| // Copyright 2014 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 ( |
| "regexp/syntax" |
| "sort" |
| "strings" |
| "unicode" |
| ) |
| |
| // "One-pass" regexp execution. |
| // Some regexps can be analyzed to determine that they never need |
| // backtracking: they are guaranteed to run in one pass over the string |
| // without bothering to save all the usual NFA state. |
| // Detect those and execute them more quickly. |
| |
| // A onePassProg is a compiled one-pass regular expression program. |
| // It is the same as syntax.Prog except for the use of onePassInst. |
| type onePassProg struct { |
| Inst []onePassInst |
| Start int // index of start instruction |
| NumCap int // number of InstCapture insts in re |
| } |
| |
| // A onePassInst is a single instruction in a one-pass regular expression program. |
| // It is the same as syntax.Inst except for the new 'Next' field. |
| type onePassInst struct { |
| syntax.Inst |
| Next []uint32 |
| } |
| |
| // OnePassPrefix returns a literal string that all matches for the |
| // regexp must start with. Complete is true if the prefix |
| // is the entire match. Pc is the index of the last rune instruction |
| // in the string. The OnePassPrefix skips over the mandatory |
| // EmptyBeginText |
| func onePassPrefix(p *syntax.Prog) (prefix string, complete bool, pc uint32) { |
| i := &p.Inst[p.Start] |
| if i.Op != syntax.InstEmptyWidth || (syntax.EmptyOp(i.Arg))&syntax.EmptyBeginText == 0 { |
| return "", i.Op == syntax.InstMatch, uint32(p.Start) |
| } |
| pc = i.Out |
| i = &p.Inst[pc] |
| for i.Op == syntax.InstNop { |
| pc = i.Out |
| i = &p.Inst[pc] |
| } |
| // Avoid allocation of buffer if prefix is empty. |
| if iop(i) != syntax.InstRune || len(i.Rune) != 1 { |
| return "", i.Op == syntax.InstMatch, uint32(p.Start) |
| } |
| |
| // Have prefix; gather characters. |
| var buf strings.Builder |
| for iop(i) == syntax.InstRune && len(i.Rune) == 1 && syntax.Flags(i.Arg)&syntax.FoldCase == 0 { |
| buf.WriteRune(i.Rune[0]) |
| pc, i = i.Out, &p.Inst[i.Out] |
| } |
| if i.Op == syntax.InstEmptyWidth && |
| syntax.EmptyOp(i.Arg)&syntax.EmptyEndText != 0 && |
| p.Inst[i.Out].Op == syntax.InstMatch { |
| complete = true |
| } |
| return buf.String(), complete, pc |
| } |
| |
| // OnePassNext selects the next actionable state of the prog, based on the input character. |
| // It should only be called when i.Op == InstAlt or InstAltMatch, and from the one-pass machine. |
| // One of the alternates may ultimately lead without input to end of line. If the instruction |
| // is InstAltMatch the path to the InstMatch is in i.Out, the normal node in i.Next. |
| func onePassNext(i *onePassInst, r rune) uint32 { |
| next := i.MatchRunePos(r) |
| if next >= 0 { |
| return i.Next[next] |
| } |
| if i.Op == syntax.InstAltMatch { |
| return i.Out |
| } |
| return 0 |
| } |
| |
| func iop(i *syntax.Inst) syntax.InstOp { |
| op := i.Op |
| switch op { |
| case syntax.InstRune1, syntax.InstRuneAny, syntax.InstRuneAnyNotNL: |
| op = syntax.InstRune |
| } |
