ErrBadBackslash = Error("illegal backslash escape")
)
-// An instruction executed by the NFA
-type instr interface {
- kind() int // the type of this instruction: _CHAR, _ANY, etc.
- next() instr // the instruction to execute after this one
- setNext(i instr)
- index() int
- setIndex(i int)
- print()
-}
+const (
+ iStart = iota // beginning of program
+ iEnd // end of program: success
+ iBOT // '^' beginning of text
+ iEOT // '$' end of text
+ iChar // 'a' regular character
+ iCharClass // [a-z] character class
+ iAny // '.' any character including newline
+ iNotNL // [^\n] special case: any character but newline
+ iBra // '(' parenthesized expression: 2*braNum for left, 2*braNum+1 for right
+ iAlt // '|' alternation
+ iNop // do nothing; makes it easy to link without patching
+)
-// Fields and methods common to all instructions
-type common struct {
- _next instr
- _index int
+// An instruction executed by the NFA
+type instr struct {
+ kind int // the type of this instruction: iChar, iAny, etc.
+ index int // used only in debugging; could be eliminated
+ next *instr // the instruction to execute after this one
+ // Special fields valid only for some items.
+ char int // iChar
+ braNum int // iBra, iEbra
+ cclass *charClass // iCharClass
+ left *instr // iAlt, other branch
+}
+
+func (i *instr) print() {
+ switch i.kind {
+ case iStart:
+ print("start")
+ case iEnd:
+ print("end")
+ case iBOT:
+ print("bot")
+ case iEOT:
+ print("eot")
+ case iChar:
+ print("char ", string(i.char))
+ case iCharClass:
+ i.cclass.print()
+ case iAny:
+ print("any")
+ case iNotNL:
+ print("notnl")
+ case iBra:
+ if i.braNum&1 == 0 {
+ print("bra", i.braNum/2)
+ } else {
+ print("ebra", i.braNum/2)
+ }
+ case iAlt:
+ print("alt(", i.left.index, ")")
+ case iNop:
+ print("nop")
+ }
}
-func (c *common) next() instr { return c._next }
-func (c *common) setNext(i instr) { c._next = i }
-func (c *common) index() int { return c._index }
-func (c *common) setIndex(i int) { c._index = i }
-
// Regexp is the representation of a compiled regular expression.
// The public interface is entirely through methods.
type Regexp struct {
expr string // the original expression
prefix string // initial plain text string
prefixBytes []byte // initial plain text bytes
- inst []instr
- start instr // first instruction of machine
- prefixStart instr // where to start if there is a prefix
- nbra int // number of brackets in expression, for subexpressions
-}
-
-const (
- _START = iota // beginning of program
- _END // end of program: success
- _BOT // '^' beginning of text
- _EOT // '$' end of text
- _CHAR // 'a' regular character
- _CHARCLASS // [a-z] character class
- _ANY // '.' any character including newline
- _NOTNL // [^\n] special case: any character but newline
- _BRA // '(' parenthesized expression
- _EBRA // ')'; end of '(' parenthesized expression
- _ALT // '|' alternation
- _NOP // do nothing; makes it easy to link without patching
-)
-
-// --- START start of program
-type _Start struct {
- common
-}
-
-func (start *_Start) kind() int { return _START }
-func (start *_Start) print() { print("start") }
-
-// --- END end of program
-type _End struct {
- common
-}
-
-func (end *_End) kind() int { return _END }
-func (end *_End) print() { print("end") }
-
-// --- BOT beginning of text
-type _Bot struct {
- common
-}
-
