// 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 syntax.EmptyOp) {
if pc == 0 {
return
}
if j := q.sparse[pc]; j < uint32(len(q.dense)) && q.dense[j].pc == pc {
return
}
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:
m.add(q, i.Out, pos, cap, cond)
m.add(q, i.Arg, pos, cap, cond)
case syntax.InstEmptyWidth:
if syntax.EmptyOp(i.Arg)&^cond == 0 {
m.add(q, i.Out, pos, cap, cond)
}
case syntax.InstNop:
m.add(q, i.Out, pos, cap, cond)
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)
cap[i.Arg] = opos
} else {
m.add(q, i.Out, pos, cap, cond)
}
case syntax.InstMatch, syntax.InstRune:
t := m.alloc(i)
if len(t.cap) > 0 {
copy(t.cap, cap)
}
d.t = t
}
}
// 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
rune, rune1 := endOfText, endOfText
width, width1 := 0, 0
rune, width = i.step(pos)
if rune != endOfText {
rune1, width1 = i.step(pos + width)
}
// TODO: Let caller specify the initial flag setting.
// For now assume pos == 0 is beginning of text and
// pos != 0 is not even beginning of line.
// TODO: Word boundary.
var flag syntax.EmptyOp
if pos == 0 {
flag = syntax.EmptyBeginText | syntax.EmptyBeginLine
}
// Update flag using lookahead rune.
if rune1 == '\n' {
flag |= syntax.EmptyEndLine
}
if rune1 == endOfText {
flag |= syntax.EmptyEndText
}
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 && rune1 != 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
rune, width = i.step(pos)
rune1, 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)
}
// TODO: word boundary
flag = 0
if rune == '\n' {
flag |= syntax.EmptyBeginLine
}
if rune1 == '\n' {
flag |= syntax.EmptyEndLine
}
if rune1 == endOfText {
flag |= syntax.EmptyEndText
}
m.step(runq, nextq, pos, pos+width, rune, flag)
if width == 0 {
break
}
pos += width
rune, width = rune1, width1
if rune != endOfText {
rune1, width1 = i.step(pos + width)
}
runq, nextq = nextq, runq
}
m.clear(nextq)
return m.matched
}