| return op |
| } |
| |
| // Sparse Array implementation is used as a queueOnePass. |
| type queueOnePass struct { |
| sparse []uint32 |
| dense []uint32 |
| size, nextIndex uint32 |
| } |
| |
| func (q *queueOnePass) empty() bool { |
| return q.nextIndex >= q.size |
| } |
| |
| func (q *queueOnePass) next() (n uint32) { |
| n = q.dense[q.nextIndex] |
| q.nextIndex++ |
| return |
| } |
| |
| func (q *queueOnePass) clear() { |
| q.size = 0 |
| q.nextIndex = 0 |
| } |
| |
| func (q *queueOnePass) contains(u uint32) bool { |
| if u >= uint32(len(q.sparse)) { |
| return false |
| } |
| return q.sparse[u] < q.size && q.dense[q.sparse[u]] == u |
| } |
| |
| func (q *queueOnePass) insert(u uint32) { |
| if !q.contains(u) { |
| q.insertNew(u) |
| } |
| } |
| |
| func (q *queueOnePass) insertNew(u uint32) { |
| if u >= uint32(len(q.sparse)) { |
| return |
| } |
| q.sparse[u] = q.size |
| q.dense[q.size] = u |
| q.size++ |
| } |
| |
| func newQueue(size int) (q *queueOnePass) { |
| return &queueOnePass{ |
| sparse: make([]uint32, size), |
| dense: make([]uint32, size), |
| } |
| } |
| |
| // mergeRuneSets merges two non-intersecting runesets, and returns the merged result, |
| // and a NextIp array. The idea is that if a rune matches the OnePassRunes at index |
| // i, NextIp[i/2] is the target. If the input sets intersect, an empty runeset and a |
| // NextIp array with the single element mergeFailed is returned. |
| // The code assumes that both inputs contain ordered and non-intersecting rune pairs. |
| const mergeFailed = uint32(0xffffffff) |
| |
| var ( |
| noRune = []rune{} |
| noNext = []uint32{mergeFailed} |
| ) |
| |
| func mergeRuneSets(leftRunes, rightRunes *[]rune, leftPC, rightPC uint32) ([]rune, []uint32) { |
| leftLen := len(*leftRunes) |
| rightLen := len(*rightRunes) |
| if leftLen&0x1 != 0 || rightLen&0x1 != 0 { |
| panic("mergeRuneSets odd length []rune") |
| } |
| var ( |
| lx, rx int |
| ) |
| merged := make([]rune, 0) |
| next := make([]uint32, 0) |
| ok := true |
| defer func() { |
| if !ok { |
| merged = nil |
| next = nil |
| } |
| }() |
| |
| ix := -1 |
| extend := func(newLow *int, newArray *[]rune, pc uint32) bool { |
| if ix > 0 && (*newArray)[*newLow] <= merged[ix] { |
| return false |
| } |
| merged = append(merged, (*newArray)[*newLow], (*newArray)[*newLow+1]) |
| *newLow += 2 |
| ix += 2 |
| next = append(next, pc) |
| return true |
| } |
| |
| for lx < leftLen || rx < rightLen { |
| switch { |
| case rx >= rightLen: |
| ok = extend(&lx, leftRunes, leftPC) |
| case lx >= leftLen: |
| ok = extend(&rx, rightRunes, rightPC) |
| case (*rightRunes)[rx] < (*leftRunes)[lx]: |
| ok = extend(&rx, rightRunes, rightPC) |
| default: |
| ok = extend(&lx, leftRunes, leftPC) |
| } |
| if !ok { |
| return noRune, noNext |
| } |
| } |
| return merged, next |
| } |
| |
| // cleanupOnePass drops working memory, and restores certain shortcut instructions. |
| func cleanupOnePass(prog *onePassProg, original *syntax.Prog) { |
| for ix, instOriginal := range original.Inst { |
| switch instOriginal.Op { |