-func (bot *_Bot) kind() int { return _BOT }
-func (bot *_Bot) print() { print("bot") }
-
-// --- EOT end of text
-type _Eot struct {
- common
-}
-
-func (eot *_Eot) kind() int { return _EOT }
-func (eot *_Eot) print() { print("eot") }
-
-// --- CHAR a regular character
-type _Char struct {
- common
- char int
+ inst []*instr
+ start *instr // first instruction of machine
+ prefixStart *instr // where to start if there is a prefix
+ nbra int // number of brackets in expression, for subexpressions
}
-func (char *_Char) kind() int { return _CHAR }
-func (char *_Char) print() { print("char ", string(char.char)) }
-
-func newChar(char int) *_Char {
- c := new(_Char)
- c.char = char
- return c
-}
-
-// --- CHARCLASS [a-z]
-
-type _CharClass struct {
- common
+type charClass struct {
negate bool // is character class negated? ([^a-z])
// slice of int, stored pairwise: [a-z] is (a,z); x is (x,x):
ranges []int
cmin, cmax int
}
-func (cclass *_CharClass) kind() int { return _CHARCLASS }
-
-func (cclass *_CharClass) print() {
+func (cclass *charClass) print() {
print("charclass")
if cclass.negate {
print(" (negated)")
}
}
-func (cclass *_CharClass) addRange(a, b int) {
+func (cclass *charClass) addRange(a, b int) {
// range is a through b inclusive
cclass.ranges = append(cclass.ranges, a, b)
if a < cclass.cmin {
}
}
-func (cclass *_CharClass) matches(c int) bool {
+func (cclass *charClass) matches(c int) bool {
if c < cclass.cmin || c > cclass.cmax {
return cclass.negate
}
return cclass.negate
}
-func newCharClass() *_CharClass {
- c := new(_CharClass)
- c.ranges = make([]int, 0, 4)
- c.cmin = 0x10FFFF + 1 // MaxRune + 1
- c.cmax = -1
- return c
-}
-
-// --- ANY any character
-type _Any struct {
- common
-}
-
-func (any *_Any) kind() int { return _ANY }
-func (any *_Any) print() { print("any") }
-
-// --- NOTNL any character but newline
-type _NotNl struct {
- common
-}
-
-func (notnl *_NotNl) kind() int { return _NOTNL }
-func (notnl *_NotNl) print() { print("notnl") }
-
-// --- BRA parenthesized expression
-type _Bra struct {
- common
- n int // subexpression number
-}
-
-func (bra *_Bra) kind() int { return _BRA }
-func (bra *_Bra) print() { print("bra", bra.n) }
-
-// --- EBRA end of parenthesized expression
-type _Ebra struct {
- common
- n int // subexpression number
-}
-
-func (ebra *_Ebra) kind() int { return _EBRA }
-func (ebra *_Ebra) print() { print("ebra ", ebra.n) }
-
-// --- ALT alternation
-type _Alt struct {
- common
- left instr // other branch
-}
-
-func (alt *_Alt) kind() int { return _ALT }
-func (alt *_Alt) print() { print("alt(", alt.left.index(), ")") }
-
-// --- NOP no operation
-type _Nop struct {
- common
+func newCharClass() *instr {
+ i := &instr{kind: iCharClass}
+ i.cclass = new(charClass)
+ i.cclass.ranges = make([]int, 0, 4)
+ i.cclass.cmin = 0x10FFFF + 1 // MaxRune + 1
+ i.cclass.cmax = -1
+ return i
}
-func (nop *_Nop) kind() int { return _NOP }
-func (nop *_Nop) print() { print("nop") }
-
-func (re *Regexp) add(i instr) instr {
- i.setIndex(len(re.inst))
+func (re *Regexp) add(i *instr) *instr {
+ i.index = len(re.inst)
re.inst = append(re.inst, i)
return i
}
return -1
}
-func (p *parser) charClass() instr {
- cc := newCharClass()
+func (p *parser) charClass() *instr {
+ i := newCharClass()
+ cc := i.cclass
if p.c() == '^' {
cc.negate = true
p.nextc()
// Is it [^\n]?
