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-rw-r--r--src/regexp/exec.go554
1 files changed, 554 insertions, 0 deletions
diff --git a/src/regexp/exec.go b/src/regexp/exec.go
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--- /dev/null
+++ b/src/regexp/exec.go
@@ -0,0 +1,554 @@
+// 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 regexp
+
+import (
+ "io"
+ "regexp/syntax"
+ "sync"
+)
+
+// A queue is a 'sparse array' holding pending threads of execution.
+// See https://research.swtch.com/2008/03/using-uninitialized-memory-for-fun-and.html
+type queue struct {
+ sparse []uint32
+ dense []entry
+}
+
+// An entry is an entry on a queue.
+// It holds both the instruction pc and the actual thread.
+// Some queue entries are just place holders so that the machine
+// knows it has considered that pc. Such entries have t == nil.
+type entry struct {
+ pc uint32
+ t *thread
+}
+
+// A thread is the state of a single path through the machine:
+// an instruction and a corresponding capture array.
+// See https://swtch.com/~rsc/regexp/regexp2.html
+type thread struct {
+ inst *syntax.Inst
+ cap []int
+}
+
+// A machine holds all the state during an NFA simulation for p.
+type machine struct {
+ re *Regexp // corresponding Regexp
+ p *syntax.Prog // compiled program
+ q0, q1 queue // two queues for runq, nextq
+ pool []*thread // pool of available threads
+ matched bool // whether a match was found
+ matchcap []int // capture information for the match
+
+ inputs inputs
+}
+
+type inputs struct {
+ // cached inputs, to avoid allocation
+ bytes inputBytes
+ string inputString
+ reader inputReader
+}
+
+func (i *inputs) newBytes(b []byte) input {
+ i.bytes.str = b
+ return &i.bytes
+}
+
+func (i *inputs) newString(s string) input {
+ i.string.str = s
+ return &i.string
+}
+
+func (i *inputs) newReader(r io.RuneReader) input {
+ i.reader.r = r
+ i.reader.atEOT = false
+ i.reader.pos = 0
+ return &i.reader
+}
+
+func (i *inputs) clear() {
+ // We need to clear 1 of these.
+ // Avoid the expense of clearing the others (pointer write barrier).
+ if i.bytes.str != nil {
+ i.bytes.str = nil
+ } else if i.reader.r != nil {
+ i.reader.r = nil
+ } else {
+ i.string.str = ""
+ }
+}
+
+func (i *inputs) init(r io.RuneReader, b []byte, s string) (input, int) {
+ if r != nil {
+ return i.newReader(r), 0
+ }
+ if b != nil {
+ return i.newBytes(b), len(b)
+ }
+ return i.newString(s), len(s)
+}
+
+func (m *machine) init(ncap int) {
+ for _, t := range m.pool {
+ t.cap = t.cap[:ncap]
+ }
+ m.matchcap = m.matchcap[:ncap]
+}
+
+// alloc allocates a new thread with the given instruction.
+// It uses the free pool if possible.
+func (m *machine) alloc(i *syntax.Inst) *thread {
+ var t *thread
+ if n := len(m.pool); n > 0 {
+ t = m.pool[n-1]
+ m.pool = m.pool[:n-1]
+ } else {
+ t = new(thread)
+ t.cap = make([]int, len(m.matchcap), cap(m.matchcap))
+ }
+ t.inst = i
+ return t
+}
+
+// A lazyFlag is a lazily-evaluated syntax.EmptyOp,
+// for checking zero-width flags like ^ $ \A \z \B \b.
+// It records the pair of relevant runes and does not
+// determine the implied flags until absolutely necessary
+// (most of the time, that means never).