| case syntax.InstAlt, syntax.InstAltMatch, syntax.InstRune: |
| case syntax.InstCapture, syntax.InstEmptyWidth, syntax.InstNop, syntax.InstMatch, syntax.InstFail: |
| prog.Inst[ix].Next = nil |
| case syntax.InstRune1, syntax.InstRuneAny, syntax.InstRuneAnyNotNL: |
| prog.Inst[ix].Next = nil |
| prog.Inst[ix] = onePassInst{Inst: instOriginal} |
| } |
| } |
| } |
| |
| // onePassCopy creates a copy of the original Prog, as we'll be modifying it |
| func onePassCopy(prog *syntax.Prog) *onePassProg { |
| p := &onePassProg{ |
| Start: prog.Start, |
| NumCap: prog.NumCap, |
| Inst: make([]onePassInst, len(prog.Inst)), |
| } |
| for i, inst := range prog.Inst { |
| p.Inst[i] = onePassInst{Inst: inst} |
| } |
| |
| // rewrites one or more common Prog constructs that enable some otherwise |
| // non-onepass Progs to be onepass. A:BD (for example) means an InstAlt at |
| // ip A, that points to ips B & C. |
| // A:BC + B:DA => A:BC + B:CD |
| // A:BC + B:DC => A:DC + B:DC |
| for pc := range p.Inst { |
| switch p.Inst[pc].Op { |
| default: |
| continue |
| case syntax.InstAlt, syntax.InstAltMatch: |
| // A:Bx + B:Ay |
| p_A_Other := &p.Inst[pc].Out |
| p_A_Alt := &p.Inst[pc].Arg |
| // make sure a target is another Alt |
| instAlt := p.Inst[*p_A_Alt] |
| if !(instAlt.Op == syntax.InstAlt || instAlt.Op == syntax.InstAltMatch) { |
| p_A_Alt, p_A_Other = p_A_Other, p_A_Alt |
| instAlt = p.Inst[*p_A_Alt] |
| if !(instAlt.Op == syntax.InstAlt || instAlt.Op == syntax.InstAltMatch) { |
| continue |
| } |
| } |
| instOther := p.Inst[*p_A_Other] |
| // Analyzing both legs pointing to Alts is for another day |
| if instOther.Op == syntax.InstAlt || instOther.Op == syntax.InstAltMatch { |
| // too complicated |
| continue |
| } |
| // simple empty transition loop |
| // A:BC + B:DA => A:BC + B:DC |
| p_B_Alt := &p.Inst[*p_A_Alt].Out |
| p_B_Other := &p.Inst[*p_A_Alt].Arg |
| patch := false |
| if instAlt.Out == uint32(pc) { |
| patch = true |
| } else if instAlt.Arg == uint32(pc) { |
| patch = true |
| p_B_Alt, p_B_Other = p_B_Other, p_B_Alt |
| } |
| if patch { |
| *p_B_Alt = *p_A_Other |
| } |
| |
| // empty transition to common target |
| // A:BC + B:DC => A:DC + B:DC |
| if *p_A_Other == *p_B_Alt { |
| *p_A_Alt = *p_B_Other |
| } |
| } |
| } |
| return p |
| } |
| |
| // runeSlice exists to permit sorting the case-folded rune sets. |
| type runeSlice []rune |
| |
| func (p runeSlice) Len() int { return len(p) } |
| func (p runeSlice) Less(i, j int) bool { return p[i] < p[j] } |
| func (p runeSlice) Swap(i, j int) { p[i], p[j] = p[j], p[i] } |
| |
| var anyRuneNotNL = []rune{0, '\n' - 1, '\n' + 1, unicode.MaxRune} |
| var anyRune = []rune{0, unicode.MaxRune} |
| |
| // makeOnePass creates a onepass Prog, if possible. It is possible if at any alt, |
| // the match engine can always tell which branch to take. The routine may modify |
| // p if it is turned into a onepass Prog. If it isn't possible for this to be a |
| // onepass Prog, the Prog nil is returned. makeOnePass is recursive |
| // to the size of the Prog. |
