555 lines
12 KiB
Go
555 lines
12 KiB
Go
// Copyright 2011 The Go Authors. All rights reserved.
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// Use of this source code is governed by a BSD-style
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// license that can be found in the LICENSE file.
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package regexp
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import (
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"io"
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"regexp/syntax"
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"sync"
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)
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// A queue is a 'sparse array' holding pending threads of execution.
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// See https://research.swtch.com/2008/03/using-uninitialized-memory-for-fun-and.html
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type queue struct {
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sparse []uint32
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dense []entry
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}
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// An entry is an entry on a queue.
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// It holds both the instruction pc and the actual thread.
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// Some queue entries are just place holders so that the machine
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// knows it has considered that pc. Such entries have t == nil.
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type entry struct {
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pc uint32
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t *thread
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}
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// A thread is the state of a single path through the machine:
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// an instruction and a corresponding capture array.
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// See https://swtch.com/~rsc/regexp/regexp2.html
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type thread struct {
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inst *syntax.Inst
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cap []int
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}
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// A machine holds all the state during an NFA simulation for p.
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type machine struct {
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re *Regexp // corresponding Regexp
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p *syntax.Prog // compiled program
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q0, q1 queue // two queues for runq, nextq
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pool []*thread // pool of available threads
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matched bool // whether a match was found
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matchcap []int // capture information for the match
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inputs inputs
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}
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type inputs struct {
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// cached inputs, to avoid allocation
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bytes inputBytes
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string inputString
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reader inputReader
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}
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func (i *inputs) newBytes(b []byte) input {
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i.bytes.str = b
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return &i.bytes
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}
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func (i *inputs) newString(s string) input {
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i.string.str = s
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return &i.string
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}
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func (i *inputs) newReader(r io.RuneReader) input {
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i.reader.r = r
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i.reader.atEOT = false
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i.reader.pos = 0
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return &i.reader
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}
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func (i *inputs) clear() {
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// We need to clear 1 of these.
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// Avoid the expense of clearing the others (pointer write barrier).
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if i.bytes.str != nil {
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i.bytes.str = nil
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} else if i.reader.r != nil {
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i.reader.r = nil
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} else {
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i.string.str = ""
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}
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}
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func (i *inputs) init(r io.RuneReader, b []byte, s string) (input, int) {
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if r != nil {
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return i.newReader(r), 0
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}
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if b != nil {
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return i.newBytes(b), len(b)
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}
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return i.newString(s), len(s)
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}
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func (m *machine) init(ncap int) {
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for _, t := range m.pool {
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t.cap = t.cap[:ncap]
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}
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m.matchcap = m.matchcap[:ncap]
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}
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// alloc allocates a new thread with the given instruction.
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// It uses the free pool if possible.
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func (m *machine) alloc(i *syntax.Inst) *thread {
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var t *thread
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if n := len(m.pool); n > 0 {
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t = m.pool[n-1]
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m.pool = m.pool[:n-1]
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} else {
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t = new(thread)
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t.cap = make([]int, len(m.matchcap), cap(m.matchcap))
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}
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t.inst = i
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return t
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}
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// A lazyFlag is a lazily-evaluated syntax.EmptyOp,
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// for checking zero-width flags like ^ $ \A \z \B \b.
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// It records the pair of relevant runes and does not
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// determine the implied flags until absolutely necessary
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// (most of the time, that means never).