+type lazyFlag uint64
+
+func newLazyFlag(r1, r2 rune) lazyFlag {
+ return lazyFlag(uint64(r1)<<32 | uint64(uint32(r2)))
+}
+
+func (f lazyFlag) match(op syntax.EmptyOp) bool {
+ if op == 0 {
+ return true
+ }
+ r1 := rune(f >> 32)
+ if op&syntax.EmptyBeginLine != 0 {
+ if r1 != '\n' && r1 >= 0 {
+ return false
+ }
+ op &^= syntax.EmptyBeginLine
+ }
+ if op&syntax.EmptyBeginText != 0 {
+ if r1 >= 0 {
+ return false
+ }
+ op &^= syntax.EmptyBeginText
+ }
+ if op == 0 {
+ return true
+ }
+ r2 := rune(f)
+ if op&syntax.EmptyEndLine != 0 {
+ if r2 != '\n' && r2 >= 0 {
+ return false
+ }
+ op &^= syntax.EmptyEndLine
+ }
+ if op&syntax.EmptyEndText != 0 {
+ if r2 >= 0 {
+ return false
+ }
+ op &^= syntax.EmptyEndText
+ }
+ if op == 0 {
+ return true
+ }
+ if syntax.IsWordChar(r1) != syntax.IsWordChar(r2) {
+ op &^= syntax.EmptyWordBoundary
+ } else {
+ op &^= syntax.EmptyNoWordBoundary
+ }
+ return op == 0
+}
+
+// match runs the machine over the input starting at pos.
+// It reports whether a match was found.
+// If so, m.matchcap holds the submatch information.
+func (m *machine) match(i input, pos int) bool {
+ startCond := m.re.cond
+ if startCond == ^syntax.EmptyOp(0) { // impossible
+ return false
+ }
+ m.matched = false
+ for i := range m.matchcap {
+ m.matchcap[i] = -1
+ }
+ runq, nextq := &m.q0, &m.q1
+ r, r1 := endOfText, endOfText
+ width, width1 := 0, 0
+ r, width = i.step(pos)
+ if r != endOfText {
+ r1, width1 = i.step(pos + width)
+ }
+ var flag lazyFlag
+ if pos == 0 {
+ flag = newLazyFlag(-1, r)
+ } else {
+ flag = i.context(pos)
+ }
+ for {
+ if len(runq.dense) == 0 {
+ if startCond&syntax.EmptyBeginText != 0 && pos != 0 {
+ // Anchored match, past beginning of text.
+ break
+ }
+ if m.matched {
+ // Have match; finished exploring alternatives.
+ break
+ }
+ if len(m.re.prefix) > 0 && r1 != m.re.prefixRune && i.canCheckPrefix() {
+ // Match requires literal prefix; fast search for it.
+ advance := i.index(m.re, pos)
+ if advance < 0 {
+ break
+ }
+ pos += advance
+ r, width = i.step(pos)
+ r1, width1 = i.step(pos + width)
+ }
+ }
+ if !m.matched {
+ if len(m.matchcap) > 0 {
+ m.matchcap[0] = pos
+ }
+ m.add(runq, uint32(m.p.Start), pos, m.matchcap, &flag, nil)
+ }
+ flag = newLazyFlag(r, r1)
+ m.step(runq, nextq, pos, pos+width, r, &flag)
+ if width == 0 {
+ break
+ }
+ if len(m.matchcap) == 0 && m.matched {
+ // Found a match and not paying attention
+ // to where it is, so any match will do.
+ break
+ }
+ pos += width
+ r, width = r1, width1
+ if r != endOfText {
+ r1, width1 = i.step(pos + width)
+ }
+ runq, nextq = nextq, runq
+ }
+ m.clear(nextq)
+ return m.matched
+}
+
+// clear frees all threads on the thread queue.
+func (m *machine) clear(q *queue) {
+ for _, d := range q.dense {
+ if d.t != nil {
+ m.pool = append(m.pool, d.t)
+ }
+ }
+ q.dense = q.dense[:0]
+}
+
+// step executes one step of the machine, running each of the threads
+// on runq and appending new threads to nextq.
+// The step processes the rune c (which may be endOfText),
+// which starts at position pos and ends at nextPos.
+// nextCond gives the setting for the empty-width flags after c.
+func (m *machine) step(runq, nextq *queue, pos, nextPos int, c rune, nextCond *lazyFlag) {
+ longest := m.re.longest
+ for j := 0; j < len(runq.dense); j++ {
+ d := &runq.dense[j]
+ t := d.t
+ if t == nil {
+ continue
+ }
+ if longest && m.matched && len(t.cap) > 0 && m.matchcap[0] < t.cap[0] {
+ m.pool = append(m.pool, t)
+ continue
+ }
+ i := t.inst
+ add := false
+ switch i.Op {
+ default:
+ panic("bad inst")
+
+ case syntax.InstMatch:
+ if len(t.cap) > 0 && (!longest || !m.matched || m.matchcap[1] < pos) {
+ t.cap[1] = pos
+ copy(m.matchcap, t.cap)
+ }
+ if !longest {
+ // First-match mode: cut off all lower-priority threads.