if cc.negate && len(cc.ranges) == 2 &&
cc.ranges[0] == '\n' && cc.ranges[1] == '\n' {
- nl := new(_NotNl)
+ nl := &instr{kind: iNotNL}
p.re.add(nl)
return nl
}
// Special common case: "[a]" -> "a"
if !cc.negate && len(cc.ranges) == 2 && cc.ranges[0] == cc.ranges[1] {
- c := newChar(cc.ranges[0])
+ c := &instr{kind: iChar, char: cc.ranges[0]}
p.re.add(c)
return c
}
- p.re.add(cc)
- return cc
+ p.re.add(i)
+ return i
case '-': // do this before backslash processing
p.error(ErrBadRange)
case '\\':
return nil
}
-func (p *parser) term() (start, end instr) {
+func (p *parser) term() (start, end *instr) {
switch c := p.c(); c {
case '|', endOfFile:
return nil, nil
p.error(ErrUnmatchedRbkt)
case '^':
p.nextc()
- start = p.re.add(new(_Bot))
+ start = p.re.add(&instr{kind: iBOT})
return start, start
case '$':
p.nextc()
- start = p.re.add(new(_Eot))
+ start = p.re.add(&instr{kind: iEOT})
return start, start
case '.':
p.nextc()
- start = p.re.add(new(_Any))
+ start = p.re.add(&instr{kind: iAny})
return start, start
case '[':
p.nextc()
}
p.nlpar--
p.nextc()
- bra := new(_Bra)
+ bra := &instr{kind: iBra, braNum: 2 * nbra}
p.re.add(bra)
- ebra := new(_Ebra)
+ ebra := &instr{kind: iBra, braNum: 2*nbra + 1}
p.re.add(ebra)
- bra.n = nbra
- ebra.n = nbra
if start == nil {
if end == nil {
p.error(ErrInternal)
}
start = ebra
} else {
- end.setNext(ebra)
+ end.next = ebra
}
- bra.setNext(start)
+ bra.next = start
return bra, ebra
case '\\':
c = p.nextc()
fallthrough
default:
p.nextc()
- start = newChar(c)
+ start = &instr{kind: iChar, char: c}
p.re.add(start)
return start, start
}
panic("unreachable")
}
-func (p *parser) closure() (start, end instr) {
+func (p *parser) closure() (start, end *instr) {
start, end = p.term()
if start == nil {
return
switch p.c() {
case '*':
// (start,end)*:
- alt := new(_Alt)
+ alt := &instr{kind: iAlt}
p.re.add(alt)
- end.setNext(alt) // after end, do alt
+ end.next = alt // after end, do alt
alt.left = start // alternate brach: return to start
start = alt // alt becomes new (start, end)
end = alt
case '+':
// (start,end)+:
- alt := new(_Alt)
+ alt := &instr{kind: iAlt}
p.re.add(alt)
- end.setNext(alt) // after end, do alt
+ end.next = alt // after end, do alt
alt.left = start // alternate brach: return to start
end = alt // start is unchanged; end is alt
case '?':
// (start,end)?:
- alt := new(_Alt)
+ alt := &instr{kind: iAlt}
p.re.add(alt)
- nop := new(_Nop)
+ nop := &instr{kind: iNop}
p.re.add(nop)
alt.left = start // alternate branch is start
- alt.setNext(nop) // follow on to nop
- end.setNext(nop) // after end, go to nop
+ alt.next = nop // follow on to nop
+ end.next = nop // after end, go to nop
start = alt // start is now alt
end = nop // end is nop pointed to by both branches
default:
return
}
-func (p *parser) concatenation() (start, end instr) {
+func (p *parser) concatenation() (start, end *instr) {
for {
nstart, nend := p.closure()
switch {
case nstart == nil: // end of this concatenation
if start == nil { // this is the empty string
- nop := p.re.add(new(_Nop))
+ nop := p.re.add(&instr{kind: iNop})
return nop, nop
}
return
case start == nil: // this is first element of concatenation