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type lazyFlag uint64
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func newLazyFlag(r1, r2 rune) lazyFlag {
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return lazyFlag(uint64(r1)<<32 | uint64(uint32(r2)))
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}
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func (f lazyFlag) match(op syntax.EmptyOp) bool {
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if op == 0 {
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return true
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}
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r1 := rune(f >> 32)
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if op&syntax.EmptyBeginLine != 0 {
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if r1 != '\n' && r1 >= 0 {
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return false
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}
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op &^= syntax.EmptyBeginLine
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}
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if op&syntax.EmptyBeginText != 0 {
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if r1 >= 0 {
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return false
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}
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op &^= syntax.EmptyBeginText
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}
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if op == 0 {
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return true
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}
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r2 := rune(f)
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if op&syntax.EmptyEndLine != 0 {
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if r2 != '\n' && r2 >= 0 {
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return false
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}
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op &^= syntax.EmptyEndLine
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}
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if op&syntax.EmptyEndText != 0 {
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if r2 >= 0 {
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return false
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}
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op &^= syntax.EmptyEndText
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}
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if op == 0 {
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return true
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}
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if syntax.IsWordChar(r1) != syntax.IsWordChar(r2) {
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op &^= syntax.EmptyWordBoundary
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} else {
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op &^= syntax.EmptyNoWordBoundary
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}
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return op == 0
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}
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// match runs the machine over the input starting at pos.
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// It reports whether a match was found.
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// If so, m.matchcap holds the submatch information.
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func (m *machine) match(i input, pos int) bool {
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startCond := m.re.cond
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if startCond == ^syntax.EmptyOp(0) { // impossible
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return false
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}
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m.matched = false
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for i := range m.matchcap {
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m.matchcap[i] = -1
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}
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runq, nextq := &m.q0, &m.q1
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r, r1 := endOfText, endOfText
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width, width1 := 0, 0
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r, width = i.step(pos)
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if r != endOfText {
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r1, width1 = i.step(pos + width)
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}
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var flag lazyFlag
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if pos == 0 {
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flag = newLazyFlag(-1, r)
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} else {
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flag = i.context(pos)
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}
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for {
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if len(runq.dense) == 0 {
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if startCond&syntax.EmptyBeginText != 0 && pos != 0 {
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// Anchored match, past beginning of text.
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break
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}
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if m.matched {
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// Have match; finished exploring alternatives.
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break
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}
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if len(m.re.prefix) > 0 && r1 != m.re.prefixRune && i.canCheckPrefix() {
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// Match requires literal prefix; fast search for it.
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advance := i.index(m.re, pos)
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if advance < 0 {
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break
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}
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pos += advance
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r, width = i.step(pos)
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r1, width1 = i.step(pos + width)
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}
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}
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if !m.matched {
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if len(m.matchcap) > 0 {
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m.matchcap[0] = pos
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}
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m.add(runq, uint32(m.p.Start), pos, m.matchcap, &flag, nil)
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}
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flag = newLazyFlag(r, r1)
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m.step(runq, nextq, pos, pos+width, r, &flag)
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if width == 0 {
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break
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}
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if len(m.matchcap) == 0 && m.matched {
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// Found a match and not paying attention
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// to where it is, so any match will do.
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break
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}
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pos += width
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r, width = r1, width1
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if r != endOfText {
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r1, width1 = i.step(pos + width)
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}
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runq, nextq = nextq, runq
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}
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m.clear(nextq)
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return m.matched
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}
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// clear frees all threads on the thread queue.
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func (m *machine) clear(q *queue) {
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for _, d := range q.dense {
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if d.t != nil {
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m.pool = append(m.pool, d.t)
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}
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}
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q.dense = q.dense[:0]
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}
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// step executes one step of the machine, running each of the threads
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// on runq and appending new threads to nextq.
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// The step processes the rune c (which may be endOfText),
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// which starts at position pos and ends at nextPos.
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// nextCond gives the setting for the empty-width flags after c.
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func (m *machine) step(runq, nextq *queue, pos, nextPos int, c rune, nextCond *lazyFlag) {
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longest := m.re.longest
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for j := 0; j < len(runq.dense); j++ {
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d := &runq.dense[j]
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t := d.t
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if t == nil {
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continue
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}
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if longest && m.matched && len(t.cap) > 0 && m.matchcap[0] < t.cap[0] {
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m.pool = append(m.pool, t)
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continue
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}
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i := t.inst
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add := false
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switch i.Op {
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default:
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panic("bad inst")
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case syntax.InstMatch:
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if len(t.cap) > 0 && (!longest || !m.matched || m.matchcap[1] < pos) {
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t.cap[1] = pos
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copy(m.matchcap, t.cap)
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}
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if !longest {
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// First-match mode: cut off all lower-priority threads.
