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// 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.
// Copy of code.google.com/p/codesearch/regexp/utf.go.
package main
import (
"regexp/syntax"
"unicode"
"unicode/utf8"
)
const (
instFail = syntax.InstFail
instAlt = syntax.InstAlt
instByteRange = syntax.InstRune | 0x80 // local opcode
argFold = 1 << 16
)
func toByteProg(prog *syntax.Prog) error {
var b runeBuilder
for pc := range prog.Inst {
i := &prog.Inst[pc]
switch i.Op {
case syntax.InstRune, syntax.InstRune1:
// General rune range. PIA.
// TODO: Pick off single-byte case.
if lo, hi, fold, ok := oneByteRange(i); ok {
i.Op = instByteRange
i.Arg = uint32(lo)<<8 | uint32(hi)
if fold {
i.Arg |= argFold
}
break
}
r := i.Rune
if syntax.Flags(i.Arg)&syntax.FoldCase != 0 {
// Build folded list.
var rr []rune
if len(r) == 1 {
rr = appendFoldedRange(rr, r[0], r[0])
} else {
for j := 0; j < len(r); j += 2 {
rr = appendFoldedRange(rr, r[j], r[j+1])
}
}
r = rr
}
b.init(prog, uint32(pc), i.Out)
if len(r) == 1 {
b.addRange(r[0], r[0], false)
} else {
for j := 0; j < len(r); j += 2 {
b.addRange(r[j], r[j+1], false)
}
}
case syntax.InstRuneAny, syntax.InstRuneAnyNotNL:
// All runes.
// AnyNotNL should exclude \n but the line-at-a-time
// execution takes care of that for us.
b.init(prog, uint32(pc), i.Out)
b.addRange(0, unicode.MaxRune, false)
}
}
return nil
}
func oneByteRange(i *syntax.Inst) (lo, hi byte, fold, ok bool) {
if i.Op == syntax.InstRune1 {
r := i.Rune[0]
if r < utf8.RuneSelf {
return byte(r), byte(r), false, true
}
}
if i.Op != syntax.InstRune {
return
}
fold = syntax.Flags(i.Arg)&syntax.FoldCase != 0
if len(i.Rune) == 1 || len(i.Rune) == 2 && i.Rune[0] == i.Rune[1] {
r := i.Rune[0]
if r >= utf8.RuneSelf {
return
}
if fold && !asciiFold(r) {
return
}
return byte(r), byte(r), fold, true
}
if len(i.Rune) == 2 && i.Rune[1] < utf8.RuneSelf {
if fold {
for r := i.Rune[0]; r <= i.Rune[1]; r++ {
if asciiFold(r) {
return
}
}
}
return byte(i.Rune[0]), byte(i.Rune[1]), fold, true
}
if len(i.Rune) == 4 && i.Rune[0] == i.Rune[1] && i.Rune[2] == i.Rune[3] && unicode.SimpleFold(i.Rune[0]) == i.Rune[2] && unicode.SimpleFold(i.Rune[2]) == i.Rune[0] {
return byte(i.Rune[0]), byte(i.Rune[0]), true, true
}
return
}
func asciiFold(r rune) bool {
if r >= utf8.RuneSelf {
return false
}
r1 := unicode.SimpleFold(r)
if r1 >= utf8.RuneSelf {
return false
}
if r1 == r {
return true
}
return unicode.SimpleFold(r1) == r
}
func maxRune(n int) rune {
b := 0
if n == 1 {
b = 7
} else {
b = 8 - (n + 1) + 6*(n-1)
}
return 1<<uint(b) - 1
}
type cacheKey struct {
lo, hi uint8
fold bool
next uint32
}
type runeBuilder struct {
begin uint32
out uint32
cache map[cacheKey]uint32
p *syntax.Prog
}
func (b *runeBuilder) init(p *syntax.Prog, begin, out uint32) {
// We will rewrite p.Inst[begin] to hold the accumulated
// machine. For now, there is no match.
p.Inst[begin].Op = instFail
b.begin = begin
b.out = out
if b.cache == nil {
b.cache = make(map[cacheKey]uint32)
}
for k := range b.cache {
delete(b.cache, k)
}
b.p = p
}
func (b *runeBuilder) uncachedSuffix(lo, hi byte, fold bool, next uint32) uint32 {
if next == 0 {
next = b.out
}
pc := len(b.p.Inst)
i := syntax.Inst{Op: instByteRange, Arg: uint32(lo)<<8 | uint32(hi), Out: next}
if fold {
i.Arg |= argFold
}
b.p.Inst = append(b.p.Inst, i)
return uint32(pc)
}
func (b *runeBuilder) suffix(lo, hi byte, fold bool, next uint32) uint32 {
if lo < 0x80 || hi > 0xbf {
// Not a continuation byte, no need to cache.
return b.uncachedSuffix(lo, hi, fold, next)
}
key := cacheKey{lo, hi, fold, next}
if pc, ok := b.cache[key]; ok {
return pc
}
pc := b.uncachedSuffix(lo, hi, fold, next)
b.cache[key] = pc
return pc
}
func (b *runeBuilder) addBranch(pc uint32) {
// Add pc to the branch at the beginning.
i := &b.p.Inst[b.begin]
switch i.Op {
case syntax.InstFail:
i.Op = syntax.InstNop
i.Out = pc
return
case syntax.InstNop:
i.Op = syntax.InstAlt
i.Arg = pc
return
case syntax.InstAlt:
apc := uint32(len(b.p.Inst))
b.p.Inst = append(b.p.Inst, syntax.Inst{Op: instAlt, Out: i.Arg, Arg: pc})
i = &b.p.Inst[b.begin]
i.Arg = apc
b.begin = apc
}
}
func (b *runeBuilder) addRange(lo, hi rune, fold bool) {
if lo > hi {
return
}
// TODO: Pick off 80-10FFFF for special handling?
if lo == 0x80 && hi == 0x10FFFF {
}
// Split range into same-length sized ranges.
for i := 1; i < utf8.UTFMax; i++ {
max := maxRune(i)
if lo <= max && max < hi {
b.addRange(lo, max, fold)
b.addRange(max+1, hi, fold)
return
}
}
// ASCII range is special.
if hi < utf8.RuneSelf {
b.addBranch(b.suffix(byte(lo), byte(hi), fold, 0))
return
}
// Split range into sections that agree on leading bytes.
for i := 1; i < utf8.UTFMax; i++ {
m := rune(1)<<uint(6*i) - 1 // last i bytes of UTF-8 sequence
if lo&^m != hi&^m {
if lo&m != 0 {
b.addRange(lo, lo|m, fold)
b.addRange((lo|m)+1, hi, fold)
return
}
if hi&m != m {
b.addRange(lo, hi&^m-1, fold)
b.addRange(hi&^m, hi, fold)
return
}
}
}
// Finally. Generate byte matching equivalent for lo-hi.
var ulo, uhi [utf8.UTFMax]byte
n := utf8.EncodeRune(ulo[:], lo)
m := utf8.EncodeRune(uhi[:], hi)
if n != m {
panic("codesearch/regexp: bad utf-8 math")
}
pc := uint32(0)
for i := n - 1; i >= 0; i-- {
pc = b.suffix(ulo[i], uhi[i], false, pc)
}
b.addBranch(pc)
}
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