+ for _, d := range runq.dense[j+1:] {
+ if d.t != nil {
+ m.pool = append(m.pool, d.t)
+ }
+ }
+ runq.dense = runq.dense[:0]
+ }
+ m.matched = true
+
+ case syntax.InstRune:
+ add = i.MatchRune(c)
+ case syntax.InstRune1:
+ add = c == i.Rune[0]
+ case syntax.InstRuneAny:
+ add = true
+ case syntax.InstRuneAnyNotNL:
+ add = c != '\n'
+ }
+ if add {
+ t = m.add(nextq, i.Out, nextPos, t.cap, nextCond, t)
+ }
+ if t != nil {
+ m.pool = append(m.pool, t)
+ }
+ }
+ runq.dense = runq.dense[:0]
+}
+
+// add adds an entry to q for pc, unless the q already has such an entry.
+// It also recursively adds an entry for all instructions reachable from pc by following
+// empty-width conditions satisfied by cond. pos gives the current position
+// in the input.
+func (m *machine) add(q *queue, pc uint32, pos int, cap []int, cond *lazyFlag, t *thread) *thread {
+Again:
+ if pc == 0 {
+ return t
+ }
+ if j := q.sparse[pc]; j < uint32(len(q.dense)) && q.dense[j].pc == pc {
+ return t
+ }
+
+ j := len(q.dense)
+ q.dense = q.dense[:j+1]
+ d := &q.dense[j]
+ d.t = nil
+ d.pc = pc
+ q.sparse[pc] = uint32(j)
+
+ i := &m.p.Inst[pc]
+ switch i.Op {
+ default:
+ panic("unhandled")
+ case syntax.InstFail:
+ // nothing
+ case syntax.InstAlt, syntax.InstAltMatch:
+ t = m.add(q, i.Out, pos, cap, cond, t)
+ pc = i.Arg
+ goto Again
+ case syntax.InstEmptyWidth:
+ if cond.match(syntax.EmptyOp(i.Arg)) {
+ pc = i.Out
+ goto Again
+ }
+ case syntax.InstNop:
+ pc = i.Out
+ goto Again
+ case syntax.InstCapture:
+ if int(i.Arg) < len(cap) {
+ opos := cap[i.Arg]
+ cap[i.Arg] = pos
+ m.add(q, i.Out, pos, cap, cond, nil)
+ cap[i.Arg] = opos
+ } else {
+ pc = i.Out
+ goto Again
+ }
+ case syntax.InstMatch, syntax.InstRune, syntax.InstRune1, syntax.InstRuneAny, syntax.InstRuneAnyNotNL:
+ if t == nil {
+ t = m.alloc(i)
+ } else {
+ t.inst = i
+ }
+ if len(cap) > 0 && &t.cap[0] != &cap[0] {
+ copy(t.cap, cap)
+ }
+ d.t = t
+ t = nil
+ }
+ return t
+}
+
+type onePassMachine struct {
+ inputs inputs
+ matchcap []int
+}
+
+var onePassPool sync.Pool
+
+func newOnePassMachine() *onePassMachine {
+ m, ok := onePassPool.Get().(*onePassMachine)
+ if !ok {
+ m = new(onePassMachine)
+ }
+ return m
+}
+
+func freeOnePassMachine(m *onePassMachine) {
+ m.inputs.clear()
+ onePassPool.Put(m)
+}
+
+// doOnePass implements r.doExecute using the one-pass execution engine.
+func (re *Regexp) doOnePass(ir io.RuneReader, ib []byte, is string, pos, ncap int, dstCap []int) []int {
+ startCond := re.cond
+ if startCond == ^syntax.EmptyOp(0) { // impossible
+ return nil
+ }
+
+ m := newOnePassMachine()
+ if cap(m.matchcap) < ncap {
+ m.matchcap = make([]int, ncap)
+ } else {
+ m.matchcap = m.matchcap[:ncap]
+ }
+
+ matched := false
+ for i := range m.matchcap {
+ m.matchcap[i] = -1
+ }
+
+ i, _ := m.inputs.init(ir, ib, is)
+
+ r, r1 := endOfText, endOfText
+ width, width1 := 0, 0
+ r, width = i.step(pos)
+ if r != endOfText {
+ r1, width1 = i.step(pos + width)
+ }
+ var flag lazyFlag
+ if pos == 0 {
+ flag = newLazyFlag(-1, r)
+ } else {
+ flag = i.context(pos)
+ }
+ pc := re.onepass.Start
+ inst := &re.onepass.Inst[pc]
+ // If there is a simple literal prefix, skip over it.