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for _, d := range runq.dense[j+1:] {
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if d.t != nil {
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m.pool = append(m.pool, d.t)
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}
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}
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runq.dense = runq.dense[:0]
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}
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m.matched = true
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case syntax.InstRune:
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add = i.MatchRune(c)
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case syntax.InstRune1:
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add = c == i.Rune[0]
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case syntax.InstRuneAny:
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add = true
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case syntax.InstRuneAnyNotNL:
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add = c != '\n'
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}
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if add {
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t = m.add(nextq, i.Out, nextPos, t.cap, nextCond, t)
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}
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if t != nil {
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m.pool = append(m.pool, t)
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}
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}
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runq.dense = runq.dense[:0]
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}
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// add adds an entry to q for pc, unless the q already has such an entry.
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// It also recursively adds an entry for all instructions reachable from pc by following
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// empty-width conditions satisfied by cond. pos gives the current position
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// in the input.
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func (m *machine) add(q *queue, pc uint32, pos int, cap []int, cond *lazyFlag, t *thread) *thread {
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Again:
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if pc == 0 {
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return t
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}
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if j := q.sparse[pc]; j < uint32(len(q.dense)) && q.dense[j].pc == pc {
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return t
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}
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j := len(q.dense)
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q.dense = q.dense[:j+1]
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d := &q.dense[j]
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d.t = nil
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d.pc = pc
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q.sparse[pc] = uint32(j)
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i := &m.p.Inst[pc]
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switch i.Op {
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default:
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panic("unhandled")
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case syntax.InstFail:
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// nothing
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case syntax.InstAlt, syntax.InstAltMatch:
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t = m.add(q, i.Out, pos, cap, cond, t)
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pc = i.Arg
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goto Again
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case syntax.InstEmptyWidth:
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if cond.match(syntax.EmptyOp(i.Arg)) {
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pc = i.Out
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goto Again
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}
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case syntax.InstNop:
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pc = i.Out
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goto Again
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case syntax.InstCapture:
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if int(i.Arg) < len(cap) {
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opos := cap[i.Arg]
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cap[i.Arg] = pos
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m.add(q, i.Out, pos, cap, cond, nil)
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cap[i.Arg] = opos
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} else {
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pc = i.Out
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goto Again
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}
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case syntax.InstMatch, syntax.InstRune, syntax.InstRune1, syntax.InstRuneAny, syntax.InstRuneAnyNotNL:
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if t == nil {
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t = m.alloc(i)
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} else {
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t.inst = i
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}
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if len(cap) > 0 && &t.cap[0] != &cap[0] {
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copy(t.cap, cap)
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}
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d.t = t
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t = nil
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}
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return t
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}
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type onePassMachine struct {
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inputs inputs
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matchcap []int
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}
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var onePassPool sync.Pool
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func newOnePassMachine() *onePassMachine {
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m, ok := onePassPool.Get().(*onePassMachine)
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if !ok {
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m = new(onePassMachine)
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}
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return m
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}
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func freeOnePassMachine(m *onePassMachine) {
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m.inputs.clear()
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onePassPool.Put(m)
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}
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// doOnePass implements r.doExecute using the one-pass execution engine.
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func (re *Regexp) doOnePass(ir io.RuneReader, ib []byte, is string, pos, ncap int, dstCap []int) []int {
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startCond := re.cond
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if startCond == ^syntax.EmptyOp(0) { // impossible
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return nil
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}
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m := newOnePassMachine()
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if cap(m.matchcap) < ncap {
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m.matchcap = make([]int, ncap)
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} else {
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m.matchcap = m.matchcap[:ncap]
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}
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matched := false
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for i := range m.matchcap {
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m.matchcap[i] = -1
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}
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i, _ := m.inputs.init(ir, ib, is)
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r, r1 := endOfText, endOfText
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width, width1 := 0, 0
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r, width = i.step(pos)
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if r != endOfText {
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r1, width1 = i.step(pos + width)
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}
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var flag lazyFlag
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if pos == 0 {
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flag = newLazyFlag(-1, r)
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} else {
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flag = i.context(pos)
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}
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pc := re.onepass.Start
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inst := re.onepass.Inst[pc]
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// If there is a simple literal prefix, skip over it.
