.Op)) + ">")
case OpNoMatch:
b.WriteString(`[^\x00-\x{10FFFF}]`)
case OpEmptyMatch:
b.WriteString(`(?:)`)
case OpLiteral:
for _, r := range re.Rune {
escape(b, r, false)
}
case OpCharClass:
if len(re.Rune)%2 != 0 {
b.WriteString(`[invalid char class]`)
break
}
b.WriteRune('[')
if len(re.Rune) > 0 && re.Rune[0] == 0 && re.Rune[len(re.Rune)-1] == unicode.MaxRune {
// Contains 0 and MaxRune. Probably a negated class.
// Print the gaps.
b.WriteRune('^')
for i := 1; i < len(re.Rune)-1; i += 2 {
lo, hi := re.Rune[i]+1, re.Rune[i+1]-1
escape(b, lo, lo == '-')
if lo != hi {
b.WriteRune('-')
escape(b, hi, hi == '-')
}
}
} else {
for i := 0; i < len(re.Rune); i += 2 {
lo, hi := re.Rune[i], re.Rune[i+1]
escape(b, lo, lo == '-')
if lo != hi {
b.WriteRune('-')
escape(b, hi, hi == '-')
}
}
}
b.WriteRune(']')
case OpAnyCharNotNL:
b.WriteString(`[^\n]`)
case OpAnyChar:
b.WriteRune('.')
case OpBeginLine:
b.WriteRune('^')
case OpEndLine:
b.WriteRune('$')
case OpBeginText:
b.WriteString(`\A`)
case OpEndText:
b.WriteString(`\z`)
case OpWordBoundary:
b.WriteString(`\b`)
case OpNoWordBoundary:
b.WriteString(`\B`)
case OpCapture:
if re.Name != "" {
b.WriteString(`(?P<`)
b.WriteString(re.Name)
b.WriteRune('>')
} else {
b.WriteRune('(')
}
writeRegexp(b, re.Sub[0])
b.WriteRune(')')
case OpStar, OpPlus, OpQuest, OpRepeat:
if sub := re.Sub[0]; sub.Op > OpCapture {
b.WriteString(`(?:`)
writeRegexp(b, sub)
b.WriteString(`)`)
} else {
writeRegexp(b, sub)
}
switch re.Op {
case OpStar:
b.WriteRune('*')
case OpPlus:
b.WriteRune('+')
case OpQuest:
b.WriteRune('?')
case OpRepeat:
b.WriteRune('{')
b.WriteString(strconv.Itoa(re.Min))
if re.Max != re.Min {
b.WriteRune(',')
if re.Max >= 0 {
b.WriteString(strconv.Itoa(re.Max))
}
}
b.WriteRune('}')
}
case OpConcat:
for _, sub := range re.Sub {
if sub.Op == OpAlternate {
b.WriteString(`(?:`)
writeRegexp(b, sub)
b.WriteString(`)`)
} else {
writeRegexp(b, sub)
}
}
case OpAlternate:
for i, sub := range re.Sub {
if i > 0 {
b.WriteRune('|')
}
writeRegexp(b, sub)
}
}
}
func (re *Regexp) String() string {
var b bytes.Buffer
writeRegexp(&b, re)
return b.String()
}
const meta = `\.+*?()|[]{}^$`
func escape(b *bytes.Buffer, r int, force bool) {
if unicode.IsPrint(r) {
if strings.IndexRune(meta, r) >= 0 || force {
b.WriteRune('\\')
}
b.WriteRune(r)
return
}
switch r {
case '\a':
b.WriteString(`\a`)
case '\f':
b.WriteString(`\f`)
case '\n':
b.WriteString(`\n`)
case '\r':
b.WriteString(`\r`)
case '\t':
b.WriteString(`\t`)
case '\v':
b.WriteString(`\v`)
default:
b.WriteString(`\x{`)
b.WriteString(strconv.Itob(r, 16))
b.WriteString(`}`)
}
}
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