311 lines
6.8 KiB
Go
311 lines
6.8 KiB
Go
// 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"
|
|
"strconv"
|
|
"unicode"
|
|
)
|
|
|
|
// Compiled program.
|
|
// May not belong in this package, but convenient for now.
|
|
|
|
// A Prog is a compiled regular expression program.
|
|
type Prog struct {
|
|
Inst []Inst
|
|
Start int // index of start instruction
|
|
NumCap int // number of InstCapture insts in re
|
|
}
|
|
|
|
// An InstOp is an instruction opcode.
|
|
type InstOp uint8
|
|
|
|
const (
|
|
InstAlt InstOp = iota
|
|
InstAltMatch
|
|
InstCapture
|
|
InstEmptyWidth
|
|
InstMatch
|
|
InstFail
|
|
InstNop
|
|
InstRune
|
|
InstRune1
|
|
InstRuneAny
|
|
InstRuneAnyNotNL
|
|
)
|
|
|
|
// An EmptyOp specifies a kind or mixture of zero-width assertions.
|
|
type EmptyOp uint8
|
|
|
|
const (
|
|
EmptyBeginLine EmptyOp = 1 << iota
|
|
EmptyEndLine
|
|
EmptyBeginText
|
|
EmptyEndText
|
|
EmptyWordBoundary
|
|
EmptyNoWordBoundary
|
|
)
|
|
|
|
// EmptyOpContext returns the zero-width assertions
|
|
// satisfied at the position between the runes r1 and r2.
|
|
// Passing r1 == -1 indicates that the position is
|
|
// at the beginning of the text.
|
|
// Passing r2 == -1 indicates that the position is
|
|
// at the end of the text.
|
|
func EmptyOpContext(r1, r2 rune) EmptyOp {
|
|
var op EmptyOp
|
|
if r1 < 0 {
|
|
op |= EmptyBeginText | EmptyBeginLine
|
|
}
|
|
if r1 == '\n' {
|
|
op |= EmptyBeginLine
|
|
}
|
|
if r2 < 0 {
|
|
op |= EmptyEndText | EmptyEndLine
|
|
}
|
|
if r2 == '\n' {
|
|
op |= EmptyEndLine
|
|
}
|
|
if IsWordChar(r1) != IsWordChar(r2) {
|
|
op |= EmptyWordBoundary
|
|
} else {
|
|
op |= EmptyNoWordBoundary
|
|
}
|
|
return op
|
|
}
|
|
|
|
// IsWordChar reports whether r is consider a ``word character''
|
|
// during the evaluation of the \b and \B zero-width assertions.
|
|
// These assertions are ASCII-only: the word characters are [A-Za-z0-9_].
|
|
func IsWordChar(r rune) bool {
|
|
return 'A' <= r && r <= 'Z' || 'a' <= r && r <= 'z' || '0' <= r && r <= '9' || r == '_'
|
|
}
|
|
|
|
// An Inst is a single instruction in a regular expression program.
|
|
type Inst struct {
|
|
Op InstOp
|
|
Out uint32 // all but InstMatch, InstFail
|
|
Arg uint32 // InstAlt, InstAltMatch, InstCapture, InstEmptyWidth
|
|
Rune []rune
|
|
}
|
|
|
|
func (p *Prog) String() string {
|
|
var b bytes.Buffer
|
|
dumpProg(&b, p)
|
|
return b.String()
|
|
}
|
|
|
|
// skipNop follows any no-op or capturing instructions
|
|
// and returns the resulting pc.
|
|
func (p *Prog) skipNop(pc uint32) *Inst {
|
|
i := &p.Inst[pc]
|
|
for i.Op == InstNop || i.Op == InstCapture {
|
|
pc = i.Out
|
|
i = &p.Inst[pc]
|
|
}
|
|
return i
|
|
}
|
|
|
|
// op returns i.Op but merges all the Rune special cases into InstRune
|
|
func (i *Inst) op() InstOp {
|
|
op := i.Op
|
|
switch op {
|
|
case InstRune1, InstRuneAny, InstRuneAnyNotNL:
|
|
op = InstRune
|
|
}
|
|
return op
|
|
}
|
|
|
|
// Prefix returns a literal string that all matches for the
|
|
// regexp must start with. Complete is true if the prefix
|
|
// is the entire match.
|
|
func (p *Prog) Prefix() (prefix string, complete bool) {
|
|
i := p.skipNop(uint32(p.Start))
|
|
|
|
// Avoid allocation of buffer if prefix is empty.
|
|
if i.op() != InstRune || len(i.Rune) != 1 {
|
|
return "", i.Op == InstMatch
|
|
}
|
|
|
|
// Have prefix; gather characters.
|
|
var buf bytes.Buffer
|
|
for i.op() == InstRune && len(i.Rune) == 1 && Flags(i.Arg)&FoldCase == 0 {
|
|
buf.WriteRune(i.Rune[0])
|
|
i = p.skipNop(i.Out)
|
|
}
|
|
return buf.String(), i.Op == InstMatch
|
|
}
|
|
|
|
// StartCond returns the leading empty-width conditions that must
|
|
// be true in any match. It returns ^EmptyOp(0) if no matches are possible.
|
|
func (p *Prog) StartCond() EmptyOp {
|
|
var flag EmptyOp
|
|
pc := uint32(p.Start)
|
|
i := &p.Inst[pc]
|
|
Loop:
|
|
for {
|
|
switch i.Op {
|
|
case InstEmptyWidth:
|
|
flag |= EmptyOp(i.Arg)
|
|
case InstFail:
|
|
return ^EmptyOp(0)
|
|
case InstCapture, InstNop:
|
|
// skip
|
|
default:
|
|
break Loop
|
|
}
|
|
pc = i.Out
|
|
i = &p.Inst[pc]
|
|
}
|
|
return flag
|
|
}
|
|
|
|
// MatchRune returns true if the instruction matches (and consumes) r.