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if pos == 0 && flag.match(syntax.EmptyOp(inst.Arg)) &&
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len(re.prefix) > 0 && i.canCheckPrefix() {
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// Match requires literal prefix; fast search for it.
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if !i.hasPrefix(re) {
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goto Return
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}
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pos += len(re.prefix)
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r, width = i.step(pos)
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r1, width1 = i.step(pos + width)
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flag = i.context(pos)
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pc = int(re.prefixEnd)
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}
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for {
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inst = re.onepass.Inst[pc]
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pc = int(inst.Out)
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switch inst.Op {
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default:
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panic("bad inst")
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case syntax.InstMatch:
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matched = true
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if len(m.matchcap) > 0 {
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m.matchcap[0] = 0
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m.matchcap[1] = pos
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}
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goto Return
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case syntax.InstRune:
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if !inst.MatchRune(r) {
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goto Return
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}
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case syntax.InstRune1:
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if r != inst.Rune[0] {
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goto Return
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}
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case syntax.InstRuneAny:
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// Nothing
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case syntax.InstRuneAnyNotNL:
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if r == '\n' {
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goto Return
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}
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// peek at the input rune to see which branch of the Alt to take
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case syntax.InstAlt, syntax.InstAltMatch:
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pc = int(onePassNext(&inst, r))
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continue
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case syntax.InstFail:
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goto Return
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case syntax.InstNop:
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continue
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case syntax.InstEmptyWidth:
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if !flag.match(syntax.EmptyOp(inst.Arg)) {
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goto Return
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}
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continue
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case syntax.InstCapture:
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if int(inst.Arg) < len(m.matchcap) {
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m.matchcap[inst.Arg] = pos
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}
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continue
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}
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if width == 0 {
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break
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}
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flag = newLazyFlag(r, r1)
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pos += width
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r, width = r1, width1
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if r != endOfText {
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r1, width1 = i.step(pos + width)
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}
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}
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Return:
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if !matched {
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freeOnePassMachine(m)
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return nil
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}
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dstCap = append(dstCap, m.matchcap...)
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freeOnePassMachine(m)
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return dstCap
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}
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|
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// doMatch reports whether either r, b or s match the regexp.
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func (re *Regexp) doMatch(r io.RuneReader, b []byte, s string) bool {
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return re.doExecute(r, b, s, 0, 0, nil) != nil
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}
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// doExecute finds the leftmost match in the input, appends the position
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// of its subexpressions to dstCap and returns dstCap.
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//
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// nil is returned if no matches are found and non-nil if matches are found.
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func (re *Regexp) doExecute(r io.RuneReader, b []byte, s string, pos int, ncap int, dstCap []int) []int {
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if dstCap == nil {
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// Make sure 'return dstCap' is non-nil.
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dstCap = arrayNoInts[:0:0]
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}
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if r == nil && len(b)+len(s) < re.minInputLen {
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return nil
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}
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if re.onepass != nil {
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return re.doOnePass(r, b, s, pos, ncap, dstCap)
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}
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if r == nil && len(b)+len(s) < re.maxBitStateLen {
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return re.backtrack(b, s, pos, ncap, dstCap)
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}
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m := re.get()
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i, _ := m.inputs.init(r, b, s)
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m.init(ncap)
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if !m.match(i, pos) {
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re.put(m)
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return nil
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}
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dstCap = append(dstCap, m.matchcap...)
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re.put(m)
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return dstCap
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}
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// arrayNoInts is returned by doExecute match if nil dstCap is passed
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// to it with ncap=0.
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var arrayNoInts [0]int
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