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author | Daniel Baumann <daniel.baumann@progress-linux.org> | 2024-04-16 19:23:18 +0000 |
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committer | Daniel Baumann <daniel.baumann@progress-linux.org> | 2024-04-16 19:23:18 +0000 |
commit | 43a123c1ae6613b3efeed291fa552ecd909d3acf (patch) | |
tree | fd92518b7024bc74031f78a1cf9e454b65e73665 /src/regexp/syntax/prog.go | |
parent | Initial commit. (diff) | |
download | golang-1.20-43a123c1ae6613b3efeed291fa552ecd909d3acf.tar.xz golang-1.20-43a123c1ae6613b3efeed291fa552ecd909d3acf.zip |
Adding upstream version 1.20.14.upstream/1.20.14upstream
Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>
Diffstat (limited to 'src/regexp/syntax/prog.go')
-rw-r--r-- | src/regexp/syntax/prog.go | 347 |
1 files changed, 347 insertions, 0 deletions
diff --git a/src/regexp/syntax/prog.go b/src/regexp/syntax/prog.go new file mode 100644 index 0000000..896cdc4 --- /dev/null +++ b/src/regexp/syntax/prog.go @@ -0,0 +1,347 @@ +// 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 ( + "strconv" + "strings" + "unicode" + "unicode/utf8" +) + +// 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 +) + +var instOpNames = []string{ + "InstAlt", + "InstAltMatch", + "InstCapture", + "InstEmptyWidth", + "InstMatch", + "InstFail", + "InstNop", + "InstRune", + "InstRune1", + "InstRuneAny", + "InstRuneAnyNotNL", +} + +func (i InstOp) String() string { + if uint(i) >= uint(len(instOpNames)) { + return "" + } + return instOpNames[i] +} + +// 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 = EmptyNoWordBoundary + var boundary byte + switch { + case IsWordChar(r1): + boundary = 1 + case r1 == '\n': + op |= EmptyBeginLine + case r1 < 0: + op |= EmptyBeginText | EmptyBeginLine + } + switch { + case IsWordChar(r2): + boundary ^= 1 + case r2 == '\n': + op |= EmptyEndLine + case r2 < 0: + op |= EmptyEndText | EmptyEndLine + } + if boundary != 0 { // IsWordChar(r1) != IsWordChar(r2) + op ^= (EmptyWordBoundary | EmptyNoWordBoundary) + } + return op +} + +// IsWordChar reports whether r is considered 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 strings.Builder + dumpProg(&b, p) + return b.String() +} + +// skipNop follows any no-op or capturing instructions. +func (p *Prog) skipNop(pc uint32) *Inst { + i := &p.Inst[pc] + for i.Op == InstNop || i.Op == InstCapture { + i = &p.Inst[i.Out] + } + 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 strings.Builder + for i.op() == InstRune && len(i.Rune) == 1 && Flags(i.Arg)&FoldCase == 0 && i.Rune[0] != utf8.RuneError { + 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 +} + +const noMatch = -1 + +// MatchRune reports whether the instruction matches (and consumes) r. +// It should only be called when i.Op == InstRune. +func (i *Inst) MatchRune(r rune) bool { + return i.MatchRunePos(r) != noMatch +} + +// MatchRunePos checks whether the instruction matches (and consumes) r. +// If so, MatchRunePos returns the index of the matching rune pair +// (or, when len(i.Rune) == 1, rune singleton). +// If not, MatchRunePos returns -1. +// MatchRunePos should only be called when i.Op == InstRune. +func (i *Inst) MatchRunePos(r rune) int { + rune := i.Rune + + switch len(rune) { + case 0: + return noMatch + + case 1: + // Special case: single-rune slice is from literal string, not char class. + r0 := rune[0] + if r == r0 { + return 0 + } + if Flags(i.Arg)&FoldCase != 0 { + for r1 := unicode.SimpleFold(r0); r1 != r0; r1 = unicode.SimpleFold(r1) { + if r == r1 { + return 0 + } + } + } + return noMatch + + case 2: + if r >= rune[0] && r <= rune[1] { + return 0 + } + return noMatch + + case 4, 6, 8: + // Linear search for a few pairs. + // Should handle ASCII well. + for j := 0; j < len(rune); j += 2 { + if r < rune[j] { + return noMatch + } + if r <= rune[j+1] { + return j / 2 + } + } + return noMatch + } + + // 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 m + } + lo = m + 1 + } else { + hi = m + } + } + return noMatch +} + +// MatchEmptyWidth reports whether 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 IsWordChar(before) != IsWordChar(after) + case EmptyNoWordBoundary: + return IsWordChar(before) == IsWordChar(after) + } + panic("unknown empty width arg") +} + +func (i *Inst) String() string { + var b strings.Builder + dumpInst(&b, i) + return b.String() +} + +func bw(b *strings.Builder, args ...string) { + for _, s := range args { + b.WriteString(s) + } +} + +func dumpProg(b *strings.Builder, 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 *strings.Builder, 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)) + } +} |