| func makeOnePass(p *onePassProg) *onePassProg { |
| // If the machine is very long, it's not worth the time to check if we can use one pass. |
| if len(p.Inst) >= 1000 { |
| return nil |
| } |
| |
| var ( |
| instQueue = newQueue(len(p.Inst)) |
| visitQueue = newQueue(len(p.Inst)) |
| check func(uint32, []bool) bool |
| onePassRunes = make([][]rune, len(p.Inst)) |
| ) |
| |
| // check that paths from Alt instructions are unambiguous, and rebuild the new |
| // program as a onepass program |
| check = func(pc uint32, m []bool) (ok bool) { |
| ok = true |
| inst := &p.Inst[pc] |
| if visitQueue.contains(pc) { |
| return |
| } |
| visitQueue.insert(pc) |
| switch inst.Op { |
| case syntax.InstAlt, syntax.InstAltMatch: |
| ok = check(inst.Out, m) && check(inst.Arg, m) |
| // check no-input paths to InstMatch |
| matchOut := m[inst.Out] |
| matchArg := m[inst.Arg] |
| if matchOut && matchArg { |
| ok = false |
| break |
| } |
| // Match on empty goes in inst.Out |
| if matchArg { |
| inst.Out, inst.Arg = inst.Arg, inst.Out |
| matchOut, matchArg = matchArg, matchOut |
| } |
| if matchOut { |
| m[pc] = true |
| inst.Op = syntax.InstAltMatch |
| } |
| |
| // build a dispatch operator from the two legs of the alt. |
| onePassRunes[pc], inst.Next = mergeRuneSets( |
| &onePassRunes[inst.Out], &onePassRunes[inst.Arg], inst.Out, inst.Arg) |
| if len(inst.Next) > 0 && inst.Next[0] == mergeFailed { |
| ok = false |
| break |
| } |
| case syntax.InstCapture, syntax.InstNop: |
| ok = check(inst.Out, m) |
| m[pc] = m[inst.Out] |
| // pass matching runes back through these no-ops. |
| onePassRunes[pc] = append([]rune{}, onePassRunes[inst.Out]...) |
| inst.Next = make([]uint32, len(onePassRunes[pc])/2+1) |
| for i := range inst.Next { |
| inst.Next[i] = inst.Out |
| } |
| case syntax.InstEmptyWidth: |
| ok = check(inst.Out, m) |
| m[pc] = m[inst.Out] |
| onePassRunes[pc] = append([]rune{}, onePassRunes[inst.Out]...) |
| inst.Next = make([]uint32, len(onePassRunes[pc])/2+1) |
| for i := range inst.Next { |
| inst.Next[i] = inst.Out |
| } |
| case syntax.InstMatch, syntax.InstFail: |
| m[pc] = inst.Op == syntax.InstMatch |
| case syntax.InstRune: |
| m[pc] = false |
| if len(inst.Next) > 0 { |
| break |
| } |
| instQueue.insert(inst.Out) |
| if len(inst.Rune) == 0 { |
| onePassRunes[pc] = []rune{} |
| inst.Next = []uint32{inst.Out} |
| break |
| } |
| runes := make([]rune, 0) |
| if len(inst.Rune) == 1 && syntax.Flags(inst.Arg)&syntax.FoldCase != 0 { |
| r0 := inst.Rune[0] |
| runes = append(runes, r0, r0) |
| for r1 := unicode.SimpleFold(r0); r1 != r0; r1 = unicode.SimpleFold(r1) { |
| runes = append(runes, r1, r1) |
| } |
| sort.Sort(runeSlice(runes)) |
| } else { |
| runes = append(runes, inst.Rune...) |
| } |
| onePassRunes[pc] = runes |
| inst.Next = make([]uint32, len(onePassRunes[pc])/2+1) |
| for i := range inst.Next { |
| inst.Next[i] = inst.Out |
| } |
| inst.Op = syntax.InstRune |
| case syntax.InstRune1: |
| m[pc] = false |
| if len(inst.Next) > 0 { |
| break |
| } |
| instQueue.insert(inst.Out) |