start, end = nstart, nend
default:
- end.setNext(nstart)
+ end.next = nstart
end = nend
}
}
panic("unreachable")
}
-func (p *parser) regexp() (start, end instr) {
+func (p *parser) regexp() (start, end *instr) {
start, end = p.concatenation()
for {
switch p.c() {
case '|':
p.nextc()
nstart, nend := p.concatenation()
- alt := new(_Alt)
+ alt := &instr{kind: iAlt}
p.re.add(alt)
alt.left = start
- alt.setNext(nstart)
- nop := new(_Nop)
+ alt.next = nstart
+ nop := &instr{kind: iNop}
p.re.add(nop)
- end.setNext(nop)
- nend.setNext(nop)
+ end.next = nop
+ nend.next = nop
start, end = alt, nop
}
}
panic("unreachable")
}
-func unNop(i instr) instr {
- for i.kind() == _NOP {
- i = i.next()
+func unNop(i *instr) *instr {
+ for i.kind == iNop {
+ i = i.next
}
return i
}
func (re *Regexp) eliminateNops() {
for _, inst := range re.inst {
- if inst.kind() == _END {
+ if inst.kind == iEnd {
continue
}
- inst.setNext(unNop(inst.next()))
- if inst.kind() == _ALT {
- alt := inst.(*_Alt)
- alt.left = unNop(alt.left)
+ inst.next = unNop(inst.next)
+ if inst.kind == iAlt {
+ inst.left = unNop(inst.left)
}
}
}
func (re *Regexp) dump() {
print("prefix <", re.prefix, ">\n")
for _, inst := range re.inst {
- print(inst.index(), ": ")
+ print(inst.index, ": ")
inst.print()
- if inst.kind() != _END {
- print(" -> ", inst.next().index())
+ if inst.kind != iEnd {
+ print(" -> ", inst.next.index)
}
print("\n")
}
func (re *Regexp) doParse() {
p := newParser(re)
- start := new(_Start)
+ start := &instr{kind: iStart}
re.add(start)
s, e := p.regexp()
- start.setNext(s)
+ start.next = s
re.start = start
- e.setNext(re.add(new(_End)))
+ e.next = re.add(&instr{kind: iEnd})
if debug {
re.dump()
func (re *Regexp) setPrefix() {
var b []byte
var utf = make([]byte, utf8.UTFMax)
+ var inst *instr
// First instruction is start; skip that.
- i := re.inst[0].next().index()
Loop:
- for i < len(re.inst) {
- inst := re.inst[i]
+ for inst = re.inst[0].next; inst.kind != iEnd; inst = inst.next {
// stop if this is not a char
- if inst.kind() != _CHAR {
+ if inst.kind != iChar {
break
}
// stop if this char can be followed by a match for an empty string,
// which includes closures, ^, and $.
- switch re.inst[inst.next().index()].kind() {
- case _BOT, _EOT, _ALT:
+ switch inst.next.kind {
+ case iBOT, iEOT, iAlt:
break Loop
}
- n := utf8.EncodeRune(inst.(*_Char).char, utf)
- b = bytes.Add(b, utf[0:n])
- i = inst.next().index()
+ n := utf8.EncodeRune(inst.char, utf)
+ b = append(b, utf[0:n]...)
}
// point prefixStart instruction to first non-CHAR after prefix
- re.prefixStart = re.inst[i]
+ re.prefixStart = inst
re.prefixBytes = b
re.prefix = string(b)
}
}
}()
regexp.expr = str
- regexp.inst = make([]instr, 0, 10)
+ regexp.inst = make([]*instr, 0, 10)
regexp.doParse()
return
}
}
type state struct {
- inst instr // next instruction to execute
- prefixed bool // this match began with a fixed prefix
+ inst *instr // next instruction to execute
+ prefixed bool // this match began with a fixed prefix
match *matchVec
}
// Append new state to to-do list. Leftmost-longest wins so avoid
// adding a state that's already active. The matchVec will be inc-ref'ed
// if it is assigned to a state.