+ if pos == 0 && flag.match(syntax.EmptyOp(inst.Arg)) &&
+ len(re.prefix) > 0 && i.canCheckPrefix() {
+ // Match requires literal prefix; fast search for it.
+ if !i.hasPrefix(re) {
+ goto Return
+ }
+ pos += len(re.prefix)
+ r, width = i.step(pos)
+ r1, width1 = i.step(pos + width)
+ flag = i.context(pos)
+ pc = int(re.prefixEnd)
+ }
+ for {
+ inst = &re.onepass.Inst[pc]
+ pc = int(inst.Out)
+ switch inst.Op {
+ default:
+ panic("bad inst")
+ case syntax.InstMatch:
+ matched = true
+ if len(m.matchcap) > 0 {
+ m.matchcap[0] = 0
+ m.matchcap[1] = pos
+ }
+ goto Return
+ case syntax.InstRune:
+ if !inst.MatchRune(r) {
+ goto Return
+ }
+ case syntax.InstRune1:
+ if r != inst.Rune[0] {
+ goto Return
+ }
+ case syntax.InstRuneAny:
+ // Nothing
+ case syntax.InstRuneAnyNotNL:
+ if r == '\n' {
+ goto Return
+ }
+ // peek at the input rune to see which branch of the Alt to take
+ case syntax.InstAlt, syntax.InstAltMatch:
+ pc = int(onePassNext(inst, r))
+ continue
+ case syntax.InstFail:
+ goto Return
+ case syntax.InstNop:
+ continue
+ case syntax.InstEmptyWidth:
+ if !flag.match(syntax.EmptyOp(inst.Arg)) {
+ goto Return
+ }
+ continue
+ case syntax.InstCapture:
+ if int(inst.Arg) < len(m.matchcap) {
+ m.matchcap[inst.Arg] = pos
+ }
+ continue
+ }
+ if width == 0 {
+ break
+ }
+ flag = newLazyFlag(r, r1)
+ pos += width
+ r, width = r1, width1
+ if r != endOfText {
+ r1, width1 = i.step(pos + width)
+ }
+ }
+
+Return:
+ if !matched {
+ freeOnePassMachine(m)
+ return nil
+ }
+
+ dstCap = append(dstCap, m.matchcap...)
+ freeOnePassMachine(m)
+ return dstCap
+}
+
+// doMatch reports whether either r, b or s match the regexp.
+func (re *Regexp) doMatch(r io.RuneReader, b []byte, s string) bool {
+ return re.doExecute(r, b, s, 0, 0, nil) != nil
+}
+
+// doExecute finds the leftmost match in the input, appends the position
+// of its subexpressions to dstCap and returns dstCap.
+//
+// nil is returned if no matches are found and non-nil if matches are found.
+func (re *Regexp) doExecute(r io.RuneReader, b []byte, s string, pos int, ncap int, dstCap []int) []int {
+ if dstCap == nil {
+ // Make sure 'return dstCap' is non-nil.
+ dstCap = arrayNoInts[:0:0]
+ }
+
+ if r == nil && len(b)+len(s) < re.minInputLen {
+ return nil
+ }
+
+ if re.onepass != nil {
+ return re.doOnePass(r, b, s, pos, ncap, dstCap)
+ }
+ if r == nil && len(b)+len(s) < re.maxBitStateLen {
+ return re.backtrack(b, s, pos, ncap, dstCap)
+ }
+
+ m := re.get()
+ i, _ := m.inputs.init(r, b, s)
+
+ m.init(ncap)
+ if !m.match(i, pos) {
+ re.put(m)
+ return nil
+ }
+
+ dstCap = append(dstCap, m.matchcap...)
+ re.put(m)
+ return dstCap
+}
+
+// arrayNoInts is returned by doExecute match if nil dstCap is passed
+// to it with ncap=0.
+var arrayNoInts [0]int
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