| runes := []rune{} |
| // expand case-folded runes |
| if syntax.Flags(inst.Arg)&syntax.FoldCase != 0 { |
| r0 := inst.Rune[0] |
| runes = append(runes, r0, r0) |
| for r1 := unicode.SimpleFold(r0); r1 != r0; r1 = unicode.SimpleFold(r1) { |
| runes = append(runes, r1, r1) |
| } |
| sort.Sort(runeSlice(runes)) |
| } else { |
| runes = append(runes, inst.Rune[0], inst.Rune[0]) |
| } |
| onePassRunes[pc] = runes |
| inst.Next = make([]uint32, len(onePassRunes[pc])/2+1) |
| for i := range inst.Next { |
| inst.Next[i] = inst.Out |
| } |
| inst.Op = syntax.InstRune |
| case syntax.InstRuneAny: |
| m[pc] = false |
| if len(inst.Next) > 0 { |
| break |
| } |
| instQueue.insert(inst.Out) |
| onePassRunes[pc] = append([]rune{}, anyRune...) |
| inst.Next = []uint32{inst.Out} |
| case syntax.InstRuneAnyNotNL: |
| m[pc] = false |
| if len(inst.Next) > 0 { |
| break |
| } |
| instQueue.insert(inst.Out) |
| onePassRunes[pc] = append([]rune{}, anyRuneNotNL...) |
| inst.Next = make([]uint32, len(onePassRunes[pc])/2+1) |
| for i := range inst.Next { |
| inst.Next[i] = inst.Out |
| } |
| } |
| return |
| } |
| |
| instQueue.clear() |
| instQueue.insert(uint32(p.Start)) |
| m := make([]bool, len(p.Inst)) |
| for !instQueue.empty() { |
| visitQueue.clear() |
| pc := instQueue.next() |
| if !check(pc, m) { |
| p = nil |
| break |
| } |
| } |
| if p != nil { |
| for i := range p.Inst { |
| p.Inst[i].Rune = onePassRunes[i] |
| } |
| } |
| return p |
| } |
| |
| // compileOnePass returns a new *syntax.Prog suitable for onePass execution if the original Prog |
| // can be recharacterized as a one-pass regexp program, or syntax.nil if the |
| // Prog cannot be converted. For a one pass prog, the fundamental condition that must |
| // be true is: at any InstAlt, there must be no ambiguity about what branch to take. |
| func compileOnePass(prog *syntax.Prog) (p *onePassProg) { |
| if prog.Start == 0 { |
| return nil |
| } |
| // onepass regexp is anchored |
| if prog.Inst[prog.Start].Op != syntax.InstEmptyWidth || |
| syntax.EmptyOp(prog.Inst[prog.Start].Arg)&syntax.EmptyBeginText != syntax.EmptyBeginText { |
| return nil |
| } |
| // every instruction leading to InstMatch must be EmptyEndText |
| for _, inst := range prog.Inst { |
| opOut := prog.Inst[inst.Out].Op |
| switch inst.Op { |
| default: |
| if opOut == syntax.InstMatch { |
| return nil |
| } |
| case syntax.InstAlt, syntax.InstAltMatch: |
| if opOut == syntax.InstMatch || prog.Inst[inst.Arg].Op == syntax.InstMatch { |
| return nil |
| } |
| case syntax.InstEmptyWidth: |
| if opOut == syntax.InstMatch { |
| if syntax.EmptyOp(inst.Arg)&syntax.EmptyEndText == syntax.EmptyEndText { |
| continue |
| } |
| return nil |
| } |
| } |
| } |
| // Creates a slightly optimized copy of the original Prog |
| // that cleans up some Prog idioms that block valid onepass programs |
| p = onePassCopy(prog) |
| |
| // checkAmbiguity on InstAlts, build onepass Prog if possible |
| p = makeOnePass(p) |
| |
| if p != nil { |
| cleanupOnePass(p, prog) |
| } |
| return p |
| } |