|
|
// It should only be called when i.Op == InstRune.
|
|
func (i *Inst) MatchRune(r rune) bool {
|
|
rune := i.Rune
|
|
|
|
// Special case: single-rune slice is from literal string, not char class.
|
|
if len(rune) == 1 {
|
|
r0 := rune[0]
|
|
if r == r0 {
|
|
return true
|
|
}
|
|
if Flags(i.Arg)&FoldCase != 0 {
|
|
for r1 := unicode.SimpleFold(r0); r1 != r0; r1 = unicode.SimpleFold(r1) {
|
|
if r == r1 {
|
|
return true
|
|
}
|
|
}
|
|
}
|
|
return false
|
|
}
|
|
|
|
// Peek at the first few pairs.
|
|
// Should handle ASCII well.
|
|
for j := 0; j < len(rune) && j <= 8; j += 2 {
|
|
if r < rune[j] {
|
|
return false
|
|
}
|
|
if r <= rune[j+1] {
|
|
return true
|
|
}
|
|
}
|
|
|
|
// Otherwise binary search.
|
|
lo := 0
|
|
hi := len(rune) / 2
|
|
for lo < hi {
|
|
m := lo + (hi-lo)/2
|
|
if c := rune[2*m]; c <= r {
|
|
if r <= rune[2*m+1] {
|
|
return true
|
|
}
|
|
lo = m + 1
|
|
} else {
|
|
hi = m
|
|
}
|
|
}
|
|
return false
|
|
}
|
|
|
|
// As per re2's Prog::IsWordChar. Determines whether rune is an ASCII word char.
|
|
// Since we act on runes, it would be easy to support Unicode here.
|
|
func wordRune(r rune) bool {
|
|
return r == '_' ||
|
|
('A' <= r && r <= 'Z') ||
|
|
('a' <= r && r <= 'z') ||
|
|
('0' <= r && r <= '9')
|
|
}
|
|
|
|
// MatchEmptyWidth returns true if the instruction matches
|
|
// an empty string between the runes before and after.
|
|
// It should only be called when i.Op == InstEmptyWidth.
|
|
func (i *Inst) MatchEmptyWidth(before rune, after rune) bool {
|
|
switch EmptyOp(i.Arg) {
|
|
case EmptyBeginLine:
|
|
return before == '\n' || before == -1
|
|
case EmptyEndLine:
|
|
return after == '\n' || after == -1
|
|
case EmptyBeginText:
|
|
return before == -1
|
|
case EmptyEndText:
|
|
return after == -1
|
|
case EmptyWordBoundary:
|
|
return wordRune(before) != wordRune(after)
|
|
case EmptyNoWordBoundary:
|
|
return wordRune(before) == wordRune(after)
|
|
}
|
|
panic("unknown empty width arg")
|
|
}
|
|
|
|
func (i *Inst) String() string {
|
|
var b bytes.Buffer
|
|
dumpInst(&b, i)
|
|
return b.String()
|
|
}
|
|
|
|
func bw(b *bytes.Buffer, args ...string) {
|
|
for _, s := range args {
|
|
b.WriteString(s)
|
|
}
|
|
}
|
|
|
|
func dumpProg(b *bytes.Buffer, p *Prog) {
|
|
for j := range p.Inst {
|
|
i := &p.Inst[j]
|
|
pc := strconv.Itoa(j)
|
|
if len(pc) < 3 {
|
|
b.WriteString(" "[len(pc):])
|
|
}
|
|
if j == p.Start {
|
|
pc += "*"
|
|
}
|
|
bw(b, pc, "\t")
|
|
dumpInst(b, i)
|
|
bw(b, "\n")
|
|
}
|
|
}
|
|
|
|
func u32(i uint32) string {
|
|
return strconv.FormatUint(uint64(i), 10)
|
|
}
|
|
|
|
func dumpInst(b *bytes.Buffer, i *Inst) {
|
|
switch i.Op {
|
|
case InstAlt:
|
|
bw(b, "alt -> ", u32(i.Out), ", ", u32(i.Arg))
|
|
case InstAltMatch:
|
|
bw(b, "altmatch -> ", u32(i.Out), ", ", u32(i.Arg))
|
|
case InstCapture:
|
|
bw(b, "cap ", u32(i.Arg), " -> ", u32(i.Out))
|
|
case InstEmptyWidth:
|
|
bw(b, "empty ", u32(i.Arg), " -> ", u32(i.Out))
|
|
case InstMatch:
|
|
bw(b, "match")
|
|
case InstFail:
|
|
bw(b, "fail")
|
|
case InstNop:
|
|
bw(b, "nop -> ", u32(i.Out))
|
|
case InstRune:
|
|
if i.Rune == nil {
|
|
// shouldn't happen
|
|
bw(b, "rune <nil>")
|
|
}
|
|
bw(b, "rune ", strconv.QuoteToASCII(string(i.Rune)))
|
|
if Flags(i.Arg)&FoldCase != 0 {
|
|
bw(b, "/i")
|
|
}
|
|
bw(b, " -> ", u32(i.Out))
|
|
case InstRune1:
|
|
bw(b, "rune1 ", strconv.QuoteToASCII(string(i.Rune)), " -> ", u32(i.Out))
|
|
case InstRuneAny:
|
|
bw(b, "any -> ", u32(i.Out))
|
|
case InstRuneAnyNotNL:
|
|
bw(b, "anynotnl -> ", u32(i.Out))
|
|
}
|
|
}
|