-func (a *matchArena) addState(s []state, inst instr, prefixed bool, match *matchVec, pos, end int) []state {
- switch inst.kind() {
- case _BOT:
+func (a *matchArena) addState(s []state, inst *instr, prefixed bool, match *matchVec, pos, end int) []state {
+ switch inst.kind {
+ case iBOT:
if pos == 0 {
- s = a.addState(s, inst.next(), prefixed, match, pos, end)
+ s = a.addState(s, inst.next, prefixed, match, pos, end)
}
return s
- case _EOT:
+ case iEOT:
if pos == end {
- s = a.addState(s, inst.next(), prefixed, match, pos, end)
+ s = a.addState(s, inst.next, prefixed, match, pos, end)
}
return s
- case _BRA:
- n := inst.(*_Bra).n
- match.m[2*n] = pos
- s = a.addState(s, inst.next(), prefixed, match, pos, end)
- return s
- case _EBRA:
- n := inst.(*_Ebra).n
- match.m[2*n+1] = pos
- s = a.addState(s, inst.next(), prefixed, match, pos, end)
+ case iBra:
+ match.m[inst.braNum] = pos
+ s = a.addState(s, inst.next, prefixed, match, pos, end)
return s
}
- index := inst.index()
l := len(s)
// States are inserted in order so it's sufficient to see if we have the same
// instruction; no need to see if existing match is earlier (it is).
for i := 0; i < l; i++ {
- if s[i].inst.index() == index {
+ if s[i].inst == inst {
return s
}
}
s = append(s, state{inst, prefixed, match})
match.ref++
- if inst.kind() == _ALT {
- s = a.addState(s, inst.(*_Alt).left, prefixed, a.copy(match), pos, end)
+ if inst.kind == iAlt {
+ s = a.addState(s, inst.left, prefixed, a.copy(match), pos, end)
// give other branch a copy of this match vector
- s = a.addState(s, inst.next(), prefixed, a.copy(match), pos, end)
+ s = a.addState(s, inst.next, prefixed, a.copy(match), pos, end)
}
return s
}
s[out] = arena.addState(s[out], re.prefixStart, true, match, pos, end)
prefixed = false // next iteration should start at beginning of machine.
} else {
- s[out] = arena.addState(s[out], re.start.next(), false, match, pos, end)
+ s[out] = arena.addState(s[out], re.start.next, false, match, pos, end)
}
arena.free(match) // if addState saved it, ref was incremented
}
}
pos += charwidth
for _, st := range s[in] {
- switch st.inst.kind() {
- case _BOT:
- case _EOT:
- case _CHAR:
- if c == st.inst.(*_Char).char {
- s[out] = arena.addState(s[out], st.inst.next(), st.prefixed, st.match, pos, end)
+ switch st.inst.kind {
+ case iBOT:
+ case iEOT:
+ case iChar:
+ if c == st.inst.char {
+ s[out] = arena.addState(s[out], st.inst.next, st.prefixed, st.match, pos, end)
}
- case _CHARCLASS:
- if st.inst.(*_CharClass).matches(c) {
- s[out] = arena.addState(s[out], st.inst.next(), st.prefixed, st.match, pos, end)
+ case iCharClass:
+ if st.inst.cclass.matches(c) {
+ s[out] = arena.addState(s[out], st.inst.next, st.prefixed, st.match, pos, end)
}
- case _ANY:
+ case iAny:
if c != endOfFile {
- s[out] = arena.addState(s[out], st.inst.next(), st.prefixed, st.match, pos, end)
+ s[out] = arena.addState(s[out], st.inst.next, st.prefixed, st.match, pos, end)
}
- case _NOTNL:
+ case iNotNL:
if c != endOfFile && c != '\n' {
- s[out] = arena.addState(s[out], st.inst.next(), st.prefixed, st.match, pos, end)
+ s[out] = arena.addState(s[out], st.inst.next, st.prefixed, st.match, pos, end)
}
- case _BRA:
- case _EBRA:
- case _ALT:
- case _END:
+ case iBra:
+ case iAlt:
+ case iEnd:
// choose leftmost longest
if !found || // first
st.match.m[0] < final.match.m[0] || // leftmost
OSDN Git Service
